Short wave radiation systems and methods

Abstract

A short Wave Radiation (SWR) system comprising: a light source operable to emit a series of light pulses toward an ionization location to generate emission along a designated collection axis (DCA) of an SWR pulse and particles from at least one ionization target; an intermittent illumination blocker including at least one opaque portion operable to block SWR and particles, and at least one aperture within the opaque portion via which SWR can pass; and a controller operatively connected to the intermittent illumination blocker and the light source for controlling synchronization between motion of the blocker and emission of the light pulses, such that: during a first timespan that includes emission of a light pulse, the aperture intersects the DCA, permitting SWR to pass; and during a second timespan following the first timespan, the opaque portion intersects the DCA, blocking propagation of particles from continuing along the DCA.

Description

Attorney Docket No. 16978-0004.00304SHORTWAVE RADIATION SYSTEMSAND METHODSCROSS REFERENCES TO RELATED APPLICATIONS

[0001] This application claims the benefit of priority of Israel Patent Application No.318849, filed on February 5, 2025, the entirety of which is incorporated herein by reference.FIELD

[0002] The present disclosure relates to systems, methods, and computer program products for generation of short wave radiation.BACKGROUND

[0003] Short-wave Radiation (SWR), i.e., radiation having a wavelength shorter than 200nm, has a wide range of applications in fields such as lithography, material processing, and medical treatment. In particular, the use of Extreme Ultra-Violet (EUV) radiation in lithography has become increasingly important in the semiconductor industry, where it is used to pattern photoresist and other materials with high precision. However, conventional SWR light sources often suffer from limited power, brightness and stability, which can limit their usefulness in industrial applications. There is therefore a need for a new and improved light source that can generate and emit SWR radiation with high brightness power and stability, making it suitable for use in a variety of applications, such as lithography, defect inspection, metrology, and material processing or various inspections.

[0004] Ionizing radiation is a type of electromagnetic radiation that has sufficient energy to remove tightly bound electrons from atoms, a process known as ionization. Ionizing radiation is found in several sources, including nuclear reactions, radioactive decay, and high-energy particle accelerators. In recent years, there has been increasing interest in using ionizing radiation, specifically extreme ultraviolet (EUV) light, as a source for lithography, a process used in the manufacturing of microchips and other electronic devices. Lithography involves using light to transfer a pattern onto a substrate, such as a silicon wafer, and EUV light has the potential to significantly improve the resolution and accuracy of this process.

[0005] Extreme ultraviolet (EUV) light is a type of electromagnetic SWR. While the exact definitions used by different scientists may vary, within the context of this disclosure the term EUV pertains to a spectral range which includes at least the electromagnetic radiation with wavelengths ranging from 0.1-100nm. EUV light is difficult to generate and requires specialized equipment, making it challenging to produce on high volume manufacturing conditions which require high output power of the EUV system and efficient conversion ofAttorney Docket No. 16978-0004.00304electricity power to outputted EUV (the same is also true more generally for SWR systems). There are several different approaches to generating EUV light, including discharge-based and laser-based methods, and researchers are actively working to develop more efficient and cost-effective ways of producing EUV light for use in lithography and other applications.

[0006] SWR sources are crucial technologies in various high-precision fields, such as semiconductor manufacturing and materials science. These plasma sources generate high-energy photons, which are used for lithography in microchip production and for analyzing material properties at microscopic levels. Their ability to produce short-wavelength radiation allows for extremely detailed imaging and patterning, making them indispensable in cutting-edge technological applications. However, during the operation of SWR plasma sources, ions and small debris are inevitably generated. These particles are byproducts of the plasma generation process, where high-energy interactions cause materials to ablate or sputter, releasing a mix of ions and microscopic fragments. These particles can vary in size, velocity, and composition, posing significant challenges in maintaining the integrity and performance of the equipment.

[0007] The presence of ions and small debris can have detrimental effects on the optical components within SWR plasma sources. For example, these particles can deposit on mirrors and lenses, leading to scattering and absorption of the radiation, thereby reducing the efficiency and accuracy of the system. Over time, this contamination can cause irreversible damage, necessitating frequent maintenance and replacement of critical components, which increases operational costs and downtime.

[0008] European patent application serial number EP1 ,211,918 entitled “Method of stopping ions and small debris in extreme-ultraviolet and soft x-rays plasma sources by using krypton” filed on 2001 by Francesco Flora, et al. discusses a method and device for filtering ions and small debris by using krypton or its mixtures to fill the chamber of the EUV-radiation source. The disclosed method can be combined with mechanical methods of filtering debris particles with size greater than one micron and is claimed to allow obtaining plasma EUV-radiation without polluting debris and to extend the useful life of the mirrors of a microlithography apparatus.

[0009] In their publication entitled “High-efficiency clean EUV plasma source at 10-30 nm, driven by a long-pulse-width excimer laser” (Bollanti, S., Bonfigli, F., Burattini, E. et al. High-efficiency clean EUV plasma source at 10-30 nm, driven by a long-pulse-width excimer laser . Appl Phys B 76, 277-284 (2003)), Bollanti et al. details that a long-pulse-width high-output energy (120 ns FWHM, 7 J) XeCI laser has been focused on thin tape targets (Cu and Ta) to generate more than 100-ns-long (FWHM) EUV pulses in the 10-30 nm spectral region,Attorney Docket No. 16978-0004.00304suitable for projection microlithography. The conversion efficiency was more than 20% over a 2TT solid angle. They observed debris emission using a gated CCD camera, and measured the debris speed for different irradiation conditions. They found irradiation conditions such that the measured velocities were low enough that simple mechanical devices combined with krypton at low-pressure could efficiently stop both ionic debris and cluster debris. They go on to say that their results show that a suitable combination of driving-laser characteristics, target material and thickness, environment gas and mechanical choppers can make clean and increase the power of EUV solid-target laser-plasma sources.

[0010] US patent serial number 10,588,210 entitled “High brightness short-wavelength radiation source (variants)” by Aleksandr Yurievich Vinokhodov et al. discusses a High-brightness short-wavelength radiation source that contains a vacuum chamber with a rotating target assembly having an annular groove, an energy beam focused on the target, a useful short-wavelength radiation beam coming out of the interaction zone, wherein the target is a layer of molten metal formed by a centrifugal force on a surface of the annular groove facing a rotation axis. A replaceable membrane made of carbon nanotubes may be installed on a pathway of the short-wavelength radiation beam for debris mitigation. In the embodiments of the invention the energy beam is a pulsed laser beam. The pulsed laser beam may consist of pre-pulse and main-pulse, with parameters such as laser pulse repetition rate chosen in order to suppress debris. In other embodiments the energy beam is the electron beam produced by an electron gun and the rotating target assembly is a rotating anode.

[0011] Effective mitigation of ions and debris is essential to enhance the longevity and performance of EUV and soft x-ray plasma sources. While various methods have been employed to address this issue, they often come with limitations such as complexity, cost, and partial effectiveness. Thus, there is a pressing need for innovative solutions that can prevent unwanted debris from reaching to sensitive parts of a system being used for manufacturing or inspection and metrology or microscopy. Such sensitive parts may be, for example, part of the optics being used to deliver the SWR from the source to the sample being treated by the machine, other optical elements that may be used to deliver light to the laser-produced plasma (LPP) target, other optical elements or electronic elements such as sensors, the sample that can be contaminated by the target material during the process, and so on.SUMMARY

[0012] According to an aspect of the invention, there is disclosed a short Wave Radiation (SWR) system, the system including: a light source operable to emit a series of light pulses, each pulse being emitted toward an ionization location to thereby induce emission along a designated collection axis (DCA) of SWR pulse and of particles from at least one ionizationAttorney Docket No. 16978-0004.00304target positioned at the ionization location; an intermittent illumination blocker, including (a) opaque portions operable to block SWR and particles impinging on the opaque portions, and (b) at least one aperture within an opaque portion out of the opaque portions, via which SWR and particles can pass; and a controller, operatively connected to at least one of: the intermittent illumination blocker and the light source, for controlling synchronization between motion of the intermittent illumination blocker and an emission of the series of light pulses, such that: (i) during a first timespan that includes the emission of a light pulse of the series of light pulses, the at least one aperture intersects the DCA, thereby permitting SWR of a respective SWR pulse resulting from the light pulse to pass the intermittent illumination blocker along the DCA; and (ii) during a second timespan following the first timespan, the at least one opaque portion of the intermittent illumination blocker intersects the DCA, thereby blocking propagation of particles emitted from the at least one ionization target as a result of the impinging of the light pulse from continuing along the DCA.

[0013] According to a further aspect of the disclosure, during each second timespan associated with each of the series of light pulses, the at least one opaque portion of the intermittent illumination blocker intersects the DCA at a plurality of blockable locations including at least a first blockable location and a second blockable location. In some cases, the first blockable location and the second blockable location may be positioned along the DCA at a distance that exceeds 5mm.

[0014] According to a further aspect of the disclosure, the controller may be operable to control the synchronization such that during the second time span of each pulse out of the plurality of pulses: (a) particles emitted as a result of the pulse are blocked at the first blockable location, and (b) particles emitted as a result of a previous pulse of the series of light pulses are blocked at the second blockable location.

[0015] According to a further aspect of the disclosure, the controller may be operable to control the synchronization such that during each second time span, the intermittent illumination blocker concurrently blocks, by a first opaque portion located at the first blockable location, particles that are moving at a first span of velocities, and blocks, by a second opaque portion located at the second blockable location, particles that are moving at a second span of velocities; wherein the first span of velocities and the second span of velocities are nonoverlapping.

[0016] According to a further aspect of the disclosure, out of all velocities between 10m / sec and 300m / sec, at least 10% are blocked only at one of two discrete blockable locations and not in both blockable locations.Attorney Docket No. 16978-0004.00304

[0017] According to a further aspect of the disclosure, a structure of the intermittent illumination blocker and the rate of pulse emission may be such that passage of particles resulting from the emission of each respective SWR pulse at the first blockable location is intermittently permitted via a series of at least five separate apertures of the intermittent illumination blocker, thereby allowing a pulse repetition rate of above 1Khz, wherein at least 50% of the permitted particles are blocked at or after the second blockable location.

[0018] According to a further aspect of the disclosure, a structure of the intermittent illumination blocker and the rate of pulse emission yield a blocking frequency of at least 1K cycles per second of open durations for passage along the designated collection axis via an aperture of the intermittent illumination blocker at the first blockable location and close durations of blocking passage of particles at the first blockable location, corresponding to open durations shorter than 1ms, wherein a distance between the ionization location and the intermittent illumination blocker is such that any particle propagating at velocities that are slower than 300m / sec cannot pass the first blockable location via the same aperture as the corresponding SWR pulse.

[0019] According to a further aspect of the disclosure, the at least one aperture may include a series of apertures positioned along the DCA and at least 0.01% of the particles blocked by the intermittent illumination blocker may be blocked after previously passing through a first aperture of the series of apertures.

[0020] According to a further aspect of the disclosure, less than 20% of the particles blocked by the intermittent illumination blocker are blocked after previously passing through an aperture of the at least one aperture of the intermittent illumination blocker when the respective aperture was positioned along the DCA.

[0021] According to a further aspect of the disclosure, a dimension of the intermittent illumination blocker along the DCA may be greater than 1 cm and the at least one opaque portion of the intermittent illumination blocker may include at least a first blockable location and a second blockable location.

[0022] In some cases, the motion of the intermittent illumination blocker may be determined such that the first blockable location is located within the at least one aperture and the second blockable location is located outside the at least one aperture. In other cases, the motion of the intermittent illumination blocker is determined such that both the first blockable location and the second blockable location are located outside the at least one aperture.

[0023] According to a further aspect of the disclosure, the intermittent illumination blocker includes at least one rotating disc mechanical shutter optical chopper, wherein the least oneAttorney Docket No. 16978-0004.00304aperture includes a plurality of apertures at each rotating disc out of a plurality rotating discs of the at least one rotating disc mechanical shutter optical chopper; wherein the first blockable location is positioned at an intersection with the DCA of a first rotating disc out of the plurality of rotating discs, wherein the second blockable location is positioned at an intersection with the DCA of a second rotating disc out of the plurality of rotating discs; wherein projections of the first rotating disc and of the second rotating disc about a plane perpendicular to the designated collection direction rotate in the same direction.

[0024] According to a further aspect of the disclosure, the controller is operatively connected to the intermittent illumination blocker for controlling the synchronization, such that for each pulse out of the plurality of pulses of the series of light pulses: (a) during at least a portion of the first timespan that includes the emission of the respective pulse a second group of one or more apertures out of the at least one apertures intersects an illumination propagation path between light source and the ionization location, thereby permitting light of the respective pulse emitted by the light source to progress at an illumination propagation direction along the illumination propagation path to the ionization location; and (b) during the second timespan at least one second opaque portion of the intermittent illumination blocker intersects the illumination propagation path, thereby blocking propagation of particles emitted from the respective ionization target as a result of the impinging of the respective pulse from propagating along the illumination propagation path at a direction opposing the illumination propagation direction toward the light source.

[0025] According to a further aspect of the disclosure, the second group of one or more apertures include apertures that do not intersect the DCA.

[0026] According to a further aspect of the disclosure, the SWR system may further include a post blocker deflection mechanism for deflecting away from the DCA propagation directions of particles that progressed past the intermittent illumination blocker along the DCA.

[0027] According to a further aspect of the disclosure, the post blocker deflection mechanism may include at least one of: a magnetic field inducer that generates a magnetic field or an electric field inducer that generates electric field, for diverting a propagation direction of particles that progressed past the intermittent illumination blocker during the first timespan, toward an absorbent surface of the SWR system.

[0028] According to a further aspect of the disclosure, the post blocker deflection mechanism may include a pressured gas discharger operable to emit gas emissions toward particles that progressed past the intermittent illumination blocker, thereby modifying at least one of trajectories or velocities of the particles that progressed past the intermittent illumination blocker.Attorney Docket No. 16978-0004.00304

[0029] According to a further aspect of the disclosure, at least part of the emitted SWR and at least part of the emitted particles may progress along a plurality of different designated collection axes, wherein the intermittent illumination blocker includes a plurality of apertures via which SWR and particles can pass concurrently, wherein the controller may be operable to control the synchronization such that: (a) during the first timespan, each of the plurality of apertures concurrently intersects a corresponding DCA out of the plurality of designated collection axes, thereby permitting SWR emitted from the respective ionization target as a result of the impinging of the respective pulse to continue along the corresponding DCA; and (b) during the second timespan, the plurality of designated collection axes are blocked by a corresponding plurality of opaque portions of the intermittent illumination blocker, thereby blocking propagation of particles emitted from the respective ionization target as a result of the impinging of the respective pulse from continuing along the plurality of designated collection axes.

[0030] According to an aspect of the disclosure, there is disclosed a method for generation of Short Wave Radiation (SWR), the method including: (a) emitting a series of light pulses toward an ionization location, thereby generating emission along a designated collection axis (DCA) of a plurality of SWR pulses and emission of particles from at least one ionization target positioned at the ionization location; and for each SWR pulse out of the plurality of SWR pulses: during a first timespan that includes the emission of the respective SWR pulse providing a clear passage along the designated collection axis (DCA), thereby permitting SWR of the respective SWR pulse to continue past an intermittent illumination blocker along the DCA; and during a second timespan following the first timespan blocking the DCA by at least one opaque portion of the intermittent illumination blocker, the at least one opaque portion intersecting the DCA at a plurality of blockable locations distributed along the DCA, thereby blocking propagation of particles emitted from the respective ionization target as a result of the generation of the respective SWR pulse from continuing along the DCA; wherein the plurality of blockable locations includes at least a first blockable location and a second blockable location.

[0031] According to a further aspect of the disclosure, the method may include aligning during the first timespan at least one aperture that is located within the at least one opaque portion to intersect the DCA, thereby allowing the SWR of the respective SWR pulse to continue past the intermittent illumination blocker along the DCA via the at least one aperture.

[0032] According to a further aspect of the disclosure, during each second timespan associated with each of the series of light pulses, the at least one opaque portion of theAttorney Docket No. 16978-0004.00304intermittent illumination blocker may block particles at a plurality of blockable locations including at least a first blockable location and a second blockable location.

[0033] According to a further aspect of the disclosure, the blocking associated with each SWR pulse out of the plurality of SWR pulses may include: blocking particles emitted as a result of the generation of a first SWR pulse at the first blockable location, and blocking particles emitted as a result of the generation of a second previous SWR pulse at the second blockable location.

[0034] According to a further aspect of the disclosure, the blocking associated with each SWR pulse out of the plurality of SWR pulses may include: concurrently blocking by a first opaque portion located at the first blockable location particles that are moving at a first span of velocities, and blocking by a second opaque portion located at the second blockable location particles that are moving at a second span of velocities, wherein the first span of velocities and the second span of velocities are non-overlapping.

[0035] According to a further aspect of the disclosure, the first blockable location and the second blockable location may be positioned along the DCA at a distance that exceeds 1cm.

[0036] According to a further aspect of the disclosure, the blocking may include blocking at least 5% of the particles blocked by the intermittent illumination blocker after the respective particles have previously passed through a first aperture of a series of apertures of the intermittent illumination blocker when the series of apertures are positioned along the DCA.

[0037] According to a further aspect of the disclosure, the blocking may include blocking less than 20% of the particles blocked by the intermittent illumination blocker after the respective particles have previously passed through a first aperture of a series of apertures of the intermittent illumination blocker when the series of apertures are positioned along the DCA.

[0038] According to a further aspect of the disclosure, a dimension of the intermittent illumination blocker along the DCA may be greater than 1 cm and the at least one opaque portion of the intermittent illumination blocker may include at least a first blockable location and a second blockable location.

[0039] According to a further aspect of the disclosure, the intermittent illumination blocker may include a rotating disc mechanical shutter optical chopper that includes a plurality of tunnels longer than 1cm via which SWR can pass during the first time spans associated with the plurality of SWR pulses, wherein the plurality of blockable locations includes a continuum of blockable locations dispersed along a span longer than 1cm along each tunnel out of the plurality of tunnels.Attorney Docket No. 16978-0004.00304

[0040] According to a further aspect of the disclosure, the method may further include for each SWR pulse out of the plurality of SWR pulses: during at least the second timespan blocking by at least one opaque object particles emitted from the ionization target as a result of the generation of the respective SWR pulse from propagating toward a light source that emits the series of light pulses along an illumination propagation path between the ionization location and the light source, and intermittently moving the at least one opaque object away from the illumination propagation path to allow propagation of the series of light pulses along the illumination propagation path.

[0041] According to a further aspect of the disclosure, the intermittent moving of the at least one opaque object away from the illumination propagation path includes allowing the light pulses to pass via one or more apertures of an optical chopper, the one or more apertures of the optical chopper not intersecting the DCA.

