Method and system for generating x-ray emission

Abstract

A method and system for generating X-ray emission. The method comprises the steps of generating an electron beam comprising one or more electron pulses using an electron source; directing the electron beam onto a target material; and generating coherent X-ray emission as a result of the interaction between the one or more electron pulses and the target material; wherein the electron beam comprises free electrons bunched with densities that comprise periodicities that are an integer multiple or a fraction of an interlayer spacing of the target material, or / and are an integer multiple or a fraction of a structure parameter of the target material.

Description

[0001] METHOD AND SYSTEM FOR GENERATING X-RAY EMISSION

[0002] FIELD OF INVENTION

[0003] The present invention relates broadly to a method and system for generating X-ray emission, in particular to a method and system for compact, ultrafast, coherent x-ray generation and applications.

[0004] BACKGROUND

[0005] Any mention and / or discussion of prior art throughout the specification should not be considered, in any way, as an admission that this prior art is well known or forms part of common general knowledge in the field.

[0006] Ultrafast pulses are crucial for studying rapid dynamic processes such as electronic transitions in petahertz (PHz) electronics. However, ultrafast visible / infrared pulses and ultrafast electron pulses do not have the penetrative power of X-rays, needed to explore deeper optoelectronic phenomena, motivating the development of compact, accessible, and efficient sources of ultrafast X-rays. Currently, Ultrafast X-rays are available only at free electron lasers (FELs) and synchrotron facilities, which are expensive to build and operate, have large footprints, and are not widely accessible.

[0007] Ultrafast X-rays, or ultrashort X-ray pulses, are femtosecond X-ray pulses with wavelengths occurring at interatomic distances. These pulses leverage the X-ray’s inherent ability to interact at the level of atomic nuclei and core electrons, capturing rapid changes in position of atoms or molecules during phase transitions, chemical reactions, and other transient processes in physics, chemistry, and biology. This capability makes ultrafast X-rays invaluable for studying PHz dynamic at atomic scales.

[0008] For instance, the study of PHz electronics requires ultrafast X-ray pulses to capture the rapid dynamics of electronic processes \ In the realm of advanced electronics, PHz electronics could significantly speed up computations and data processing, potentially by a thousand times compared to current state-of-the-art electronic devices4,5.

[0009] As mentioned above, currently, the most prominent sources of these ultrafast X-rays are large-scale X-ray free-electron lasers (XFELs) and synchrotrons. While these facilities produce bright and coherent ultrafast X-ray pulses which are ideal for the studies of ultrafast dynamics, they are enormous in sizes and thus are expensive to build and maintain. To give a sense of scale, such a facility would typically span the size of a football field, costs around $1 billion to build and about $100 million annually to maintain its operation. On the other hand, the usage cost is around $10,000 per hour, and the average waiting time for users is about 6 months. Due

[0010]

[0011] to these limitations, access to those facilities is generally restricted to specialized, mostly government-funded research projects.

[0012] Laboratory-scale alternatives for producing ultrafast X-ray pulses, such as high harmonic generation (HHGL10and inverse Compton scattering (ICS) sources11 12, provide more accessible options but come with certain limits. High harmonic generation occurs when intense laser pulses interact with gases (typically noble gases), causing the electrons in the atoms to undergo rapid acceleration and emit radiation in harmonics of the original laser frequency. This method generates coherent X-rays, primarily in the soft X-ray regime, reaching energies only up to a few keV13 14. Additionally, HHG relies on high-intensity lasers that often suffer from stability issues and require constant maintenance, making them less user-friendly. On the other hand, inverse Compton scattering (ICS) is a process where relativistic electrons collide with counterpropagating photons (typically from a laser), causing the photons to gain energy and shift into the X-ray regime. The upshift in photon energy, proportional to the square of the electron's energy, leads to X-rays ranging from keV to MeV. However, ICS requires precise synchronization between the laser and electron beam to achieve consistent X-ray pulses. ICS often struggles with maintaining precise synchronization between the laser and electron beam, which can affect the temporal precision of the X-ray pulses, leading to reduced brightness and pulse quality. Additionally, X-rays produced by ICS lack coherence, and like HHG, the dependence on high-intensity lasers subjects it to similar stability and maintenance issues. These limitations in lab-scale setups, including synchronization issues and reduced coherence and brightness, underscore the need for novel, compact, and coherent X-ray sources that eliminate the drawbacks of current existing methods.

[0013] Embodiments of the present invention seek to address at least one of the above needs.

[0014] SUMMARY

[0015] In accordance with a first aspect of the present invention, there is provided a method for generating X-ray emission, comprising the steps of:

[0016] generating an electron beam comprising one or more electron pulses using an electron source; directing the electron beam onto a target material; and

[0017] generating coherent X-ray emission as a result of the interaction between the one or more electron pulses and the target material;

[0018] wherein the electron beam comprises free electrons bunched with densities that comprise periodicities that are an integer multiple or a fraction of an interlayer spacing of the target material, or / and are an integer multiple or a fraction of a structure parameter of the target material.