[0042] According to a further aspect of the disclosure, the method may further include deflecting away from the DCA particles that progressed past the intermittent illumination blocker along the DCA by inducing an electromagnetic field causing during the second timespan diversion of the propagation directions of particles that progressed past the intermittent illumination blocker during the first timespan toward an absorbent surface of the SWR system.

[0043] According to a further aspect of the disclosure, the method may further include deflecting away from the DCA particles that progressed past the intermittent illumination blocker along the DCA by a pressured gas discharger operable to emit during the second timespans gas emissions toward particles that progressed past the intermittent illumination blocker, thereby modifying at least one of trajectories or velocities of the particles that progressed past the intermittent illumination blocker.

[0044] According to a further aspect of the disclosure, the method may further include for each SWR pulse out of a plurality of SWR pulses of the series of SWR pulses: (a) during the first timespan that includes the emission of the respective SWR pulse providing clear passages along a plurality of DCAs, thereby permitting SWR of the respective SWR pulse to continue along the plurality of DCAs past an intermittent illumination blocking assembly that includes at least the intermittent illumination blocker; and (b) during the second timespan blocking the plurality DCAs by opaque portions of the intermittent illumination blocking assembly that intersect the DCAs, thereby blocking propagation of particles emitted from the respective ionization target as a result of the generation of the respective SWR pulse from continuing along the plurality of DCAs.Attorney Docket No. 16978-0004.00304BRIEF DESCRIPTION OF THE DRAWINGS

[0045] In order to understand the invention and to see how it may be carried out in practice, embodiments will now be described, by way of non-limiting examples only, with reference to the accompanying drawings, in which:

[0046] Figs. 1A-1D are schematical cross-section diagrams illustrating examples of a Short-wave Radiation (SWR) system;

[0047] Fig. 2 is a schematical cross-section diagram illustrating an example of an SWR system used for lithography and / or inspection;

[0048] Figs. 3A and 3B are schematic timing schedules, illustrating alternation between first timespans and second timespans;

[0049] Figs. 4A-4C illustrate photon emission count as a function of time, particle emission count as a function of time, and illustrative blocker transmittance timing scheme;

[0050] Figs. 5A, 5B, 5C, 6, 7, 8, 9A, and 9B are schematical cross-section diagrams illustrating examples of SWR systems;

[0051] Fig. 10 is a series of graph illustrating passage of particles of different velocities resulting from the generation of a single SWR pulse via a series of intermittent illumination blocker modules;

[0052] Figs. 11, 12, 13 are schematical cross-section diagrams illustrating examples of SWR systems;

[0053] Fig. 14 is a 3D illustration of an example of a SWR systems;

[0054] Figs. 15A and 15B illustrate an optical chopper disc with a plurality of apertures, used in different ways; and

[0055] Figs. 16, 17, and 18 are flow charts illustrating examples of a method for generation of SWR.

[0056] It will be appreciated that for simplicity and clarity of illustration and description, certain elements in the figures may not have been drawn to scale. This could include the exaggeration of certain element dimensions relative to others. Additionally, corresponding or analogous elements may be identified using repeated reference numerals in the figures.DETAILED DESCRIPTIONIn the following detailed description, numerous specific details are provided to ensure a comprehensive understanding of the disclosure. While these details aid in understanding,Attorney Docket No. 16978-0004.00304those skilled in the art will recognize that the disclosure can be implemented without these specific details. In addition, well-known methods, procedures, and components are not described in detail to avoid obscuring the disclosure. References to a method, system, or non-transitory computer readable medium should be interpreted inclusively, as including related aspects of the disclosure.

[0057] The functionality of the elements described herein may be implemented using circuitry or processing circuitry such as general-purpose processors, special purpose processors, integrated circuits, Application Specific Integrated Circuits (ASICs), and other conventional circuitries. Such circuitries and / or combinations thereof may be configured and / or programmed to perform the disclosed functionality. This also includes emerging technologies such as quantum processors and Al-driven systems. Processors, containing transistors and other components, are considered part of this circuitry. In this disclosure, the terms 'circuitry', 'units', or 'means' refer to hardware configured to perform the disclosed functions. Such processor may be implemented as purely hardware circuitry. In other possible implementations, processors, controllers, computers, units, or other means may be implemented using any combination of hardware with software and / or firmware.

[0058] It is appreciated that certain features of the presently disclosed subject matter, which are, for the sake of clarity of description, described in the context of separate embodiments, may also be combined in a single embodiment. Conversely, various features of the presently disclosed subject matter, which are, for brevity, described in the context of a single embodiment, may also be provided separately or in any suitable sub-combination. In embodiments of the presently disclosed subject matter one or more steps illustrated in the figures may be executed in a different order and / or one or more groups of steps may be executed simultaneously. The figures illustrate a general schematic of the system architecture in accordance with an embodiment of the presently disclosed subject matter. Each module in the figures can be made up of any combination of software, hardware and / or firmware that performs the functions as defined and explained herein. The modules in the figures may be centralized in one location or dispersed over more than one location.

[0059] Any reference in the specification to a method should be applied mutatis mutandis to a system capable of executing the method. Any reference in the specification to a method which can be executed by a computer should be applied mutatis mutandis to a non-transitory computer readable medium that stores instructions that once executed by a computer result in the execution of the method. All the details, variations, optional features, optional steps which are discussed with respect to a system are also applicable, mutatis mutandis, to suchAttorney Docket No. 16978-0004.00304a corresponding method (and non-transitory computer readable medium, where applicable), and vice versa.

[0060] The systems and methods disclosed in the present disclosure are useful for generation of SWR using ionization of ionization target (e.g., made of one or more materials out of the nonlimiting group of materials including: tin, gadolinium, gold, copper, iron, lead, and T ungsten). The systems and methods disclosed in the present disclosure utilize an intermittent illumination blocker in order to alternately permit passage of SWR in times in which SWR is emitted and while an amount of particles emitted as a result of ionization of ionization target reaching the intermittent illumination blocker is relatively low, while blocking SWR and particles at times in which SWR emission is reduced or ceased and the rate of such particles reaching the intermittent illumination blocker is higher.

[0061] The velocities of particles emitted as a result of ionization of the ionization target are much slower than that of the emitted radiation, and while some particles may move in velocities that exceed 1,000m / sec, many others move in significantly lower velocities. The large divergence in velocities of particles present a challenge for systems and methods which aim to emit SWR while limiting the propagation of emitted particles (such as electrons, ionized particles, neutral atoms and clusters (chunks) of target material of various sizes and velocities).

[0062] Figs. 1A, 1B, 1C, and 1D are schematical cross-section diagrams illustrating examples of system 200, in accordance with examples of the presently disclosed subject matter. System 200 is operable to generate Short Wave Radiation-SWR (e.g., EUV light)— and may optionally also include additional components which are not part of the light emission subsystem. For example, such components may utilize SWR generated by system 200 (e.g., EUV light) for different uses in chip manufacturing (e.g., lithography, inspection, metrology), or in any other field, such as imaging, shadowgraph, microscopy and other processes of measurement characterization and sensing of the sample structure, morphology etc. The generated SWR may have a characteristic wavelength of 13.5nm, but other SWR wavelengths may also be emitted and optionally utilized. For example, 6.7nm or shorter, 15nm or longer. Within the context of this disclosure, the terms short-wave radiation (SWR) pertains to all electromagnetic radiation having wavelength that is shorter than 200nm, and especially to radiation between 0.2-200nm. Short-wave radiation includes different parts of the electromagnetic spectrum, such as EUV and X-ray. The emitted SWR radiation (by system 200 or by any of the systems and methods disclosed herein) may have its power peak at different wavelengths, for example in order to suit the intended use of the SWR. For example, the SWR generated using the systems and methods discussed below may have a peak power at a wavelength of 1.7nm, 4.2nm, 5nm, 6.7nm, 13.5nm, 50nm, 100nm, etc. The actual emittedAttorney Docket No. 16978-0004.00304SWR spectrum may be broad with respect to the desired wavelength range (e.g., 13.5nm±1%), and the undesired emitted SWR may be filtered out, emitted anyway, lost in the system (e.g., due to optics being tailored to specific wavelengths), or handled in any other suitable fashion. By way of example, some lithography uses may require 13.5nm±1%, while other applications may require broader spectrum.

[0063] SWR system 200 (also referred to as system 200) includes at least one heating module 202 providing energy for heating one or more ionization targets 100 at ionization location 10, thereby at least partly ionizing such one or more ionization targets 100 (and exciting the atoms of such ionized parts of the targets 100) for emitting SWR (e.g., EUV light, e.g., a series of SWR pulses). For example, heating module 202 may optionally include one or more light source 210 used to illuminate one or more objects (referred to "targets" 100), thereby at least partly ionizing such targets 100 (and exciting the atoms of such ionized parts of the targets 100) for emitting SWR (e.g., EUV light). The term "light source" refers to any source capable of producing electromagnetic radiation suitable for initiating ionization at an ionization location. A light source may include, for example, a laser, a pulsed radiation emitter, an optical emitter, or a solid-state radiation device, and may operate at one or more wavelengths, power levels, or pulse durations. In general, the light source may be any component or combination of components capable of providing radiation that results in short wave radiation and particle emission when directed toward an ionization target. Different types of light sources may be used, such as lasers (e.g., Gas lasers, CO2laser, diode laser, fiber laser, Q-switched laser, diode pumped lasers and diode pumped solid state (DPSS) lasers), pulsed light source, continuous light source (e.g., continuous wave, CW, laser), etc.

[0064] It is noted that while one or more light source 210 may be used for the ionization of target material, other techniques may also be used, either in addition or instead of lighting. For example, heating module 202 may implement any one or more of the following technologies: Discharge-Produced Plasma (DPP): heating module 202 may optionally discharge a high-voltage electrical discharge to ionize and excite a material to produce plasma that emits SWR. Z-pinch or Theta pinch: heating module 202 may optionally pass a strong electrical current through a cylindrical column of material (serving as target 100 in that case, e.g., a gas or liquid metal), causing it to compress and ionize, producing SWR. The electrical current compresses the target material, causing it to heat and preventing its expansion in a vacuum, thus keeping the density high. Microwave-Induced Plasma: heating module 202 may optionally ionize or heat target 100 using high-frequency microwaves, thereby creating a plasma that can emit SWR.Attorney Docket No. 16978-0004.00304

[0065] Optionally, heating module 202 may include various optical components (collectively denoted “optics 212”) for directing light of the optional at least one light source 210 onto targets 100 within system 200. Optics 212 may include mirrors, curved mirrors, parabolic and spherical mirrors, prisms, lenses, and any other types of equipment which may be used for transforming light propagation. Optics 212 may optionally include controllable components for changing properties of light such as propagation direction, focusing properties, optical wavefront of the light beam directed toward the targets 100 (e.g., in order to accommodate for fluctuations in the positioning of different targets 100), but this is not necessarily so. Some examples for optics 212 (and any other SWR optics discussed below) include: motorized optics, deformable mirrors, piezoelectric actuators, optical modulators, Spatial Light Modulator (SLM), optical isolators, moving debris shield, transparent optical components, and so on.

[0066] System 200 may optionally include controller 220 for controlling different components of system 200. The term "controller" refers to any device, circuit, or system capable of influencing timing, coordination, or operational relationships between system components. A controller may include hardware, software, firmware, or combinations thereof, and may employ logic, processing, or control signals. In general, the controller refers to any element capable of managing system behavior. For example, controller 220 may include a computer, one or more computer processor, and any other components which may be required for its operation (e.g., memory units, cables, sensors, power supply). Optionally, one or more sensors may provide to controller 220 information needed for its control of components of SWR system 200 (e.g., heating module 202 and / or intermittent illumination blocker 270). Such information may include, for example, visual information (e.g., optical emission intensity, imaging of target material and plasma shape, surface reflectivity and quality), kinematic information (e.g., motion and position of target material, optical components, intermittent illumination blocker, vibration and stability monitoring), thermal information (e.g., temperature of critical components, heat flux measurement), electrical information (e.g., current and voltage of plasma generation systems), gas composition and pressure information (e.g., vacuum integrity, gas concentration levels), material and debris monitoring (e.g., detection of debris, material integrity of target substances), and radiation and dosimetry information (e.g., SWR intensity, monitoring of radiation damage to sensitive components). Any of this types of data may be collected by one or more suitable sensors 250, as will be clear to any person who is of ordinary skill in the art, and are therefore not detailed for reasons of brevity of the disclosure. Controller 220 may use such parameters to control the operation of heating module 202, light source 210, optics 212, intermittent illumination blocker 270, or of any other component of system 200. While only one light source 210 is exemplifiedAttorney Docket No. 16978-0004.00304in Figs. 1B and 1C, it is noted that multiple light sources 210 may optionally be implemented, directed to hit targets 100 from one or more directions and in one or more locations within SWR emission module 290. Optionally, a light of a single light source 210 (out of the one or more optionally included in heating module 202) may be split into several light beams which are projected onto a single target 100 from different directions (concurrently, partly concurrently, or otherwise). It is further noted that several light sources can be combined into one (e.g., into a single light beam).

[0067] Heating module 202 is operable to generate emission of one or more SWR pulses (e.g., a series of SWR pulses) from an ionization target 100 positioned at the ionization location 10. The term "SWR pulse" refers to a discrete instance of short wave radiation having a finite temporal duration. An SWR pulse may be characterized by a wavelength range, intensity profile, or temporal shape resulting from a corresponding light pulse. More generally, an SWR pulse refers to any burst of short wave radiation generated as a result of irradiation of an ionization target. In addition to the SWR pulse (e.g., EUV pulse), particles are also emitted from ionization target 100 as a result of heating of the respective ionization target 100 by heating module. The term "particles" refers to any material entities emitted from an ionization target as a result of interaction with a light pulse. Particles may include, for example, ions, electrons, neutral atoms, molecular fragments, or other ionization byproducts. In general, particles refer to any matter-based emissions capable of propagating along the designated collection axis. Such particles may include, for example, any combination of one or more of: microscopic solid fragments, nanoparticles, highly charged ions, neutral atoms, and reactive species. At least some of the emitted SWR pulse and of the emitted particles propagate along a designated collection axis 150 (DCA 150). For example, system 200 may include a light source operable to emit a series of light pulses, each pulse being emitted toward an ionization location 10 (where an ionization target 100 may be located) to thereby generate emission along DCA 150 of corresponding SWR pulses and of particles from an ionization target positioned at the ionization location. The phrase "emit a series of light pulses,” in the context of the present disclosure, refers to producing multiple temporally separated emissions of radiation from a light source. The series of light pulses may be periodic, aperiodic, uniform, or variable in timing, duration, or energy. More generally, the phrase refers to generating more than one radiation emission over time. The phrase "each pulse being emitted toward an ionization location,” in the context of the present disclosure, refers to directing individual light pulses along a path that intersects a defined ionization region. The ionization location may be fixed or variable and may contain one or more ionization targets. More generally, the phrase refers to orienting emitted radiation so that it interacts with a region capable of producing ionization effects.Attorney Docket No. 16978-0004.00304

[0068] Some embodiments of the present disclosure involve generating emission along a designated collection axis (DCA) of an SWR pulse and emission of particles from at least one ionization target positioned at the ionization location. The phrase "generate emission along a designated collection axis,” in the context of the present disclosure, refers to producing radiation or particles that propagate in a direction aligned with the designated collection axis. Such generation may result from optical alignment, physical confinement, or directional emission characteristics. In general, the phrase refers to causing emitted energy or matter to travel along a predefined path. The phrase "generate emission of particles from at least one ionization target positioned at the ionization location,” in the context of the present disclosure, refers to the release of particles from one or more targets located within the ionization region as a result of irradiation by a light pulse. The ionization target may include solids, liquids, gases, plasmas, or combinations thereof. More generally, the phrase refers to particle generation caused by radiation-matter interaction. It is noted that different ionization targets 100 may be positioned at ionization location 10 at different times, each being used foremission of one or more SWR pulses. The dimensions of the ionization target 100 may be selected based on the number of SWR pulses it is designed to provide. Optionally, a large ionization target 100 may be used, such that different parts of the ionization target 100 may be moved to ionization location 10 at different times, each part being used for emission of one or more SWR pulses.

[0069] SWR that propagates along DCA 150 can later be collected, directed, and / or otherwise manipulated in its progression outwards of system 200 and / or out of SWR emission module 290. For example, SWR that propagates along DCA 150 may propagate toward outward optics 240, which may be used to directing SWR out of system 200 (e.g., to another system), or from SWR emission module 290 to other parts of system 200 (e.g., optional SWR lithography components and / or SWR inspection components of system 200 as exemplified in Fig. 2). The term "designated collection axis" refers to a defined spatial direction along which radiation or particles are intended to propagate, be aligned, or be collected within the disclosed system. The designated collection axis may be defined by the geometry of system components, by optical alignment, or by physical constraints of downstream elements. In general, the designated collection axis represents any intended path along which emitted radiation is permitted to travel. DCA 150 is a direction within the respective system from which SWR can be collected. It should be noted that additional SWR and particles may be emitted to other directions, in addition to the SWR and particles propagating along DCA 150 (e.g., in a Lambertian or an isotropic emission).

[0070] While DCA 150 may point directly at outward optics 240 and / or at an egress aperture of system 200 (not illustrated, but may be positioned, for example, instead of optionalAttorney Docket No. 16978-0004.00304outward optics 240), this is not necessarily so, and the direction of progression may be manipulated in any suitable way (e.g., one or more multilayered mirrors, MLMs and / or using grazing incidence optics, Zone plates or diffraction gratings). MLMs are mirrors which may be made from a substrate material (e.g., quartz, silicon, glass), shaped in different shapes (e.g., plane, concave, convex, paraboloid, ellipsoidal etc.) which is coated in multiple layers of different coating (e.g., selected from the group consisting of Ru / Si, SiC / Mg, Mo / Si, Zr / AI, Cr / C, etc.), which assist in reflecting SWR (e.g., EUV light). In some examples, the emitted Short-Wave Radiation (SWR) emitted from target 100 is collected by an M LM (or other type of optics) and reflected towards outward optics 240. It should be noted that whenever optics 240 is mentioned, the disclosed system may also be implemented with an egress aperture or with another target for the SWR, mutatis mutandis.

[0071] While the term “designated collection direction 150” may refer to an imaginary line traversing an interior of the system (e.g., of a vacuum chamber of the system), it may also optionally have a non-zero width and / or some widening along its propagation (e.g., a beam divergence of between 1-100mrad, between 1-10mrad, between 5-50mrad, between 25-100mrad, between 100-500mrad, and / or between 1-500mrad). It is noted that the actual collection of SWR may be implemented away from the designated collection direction 150 (e.g., if the beam of SWR is being deflected or reflected along its propagation). Nevertheless, a position of intermittent illumination blocker 270 within system 200 is such that it— at least intermittently— crosses designated collection direction 150. Specifically, the at least one opaque portion 272 of intermittent illumination blocker 270 intermittently crosses designated collection direction 150. It is noted that intermittent illumination blocker 270 may consist of substantially rigid components, but this is not necessarily so, and more flexible components (even possibly flexible opaque portions 272) may also be optionally included. For example, rigid components of intermittent illumination blocker 270 may be made from suitable materials such as (but not limited to) any one or more of: Aluminum, stainless steel, Delrin, polycarbonate, carbon fiber, and specialty alloys. For example, rigid components of intermittent illumination blocker 270 may be made from suitable materials such as (but not limited to) any one or more of: Kevlar, polyimides, thermoplastic polyurethane, silicone rubber, Viton, carbon-fiber reinforced rubber, glass-fiber reinforced rubber, beryllium copper foil, titanium foil, neoprene, nylon-reinforced polymers, and Teflon.

[0072] The wavelength of the SWR emitted by system 200 is determined by the material of which an ionized target 100 is made of and the properties of heating module 202 (e.g., intensity, wavelength, and temporal duration of optional light source 210). Additional factors determining the wavelengths of the emitted SWR include wavelength of hitting radiation, geometrical properties of the interaction, temperature, and plasma density. For example,Attorney Docket No. 16978-0004.00304target 100 which are made of Tin (Sn) emit EUV light having a spectral peak at about 13.5nm. However, other materials for targets 100 (also referred to as “emitters”) can be used as well, among them, various high Z materials such as rare earth metals or higher Z metals such as gold or lead, as well as structures and materials that combine several elements, such as layered or mixed materials.

[0073] System 200 includes intermittent illumination blocker 270 (also referred to as intermittent illumination blocking arrangement 270) that includes at least one opaque portion 272 operable to block SWR and particles impinging on the at least one opaque portion. The term "intermittent illumination blocker" refers to a component configured to alternately permit and obstruct propagation along the designated collection axis. The intermittent illumination blocker may move, rotate, oscillate, or otherwise change position relative to the axis. In general, the intermittent illumination blocker refers to any structure capable of periodically blocking and unblocking radiation or particles. The at least one opaque portion 272 may give rise to one or more continuous opaque surfaces. Significantly, one or more of the opaque portions 272 is positioned such that the respective one or more opaque portions 272 may be repeatedly moved to a blocking disposition— in which the respective one or more opaque portions 272 blocks propagation of particles along DCA 150— and out of respective booking disposition. If SWR is emitted when the respective one or more opaque portions 272 is in the blocking disposition, the respective one or more opaque portions 272 will also block propagation of SWR. However, the timing of the blocking of particles by moving the respective one or more opaque portions 272 to the blocking disposition may be selected to limit or eliminate the times in which propagation of actual SWR emitted by system 200 along DCA 150 is actually blocked.

[0074] For example, the respective one or more opaque portions 272 may be moved to (or out of) a blocking disposition by changing any one or more out of: orientation, position, alignment, configuration, attitude, proximity, rotation, and tilt of the respective one or more opaque portion 272 with respect to DCA 150. It is noted that system 200 may implement a single blocking disposition for the one or more opaque portions 272 (e.g., a “closed” state of a movable opaque door), a plurality of predefined blocking dispositions (e.g., a plurality of predefined orientations of a rotating fan), one or more continuums of predefined blocking dispositions (e.g., all revolution positions of a rotating disc between a first revolution degree a and a second revolution degree P), blocking dispositions that change with time (in different degrees of controllability of the changing and / or generation process), and any combination of the above.

[0075] At times in which no opaque portion 272 coincides with DCA 150, SWR can propagate along DCA 150 (e.g., allowing SWR to progress toward outward optics 240 and / orAttorney Docket No. 16978-0004.00304toward an egress aperture of system 200) along a clear and uninterrupted propagation path. Optionally, some particles which propagate along with the SWR along DCA 150 may pass without interruption by opaque portions 272 of intermittent illumination blocker 270. Other particles may be blocked at a later time by the one or more opaque portions 272, depending on their velocity of propagation.

[0076] While not necessarily so, intermittent illumination blocker 270 may include one or more apertures 274, each of the one or more apertures 274 being an aperture within a corresponding opaque portion 272 out of the opaque portions 272, via which SWR and particles can pass. The phrase "at least one aperture within the at least one opaque portion,” in the context of the present disclosure, refers to an opening formed in the opaque portion that permits transmission of short wave radiation. The aperture may have any shape, size, or orientation suitable for allowing radiation passage while limiting particle propagation. More generally, the phrase refers to any transmissive region within a blocking structure. It is however noted that intermittent illumination blocker 270 may have openings of types other than apertures (such as slits, notches, cutouts, recesses, cavities), or may be otherwise arranged to allow passage of SWR along DCA 150 at some durations during the operation of system 200. It is noted that whenever an implementation which implements one or more apertures 274 is discussed below, equivalent implementations which implement other types of temporally controlled clear passages (e.g., slits, notches, etc., possibly in combination with fixed blocking surfaces) may also be implemented, mutatis mutandis, and are considered parts of the present disclosure.

[0077] For example, any one or more apertures 274 out of the at least one optional aperture 274 of intermittent illumination blocker 270 may include an empty window in the opaque portion, e.g., a 1x1 mm opening, a 1.5mm diameter circular opening, an elliptical opening, or any opening of any other useful shape and size. In some examples, any one or more apertures 274 out of the at least one optional aperture 274 of intermittent illumination blocker 270 may be an opening whose area is between 1-3mm2, between 2-5mm2, between 4-10mm2, or between 10-25mm2(or larger).

[0078] In another example, a slit or a notch or another type of opening may have width of about 1mm, of between 1-2mm, between 2-4mm, etc. A slit, a notice, etc. may be combined with another slit or notch or aperture (all either moving or fixed) to create a de-facto aperture in a crossing point of intermittent illumination blocker 270 and DCA 150.

[0079] At least some portions of intermittent illumination blocker 270 are movable, in order to selectively block and unblock passage of particles and SWR along DCA 150. The movable portions of intermittent illumination blocker 270 include at least one opaque portion 272.Attorney Docket No. 16978-0004.00304Intermittent illumination blocker 270 is positioned with respect to DCA 150, such that at some times an opaque portion 272 of intermittent illumination blocker 270 crosses DCA 150, and at other times clear passage via illumination blocking arrangement 270 is provided (e.g., via one or more optional apertures 274 of intermittent illumination blocker 270) for SWR and possibly for particles along parts of DCA 150 that can be blocked by the one or more opaque portions 272 at other times.

[0080] Pertaining to opaque portions 272, each opaque portion 272 may block all particles impinging on it, or a high number thereof (e.g., >95%, >99%, >99.9%). In this context, the term "opaque portion" refers to a portion of the intermittent illumination blocker that prevents transmission of short wave radiation and particles. An opaque portion may be formed from metals, ceramics, composites, or other materials capable of blocking radiation or matter. More generally, the opaque portion refers to any region that inhibits propagation through it. Consistent with the present disclosure, the opaque portion may be operable to block SWR and particles impinging on the at least one opaque portion. The phrase "at least one opaque portion operable to block SWR and particles" refers to a region of the intermittent illumination blocker that, when intersecting the designated collection axis, prevents passage of shortwave radiation and particle emissions. The blocking may occur through absorption, reflection, scattering, or physical obstruction. More generally, the phrase refers to inhibiting transmission along the axis. The phrase "particles impinging on the at least one opaque portion,” refers to particles traveling along the designated collection axis that contact the opaque portion of the intermittent illumination blocker. Such contact may result in absorption, reflection, neutralization, or containment of the particles. In general, the phrase refers to particle interception by a blocking structure. Especially, the at least one opaque portion may block ions, atoms and material chunks impinging on it (e.g., >95%, >99%, >99.9% of particles of such types of particles). For example, the at least one opaque portion 272 may be made from an opaque material such as steel, aluminum, other metals and metal alloys, reinforced carbon fiber, high end plastics, composite materials, and so on.

[0081] The clear passage through intermittent illumination blocker 270 (whether via one or more apertures 274 or in any other way) may permit passage of all SWR reaching it, or a large portion thereof (e.g., >70%, >90%, >95%, >99%, >99.9%). Especially, the clear passage may permit transmission of SWR in wavelengths usable in the SWR process for which SWR is generated, such as lithography, inspection, and so on (e.g., >95%, >99%, >99.9% of such SWR).

[0082] System 200 may further include optional controller 220, in which case the operation of heating module 202 and / or the motion of one or more components of intermittent illumination blocker 270 may be controlled by controller 220. Specifically, controller 220 mayAttorney Docket No. 16978-0004.00304be operable to control the operation of heating module 202 and / or intermittent illumination blocker 270 for synchronizing between the emission of SWR pulses (affected by heating module 202) and the intermittent blocking of particles resulting from such emissions by intermittent illumination blocker 270.

[0083] Some disclosed embodiments involve a controller, operatively connected to at least one of: the intermittent illumination blocker and the light source, for controlling synchronization between motion of the intermittent illumination blocker and an emission of the series of light pulses. The term "synchronization" refers to temporal coordination between two or more events or operations. Synchronization may involve aligning start times, durations, or relative phases of system actions. More generally, synchronization refers to timing alignment that achieves a desired operational relationship. The term "operatively connected" refers to a relationship between components that allows one component to influence the operation of another, directly or indirectly. An operative connection may be electrical, mechanical, optical, wireless, or logical in nature. More generally, the term refers to any functional linkage enabling coordinated operation. The phrase "operatively connected to at least one of the intermittent illumination blocker and the light source,” refers to a functional linkage enabling the controller to influence operation of the intermittent illumination blocker, the light source, or both. Such linkage may support timing, motion, or emission control. More generally, the phrase operatively connected refers to enabling coordinated control. The phrase "controlling synchronization between motion of the intermittent illumination blocker and an emission of the series of light pulses,” refers to managing the relative timing between movement of the intermittent illumination blocker and emission of light pulses. This control ensures a desired alignment between blocker position and radiation emission. More generally, the phrase refers to coordinated timing control. By way of example, the synchronizing may involve, for example, modulating heating scheduling (e.g., laser emission frequency) by heating module 202 for closer similarity to a blocking frequency of intermittent illumination blocker 270, modulating motion scheduling of intermittent illumination blocker 270 for closer similarity to a heating frequency of heating module 202, or both. It is noted that whenever controller 220 is discussed below throughout the disclosure in the context of controlling various functionalities and capabilities of system 200, it may control any of these components (heating module, light source 210, intermittent illumination blocker 270, and synchronization between them) in addition or instead of any of the controlling schemes discussed below, even if not explicitly elaborated, mutatis mutandis.

[0084] Optionally, the motion of one or more the movable opaque portions 272 may be controlled by controller 220, possibly the motion of all of its moving opaque portions 272. Optionally, the motion of some or all of the movable components of system 200 (whetherAttorney Docket No. 16978-0004.00304belonging to intermittent illumination blocker 270 or external thereto, like any other numbered part discussed in the present disclosure) may be controlled by controller 220. Alternatively, motion of opaque portions 272 of intermittent illumination blocker 270 (as well of other moving components of intermittent illumination blocker 270) may be guided according to preconfigured schedules (e.g., using preconfigured mechanical timing mechanisms). In the discussion below it is assumed that system 200 includes controller 220 that controls motion of moving parts of intermittent illumination blocker 270, and possibly of other components of system 200. Implementation that do not include a controller 220 may also be used, mutatis mutandis, and are considered parts of the present disclosure.

[0085] Controller 220 is operatively connected to at least one of: intermittent illumination blocker 270 (i.e., of at least some portions of it) and heating module 202 (e.g., light source 210), for controlling synchronization between motion of the intermittent illumination blocker and the series of SWR pulses, such that for each pulse out of a plurality of pulses of the series of light pulses: During a first timespan 120 that includes the emission of a light pulse of the series of light pulses (at timing 110), a disposition of intermittent illumination blocking arrangement 270 is such that no opaque portion 272 of intermittent illumination blocker 270 intersects DCA 150 (offering a clear passage to SWR the DCA 150), thereby permitting SWR of a respective SWR pulse resulting from the light pulse to pass intermittent illumination blocking arrangement 270 along DCA 150.

[0086] In some embodiments, during a first timespan that includes the emission of a light pulse of the series of light pulses, the at least one aperture intersects the DCA, thereby permitting SWR of a respective SWR pulse resulting from the light pulse to pass the intermittent illumination blocker along the DCA. The term "timespan" refers to a finite duration of time during which a particular condition or operation occurs. A timespan may be fixed, variable, predetermined, or dynamically controlled. More generally, timespan refers to any interval over which an event takes place. The phrase "during a first timespan that includes the emission of a light pulse,” refers to a time interval that overlaps with generation of a light pulse from the light source. The first timespan may begin before, during, or after pulse initiation. More generally, the phrase refers to a period associated with radiation emission. The phrase "the at least one aperture intersects the DCA,” refers to the aperture being positioned such that the designated collection axis passes through the aperture. This positioning allows radiation traveling along the axis to propagate through the blocker. More generally, the phrase refers to spatial alignment enabling transmission. The phrase "thereby permitting SWR of a respective SWR pulse to pass,” refers to allowing short wave radiation generated by a corresponding light pulse to propagate beyond the intermittent illumination blocker. The permission may result from spatial alignment or timing coordination. More generally, theAttorney Docket No. 16978-0004.00304phrase refers to enabling radiation transmission. For example, this may be implemented by the at least one aperture 274 of intermittent illumination blocker 270 intersecting the designated collection axis, thereby permitting SWR of the respective SWR pulse resulting from the light pulse to pass intermittent illumination blocker 270 along DCA 150 (e.g., towards collection optics 240, egress aperture, auxiliary machine, a SWR refraction element, etc.). It is noted that optionally, the SWR may include optics for directing the SWR passing via the opening of the intermittent illumination blocker along the aforementioned designated collection direction toward the collection optics and / or auxiliary machine (e.g., folding SWR optics, such as multilayer mirrors, MLM (Multi-layer Mirror), grazing incidence optics, diffraction crystal). The duration of the first timespan, and especially the timing of a termination of the first timespan with respect to the emission of the pulse toward the ionization target, depends on various factors. For example, the duration of the first timespan may depend on a distance between the ionization target and the opening of the intermittent illumination blocker, such that the first time span is long enough to allow sufficient SWR to pass through the opening, while stopping particles slower than a threshold speed, such as 600m / s, 800m / s, 1500m / s etc. For example, a duration of the first timespan may be between 1-5psec, between 3- 10psec, between 5-20psec, between 10-50psec, etc. The first timespan may begin with the emission of the SWR pulse, substantially with the emission of the SWR pulse, or slightly beforehand or afterwards.

[0087] During a second timespan 130 that follows the first time span 120, the at least one opaque portion 272 of intermittent illumination blocker 270 intersects with designated collection direction 150, thereby blocking propagation of particles (emitted from the respective ionization target 100 as a result of the impinging of the light pulse) from continuing along designated collection direction 150. Specifically, in some embodiments, during a second timespan following the first timespan, the at least one opaque portion of the intermittent illumination blocker intersects the DCA, thereby blocking propagation of particles emitted from the at least one ionization target as a result of the impinging of the light pulse from continuing along the DCA. The phrase "during a second timespan following the first timespan,” refers to a subsequent time interval occurring after the first timespan. The second timespan may immediately follow or may be separated by a delay. More generally, the phrase refers to a later operational period. The phrase "the at least one opaque portion intersects the DCA,” refers to positioning the opaque portion such that it lies along the designated collection axis. This positioning obstructs propagation along the axis. The phrase "thereby blocking propagation of particles emitted from the at least one ionization target,” refers to preventing particles generated at the ionization location from continuing along the designated collection axis. The blocking may occur through interception or containment by the opaque portion. WhileAttorney Docket No. 16978-0004.00304SWR may also get blocked during the second time span, a main purpose of the blocking during that duration is to prevent particles from progressing along designated collection direction 150, and thus preventing such particles from interfering with an operation of SWR system 200 or any other machine or process (e.g., by contaminating and / or harming optical equipment). In some implementations, during the second timespan following the first timespan, the at least one opaque portion 272 of intermittent illumination blocker 270 may intersect designated collection axis 272 at a plurality of blockable locations 276 distributed along DCA 150 (i.e., at different distances from ionization location 10), thereby blocking propagation of particles emitted from the respective ionization target 10 as a result of the impinging of the light pulse from continuing along DCA 150. It is noted that the plurality of blockable locations 276 may include at least a first blockable location and a second blockable location. As used herein, the phrase "blockable location" refers to a location, e.g., a location along DCA 150, that can be selectively blocked by intermittent illumination blocker 270 to prevent passage of particles (and, with it, also of SWR). In some cases, the blockable locations 276 may be distinguished blockable locations (e.g., 276A, 276B and 276C of Figs. 9A and 9B), and may also be locations on a longer continuous surface. By way of example, when a dimension of the intermittent illumination blocker along the DCA is greater than 1 cm the first and second blockable locations may be on a continuous surface (e.g., 276E’ and 276E” of Fig. 11). Moreover, the blockable locations 276 may be substantially perpendicular to DCA 150 (e.g., 276A, 276B, 276C, 276D), substantially parallel to DCA 150 (e.g., 276E’ and 276E”), or positioned in any other orientation or way. A person skilled in the art would recognize that the specific locations on intermittent illumination blocker 270 may change over time, for example, due to a rotation of a disc, different portions of the opaque material sequentially pass through and block SWR and particles as the disc rotates.

[0088] The second timespan may optionally start immediately (or practically immediately, e.g., shorter than 1psec) after the first timespan, or shortly thereafter. It should be noted that in some cases, the transition between opening and closing of the passage through intermittent illumination blocker 270 along designated collection direction 150 may be a gradual process. In such cases, the transition between a fully open (transmitting) state of the intermittent illumination blocker and a close (blocking) state of the intermittent illumination blocker may start immediately or practically immediately after the first timespan (e.g., shorter than 1psec), but the closing process itself may last several microseconds. Such transition duration may be significantly shorter than the second time span (e.g., <10%, <20% thereof).

[0089] It should be noted that the term “first timespan” may pertain only to the duration starting with the emission of the respective pulse of the series of light pulses, to all the time during which SWR may propagate via intermittent illumination blocker 270 before beingAttorney Docket No. 16978-0004.00304blocked again, starting with the first moment of SWR propagation (this duration is also referred to as “open” duration 122), or to another other duration that includes the emission of the respective pulse of the series of light pulses and during which SWR can propagate via intermittent illumination blocker 270.