[0019]

[0020] In accordance with a second aspect of the present invention, there is provided a system for generating X-ray emission, comprising:

[0021] a holder for a target material,

[0022] an electron source for generating an electron beam comprising one or more electron pulses and for directing the electron beam onto the target material on the holder to generate coherent X-ray emission as a result of the interaction between the one or more electron pulses and the target material;

[0023] wherein the electron source is configured such that the electron beam comprises free electrons bunched widr densities that comprise periodicities that are an integer multiple or a fraction of an interlayer spacing of the target material, or / and are an integer multiple or a fraction of a structure parameter of the target material.

[0024] BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Embodiments of the invention will be better understood and readily apparent to one of ordinary skill in the art from the following written description, by way of example only, and in conjunction with the drawings, in which:

[0026] FIG. 1 A shows a schematic drawing illustrating incident electron from ultrafast electron source knocking out a shell electron in low energy level (K-shell) of target sample atom, causing the shell electron to be ejected out the atom and results in a “hole”. Electron transition occurs when an electron in higher energy shell (L-shell) drops to lower energy shell to occupy the “hole”, leading to emission of X-ray photon with characteristic energy, which is captured by the X-ray detector.

[0027] FIG. IB shows a schematic drawing illustrating ultrafast free-electron penetrating van der Waals (vdW) material comprises multilayer heterostructure, while during the process the free-electron Coulomb fields are scattered off the periodic lattice, leading to emission of X-ray photon. The emitted X-ray photon energy and intensity is tunable via varying the incident electron energy, the vdW materials’ interlayer spacings and tilting angle of the structure. Coincidence detection is applied to reduce the signal-to-noise ratio (SNR) at the X-ray detector. In an example embodiment, the X-rays produced by multiple / many free electrons emitting via parametric X-ray radiation and coherent bremsstrahlung are also coherent as long as the free electrons are bunched with densities that contain periodicities that are an integer multiple or a fraction of the interlayer spacing of the target material, or / and are an integer multiple or a fraction of a structure parameter of the target material.

[0028] FIG. 1C shows a schematic drawing illustrating an X-ray emission mechanism similar to that in (b), the difference being to have ultrafast free-electron grazes the edge of the vdW material and emits X-ray (similar to Smith-Purcell radiation), which reduces incoherent scattering of the incident electron. Coincidence detection is also applied to reduce the SNR at the X-ray

[0029]

[0030] detector. The ultrafast electrons are envisioned to be of duration on the order of femtoseconds but can in fact be of any pulse duration, including milliseconds or zeptoseconds. The setups can be expanded into a complete imaging system by inserting the sample to be imaged in the path of the emitted X-ray and / or the scattered electrons (in addition to any other needed optics like additional X-ray focusing elements, monochromators or apertures). The X-ray detector can be replaced by a CCD camera (single pixel or multi-pixel) for this imaging system. If the sample to be imaged is placed in the path of the scattered electron beam, a device (e.g., fluorescent screen) should also be inserted that captures the electrons reflected from or transmitted through this sample. In an alternative set of realizations, the coincidence detection component can be removed, leading to potentially faster signal processing at the expense of a lower SNR.). In an example embodiment, the X-rays produced by multiple / many free electrons emitting via parametric X-ray radiation and coherent bremsstrahlung are also coherent as long as the free electrons are bunched with densities that contain periodicities that are an integer multiple or a fraction of the interlayer spacing of the target material, or / and are an integer multiple or a fraction of a structure parameter of the target material.

[0031] FIG. 2 shows a schematic diagram illustrating an imaging system according to an example embodiment.

[0032] FIG. 3 shows a flowchart illustrating a method for generating X-ray emission, according to an example embodiment.

[0033] DETAILED DESCRIPTION

[0034] Example embodiments of the present invention can provide a compact, tabletop source of coherent ultrafast X-rays which can address one or more of the above-mentioned needs by utilizing ultrafast electron pulses interacting with target materials, including crystalline materials such as van der Waals (vdW) materials, as well as amorphous substances in either solid or molten liquid form. With real-time energy tunability, embodiments of the present invention can provide unprecedented versatility to PHz spectroscopy and a wide range of other applications requiring ultrafast X-ray pulses.

[0035] In an example embodiment, a method for generating ultrafast coherent X-ray pulses in a compact tabletop setup is provided, without the need for high-power lasers. An example embodiment leverages recent advancements in ultrafast electron beam technology and tunable X-ray generation from free electron-driven van der Waals (vdW) materials. By directing ultrafast electron pulses through a vdW crystalline material, an example embodiment produces continuously tunable, narrow-band coherent ultrafast X-ray pulses. The short duration of these pulses ensures that the emitted X-rays can capture rapid transitions and transient phenomena with high temporal resolution. An example embodiment, by shooting pulsed electrons through crystalline materials to generate pulsed X-rays not only addresses the stability issues associated with traditional high-power lasers but also significantly enhances accessibility due to its compact size, providing a versatile and efficient tool for probing rapid electronic dynamics.