[0090] Optionally, controller 220 may be operable to control the synchronization between the series of SWR pulses and the motion of one or more components of intermittent illumination blocker 270, such that any combination of any one or more of the following operational criteria is implemented: During a first timespan 120 that includes the emission of each pulse of the series of light pulses (at timing 110, P1, P2, P3, etc.), no opaque portion 272 intersects DCA 150, thereby permitting SWR emitted from the respective ionization target 100 as a result of the impinging of the respective pulse to continue along DCA 150. This may be implemented by having an aperture 274 intersecting DCA 150 during the respective first timespan 120, or in any other way. Such a series may include tens, thousands, hundreds of thousands, millions, billions, hundreds of billions, etc. of pulses. For example, system 200 may operate for days and weeks in a continuous manner, at a pulse frequency of 10-100KHz. Such a series may include any such numbers of pulses emitted at constant (or substantially constant) intervals (e.g., every 1psec, 5psec, 10psec, every constant? such that 1<T< 10psec, 10<T<20psec, 20<T<100psec, 100<T<1,000psec, etc.). The series of pulses may include any pulse emitted by SWR system 200 in the duration of the respective series of pulses, but this is not necessarily so (for example, one or more intermittent illumination blocker 270 may only protect a secondary SWR emittance channel in which only SWR of a fraction of the pulses is collected, and the rest are blocked). During a second timespan 130 following each pulse of the series (after the respective first timespan 120), the one or more opaque portions 272 intersect DCA 150, thereby blocking propagation of particles emitted from the respective ionization target 100 from continuing along DCA 150.

[0091] First timespan 120 may optionally begin with, or substantially with, the timing of the pulse emission (denoted 110 in Figs. 3A, 3B, and P1 , P2, and P3 in Figs. 4A, 4B and 4C). First timespan 120 may optionally begin before the timing of the pulse emission, e.g., in cases in which no particles are expected to reach intermittent illumination blocker 270, and in order to make sure that even the initial SWR emitted from the target would pass through the opening.

[0092] Referring to the way in which controller 220 controls the movement of one or more opaque portions 272 (and possibly of other parts of intermittent illumination blocker 270, or other parts of system 200), it is noted that this motion may be characterized as any one or more of the following: recurrent, periodic, oscillatory, cyclic, rotational, reciprocal, harmonic, non-harmonic, isochronous, continuous, and intermittent. Selection of the specific type of movement may depend on factors such as structure of intermittent illumination blocker 270,Attorney Docket No. 16978-0004.00304type of motor used, synchronization requirements, power usage, reliability, precision requirements, environmental conditions, load characteristics, speed requirements, vibration tolerance, space constraints, maintenance requirements, cost efficiency, and so on.

[0093] SWR system 200 may include at least one motor 280 and / or any other mobilization module inducing the motion of intermittent illumination blocker 270. The control of the movement of intermittent illumination blocker 270 by controller 220 may be achieved by controlling mobilization parameters of the at least one motor 280 or other mobilization module (e.g., changing RPM of motor 280), by controllably braking the motion (e.g., using one or more brake 282 like a controllable friction brake or magnetic brake), or in any other suitable fashion, many of which are known in the art.

[0094] Controller 220 may be operable to control movement and / or other aspects of operation of various components of system 200 (e.g., controlling the motion of intermittent illumination blocker 270 or parts thereof) of according to various types of data, such as sensor data (e.g., by one or more sensors 250), pre-programmed instructions, environmental conditions, instructions or requests received from external systems, user input, feedback data, historical data, and / or real-time operational parameters. For example, controller 220 may be operable to control the motion of intermittent illumination blocker 270 according to any one or more of: visual information, e.g., optical emission intensity, imaging of target material and plasma shape, surface reflectivity and quality. Kinematic information, e.g., motion and position of target material, optical components, intermittent illumination blocker, vibration and stability monitoring. Thermal information (e.g., temperature of critical components, heat flux measurement); electrical information (e.g., current and voltage of plasma generation systems), Gas composition and pressure information (e.g., vacuum integrity, gas concentration levels); material and debris monitoring (e.g., detection of debris, material integrity of target substances); and radiation and dosimetry information (e.g., SWR intensity, monitoring of radiation damage to sensitive components).

[0095] Especially, controller 220 may optionally be operable to synchronize the timing of first timespans 120 and / or of second timespans 130 with the events of target ionization. A single controller 220 may optionally control both the ionization of ionization targets (e.g., by controlling heating module 202)

[0096] Controller 220 may optionally be operable to control the motion of intermittent illumination blocker 270 by controlling operational parameters (e.g., mobilization parameters) of one or more motors 280 which provide kinetic energy to intermittent illumination blocker 270, thereby mobilizing it. For example, controller 220 may control change of the rotational speed of motor 280, of the torque of motor 280, of the voltage provided to motor 280, of theAttorney Docket No. 16978-0004.00304pulse width modulation signal provided to motor 280, and so on. It is noted that any suitable type of motor 280 may be implemented, such as stepper motor, servo motor, switched reluctance motor, brushless motor, and so on. Motor 280 may be coupled to intermittent illumination blocker 270 directly (e.g., via a direct mechanical coupling such as a rotating axis), or indirectly (e.g., via an external gearing system).

[0097] Controller 220 may optionally be operable to control the motion of intermittent illumination blocker 270 by controlling operational parameters (e.g., mobilization parameters) of one or more other systems that are adapted to modify the motion of intermittent illumination blocker 270, such as optional brake 282 (e.g., a controllable friction brake or magnetic brake), or in any other suitable fashion, many of which are known in the art.

[0098] As aforementioned, controller 220 may be operable to control additional components of system 200 in addition to controlling the movement of intermittent illumination blocker 270 or parts thereof. Especially, controller 220 may optionally be operable to control operation of heating module 202 (e.g., of one or more light sources 210), and optionally to synchronize an operation of heating module 202 (e.g., of one or more light sources 210) with the movement of one or more components of intermittent illumination blocker 270 (e.g., one or opaque portions 272). For example, controller 220 may be operable to control synchronized operation of any component of heating module 202 with control of motor 280 and / or brake 282, to control synchronized operation of ionization and intermittent blocking of particles while allowing passage of SWR. For example, controller 220 may synchronize the rate of generated SWR pulses with the dispositioning of clear passage for SWR by intermittent illumination blocker 270, and with a following blocking of particles propagating along DCA 150 by one or more opaque portions 272.

[0099] Reverting to optional light source 210 (e.g., laser), it is noted that the same light source may be put to other uses other than the actual ionization and excitation of targets 100. For example, light source 210 may emit weaker pulses prior to the main, ionizing pulses for modifying a shape of the hit target 100 (e.g., from a sphere-like shape to a disk-like shape). Such weaker pulses are also referred to as “pre-pulses”. Additionally or alternatively, such pre-pulses can cause some initial ionization and heating of the plasma enhancing the efficiency of main pulse ionization and excitation. Alternatively, such pre-pulses may be emitted by one or more light sources that are not used for the target excitation that leads to the emission of SWR as discussed above. Optionally, an energy level of the pre-pulse may be significantly lower (e.g., <10%) than the ionizing main pulse, and may optionally have the same wavelength or a hormonic of the wavelength of the main (ionizing) pulse. A nonlimiting example may include a main pulse of an Nd:YAG laser having energy of 100m J at 1064nm wavelength, while the pre-pulse is emitted by the same laser, has energy of less than 10mJAttorney Docket No. 16978-0004.00304and wavelength of either 1064, 532 or 266nm. Optionally, the pre-pulse may also be emitted by a different laser system with a different wavelength from the main pulse. Optionally, the pre-pulse may have different time duration than the main pulse (e.g., much shorter, such as by a scale of *10, *100 *1,000 and so on) and / or different spatial properties (e.g., different focal spot or position). For example, the main pulse can be emitted by a CO2laser or Nd:Yag and the pre-pulse may be emitted by a TI:Sa laser, Ytterbium laser, solid-state laser, and so on. It is noted that such pre-pulses may also ionize parts of the target, but to a lesser extent due to their much lower intensity and / or energy. Any other technique used in SWR generation (e.g., EUV generation) may also be implemented as part of system 200.

[0100] It is noted that in addition to intermittent illumination blocker 270, system 200 may optionally also include additional blockers, shields, and / or protective modules 260 protect various sensitive components of system 200. Such modules 260 may be permanent, semipermanent, or movable.

[0101] Pertaining to Figs. 1B and 1C, it is noted that Figs. 1B and 1C schematically illustrate a single system 200 at two different states, at two different times, in accordance with examples of the presently disclosed subject matter. Fig. 1B illustrates the respective system 200 during first timespan 120, when aperture 274 intersects DCA 150, thereby permitting passage of SWR (and possibly also of particles) along DCA 150, while Fig. 1C illustrates the respective system 200 during second timespan 130, when opaque portion 272 intersects DCA 150, thereby preventing passage particles (and also possibly preventing or limiting passage of SWR) along DCA 150. The implementation of Figs. 1B and 1C may include a rotating disc with one or more openings 272 in it, shown in cross section in the respective figures (e.g., similarly to the example of Fig. 1 A). For example, intermittent illumination blocker 270 may be a rotating disc or plate of an optical chopper, including one or more openings 272 positioned such that they intermittently cross DCA 150 as the chopper plate rotates at high velocities (e.g., between 1,000 and 100,000 revolutions per minute— rpm). The disc may be mobilized by an electric motor 280 of the optical chopper, and the velocity of rotation may be regulated or otherwise controlled by a respective controller 220 of the SWR system (such a controller could be a component of the optical chopper or external thereto).

[0102] Fig. 2 is a schematical cross-section diagram illustrating an example of system 200 used for lithography and / or inspection, in accordance with examples of the presently disclosed subject matter. In the example of Fig. 2, SWR (e.g., EUV light) generated by ionization of one or more targets 100 is directed by outward optics 240 via clear passage along the DCA 150 awarded by the controlled dispositioning of intermittent illumination blocker 270 (e.g., via one or more apertures 274, e.g., during first timespans 120) toward lithography maskAttorney Docket No. 16978-0004.00304980 264 via various optical components (such as but not limited to mirrors 262). From lithography mask 264, patterned short-wave light (patterned and / or modulated by mask 264) is deflected via various optical components (such as but not limited to mirrors 262, steerable mirrors 266) toward wafer 268 (e.g., a silicon wafer, a germanium wafer, silicon oxide wafer) where it is used to pattern parts of the wafer using lithography. It is noted that other types of optical 985 components may be used for directing and managing light in its path from outward optics 240 to an aiming point of system 200 (e.g., on the wafer), such as but not limited to: mirrors, multi-layer mirrors (MLM), grazing incidence reflectors, Curved MLM, spherical or parabolic MLM, reflection masks, masks, beam blockers, pellicles, lenses, prisms, waveguides, and so on, all of which could be controllable (e.g., steerable) or not. A few other examples of uses for 990 short-wave radiation (e.g., EUV light) of system 200 which are not illustrated in Figs. 2 include wafer inspection during wafer manufacturing, mask inspection for lithography masks used in lithography (whether of wafers or other), MLM inspection, ptychography, and light source used for research, and so on. Blocking DCA 150 by one or more opaque portions 272 at second timespans limit (or prevent) propagation of particles out of SWR emission module 290, and 995 thus prevent harm to components of such external modules used, by way of example, to any of the aforementioned uses.

[0103] Figs. 3A and 3B are schematic timing schedules, illustrating alternation between first timespans 120 and second timespans 130, in accordance with examples of the presently disclosed subject matter. Different first timespans 120 may be of the same (or similar) duration 1000 as one another (e.g., about 0.2psec, about 1 psec, about 3psec, about 5psec, etc.), but this is not necessarily so. Different second timespans 130 may be of the same (or similar) duration as one another (e.g., about 1psec, about 5psec, about 20psec, about 100psec, etc.), but this is not necessarily so. First durations 120 may start at constant (or substantially constant) intervals (e.g., every 1psec, 5psec, 10psec, every constant T such that 1<T<10psec, 1005 10<T<20psec, 20<T<100psec, 100<T<1,000psec, etc.), but this is not necessarily so. It is noted that while Fig. 3 illustrates a transition directly from first duration 120 to second duration 130 and vice versa, transitional change may be implemented, or the two may be somewhat separated from one another temporally. It is noted that at some durations (e.g., during such transitional durations), the passage of SWR and particles along DCA 150 may be partly 1010 opened and partly blocked. Optionally, a timespan during which aperture 274 of intermittent illumination blocker 272 transmits radiation of each pulse along the designated collection direction is shorter than 5psec.

[0104] As exemplified in Figs. 3A and 3B, the durations 122 in which intermittent illumination blocker 270 does not block propagation along DCA 150 may be longer than the 1015 corresponding first timespans 120. Furthermore, the durations 122 in which intermittentAttorney Docket No. 16978-0004.00304illumination blocker 270 does not block propagation along DCA 150 may start before the corresponding first timespans 120 (the latter starting with the emission of the SWR pulse resulting from the ionization of the target). The exact timing of the emission of the SWR pulse with respect to the “open” duration 122 may be selected based on various considerations, 1020 depending, for example, on the intermittent blocking mechanism of intermittent illumination blocker 270, on the control scheme, on maximizing the amount of SWR that passes along DCA 150, and so on. It is noted that in some of the mechanisms which may be used for the intermittent blocking, the dimension and / or permissibility factor of the clear passage may change over time during “open” duration 122 (e.g., in the case of a rotating disc of an optical 1025 chopper than includes one or more apertures), and the timing of the pulse may be selected to maximize that amount of SWR passing along DCA 150.

[0105] Figs. 3A and 3B show the transmittance across the intermittent illumination blocker 270, which is complementary to the intermittent blocking of DCA 150, gradually increasing, potentially plateauing (not shown), and then gradually decreasing to zero or near zero. It 1030 should be noted that these are only two illustrative examples, and that any other variation of blocking and transmittance pattern may be implemented, depending on the specific application requirements. For instance, the transmittance could follow a stepped, triangular, or any other pattern. These variations can be tailored to optimize performance characteristics, as needed for the particular use case.1035

[0106] Fig. 4A illustrates photon emission count as a function of time, and particle count at a blockable location (e.g., a first blockable location of intermittent illumination blocker 270) as a function of time, all resulting from a series of ionizations of one or more ionization targets (e.g., ionization targets 100), all in accordance with examples of the presently disclosed subject matter. As can be seen, the vast majority of SWR photons resulting from ionization of 1040 an ionization target (or a part thereof) are emitted substantially simultaneously with the emission of the pulse (e.g., 1-10ns); the timing of each pulse emission is denoted P1 , P2,and P3., and the corresponding emitted photon count is denoted 140(1), 140(2), and 140(3), respectively. The SWR photons travel at the speed of light, and therefore this photon count is also representative of the number of photons projected along DCA 150 which cross 1045 intermittent illumination blocker 270.

[0107] It should be noted that the graphs of Figs. 4A, 4B, and 4C intentionally present a noncontinuous time axis and temporal emission profiles that are not to scale and that are not accurately representative of actual temporal relationships; this deliberate distortion is employed to enhance clarity and facilitate a better understanding of the progression and 1050 interaction of different processes depicted. It is noted that the underlying physical principles and actual emission profiles will be evident to a person skilled in the art, ensuring accurateAttorney Docket No. 16978-0004.00304interpretation within the relevant technical context. In practice, SWR photons emission is expected to be many orders of magnitude shorter, which could be represented as delta functions or spikes in the diagrams.1055

[0108] By way of example, likely time scales could be light emission time scale: Laser time 1-10ns; very short compared to anything else. This is also the time scale of resulting SWR radiation emission; hydrodynamic timescale (“Hydro time”) or particle emission time: this duration starts with the laser and may extend beyond the laser pulse itself by one or two orders of magnitude (e.g., 100ns), particles travel time: this timescale pertains to the time in which 1060 particles resulting from the ionization take to reach and possibly interact with intermittent illumination blocker 270. This timescale, depending on the type of particles and on the geometry of system 200, is longer by several orders of magnitude than the SWR emission time scale, e.g., measured in microseconds to tens of microseconds. Traveling the distance between ionization location 10 and the first blockable location 276 (e.g., propagation of a few 1065 centimeters) at different velocities results in “arrival time” of the different particles being spread over a wider duration, e.g., between a few microseconds for the fastest moving particles to a few milliseconds for the slowest moving particles.

[0109] The second timespan during which one or more opaque portions 272 block propagation of particles along DCA 150 can be implemented in the microseconds timescale, 1070 for example, and can therefore block the particles.

[0110] Particles emitted as a result of the ionization caused by each pulse move in different velocities, all much slower than the speed of light of course. Therefore, the number of particles resulting from the ionization which are projected at DCA 150 and that reach the frontmost blockable locations (nearest ionization location 10, the plane of first aperture 274) 1075 is spread over a significantly longer duration, as demonstrated by the corresponding graph curves 150(1), 150(2), and 150(3). The velocity distribution of the different types of particles in SWR generation (e.g., LPP EUV generation) depends on various factors, such as particle mass, initial energy, electrical charge, plasma temperature, and laser intensity and pulse shape. For example, in many cases charged particles may be faster than uncharged particles, 1080 e.g., due to being subject to acceleration by the electromagnetic fields within the plasma, which can impart significant additional energy. Uncharged particles, being neutral, do not experience these electromagnetic forces and may therefore have lower velocities, limited primarily by thermal motion and the initial energy imparted during plasma formation. Therefore, referring to particles emitted as a result of the first pulse (150(1)), the charged particles that 1085 are relatively very fast would usually arrive the blockable location before a certain point in time (denoted T in the diagram, with the total number of particles arriving before T being denoted 172), while most of the particles who arrives at the respective blockable location after T areAttorney Docket No. 16978-0004.00304uncharged particles (the total number of particles arriving after T denoted being denoted in the diagram as 174). It is noted that charged particles may be diverted from DCA 150 and / or 1090 slowed down (by inducing collisions between particles) applying electric, magnetic, and / or electromagnetic forces onto them (e.g., magnetic inducer 2100). However, such electric, magnetic, and / or electromagnetic means have no direct effect on the generally slower uncharged particles, which have to be blocked by intermittent illumination blocker 270.

[0111] Fig. 4B, the illustrative timing scheme of Fig. 3B is adapted to the corresponding 1095 to the scale used in Fig. 4A. The positive transmittance levels corresponding to the first durations associated with “open” durations 122 of the pulses emitted at P1 , P2, and P3 are denoted 160(1), 160(2), and 160(3), respectively.

[0112] In Fig. 4C, the illustrative timing scheme of Fig. 4B is overlaid on the graph of Fig.4A, such that the emission of each pulse (denoted P1, P2, P3) occurs during an “open” 1100 duration 122 (with the corresponding first timespan 120 beginning with the emission of the pulse). The timing of “open” duration 122 in the illustrated example is selected such that the greatest transmittance offered by intermittent illumination blocker 270 is timed to synchronize with the emission of the SWR peak, thus providing the maximal transmittance for the generated SWR to propagate along CDA 150. Considering the propagation of particles (such 1105 as microscopic solid fragments, nanoparticles, highly charged ions, neutral atoms, and reactive species), as demonstrated by curves 150, only the fastest particles can cross the nearest blockable location 276 (e.g., a first blocking plane of intermittent illumination blocker 270) before opaque portion 272 blocks the passage of further particles at timings B1, B2, etc., while later particles are being blocked. However, while many particles are blocked in the 1110 following second timespan 130 (e.g., second timespan 130(1)with respect to the pulse emitted at P1 ), slower particles may be able to pass the respective blockable location 276 at later open durations 122 (e.g., 160(2), and even 160(3), with respect to the same pulse).

[0113] While it is possible to extend the second time spans 130 in which the DCA is blocked in order to block even slower particles, these would reduce the operational frequency 1115 of SWR emission of the system. As discussed in greater detail below (e.g., with respect to Fig.10), the presently disclosed systems and methods demonstrate how to block the slower moving particles while keeping the second time spans 130 relatively short, e.g., by blocking propagation of particles in different blockable locations 276 along DCA 150. It is noted that while the number of particles resulting from a certain pulse reaching a certain blockable 1120 location 276 at least open spans 122 is relatively low, in many use cases even such a relatively small number of particles may still pose a significant problem (e.g., to the safety and operativity of components of the system), which requires implementing such additional blocking and / or diverting means, e.g., as discussed below in greater detail.Attorney Docket No. 16978-0004.00304

[0114] Optionally, controller 220 may be operable to control the movement of intermittent 1125 illumination blocker 270 such that it permits transmission of SWR along DCA 150 at least 100 distinct times per second, at least 500 distinct times per second, at least 1,000 distinct times per second, at least 10,000 distinct times per second, at least 50,000 distinct times per second, at least 100,000 distinct times per second, and so on. Optionally, controller 220 may be operable to control the movement of intermittent illumination blocker 270 such that it permits 1130 transmission of SWR along DCA 150 between 100-1 ,000 distinct times per second, between 1,000-10,000 distinct times per second, between 10,000-100,000 distinct times per second, between 100,000-1,000,000 distinct times per second, between 1,000,000-10,000,000 distinct times per second, and so on. One or more opaque portions 272 block propagation of SWR photons and of particles between these times.1135

[0115] For example, distance 902 between the location in which targets 100 are ionized to a location in which aperture 274 crosses DCA 150 may be between 1-4cm, between 3-10cm, etc. Optionally, at the time of emission of the SWR, a distance between the ionization target 100 and aperture 274 of intermittent illumination blocker 270 that transmits the SWR via intermittent illumination blocker 270 is shorter than 10cm. A characteristic dimension of 1140 aperture 274 (e.g., diameter if circular, diagonal if square) may be about 1mm, between 0.5-2mm, between 1-5mm, etc. An area of aperture 274 may be about 1mm2, between 0.25-22mm, between 1-10mm2, etc. The duration of first timespan 120 may be between 0.25- 1psec, between 0.5-2psec, between 1-10psec, etc. The repetition rate of the plasma source may be, for example, about 100KHz, between 10-50KHz, between 50-200KHz, between 1145 100-500KHz, etc. The size of ionization target 100 may be, for example, between 10- 100pm.A duration of the plasma source (as reflected, for example, in curves 140) may be, for example, between 0.1-100ns. Optionally, a spatial angle of a cone of light initiating at the ionization target 100 and defined by a size of aperture 274 as it crosses DCA 150 (and possibly by other geometric parameters of system 200) is at least 0.005str.1150

[0116] Fig. 5A is a schematical cross-section diagram illustrating an example of system 200 in which intermittent illumination blocker 270 includes a plurality of openings 274 which permit passage of SWR and of particles along DCA 150 at different times, in accordance with examples of the presently disclosed subject matter. It is noted that multiple openings 274 may also be implemented if intermittent blocking of particles 190 is required in several directions, 1155 e.g., concurrently. For example, optionally, some of the emitted SWR and a part of the emitted particles progress along a plurality of different designated collection directions 150, wherein intermittent illumination blocker 270 (or a plurality of intermittent illumination blockers 270) includes a plurality of openings 274 via which SWR and particles can pass concurrently. In such case, controller 220 may be operable to control the repetitive motion of intermittentAttorney Docket No. 16978-0004.003041160 illumination blocker 270 such that: during first timespan 120 each of the plurality of openings 274 concurrently intersects a corresponding DCA 150 out of the plurality of designated collection directions 150 (not illustrated) , thereby permitting SWR emitted from the respective ionization target 100 as a result of the impinging of a single respective pulse to continue along the designated collection directions; and during a second timespan, one or more opaque 1165 portions of the corresponding at least one intermittent illumination blocker 270 intersect the plurality of designated collection directions, thereby blocking propagation of particles emitted from the respective ionization target as a result of the impinging of the respective pulse from continuing along the plurality of designated collection directions.

[0117] Fig. 5B is a schematical cross-section diagram illustrating an example of system 1170 200 in which intermittent illumination blocker 270 includes one (or more) elongated openings 274 in intermittent illumination blocker 270, in accordance with examples of the presently disclosed subject matter. Implementing openings 274 that are elongated along the radial direction may be implemented, for example, in order to reduce the duration of first timespans 120 while permitting a relatively large amount of SWR to pass, due to the relatively large solid 1175 angle. The passing SWR may optionally be shaped after passing intermittent illumination blocker 270, or used in an elongated form. Optionally, the repetitive motion of intermittent illumination blocker 270 during first timespans 120 causes aperture 274 to move in an instantaneous motion direction (not illustrated, e.g., a tangential movement in the illustrated example); in such case a shape of one or mor openings 274 of intermittent illumination blocker 1180 270 may be such that it is at least 1.2*, at least 1.5*, at least 2x, at least 3x, or at least 5x times longer at an axis perpendicular to the instantaneous motion direction relative to its length along the instantaneous motion direction.

[0118] As aforementioned, and as exemplified in several of the illustration, system 200 may optionally also include additional blockers, shields, and / or protective modules 260 protect 1185 various sensitive components of system 200. Such modules 260 may be permanent, semipermanent, or movable. In some cases, such modules 260 may include one or more dedicated apertures for passage of SWR along DCA 150 and / or for the passage of light along illumination propagation path 154. In such cases, the dimensions of the apertures are usually such which only allow passage of the relevant beam of photons (e.g., a beam width that is transferable 1190 via intermittent illumination blocker 270), and not much wider. For example, the size of several of the apertures of several of the diagrams (e.g., Fig. 5A) are exaggerated for the sake of visibility of various components. In practice, such apertures are likely to be significantly tighter around the respective beam.

[0119] As discussed above, different mechanisms may be implemented for intermittently 1195 blocking and unblocking passage along CDA 150. For example, intermittent illuminationAttorney Docket No. 16978-0004.00304blocker 270 may be (or include) a rotating disc or plate of an optical chopper, including one or more openings positioned such that they intermittently cross DCA 150 as the chopper plate rotates at high velocities (e.g., between 10-50 kilo revolutions per minute— Krpm, between 10-100Krpm). The disc may be mobilized by an electric motor 280 of the optical chopper, and 1200 the velocity of rotation may be regulated or otherwise controlled by controller 220 (such a controller could be a component of the optical chopper or external thereto).

[0120] As discussed below in greater detail (e.g., with respect to Figs. 8, 9A, 9B, 12, and 13), intermittent illumination blocking assembly 270 may include a plurality of rotating chopper plate discs, arranged serially, such that SWR and particles that cross a plane of a nearest 1205 chopper plate (i.e. , nearest to ionization location 10) continue along DCA 150 towards a series of one or more planes of additional one or more chopper plates. Such serially arranged chopper plates may be moved by a single motor (e.g., rotated by a single axle or about a single rod), but this is not necessarily so. Such serially arranged chopper plates may have the same number of openings, but this is not necessarily so. Such serially arranged chopper plates 1210 may rotate at the same frequency, but this is not necessarily so. The rotating chopper plates discs may be made from any suitable material, such as (but not limited to) any one or more of: Aluminum, stainless steel, Delrin, polycarbonate, carbon fiber, and specialty alloys.

[0121] Intermittent illumination blocker 270 may be (or may include) an optical chopper, such as a rotating disc mechanical shutter optical chopper. Other types of optical choppers 1215 and / or other types of intermittent illumination blocker 270 may also be implemented, e.g., based on rotational motion of intermittent illumination blocker 270 about an axis that is parallel (or about parallel) to DCA 150 (e.g., up to 5° deviation therefrom), based on rotational motion of intermittent illumination blocker 270 about an axis that is perpendicular (or about perpendicular) to DCA 150 (e.g., up to 5° deviation therefrom), or in any other way (e.g., a 1220 moving belt such as a conveyor belt, in which multiple openings are opened along the belt), or in any other suitable way.

[0122] Optionally, intermittent illumination blocker 270 may include one or more rotating wheels similar to those of a turbo molecular pump (TMP), possibly with apertures 274 drilled or otherwise manufactured in them. Each such wheel includes a series of rotor blades, 1225 typically made from high-strength, lightweight materials such as titanium or aluminum alloys.These blades are configured at suitable angles and intervals to interact with optional corresponding stator blades (which may also include suitable apertures 274), ensuring molecular transfer and compression. The wheels are mounted on a central shaft supported by bearing systems, such as magnetic or ceramic bearings, to minimize friction and wear during 1230 operation. The bearing system may be used to balance the disc moving at high velocity, in particular after some time of operation, the initial balancing may change due to wearing orAttorney Docket No. 16978-0004.00304accumulation of debris on the disc. The bearings may compensate for the unbalancing of the disc over the time of operation. Optionally, intermittent illumination blocker 270 may include a TMP, confining particles (fully or mostly) to a chamber in which ionization location is 1235 positioned, and assisting in maintaining vacuum on the other side of the TMP intermittent illumination blocker 270.

[0123] Fig. 5C is a schematical cross-section diagram illustrating another implementation of system 200, in accordance with present disclosure. In this implementation, intermittent illumination blocker 270 includes intermittent illumination blocking module 278 having 1240 elongated apertures 274, also referred to as tunnels, through which SWR can pass. This tunnel embodiment provides an alternative to the multiple disc embodiment described elsewhere (e.g., with respect to Figs. 8, 9A, 9B, 12, and 13). In the tunnel embodiment, a dimension of intermittent illumination blocker 270 along the DCA may be greater than 1 cm, greater than 2 cm, greater than 3 cm, or greater than 5 cm, the at least one opaque portion of 1245 intermittent illumination blocker 270 may include at least a first blockable location 276A and a second blockable location 276B. By way of example, the motion of intermittent illumination blocker 270 may be determined such that the first blockable location 276A is located within the at least one aperture 274 (i.e. , within the tunnel) and the second blockable location 276B is located outside the at least one aperture 274. Alternatively, the motion of intermittent 1250 illumination blocker 270 may be determined such that both the first blockable location 276A and the second blockable location 276B are located outside the at least one aperture 274. Moreover, the area that particles hit may be a continuous area with overlapping locations such that particles may hit the space between the first blockable location 276A and the second blockable location 276B. Alternatively, the first blockable location 276A and the second 1255 blockable location 276B may be in separate non-overlapping parts of intermittent illumination blocker 270 such that no particle may hit the space between them. The configuration of blockable locations may depend on the type of particles and their velocities. As the tunnel keeps moving while particles move through it, the sides of the tunnel (which are opaque portions) may hit such particles and prevent them from continuing their propagation along DCA 1260 150. The tunnel embodiment allows for a continuum of blockable locations dispersed along the length of the tunnel, providing effective particle blocking while permitting SWR to pass during the first timespans. Additional details are described below with reference to Fig. 11.

[0124] Referring by way of example to Figs. 6, 7A, and 7B, it is noted that system 200 may optionally include one or more post-blocker deflection mechanism (PBDM) for deflecting 1265 away from DCA 150 directions of particles that progressed past intermittent illumination blocker 270 along DCA 150 (e.g., past the furthest blockable location 276 of intermittent illumination blocker 270). Particles that progress past intermittent illumination blocker 270 areAttorney Docket No. 16978-0004.00304also referred to as “residual particles”. Such PBDMs may include, for example, magnetic deflectors (e.g., magnetic inducer 2100) and / or pressured gas deflectors (e.g., pressured gas 1270 discharger 206). Any one of the one or more PBDMs optionally implemented may operate in a constant mode, at an intermitted mode, or in a fluctuating mode.

[0125] Optionally, pressured gas discharger 206 may utilize cooled gas which not only slows down / divert debris, but is also used to remove heat from system 200 or from part of it (e.g., from target chamber 286 discussed below).1275

[0126] Optionally, post-blocker deflection mechanism may include one or more magnetic field inducers 2100 that generate a magnetic field diverting during the second timespan a propagation direction of particles that progressed past intermittent illumination blocker 270 during the first timespan, e.g., toward an absorbent surface of the SWR system. Additionally or alternatively, the post-blocker deflection mechanism may include an electric field inducer 1280 that generates electric field for diverting the propagation direction of such particles.

[0127] It is noted that whenever the terms “first time span” and “second time span” are used, as well as similar time spans (e.g., “open” time span, “open” duration etc.), such phrases may also pertain to the respective durations associated with other SWR pulses— before or after the respective SWR pulse, as applicable.1285

[0128] Fig. 6 is a schematical cross-section diagram illustrating an example of system 200 that includes a post blocker deflection mechanism for diverting a propagation direction of residual particles 190 that passed through aperture 274 during first timespan 120, toward an absorbent surface of SWR system 200 (denoted 260A), in accordance with examples of the presently disclosed subject matter. The post blocker deflection mechanism may include at 1290 least one of: a magnetic field inducer that generates a magnetic field or an electric field inducer that generates electric field, for diverting the propagation direction of particles that progressed past the intermittent illumination blocker during the first timespan, toward an absorbent surface of the SWR system. Fig. 6 specifically illustrates an example using a magnetic field inducer 2100 that generates a magnetic field. Although only a magnetic field is illustrated in Fig. 6, the 1295 disclosed system may operate an electric field to divert a propagation direction of residual particles. Magnetic field inducer 2100 may generate that magnetic field diverting the propagation direction of residual particles during part or all of second timespan 130, and optionally also during part or all of first timespan 140. Significantly, magnetic field inducer2100 generates magnetic field to particles that have passed through one or more openings 274.1300 Since the spatial angle dictated for passage by aperture 274 is relatively small (e.g., between 0.001- 0.5 steradians), only a relatively small diversion is required (e.g., as exemplified in an illustrative manner in Fig. 6) in order to prevent from such residual particles 190 to progressAttorney Docket No. 16978-0004.00304along DCA 150. More generally, system 200 may include an electromagnetic PBDM, generating magnetic and / or electric fields. For example, the post blocker deflection 1305 mechanism may include at least one of: a magnetic field inducer that generates a magnetic field or an electric field inducer that generates electric field. The resulting trajectories of particles affected by such a magnetic or electromagnetic field may vary, depending for example on their mass, charge, and the direction of force applied thereto. For example, some particles will be locked in circular trajectories. System 200 may include shielding of the 1310 magnets, magnetic field inducers, electric field inducers, and / or electromagnetic inducers from debris, e.g., using a disposable or replaceable shield (e.g., made from materials such as Aluminum, Capton, etc.).

[0129] Any magnets used in the system may optionally be shielded from magnetic fields to prevent unwanted effects on other parts of the system. For example, the magnetic field may 1315 have an unwanted effect on motor 280 or on the communication channel between controller 220 and motor 280. To prevent this, the magnets or the magnetic field may be shielded by p- metal and\or any other suitable means of shielding of magnetic field. The shielding may surround the magnets to prevent the stray magnetic field or alternatively, sensitive parts of the system (such as the motor) may be shielded from the magnetic field, for example, by 1320 surrounding them with shielding material such as p-metal.

[0130] Optionally, the post blocker deflection mechanism includes a pressured gas discharger 206 operable to emit— at least during the second timespans— gas emissions (e.g., gas pulses, continuous gas emissions) toward particles that progressed past intermittent illumination blocker 270, thereby diverting a propagation direction of the particles toward an 1325 absorbent surface of the SWR system.

[0131] Referring to system 200 as a whole, it is noted that optionally heating module 202 may include multiple light sources 210 (e.g., light sources 210A and 210B) that are operable to illuminate ionization location 10 (e.g., a single target 100 positioned illuminate ionization location 10) concurrently or substantially concurrently. Optionally, light pulses of these multiple 1330 light sources 210 may overlap on ionization target 100 (spatially and temporally). The multiple light sources 210 may be arranged in a symmetrical fashion around ionization location (e.g., symmetrical around DCA 150), but this is not necessarily so. Optionally, the multiple light sources 210 may be identical to one another, but this is not necessarily so. For example, one or more light sources 210 may issue ionization illumination pulses, while other one or more 1335 light sources 210 may issue pre-pulses.

[0132] Figs. 7A and 7B are schematical cross-section diagrams illustrating examples of system 200 which include pressured gas discharger 206, in accordance with examples of theAttorney Docket No. 16978-0004.00304presently disclosed subject matter. Pressured gas discharger 206, if implemented, is operable to emit— at least during parts of second timespans 130— gas emissions (e.g., pulsed, 1340 continuous) toward particles 190 that move along DCA 150, thereby diverting a propagation direction of these particles 190-toward an absorbent surface of the SWR system (e.g., surface 260A). For example, pressured gas discharger 206 may emit gas emissions 104 diverting the propagation direction of residual particles during one or more short spans of time within second timespan 130 (e.g., each extending 1us), and optionally also during one or more short 1345 spans of time within during first timespan 140 (e.g., in order to divert particles which may nevertheless stay between intermittent illumination blocker 270 and outward optics 240). Significantly, one or more pressured gas dischargers 206 may be operable to discharge gas emissions onto particles 190 that have passed through one or more openings 274 and / or onto particles that did not yet reach a plane of intermittent illumination blocker 270. Pertaining to 1350 the former option, since the spatial angle dictated for passage by aperture 274 is relatively small (e.g., between 0.01-0.5 steradians), only a relatively small diversion is required (e.g., as exemplified in an illustrative manner in Figs. 7A and 7B) in order to prevent from such residual particles 190 to progress along DCA 150. Optionally, the operation of pressured gas discharger 206 may be controlled (e.g., by controller 220) such that the operation is 1355 synchronized so the gas is discharged by pressured gas discharger 206 a few microseconds after each ionization (e.g., after each light pulse is directed onto an ionization target 100).

[0133] In cases in which one or more pressured gas dischargers 260 discharge gas in a continuous manner (i.e. , not in short pulses), such continuous gas emission may sustain a certain constant pressure in the chamber. The rate at which the pressured gas discharger 260 1360 (e.g., nozzle) may emit the gas can be controlled by a controller 220. in such cases the gas does not significantly block SWR but slows the debris and ions. Slowing the debris particles before they reach intermittent illumination blocker 270 (e.g., before they reach the first blockable location) increases the time period between the SWR pulse and the particle reaching the intermittent illumination blocker 270 and thus reduces the number of unwanted 1365 particles managing to pass the respective blockable location before it moves to its blocked configuration.

[0134] Fig. 7A illustrates an example of system 200 in which only pressurized gas discharger 206 is used for diverting particles 190 after they have passed via one or more openings 204, and Fig. 7B an example of system 200 in which both pressurized gas discharger 1370 206 and magnetic inducer 2100 are used for diverting particles 190 after they have passed via one or more openings 204. The divergence of particles from the one or more PBDMs of system 200 may result from direct application on force on the respective particles by the respective PBDM and / or from indirect effect resulting from different particles colliding with oneAttorney Docket No. 16978-0004.00304another after being affected by the force induced by the respective PBDM, and changing 1375 course (and possibly slowing down) as a result of the collisions. Referring to all possible implementations of pressured gas discharger 206, it is noted that optionally the gas may be emitted at a relatively cool temperature, significantly cooler than the ambient environment. This may be achieved, for example, by applying liquid Nitrogen, or by other means. Using a relatively cool gas can be implemented for evacuating heat from various parts of the system 1380 and can assist in reducing the velocity of the debris particles.

[0135] It should be noted that in case intermittent illumination blocking assembly 270 includes relatively distanced blockable locations 276, system 200 may also include Midblocker diversion mechanisms (MBDMs) operating between the nearest blockable location 276 and the furthest blockable location 276. Such MBDMs may include any of the variations 1385 discussed above with respect to PBDMs, and may be implemented— if implemented at all— with or without one or more PBDMs. It should be noted that in case intermittent illumination blocking assembly 270 includes relatively distanced blockable locations 276, system 200 may also include front diversion mechanisms (FDMs) operating between ionization location 10 and the nearest blockable location 276. Such FDMs may include any of 1390 the variations discussed above with respect to FDMs (e.g., one or more gas dischargers, one or more magnetic or electromagnetic inducers) , and may be implemented— if implemented at all— with or without one or more PBDMs and / or MBDMs.

[0136] Optionally, system 200 may include one or more magnets, coils, or other ways of forming a magnetic field for diverting unwanted ions or other charged particles resulting from 1395 ionization of target 100, and / or for directing ionized particles in desired direction (e.g., may also be used to confine the plasma). Optionally, system 200 may include one or more injector for injecting gas into at least a portion of system 200 for reducing unwanted effects of such debris or for any other reason. Optionally, system 200 may include at least one pellicle having good transmission of SWR for reducing unwanted effects of such debris. It is noted that system 1400 200 may include any one or more of the different mechanisms discussed in this paragraph, alternative mechanisms for the same end, or none.

[0137] Such a pellicle may be made of, for example, a material with relatively good transmission of SWR at the desired wavelength but no (or little) transmission to debris, may be placed. For example, such a pellicle, if implemented, may be placed after the intermittent 1405 illumination blocker 270 and right before collecting optics 240, in order to protect optics 240 (or a recipient system following optics 240) from the residual debris that have managed to pass all the previous mechanisms. Optionally, a pellicle may be positioned after the optics 240 to protect additional modules down the line from unwanted debris or gases. Optionally, system 200 may be completely isolated from such additional modules (e.g., 262, 264, 266, 268) withAttorney Docket No. 16978-0004.003041410 the only opening that allows SWR transmission into the such modules is through the pellicle, thus sealing transmission of particles.Optionally, system 200 may include a post blocker deflection mechanism (PBDM) for deflecting away from DCA 150 propagation directions of particles that progressed past intermittent illumination blocker 270 along DCA 150. Optionally, the post blocker deflection 1415 mechanism includes at least one of: a magnetic field inducer that generates a magnetic field or an electric field inducer that generates electric field, for diverting during the second timespan a propagation direction of particles that progressed past intermittent illumination blocker 270 during the first time span, toward an absorbent surface of the SWR system. Optionally, the post blocker deflection mechanism includes a pressured gas discharger operable to emit gas 1420 emissions (e.g., gas pulses, continuous gas emissions) toward particles that progressed past intermittent illumination blocker 270, thereby modifying at least one of trajectories or velocities of the particles that progressed past the intermittent illumination blocker.

[0138] Fig. 8 is a schematical cross-section diagram illustrating an example of system 200, in accordance with examples of the presently disclosed subject matter. Optionally, 1425 intermittent illumination blocking assembly 270 includes a plurality of intermittent illumination blocking modules 278. In the illustrated example, a first intermittent illumination blocking modules (II BM) is denoted 278A and a second 11 BM 278 is denoted 278B, but more than two HBMs can be implemented. Each of the plurality of HBMs 278 includes at least one opaque portion which can be controllably moved in and out of a blocking disposition in which it blocks 1430 propagation of particles along DCA 150. Controller 220 in such case may be operable to control synchronized motion of the plurality of HBMs 278, such that the clear passages intermittently offered by each of the respective HBMs 278 (e.g., via an aperture of that HBM 278) are aligned during the first timespan and such that one or more opaque portions 278 of each I IBM 278 (except the first HBM 278) blocks propagation of at least one particle that 1435 passed through a clear passage offered by an HBM 278 nearer to the ionization location (e.g., at an earlier time). It is noted that system 200 may include a larger number of such serialized and synchronized HBMs 278. It is further noted that instead of implementing two or more independently motorized HBMs 278, system 200 may instead include a thick HBM 278 (e.g., a mechanical optic chopper with a thick rotating disc), e.g., thicker than 1cm, such that SWR 1440 and particles may propagate via tunnels in that thick HBM 278. Additional details are provided below. It is noted that such elongated tunnels may be implemented in other types of HBMs 278, e.g., in discs rotating about an axis that is perpendicular to a direction of such a tunnel opening.

[0139] Figs. 9A and 9B are a schematical cross-section diagram illustrating examples of 1445 system 200, in accordance with examples of the presently disclosed subject matter, at twoAttorney Docket No. 16978-0004.00304different points in time. Intermittent illumination blocker 270 of Figs. 9A and 9B include a plurality of HBMs 278, e.g., three optical choppers denoted 278A, 278B, and 278C. Each of the plurality of HBMs may include one or more apertures (or otherwise selectively block DCA 150 at some of the times). Being a cross section, Figs. 9A and 9B only illustrate a single 1450 aperture for each of the HBMs, denoted in the illustrations 274A, 274B, 274C. It is noted that system 200 may implement apertures of different cross sections, whether symmetric or asymmetric. For example, tapered walls like these of apertures 274B and 278C may be implemented in order to reject particles backwards diagonally, possibly interfering with movement of particles progressing along DCA 150. It is noted that intermittent illumination 1455 blocker 270 may include HBMs 278 with different sizes of apertures 274, e.g., in order to accommodate for divergence of the SWR beam propagating along DCA 150. For example, in Figs. 9A and 9B, each HBMs have aperture(s) of differing dimensions, where HBMs 278 that are located further away from ionization location 10 include wider apertures 274. If the plurality of HBMs 278 include a plurality of discs of one or more optical choppers, two or more of the 1460 discs may rotate in the same direction of rotation, e.g., by being motored by the same axis.This may be implemented, for example, to ease the synchronization between the different discs.

[0140] Fig. 10 is a series of graphs illustrating passage of particles of different velocities resulting from the generation of a single SWR pulse via a series of HBMs, in accordance with 1465 examples of the presently disclosed subject matter. The graphs represent passage of particles emitted as a result of ionization of an ionization target which progress at different velocities. For simplicity of the graphs and explanation, a binary passage / blocked scenario is illustrated, corresponding for example to a single line of propagation with CDA 150.

[0141] The intermittent illumination blocker in the example includes two individual optical 1470 choppers, each including a series of Ni apertures of the same size (per optical chopper) arranged in radial symmetry about a rotation axis of the respective optical chopper (e.g., similarly to the example of Fig. 14). The two optical choppers are arranged at different distances Di from the ionization location. Each of the optical choppers moves at a constant velocity and therefore passage through its apertures is enabled for a time T(open)i out of each 1475 cycle duration T(cycle)i.

[0142] The top graph represents passage of particles through a nearest chopper to the ionization location, the intermediate graph represents passage of particles through a furthest chopper from the ionization location, and the bottom graph represents an overall transmission through both choppers, as the product of the two above binary graphs. As can be seen in the 1480 right side, the fastest particles (e.g., faster than about 500m-sec“1) are fast enough to passAttorney Docket No. 16978-0004.00304through both apertures via which the SWR pulse passes, and should therefore be blocked by another means (e.g., magnetic field, gas discharge, etc.). Regarding the slower particles, such particles may pass via apertures intended for the following pulse (shown in the middle), the second pulse thereafter (shown in the left), and possibly via consequent apertures (not 1485 shown). However, due to the distances between the two discs of the two optic choppers, there is a difference between the ranges velocities of particles that can pass through the following apertures of both discs (top center vs middle center) and there is a difference between the ranges velocities of particles that can pass through the second following apertures of both discs (top left vs middle left).1490

[0143] However, for particles to pass the intermittent illumination blocker, such particles must pass through all of the HBMs of the intermittent illumination blocker. In the illustrated example, this means passing both choppers. However, since both ranges of velocities for the slower particles are nonoverlapping, respectively, none of these particles can pass the intermittent illumination blocker . Preventing propagation of particles traveling in the fastest 1495 span of velocities may be handled by any of the ways discussed above (e.g., additional HBMs such as additional chopper), PBDMs, MBDMs, and so on.

[0144] It should be noted that the velocity based blocking of the different intermittent illumination blocking modules may be constant during the operation of the system, across many pulses. Optionally, out of all velocities between 10m / sec and 300m / sec, at least 10% 1500 are blocked only at one of two discrete blockable locations (e.g., by one chopper) and not in both blockable locations.

[0145] Optionally, a structure of intermittent illumination blocker 270 and the rate of pulse emission of system 200 are such that passage of particles resulting from the emission of each respective SWR pulse at the first blockable location 276 is intermittently permitted via a series 1505 of at least five separate apertures 274 of intermittent illumination blocker 270 (e.g., at least five separate aperture of a first optical chopper disc). For example, the different apertures may let particles of differing velocities spans to pass along DCA 150 at different times. Optionally, the plurality of apertures of the first disc (be it two, three, four, five, or more apertures) via which particles resulting from the emission of a single SWR pulse allow passage along the 1510 DCA at the first blockable location 276 of more than 1 % of the emitted particles (possibly even >2%, >4%. >6%. Etc.). Such number of permitted particles may render the system not usable for prolonged operational periods. However, system 200 may implement blocking of particles at additional blockable locations 276 along DCA 150 (e.g., distanced more than 5mm along DCA 150), e.g., such that at least 50% of the permitted particles are blocked at or after the 1515 second blockable location (and possibly much more, e.g., >70%, >80%, etc.), at least of the particles traveling at velocities below a threshold (e.g., 300m / sec). Faster particles (e.g.,Attorney Docket No. 16978-0004.00304charged particles) may be diverted or otherwise dealt with. Such configurations may thereby allow system 200 to operate at pulse repetition rates of above 1Khz, above 5Khz, above 10Khz, and more.1520

[0146] It should be noted that in many implementations of system 200, the overall portion of particles being blocked by system 200 (at least at the different blockable locations along the one or more CDAs 150, and possibly by other means such as diversion using gas emissions, magnetic field, electromagnetic field, etc.) should be extremely high, in order to allow system 200 to operate for prolonged periods of time (e.g., hours, days, weeks) without 1525 having to be stopped for maintenance. This is especially important in implementations in which system 200 operates at high SWR pulse rates (e.g., exceeding 1KHz, exceeding 5KHz, exceeding 10KHz, etc.). For example, a combination of any one or more of the following aspects: structure of intermittent illumination blocker 270, number of blockable locations, spatial span of blockable locations, ionization rate, intermittent blockage rate, structure and 1530 position of diversion mechanisms, etc. may be implemented (e.g., in accordance with the various teachings throughout the present disclosure) to ensure that the rate of particles that progress along the one or more DCAs 150 is less than a threshold ratio than the number of particles originally emitted along the one or more DCAs 150 (e.g., less than 1%, less than 0.5%, less than 0.1%, less than 0.05%, less than 0.01%).1535

[0147] Optionally, the structure of intermittent illumination blocker 270 (e.g. the amount and size of its apertures 274) and the rate of pulse emission (e.g., measured in pulses per minute, PPM, thereby dictating the rotation rate of the optical chopper, RPM) yield a blocking frequency of at least 1K cycles per second (i.e. , in each duration of one second at least 1,000 open durations during which passage is permitted along the designated collection axis via an 1540 aperture of the intermittent illumination blocker at the first blockable location, and at least 1 ,000 intertwined close durations during which the intermittent illumination blocker 270 is blocking passage of particles at the first blockable location). This corresponds by definition (assuming similar apertures and constant rotation speed) to open durations shorter than 1ms. The distance between ionization location 10 and intermittent illumination blocker 270 may be such 1545 that any particle resulting from that SWR pulse that is propagating at velocities that are slower than 300m / sec cannot pass the first blockable location via the same aperture as the corresponding SWR pulse. The distance between ionization location 10 and intermittent illumination blocker 270 may be such that any particle resulting from that SWR pulse that is propagating at velocities that are slower than 300m / sec cannot pass the first blockable location 1550 within the same open duration as the corresponding SWR pulse. That means that slower particles are either blocked by one or more opaque portions 272, or pass via one or more next apertures.Attorney Docket No. 16978-0004.00304

[0148] Optionally, controller 220 controls the synchronization between light source 210 (or, more generally, heating source 202) and intermittent illumination blocker 270 for operating 1555 at a pulse rate exceeding 1KHz, resulting of closed durations at the first blockable location (e.g., by the first optical chopper) that are shorter than 1msec. As explained above, this corresponds to slower moving particles passing by definition through one or more of the next apertures to intersect DCA 150. Controller 220 in such case may further control synchronization between heating source 202 and the intermittent blocking of DCA 150 at one 1560 or more additional blockable locations (e.g., at a distance exceeding 5mm, 10mm, etc.; e.g., by one or more other optical chopper) for catching these by-definition passing particles, thereby allowing system 200 to operate at rates exceeding 1,000PPM.

[0149] Optionally, controller 220 may be operable to control the motion of intermittent illumination blocker 270 such that during the second time span of each pulse out of the plurality 1565 of pulses: particles emitted as a result of the respective pulse are blocked at the first blockable location (e.g., by a first 11 BM 278, by a first optical chopper, or at a first location inside a tunnel opening 274), and particles emitted as a result of a previous pulse of the series of light pulses are blocked at the second blockable location (e.g., by a second I IBM 278, by a second optical chopper, or at a second location further away inside a tunnel opening 274). The previous pulse 1570 may be the immediately preceding pulse in the sequence of pulses, or any earlier pulse in the sequence.

[0150] Optionally, particles emitted as a result of even previously emitted pulse (or pulses) may be blocked at the same second time span at a third blockable location, or even further blockable locations (e.g., by another one or more HBMs 278, by another one or more 1575 optical choppers, or at one or more further locations inside a tunnel opening 274).

[0151] Optionally, controller 220 may be operable to control the motion of intermittent illumination blocker 270 such that during the second time span of each pulse out of the plurality of pulses, intermittent illumination blocker 270 blocks— concurrently, substantially concurrently, or simply within the same second time span— by a first opaque portion 272 1580 located at the first blockable location 276 particles that are moving at a first span of velocities, and blocks by a second opaque portion 272 located at the second blockable location 276 particles that are moving at a second span of velocities and that passed the first blockable location 276 via an aperture 274 (or another type of opening or passage) of intermittent illumination blocker 270 before the respective second time span, and the first span of velocities 1585 and the second span of velocities are non-overlapping. Optionally, the slowest velocity of the first span of velocities is at least 10% faster than the fastest velocity of the second span of velocities. Examples of non-overlapping spans of velocities that are stopped at differentAttorney Docket No. 16978-0004.00304blockable locations along the DCA are provided at the left and central panes of Fig. 10, in the top two graphs. Optionally, the particles propagating at velocities within the first span of 1590 velocities that are stopped at the first blockable location 276 are the result of a different SWR pulse than the particles propagating at velocities within the second span of velocities that are stopped at the second blockable location 276.

[0152] Optionally, each of the first span of velocities and the second span of velocities may span velocities differing by at least 10m / sec. Optionally, each of the first span of velocities 1595 and the second span of velocities may span velocities differing by at least 25m / sec. Optionally, each of the first span of velocities and the second span of velocities may span velocities differing by at least 50m / sec. Optionally, each of the first span of velocities and the second span of velocities may span velocities differing by at least 5% (between the slowest and fastest velocities of the respective span of velocities). Optionally, each of the first span of velocities 1600 and the second span of velocities may span velocities differing by at least 10% (between the slowest and fastest velocities of the respective span of velocities).

[0153] Optionally, at least a certain fraction (e.g., at least 0.01%, at least 0.05%, at least 0.1%, at least 0.5%, at least 1%, at least 5%) of the particles blocked by intermittent illumination blocker 270 are blocked after previously passing through one or more apertures 1605 (or another type of opening or passage) of intermittent illumination blocker 270 when the respective aperture 274 (or the respective another type of opening or passage) was positioned along the DCA 150.

[0154] Optionally, less than a certain fraction (e.g., less than 20%, less than 10%, less than 5%, less than 2%, less than 1%) of the particles blocked by intermittent illumination 1610 blocker 270 are blocked after previously passing through one or more apertures (or another type of opening or passage) of intermittent illumination blocker 270 when the respective aperture 274 (or the respective another type of opening or passage) was positioned along the DCA 150.

[0155] While in the example of Fig. 8 only two discrete blockable locations 276 along DCA 1615 150 were illustrated (not denoted) and in the example of Figs. 9A and 9B only three discrete blockable locations 276 along DCA 150 were illustrated (276A, 276B, and 276C), it is possible to implement a continuous span of blockable locations, as demonstrated, for example, in Fig.11. Opaque portions corresponding to the three discrete blockable locations 276A, 276B, and 276C - i.e., opaque portions which block propagation of particles via these three discrete 1620 blockable locations during some of the times - were denoted 272A, 272B, and 272C, correspondingly.Attorney Docket No. 16978-0004.00304

[0156] Fig. 11 is a schematical cross-section diagram illustrating an example of system 200, in accordance with examples of the presently disclosed subject matter. As can be seen, intermittent illumination blocker 270 may include an elongated aperture 274 (also referred to 1625 as a tunnel) having sides that are opaque portions 272. As the elongated aperture 274 keeps moving while particles move through it, the sides of the tunnel may hit such particles and prevent them from continuing their propagation along DCA 150 (e.g., by collecting or deflecting them).

[0157] Referring to system 200 as a whole, in cases in which system 200 includes a 1630 plurality of blockable locations dispersed along DCA 150, a distance between a first blockable location 276 and a second blockable location 276 (e.g., the nearest and the furthest to ionization location, or defined by two adjacent IIMBs 278 out of three or more HBMs 278) that are positioned along the designated collection axis may exceed 1mm, 0.5cm, 1cm, or 2cm, etc. Optionally, the distance between such a first blockable location 276and a second 1635 blockable location 276 along DCA 150 may exceed 10%, 20%, 30%, etc. of the distance between the nearest blockable location 276 (nearest to ionization location 10) and the ionization location. For example, a distance between ionization location 10 and the nearest blockable location 276 may be about 4cm, and the distance between first blockable location 276 and second blockable location may be about 1cm, equal to about 25%.1640

[0158] Optionally, intermittent illumination blocker 270 may include at least one rotating disc mechanical shutter optical chopper including a plurality of rotating discs of the at least one rotating disc mechanical shutter optical chopper, each such disc including a plurality of apertures 274. In such case, the first blockable location 276 may be positioned at an intersection with DCA 150 of a first rotating disc out of the plurality of rotating discs, the second 1645 blockable location 276 may be positioned at an intersection with DCA 150 of a second rotating disc out of the plurality of rotating discs; and projections of the first rotating disc and of the second rotating disc about a plane perpendicular to the designated collection direction rotate in the same direction. Optionally, different discs (or other forms of movements, like of conveyer belts) may also move in opposite directions.1650

[0159] Optionally, controller 220 may be operatively connected to at least one of intermittent illumination blocker 270 and heating module 220 (e.g., light source 210) further for controlling synchronization between the series of SWR pulses and the synchronized motion (e.g., repetitive motion) of the plurality of rotating discs, for synchronizing concurrent alignment of an aperture of each rotating disc out of the plurality of rotating discs with the designated 1655 collection axis during at least a portion of the first time span.Attorney Docket No. 16978-0004.00304

[0160] Optionally, controller 220 may be operable to control synchronization between the moving portions of intermittent illumination blocker 270 and heating module 220 (e.g., light source 210) such that a group of at least one aperture of intermittent illumination blocker 270 permits transmission of SWR along the designated collection direction at least 100, at least 1660 200, at least 500, or at least 1,000 distinct times per second. These times in which transmission of SWR is permitted are intermittent by times in which passage of SWR is blocked (for blocking passage of particles).

[0161] Fig. 12 is a schematical cross-section diagram illustrating an example of system 200, in accordance with examples of the presently disclosed subject matter. Optionally, 1665 system 200 may be operable to output a plurality of SWR beams, over two or more distinct DCAs 150 (e.g., DCA 150A and DCA 150B in the diagram), each SWR beam passing via an intermittent illumination blocker 270. Different beams may pass via different intermittent illumination blockers 270 (not shown) and / or via the same intermittent illumination blocker 270, e.g., as illustrated. If passing via the same intermittent illumination blocker 270, such different 1670 SWR beams may pass via the same apertures 274 (e.g., as shown), or via different apertures 274 on the same intermittent illumination blocker 270. For example, apertures 274 may be arranged at two or more concentric circles, where one SWR beam is outputted as SWR pulses passing via the apertures 274 of a first ring of apertures 274, and another SWR beam is outputted as SWR pulses passing via the apertures 274 of a second ring of apertures 274 on 1675 the same disc of an optical chopper. It is noted that the SWR pulses of the different SWR beams may be emitted concurrently, as different SWR pulses of different beams propagating along the different DCAs 150 result from the same instance of ionization of ionization target 100.

[0162] Optionally, at least part of the emitted SWR and at least part of the emitted 1680 particles progress along a plurality of different DCAs 150, as intermittent illumination blocker 270 includes a plurality of apertures 274 via which SWR and particles can pass concurrently. For example, the plurality of apertures 274 may include two or more of the larger number of apertures 274 via which SWR beams can progress concurrently. In such cases, controller 220 may be operable to control the motion (e.g., repetitive motion) of intermittent illumination 1685 blocker 270 such that: during the first timespan each of the plurality of apertures concurrently intersects a corresponding designated collection axis out of the plurality of DCAs, thereby permitting SWR emitted from ionization target 10 as a result of the impinging of the respective pulse to continue along the corresponding DCA (e.g., towards different collection optics such as 240A and 240B, toward inlet ports of one or more auxiliary machines, etc.; and during the 1690 second timespan the plurality of DCAs 150 are blocked by a corresponding plurality of opaque portions 272 out of the opaque portions 272 of intermittent illumination blocker 270, therebyAttorney Docket No. 16978-0004.00304blocking propagation of particles emitted from ionization target 10 as a result of the impinging of the respective pulse from continuing along the plurality of DCAs 150.

[0163] Referring to system 200 generally, it is noted that light pulses of light source 210 1695 may optionally traverse via openings of an intermittent illumination blocker— whether the same intermittent illumination blocker 270 which serves for intermittently blocking particles progressing along DCA 150 (e.g., as exemplified in Figs. 12 and 13), or via a dedicated intermittent illumination blocker (not shown) intended to protect light source 210 itself and / or other components of system 200 (e.g., optical components intended for directing light of light 1700 source 210 onto ionization location 10). In case the light of light source 210 passes via intermittent illumination blocker 270, it may pass through apertures 274 that are also used for allowing propagation of the outgoing SWR beam (e.g., as exemplified in Fig. 13) and / or via dedicated apertures 275 (e.g., as exemplified in Fig. 12). It is noted that in case intermittent illumination blocker 270 includes a plurality of HBMs 278, light of light source 210 may pass 1705 via illumination blockable locations 277 of one, some, or all of these HBMs 278 (e.g., as exemplified in Fig. 12), or via none at all (e.g., as exemplified in Fig. 8).

[0164] Optionally, e.g., as exemplified in Fig 12, the size of apertures in different blockable locations (e.g., in different optical chopper discs positions at different distances along DCA 150) gradually increases along DCA 150, to maintain a constant solid angle of the 1710 propagating SWR pulses along DCA 150.

[0165] Fig. 13 is a schematical cross-section diagram illustrating an example of system 200, in accordance with examples of the presently disclosed subject matter. In the example of Fig. 13, light pulses of light source 210 pass via the same apertures 274 as the generated SWR pulses.1715

[0166] In cases light of light source 210 passes through the same intermittent illumination blocker 270 but via different dedicated apertures 275, controller 220 may be operatively connected to at least one of heating module 202 (e.g., light source 210) and intermittent illumination blocker 270 for controlling the synchronization between them such that for each pulse out of the plurality of pulses of the series of light pulses: during at least a portion of the 1720 first timespan that includes the emission of the respective pulse a group (“second group”) of one or more apertures 275 intersects an illumination propagation path 154 between light source 210 and ionization location 10, thereby permitting light of the respective pulse emitted by light source 210 to progress at illumination propagation direction 152 along illumination propagation path 154 to the ionization location. The duration required for passage of light 1725 between light source 210 and ionization location 10 is very short, and therefore a significantly shorter time frame can be allotted for this intermittent passage for light compared to theAttorney Docket No. 16978-0004.00304duration of the “open” duration 122. During the second timespan at least one second opaque portion of intermittent illumination blocker 270 (e.g., on the other side of the respective disc of the optical chopper, the first side being that of opaque portions 282, or on a dedicated 1730 intermittent illumination blocker for protecting light source 210) intersects illumination propagation path 154, thereby blocking propagation of particles emitted from the respective ionization target 10 as a result of the impinging of the respective pulse from propagating along illumination propagation path 154 at direction 156 opposing the illumination propagation direction 152 toward light source 210.1735

[0167] Optionally, the second group of one or more apertures 275 consist of apertures that do not intersect DCA 150.

[0168] Referring to system 200 as a whole, it is noted that one or more sensors may collect data indicative of parameters (e.g., magnitude, power) of a generated SWR pulse. Such data may be processed by a processor of system 200 and / or by a processor or another system 1740 (e.g., a system which utilizes the SWR pulse) for various reasons, such as any one or more of the following: amending operational parameters of a client system / client module in response to the parameters of the pulse; amending operational parameters of system 200 to be used in the generation of later SWR pulses (e.g., illumination pulse duration, timing, intermittent illumination blocker timing); feedback control; stabilization of output SWR power under varying 1745 conditions; quality assurance (e.g., detecting anomalies in beam characteristics for reliability);diagnostics and maintenance (e.g., identifying issues such as misalignment, degradation, or overheating, debris accumulation, scheduling maintenance based on performance trends); safety monitoring (e.g., ensuring output does not exceed safety thresholds); calibration (e.g., fine-tuning system parameters for precise operation, comparing measured values to reference 1750 standards); process optimization (e.g., adapting operational parameters to enhance efficiency or material interaction, customizing output for specific applications); data logging and compliance; research and development; user interface and reporting (e.g., displaying realtime status to operators, generating reports for operational analysis or customer record).

[0169] Optionally, reporting SWR pulse parameters may be used instead of or in addition 1755 to the requirement for absolute stability of the source.

[0170] Optionally, system 200 may include optional particle-filtering membrane 208, positioned between intermittent illumination blocker 270 and optics 240. Particle-filtering membrane 208 may be implemented, for example, to reduce particle contamination while allowing the transmission of SWR. For example, such a membrane may include a free1760 standing silicon nitride (Si3N4), polysilicon, metal ceramic, graphene, silicon carbide or carbon nano-tubes film, known for high strength and excellent SWR transparency, making it well-Attorney Docket No. 16978-0004.00304suited for maintaining system cleanliness without significantly attenuating the SWR beam. Alternatively, a perforated metallic mesh, such as one made from molybdenum or tungsten, may be employed; these materials offer robustness and thermal stability, with precision- 1765 engineered holes to facilitate SWR transmission while trapping contaminants. Another example includes ultra-thin carbon-based films, such as diamond-like carbon or amorphous carbon membranes or carbon nanotubes, which combine high SWR transmittance with chemical and thermal resistance, making them ideal for environments exposed to high-energy photons and reactive gases. It is noted that these are just examples, and any suitable 1770 membrane capable of achieving the desired balance of particle filtration and EUV transparency may be employed, if implemented.

[0171] Fig. 14 is a 3D illustration of an example of system 200, in accordance with examples of the presently disclosed subject matter. In addition to intermittent illumination blocker 270, system 200 may optionally also include additional blockers, shields, and / or 1775 protective modules 260 protect various sensitive components of system 200 and / or of other systems. Such modules 260 may be permanent, semi-permanent, or movable. Such blocking modules 260, if implemented, are usually located away from DCA 150 and from illumination propagation path 154 (in case illumination is used for ionization of ionization target 100).

[0172] Optionally, system 200 may include a target chamber 286 that includes target 1780 location 10, target-associated modules of system 200 (such as any one or more of the following optional components of system 200: a target support structure, a target-mobilization module 282 for moving different parts of ionization target 100 to ionization location 10 at different times— e.g., a motor, conveyer belt, shaft, axle, etc.— ionization sensor, and so on), and possibly additional components. While not necessarily so, part or all of each out of one or 1785 more intermittent illumination blockers 270 of system 200 may be positioned within target chamber 286. Target chamber 286 may optionally include one or more optional ingress apertures (also referred to as “entry apertures” or “light entry apertures”) to allow incoming light pulse from outside target chamber 286 to reach target location 10. It is noted that optionally heating module 202 or any one or more parts thereof may be positioned inside 1790 target chamber 286. Target chamber 286 may include one or more egress apertures coinciding with DCA 150 to allow SWR pulse to escape target chamber 286 along DCA 150. The outer walls of target chamber 286 may be made, for example, from blocking module 260 components. Optionally, target chamber 286 may include one or more front diversion mechanisms (FDMs), such as pressured gas discharger 206. In such cases, target chamber 1795 286 may be isolated from the vacuum in other parts of system 200. Intermittent illumination blocker 270 in such cases may optionally take part in maintaining the pressure differencesAttorney Docket No. 16978-0004.00304between target chamber 286 and the vacuum outside of it, e.g., by being shaped as a turbo molecular pump (TMP), with openings in and / or between its fins.

[0173] Optionally, system 200 may include intermittent illumination blocker chamber 288 1800 that includes intermittent illumination blocker 270 and isolates intermittent illumination blocker 270 from other parts of system 200. Other parts (e.g., one or more sensors 250, motor 280) may be included in intermittent illumination blocker chamber 288. System 200 may include any one or both of target chamber 286 and intermittent illumination blocker chamber 288, or none of them. Optionally, target chamber 286 and intermittent illumination blocker chamber 1805 288 may be implemented as a single chamber. It is noted that while target chamber 286 and intermittent illumination blocker chamber 288 are illustrated only in Fig. 13, they may be implemented in any implementation of system 200, mutatis mutandis. More generally, any components and variations that were discussed in the context of one or more figures can be used in any suitable implementation of system 200. Any combination of systems, components, 1810 variations, functionalities, etc. may be implemented, even if not explicitly stated.

[0174] Optionally, system 200 may include an intermediate focus, which refers to a location within the optical path (e.g., along DCA 150) where SWR pulses are temporarily concentrated, creating a localized intensity peak before continuing onward, enabling enhanced control over pulse shaping, energy distribution, or integration with additional optical 1815 or temporal-modulation elements. Optionally, intermittent illumination blocker 270 may be implemented such that one of the blockable locations 276 of intermittent illumination blocker 270 is positioned at the intermediate focus, or very near it, such as at a distance of 0-2mm, 2-5mm, etc. from it. For example, system 200 may include one or more parabolic collectors (not shown), each being configured to concentrate SWR pulses toward an intermediate focus.1820

[0175] Referring to the example of Fig. 14, it is noted that optionally, apertures 274 and apertures 275 may be arranged in two concentric circles of apertures. Alternatively, e.g., as exemplified in Fig. 13, a single circle of apertures may serve as both apertures 274 and apertures 275.

[0176] Figs. 15Aand 15B illustrate an optical chopper disc (e.g., serving as an intermittent 1825 illumination blocking module 278) with a plurality of eight apertures, used in two different ways, in accordance with examples of the presently disclosed subject matter. In Fig. 15A, light of light source 202 is projected onto ionization location 10 without passing through the respective intermittent illumination blocking module 278 (notably, it may optionally be protected by another dedicated optical chopper, but not necessarily so). In such case, system 200 may 1830 support four different beamlines, corresponding to the four DCAs 150 depicted. Each SWR pulse results in transmittance of light of four different directions concurrently, via differentAttorney Docket No. 16978-0004.00304apertures of the optical disc. In Fig. 15B, by comparison, the light of light source 202 propagates via the same apertures, passing via one of the apertures (denoted 275) coinciding with laser propagation path 154 substantially concurrently with the passage of SWR pulse via 1835 three other apertures 274 of the same optical chopper disc. It should be noted that the number of apertures, discs, beamlines, etc., is merely an example, and that any suitable combination may be implemented.

[0177] Fig. 16 is a flow chart illustrating an example of method 500, in accordance with the presently disclosed subject matter. Method 500 is a method for generation of Short Wave 1840 Radiation (SWR). Referring to the examples set forth with respect to the previous drawings, method 500 may optionally be executed by SWR system 200.

[0178] Method 500 includes step 510 of intermittently ionizing one or more ionization targets at an ionization location of a SWR system, thereby generating emission at different times and at least along a designated collection axis (DCA) of a plurality of SWR pulses and 1845 emission of particles from at least one ionization target positioned at the ionization location.Referring to the examples set forth with respect to the previous drawings, step 510 may optionally be executed by one or more heating modules 202. For example, step 510 may include step 512 of emitting a series of light pulses toward the ionization location, thereby generating emission along the DCA of a plurality of SWR pulses and emission of particles 1850 from the at least one ionization target positioned at the ionization location. Referring to the examples set forth with respect to the previous drawings, step 510 may optionally be executed by one or more light sources 210. Alternatively, step 510 may be implemented in any other suitable way, such as: Discharge-Produced Plasma (DPP), in which case step 510 includes discharging a series of high-voltage electrical discharges to ionize material to produce plasma 1855 that emits the SWR pulses; Z-pinch, in which case step 510 includes passing strong electrical currents through a cylindrical column of material (serving as target 100 in that case, e.g., a gas or liquid metal), causing it to compress and ionize, producing the SWR pulses. Microwave- Induced Plasma, in which case step 510 includes optionally ionizing the one or more ionization targets using high-frequency microwaves, thereby creating plasma that can emit the SWR 1860 pulses.

[0179] For each SWR pulse out of a plurality of SWR pulses of the series of SWR pulses, method 500 includes executing at least steps 520 and 530. It is noted that steps 520 and 530 may be executed alternately, for hundreds, thousands, tens of thousands, hundreds of thousands, millions, tens of millions, hundreds of millions, or more of alternations (e.g., for 1865 several minutes, hours, days, weeks, etc.). Steps 520 and 530 may optionally be executed by implementing one continuous motion (e.g., rotating or revolving a disc, a conveyer belt, and so on). Other types of movements may also optionally connect the alternating execution ofAttorney Docket No. 16978-0004.00304instances of steps 520 and 530, such as: recurrent, periodic, oscillatory, cyclic, rotational, reciprocal, harmonic, non-harmonic, isochronous, continuous, and intermittent. Steps 520 and 1870 530 may also be executed in any other suitable way.

[0180] Step 520 includes providing a clear passage along the DCA during a first timespan that includes the emission of a respective SWR pulse, thereby permitting SWR of the respective SWR pulse to continue past an intermittent illumination blocker along the DCA during the first time span. Referring to the examples set forth with respect to the previous 1875 drawings, step 520 may optionally be executed by controller 220, by intermittent illumination blocker 270, by heating module 202 (e.g., heating module 210), or by a combination of any two or more of these components. For example, step 520 may include moving one or more apertures (or other openings) of the intermittent illumination blocker to coincide with the DCA and / or by otherwise removing any opaque portion of the intermittent illumination blocker from 1880 the DCA.

[0181] For example, step 520 may include aligning during the first timespan at least one aperture that is located within the at least one opaque portion to intersect the DCA, thereby allowing the SWR of the respective SWR pulse to continue past the intermittent illumination blocker along the DCA via the at least one aperture. Referring to the examples set forth with 1885 respect to the previous drawings, the at least one aperture may include at least one aperture 274.

[0182] Step 530 includes blocking the DCA by at least one opaque portion of the intermittent illumination blocker during a second timespan which follows the first time span, thereby blocking propagation of particles emitted from the respective ionization target as a 1890 result of the generation of the respective SWR pulse from continuing along the DCA (e.g., due to the particles being significantly slower than the SWR, therefore arriving to the intermittent illumination blocker when the at least one opaque portion already positioned in a blocking position of the DCA). Referring to the examples set forth with respect to the previous drawings, step 530 may optionally be executed by controller 220, by intermittent illumination blocker 270, 1895 by heating module 202 (e.g., heating module 210), or by a combination of any two or more of these components.

[0183] Optionally, during each second timespan associated with each of the series of light pulses, the at least one opaque portion of the intermittent illumination blocker may block particles at a plurality of blockable locations including at least a first blockable location and a 1900 second blockable location. Optionally, the first blockable location and the second blockable location may be positioned along the DCA at a distance that exceeds 5mm. Optionally, the first blockable location and the second blockable location may be positioned along the DCAAttorney Docket No. 16978-0004.00304at a distance that exceeds 10mm. Optionally, the first blockable location and the second blockable location may be positioned along the DCA at a distance that exceeds 1cm.1905 Optionally, the first blockable location and the second blockable location may be positioned along the DCA at a distance that exceeds 20mm.

[0184] For example, the intermittent illumination blocker may include a rotating disc mechanical shutter optical chopper that includes a plurality of tunnels longer than 1cm via which SWR can pass during the first time spans associated with the plurality of SWR pulses, 1910 and the plurality of blockable locations includes a continuum of blockable locations dispersed along a span longer than 1cm along each tunnel out of the plurality of tunnels.

[0185] For example, the intermittent illumination blocker may include at least one rotating disc mechanical shutter optical chopper that include a plurality rotating discs, each including an opening for permitting intermittent passage of SWR, and the first blockable location may 1915 be positioned at an intersection with the DCA of a first rotating disc out of the plurality of rotating discs, and the second blockable location may be positioned at an intersection with the DCA of a second rotating disc out of the plurality of rotating discs. The movement of the intermittent illumination blocker during step 530 may include moving the discs such that projections of the first rotating disc and of the second rotating disc about a plane perpendicular 1920 to the designated collection direction rotate in the same direction.

[0186] For example, the blocking of step 530 associated with each SWR pulse out of the plurality of SWR pulses may include: blocking particles emitted as a result of the generation of a first SWR pulse at the first blockable location, and blocking particles emitted as a result of the generation of a second previous SWR pulse at the second blockable location.1925

[0187] For example, the blocking of step 530 associated with each SWR pulse out of the plurality of SWR pulses may include: concurrently blocking by a first opaque portion located at the first blockable location particles that are moving at a first span of velocities, and blocking by a second opaque portion located at the second blockable location particles that are moving at a second span of velocities, wherein the first span of velocities and the second span of 1930 velocities are non-overlapping.

[0188] For example, the blocking of step 530 may include: blocking at least 5% of the particles blocked by the intermittent illumination blocker after the respective particles have previously passed through a first aperture of a series of apertures of the intermittent illumination blocker when the series of apertures are positioned along the DCA. For example, 1935 the blocking of step 530 may include: blocking less than 20% of the particles blocked by the intermittent illumination blocker after the respective particles have previously passed throughAttorney Docket No. 16978-0004.00304a first aperture of a series of apertures of the intermittent illumination blocker when the series of apertures are positioned along the DCA.

[0189] Optionally, method 500 may include deflecting away from the DCA particles that 1940 progressed past the intermittent illumination blocker along the DCA by inducing an electromagnetic field (e.g., during the second timespan) causing diversion of the propagation directions of particles that progressed past the intermittent illumination blocker during the first timespan toward an absorbent surface of the SWR system. For example, the deflecting may include using at least one of: a magnetic field inducer that generates a magnetic field or an 1945 electric field inducer that generates electric field. Referring to the examples set forth with respect to the previous drawings, these deflecting may optionally be executed by controller 220, by magnetic field inducer 2100, or by a combination of both. Optionally, method 500 may include deflecting away from the DCA particles before and / or after they reached the intermittent illumination blocker (or, in some cases, before and / or after they reached at least 1950 one blocking component of the intermittent illumination blocker) by inducing an electromagnetic field (e.g., during the second timespan) causing diversion of the propagation directions of particles that progressed past the intermittent illumination blocker during the first timespan toward an absorbent surface of the SWR system. Referring to the examples set forth with respect to the previous drawings, these deflecting may optionally be executed by 1955 controller 220, by magnetic field inducer, or by a combination of both. Optionally, method 500 may include slowing down particles before they reached the intermittent illumination blocker (or, in some cases, before they reached at least one blocking component of the intermittent illumination blocker) by inducing an electromagnetic field (e.g., during the second timespan).

[0190] Optionally, method 500 may include deflecting away from the DCA particles that 1960 progressed past the intermittent illumination blocker along the DCA by a pressured gas discharger operable to emit during the second timespans gas emissions (e.g., gas pulses, continuous gas emissions) toward particles that progressed past the intermittent illumination blocker, thereby modifying at least one of trajectories or velocities of the particles that progressed past the intermittent illumination blocker. Referring to the examples set forth with 1965 respect to the previous drawings, these deflecting may optionally be executed by controller 220, by pressured gas discharger 206, or by a combination of both. Optionally, method 500 may include deflecting away from the DCA particles before they reached the intermittent illumination blocker (or, in some cases, before they reached at least one blocking component of the intermittent illumination blocker) by a pressured gas discharger operable to emit (e.g., 1970 during the second timespans) gas emissions toward particles that progressed past the intermittent illumination blocker, thereby modifying at least one of trajectories or velocities of the particles. Referring to the examples set forth with respect to the previous drawings, theseAttorney Docket No. 16978-0004.00304deflecting may optionally be executed by controller 220, by pressured gas discharger 206, or by a combination of both.1975

[0191] Fig. 17 is a flow chart illustrating an example of method 550 associated with method 500, in accordance with the presently disclosed subject matter. Optionally, method 550 may include executing for each SWR pulse out of the plurality of SWR pulses steps 522 and 532.

[0192] Step 532 includes: during at least the second timespan, blocking by at least one 1980 opaque object particles emitted from the ionization target (as a result of the generation of the respective SWR pulse) from propagating toward a light source that emits the series of light pulses along an illumination propagation path between the ionization location and the light source. For example, the at least one opaque objects may include any combination of one or more of: opaque portion(s) of the same intermittent illumination blocker, opaque portion(s) of 1985 another SWR intermittent illumination blocker, opaque portion(s) of an intermittent illumination blocker that is also performing as illumination-path intermittent illumination blocker (e.g., blocking path of laser illumination of one or more lasers at times when the laser do not emit pulses), and opaque portion(s) of a dedicated illumination-path intermittent illumination blocker (denoted “I IB" in Figs. 17 and 18).1990

[0193] Step 522 includes intermittently moving the at least one opaque object away from the illumination propagation path to allow propagation of the series of light pulses along the illumination propagation path. Optionally, the intermittently moving of the at least one opaque object away from the illumination propagation path may include allowing the light pulses to pass via one or more apertures of an optical chopper, the one or more apertures of the optical 1995 chopper not intersecting the DCA.

[0194] Fig. 18 is a flow chart illustrating an example of method 570 associated with method 500, in accordance with the presently disclosed subject matter. Optionally, method 570 may include executing for each SWR pulse out of the plurality of SWR pulses steps 524 and 534.2000

[0195] Step 524 includes providing, during the first time span clear passages along a plurality of DCAs, thereby permitting SWR of the respective SWR pulse to continue along the plurality of DCAs past an intermittent illumination blocking assembly that includes at least the intermittent illumination blocker.

[0196] Step 534 includes blocking during the second time span the plurality DCAs by 2005 opaque portions of the intermittent illumination blocking assembly that intersect the DCAs, thereby blocking propagation of particles emitted from the respective ionization target as aAttorney Docket No. 16978-0004.00304result of the generation of the respective SWR pulse from continuing along the plurality of DCAs.

[0197] It should be noted that methods 500, 550, and 570 may include executing steps 2010 corresponding to any of the above-mentioned functionalities and variations of any of the components of SWR system 200. Many such details are not repeated in the interest of concision.

[0198] while the embodiments described above are provided as examples, it should be understood that various modifications and substitutions may be made without departing from 2015 the scope of the invention as defined in the appended claims.

Claims

Attorney Docket No. 16978-0004.00304CLAIMSWhat is claimed is:

1. A shortwave Radiation (SWR) system, the system comprising:2020 a light source operable to emit a series of light pulses, each pulse being emitted toward an ionization location to generate emission along a designated collection axis (DCA) of an SWR pulse and emission of particles from at least one ionization target positioned at the ionization location;an intermittent illumination blocker, including at least one opaque portion 025 operable to block SWR and particles impinging on the at least one opaque portion, and at least one aperture within the at least one opaque portion, via which SWR can pass; anda controller, operatively connected to at least one of: the intermittent illumination blocker and the light source, for controlling synchronization between 030 motion of the intermittent illumination blocker and an emission of the series of light pulses, such that:during a first timespan that includes the emission of a light pulse of the series of light pulses, the at least one aperture intersects the DCA, thereby permitting SWR of a respective SWR pulse resulting from the light pulse to 035 pass the intermittent illumination blocker along the DCA; andduring a second timespan following the first timespan, the at least one opaque portion of the intermittent illumination blocker intersects the DCA, thereby blocking propagation of particles emitted from the at least one ionization target as a result of the impinging of the light pulse from continuing 040 along the DCA.

2. The SWR system according to claim 1, wherein during each second timespan associated with each of the series of light pulses, the at least one opaque portion of the intermittent illumination blocker intersects the DCA at a plurality of blockable locations including at least a first blockable location and a second blockable 045 location.

3. The SWR system according to claim 2, wherein the controller is operable to control the synchronization such that during each second time span particles emitted as a result of generation of a first SWR pulse are blocked at the first blockable location, and particles emitted as a result of generation of a preceding SWR pulse are 050 blocked at the second blockable location.Attorney Docket No. 16978-0004.003044. The SWR system according to claim 2, wherein the controller is operable to control the synchronization such that during each second time span, the intermittent illumination blocker concurrently blocks, by a first opaque portion located at the first 2055 blockable location, particles that are moving at a first span of velocities, and blocks, by a second opaque portion located at the second blockable location, particles that are moving at a second span of velocities; wherein the first span of velocities and the second span of velocities are non-overlapping.060 5. The SWR system according to claim 4, wherein out of all velocities between 10m / sec and 300m / sec, at least 10% are blocked only at one of two discrete blockable locations and not in both blockable locations.

6. The SWR system according to claim 2, wherein the first blockable location and the 065 second blockable location are positioned along the DCA at a distance that exceeds 5mm.

7. The SWR system according to claim 6, wherein a structure of the intermittent illumination blocker and the rate of pulse emission are such that passage of 070 particles resulting from the emission of each respective SWR pulse at the first blockable location is intermittently permitted via a series of at least five separate apertures of the intermittent illumination blocker, thereby allowing a pulse repetition rate of above 1Khz, wherein at least 50% of the permitted particles are blocked at or after the second blockable location.0758. The SWR system according to claim 6, wherein a structure of the intermittent illumination blocker and the rate of pulse emission yield a blocking frequency of at least 1K cycles per second of open durations for passage along the designated collection axis via an aperture of the intermittent illumination blocker at the first 080 blockable location and close durations of blocking passage of particles at the first blockable location, corresponding to open durations shorter than 1ms, wherein a distance between the ionization location and the intermittent illumination blocker is such that any particle propagating at velocities that are slower than 300m / sec cannot pass the first blockable location via the same aperture as the corresponding 085 SWR pulse.Attorney Docket No. 16978-0004.003049. The SWR system according to claim 1, wherein the at least one aperture includes a series of apertures positioned along the DCA and at least 0.01% of the particles blocked by the intermittent illumination blocker are blocked after previously passing 2090 through a first aperture of the series of apertures.

10. The SWR system according to claim 1, wherein the at least one aperture includes a series of apertures positioned along the DCA and less than 20% of the particles blocked by the intermittent illumination blocker are blocked after previously passing 095 through a first aperture of the series of apertures.

11. The SWR system according to claim 1, wherein a dimension of the intermittent illumination blocker along the DCA is greater than 1 cm and the at least one opaque portion of the intermittent illumination blocker includes at least a first blockable 100 location and a second blockable location.

12. The SWR system according to claim 11, wherein the motion of the intermittent illumination blocker is determined such that the first blockable location is located within the at least one aperture and the second blockable location is located outside 105 the at least one aperture.

13. The SWR system according to claim 11, wherein the motion of the intermittent illumination blocker is determined such that both the first blockable location and the second blockable location are located outside the at least one aperture.11014. The SWR system according to claim 11, wherein the intermittent illumination blocker includes a rotating disc, wherein the at least one aperture includes a plurality of apertures at the rotating disc.115 15. The SWR system according to claim 1 , further comprising a post blocker deflection mechanism for deflecting away from the DCA propagation directions of particles that progressed past the intermittent illumination blocker along the DCA.

16. The SWR system according to claim 15, wherein the post blocker deflection 120 mechanism includes at least one of: a magnetic field inducer that generates a magnetic field, or an electric field inducer that generates electric field, for diverting a propagation direction of particles that progressed past the intermittentAttorney Docket No. 16978-0004.00304illumination blocker during the first timespan, toward an absorbent surface of the SWR system.212517. The SWR system according to claim 15, wherein the post blocker deflection mechanism comprises a pressured gas discharger operable to emit gas emissions toward particles that progressed past the intermittent illumination blocker, thereby modifying at least one of trajectories or velocities of the particles that progressed 130 past the intermittent illumination blocker.

18. The SWR system according to claim 1, wherein at least part of the emitted SWR and at least part of the emitted particles progress along a plurality of different designated collection axes, wherein the intermittent illumination blocker comprises 135 a plurality of apertures via which SWR and particles can pass concurrently, wherein the controller is operable to control the synchronization such that: during the first timespan, each of the plurality of apertures concurrently intersects a corresponding DCA out of the plurality of designated collection axes, thereby permitting SWR emitted from the respective ionization target as a result of the impinging of the 140 respective pulse to continue along the corresponding DCA; and during the second timespan, the plurality of designated collection axes are blocked by a corresponding plurality of opaque portions of the intermittent illumination blocker, thereby blocking propagation of particles emitted from the respective ionization target as a result of the impinging of the respective pulse from continuing along the 145 plurality of designated collection axes.

19. A method for generation of Short Wave Radiation (SWR), the method comprising:emitting a series of light pulses toward an ionization location, thereby generating emission along a designated collection axis (DCA) of a plurality of SWR 150 pulses and emission of particles from at least one ionization target positioned at the ionization location; andfor each SWR pulse out of the plurality of SWR pulses:during a first timespan that includes the emission of a respective SWR pulse, providing a clear passage along the DCA, thereby permitting SWR of the 155 respective SWR pulse to continue past an intermittent illumination blocker along the DCA; andduring a second timespan following the first timespan, blocking the DCA by at least one opaque portion of the intermittent illumination blocker, thereby blocking propagation of particles emitted from the respective ionization targetAttorney Docket No. 16978-0004.003042160 as a result of the generation of the respective SWR pulse from continuing along the DCA.

20. The method according claim 19, further comprising aligning, during the first timespan, at least one aperture that is located within the at least one opaque 2165 portion to intersect the DCA, thereby allowing the SWR of the respective SWR pulse to continue past the intermittent illumination blocker along the DCA via the at least one aperture.

21. The method according claim 19, wherein during each second timespan associated 170 with each of the series of light pulses, the at least one opaque portion of the intermittent illumination blocker blocks particles at a plurality of blockable locations including at least a first blockable location and a second blockable location.

22. The method according to claim 21 , wherein the blocking associated with each SWR 175 pulse out of the plurality of SWR pulses comprises: blocking particles emitted as a result of the generation of a first SWR pulse at the first blockable location, and blocking particles emitted as a result of the generation of a second previous SWR pulse at the second blockable location.180 23. The method according to claim 21 , wherein the blocking associated with each SWR pulse out of the plurality of SWR pulses includes: concurrently blocking by a first opaque portion located at the first blockable location particles that are moving at a first span of velocities, and blocking by a second opaque portion located at the second blockable location particles that are moving at a second span of velocities, 185 wherein the first span of velocities and the second span of velocities are nonoverlapping.

24. The method according to claim 21, wherein the first blockable location and the second blockable location are positioned along the DCA at a distance that exceeds 190 1cm.

25. The method according to claim 24, wherein the blocking includes blocking at least 5% of the particles blocked by the intermittent illumination blocker after the respective particles have previously passed through a first aperture of a series of 195 apertures of the intermittent illumination blocker when the series of apertures are positioned along the DCA.Attorney Docket No. 16978-0004.0030426. The method according to claim 24, wherein the blocking comprises blocking less than 20% of the particles blocked by the intermittent illumination blocker after the 2200 respective particles have previously passed through a first aperture of a series of apertures of the intermittent illumination blocker when the series of apertures are positioned along the DCA.

27. The method according to claim 21, wherein a dimension of the intermittent 205 illumination blocker along the DCA is greater than 1 cm and the at least one opaque portion of the intermittent illumination blocker includes at least a first blockable location and a second blockable location.

28. The method according to claim 27, wherein the intermittent illumination blocker 210 includes a rotating disc mechanical shutter optical chopper that includes a plurality of tunnels longer than 1cm via which SWR can pass during the first time spans associated with the plurality of SWR pulses, wherein the plurality of blockable locations comprises a continuum of blockable locations dispersed along a span longer than 1cm along each tunnel out of the plurality of tunnels.21529. The method according to claim 19, further comprising for each SWR pulse out of the plurality of SWR pulses: during at least the second timespan, blocking by at least one opaque object particles emitted from the ionization target as a result of the generation of the respective SWR pulse from propagating toward a light source 220 that emits the series of light pulses along an illumination propagation path between the ionization location and the light source, and intermittently moving the at least one opaque object away from the illumination propagation path to allow propagation of the series of light pulses along the illumination propagation path.225 30. The method according to claim 29, wherein the intermittently moving of the at least one opaque object away from the illumination propagation path includes allowing the light pulses to pass via one or more apertures of an optical chopper, wherein the one or more apertures of the optical chopper do not intersect the DCA.230 31. The method according to claim 19, further comprising deflecting away from the DCA particles that progressed past the intermittent illumination blocker along the DCA by inducing an electromagnetic field causing during the second timespan diversion of the propagation directions of particles that progressed past theAttorney Docket No. 16978-0004.00304intermittent illumination blocker during the first timespan toward an absorbent 2235 surface of the SWR system.

32. The method according to claim 19, further comprising deflecting away from the DCA particles that progressed past the intermittent illumination blocker along the DCA by a pressured gas discharger operable to emit during the second timespans 2240 gas emissions toward particles that progressed past the intermittent illumination blocker, thereby modifying at least one of trajectories or velocities of the particles that progressed past the intermittent illumination blocker.

33. The method according to claim 19, comprising for each SWR pulse out of a plurality 245 of SWR pulses: during the first timespan that includes the emission of the respective SWR pulse, providing clear passages along a plurality of DCAs, thereby permitting SWR of the respective SWR pulse to continue along the plurality of DCAs past an intermittent illumination blocking assembly that comprises at least the intermittent illumination blocker; and during the second timespan blocking the 250 plurality DCAs by opaque portions of the intermittent illumination blocking assembly that intersect the DCAs, thereby blocking propagation of particles emitted from the respective ionization target as a result of the generation of the respective SWR pulse from continuing along the plurality of DCAs.255

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