[0036]

[0037] Compared to other laboratory-based sources, such as High Harmonic Generation10(HHG) and Inverse Compton Scattering11 ,2(ICS) setups - both of which have flux ranges of around 10fi- 107photons / sec / eV - a source according to an example embodiment delivers a comparable flux of approximately 107photons / sec / eV, making it a complementary and practical alternative. However, unlike ICS, which produces incoherent X-ray pulses, a source according to an example embodiment generates coherent X-ray pulses. This coherence is crucial for high-precision applications, significantly improving measurement precision and expanding the range of potential applications15.

[0038] Furthermore, the integration of electron wave shaping18 18and edge configuration20techniques enhances the X-ray emission process, improving brightness, coherence, and flux, advantageously without the complexity and instability of high-power lasers or the synchronization challenges of ICS. These advancements make embodiments of the present invention superior in performance and versatility, ideal for cutting-edge research and industrial applications.

[0039] In an example embodiment, the X-rays produced from a single free electron emitting via parametric X-ray radiation and coherent bremsstrahlung are coherent (see e.g. Fig. IB). In an example embodiment, the X-rays produced by multiple / many free electrons emitting via parametric X-ray radiation and coherent bremsstrahlung are also coherent as long as the free electrons are bunched with densities that contain periodicities that are an integer multiple or a fraction of the interlayer spacing of the target material, or / and are an integer multiple or a fraction of a structure parameter of the target material. As will be appreciated by a person skilled in the art, structure parameters are measurable characteristics that describe the arrangement of the material at a microscopic or macroscopic level, including, but not limited to, the thickness, density gradient, refractive index. This coherence (absent from existing table-top X-ray tubes) can be exploited for coherent imaging techniques like phase contrast imaging and diffraction enhanced imaging, which have applications in medical imaging, industrial inspection, security scanning etc., but which typically require synchrotrons or free electron laser facilities. With the addition of time resolution (potentially picosecond (ps), femtosecond (fs), attosecond (as) or even zeptosecond (zs)) that example embodiments can provide, it becomes possible to realize ultrafast phase contrast imaging and ultrafast diffraction enhanced imaging, which uses these phase-sensitive imaging techniques to take snapshots of various processes or reactions as a function of time at extremely high time resolution (ps, fs, as, zs etc.), e.g. to compose a movie of that ultrafast process or reaction.

[0040] In an example embodiment, a method for generating X-ray pulses comprises directing a pulsed electron beam through a target material, which can be of various types including crystalline materials, van der Waals (vdW) materials, and amorphous substances in solid or molten liquid form; wherein the directed pulsed electron beam can be of any pulse duration, including milliseconds, nanoseconds picoseconds, femtoseconds, and beyond.

[0041] The development of a compact, coherent ultrafast X-ray source according to an example embodiment leverages the generation of ultrafast electron beams and tunable X-ray emission

[0042]

[0043] from free-electron-driven van der Waals (vdW) materials and their nanoscale heterostructures. Individually and independently, these technologies have only recently become viable due to rapid advancements of nano-scale devices.

[0044] More specifically, an ultrafast electron beam source for use in an example embodiment relies on field-emission technologies, which have emerged through the development of nanometrescale devices capable of quantum mechanical tunnelling under high electric fields21 23. This was made possible by advancements in materials engineering, particularly in the design of nanomaterials, a field that has only matured in the past decade. Previously, manufacturing such high-performance electron sources was technically infeasible.

[0045] On the other hand, example embodiments leverage free-electron-driven vdW materials for tunable X-ray generation24-27.

[0046] Tunable parametric X-ray generation from vdW materials28can optimize X-ray output while significantly reducing energy consumption. For context, a FELs facility produces approximately 4,900 kg of CO2 per hour due to its high-power demands, whereas our system produces million times lesser amount of CO2, i.e., 0.49 kg per hour. This drastic decrease in energy consumption not only lowers operational costs but also makes example embodiments of the present invention far more environmentally sustainable and increases its practicality for widespread use.

[0047] Coherent ultrafast X-rays from free-electron-driven crystalline materials according to example embodiments

[0048] An example embodiment provides a compact ultrafast pulsed X-ray source that operates by directing ultrafast electron pulses through crystalline materials, such as vdW crystals and their heterostructures. As these ultrafast electron pulses interact with the periodic lattice structure of the target crystals, they emit coherent, narrow-band ultrafast X-ray pulses. Notably, in an example embodiment, although the incident electron pulses are envisioned to be of femtosecond duration, they can actually be of any pulse duration, including milliseconds, nanoseconds, picoseconds, and beyond. This flexibility enhances the versatility of our technology, allowing it to be tailored for various application needs.

[0049] Furthermore, in an example embodiment, the spectral properties of the emitted X-rays pulses are fine-tuned by shaping ultrafast electron beams. The present inventors have recognized that shaping electrons in either spatial or temporal manners, which can significantly tailor the free-electron radiation29-33, can be applied in an example embodiment of the present invention. Particularly, the inventors have recognized that electron waveshaping, which can enhance the intensities and even manipulate the directionalities of the output X-rays, for bremsstrahlung29,34and parametric X-ray radiation (PXR)35, can be exploited in an example embodiment. By employing electron wave-shaping techniques, a method according to an example embodiment allows for precise control over the spatiotemporal profile of the generated ultrafast X-ray pulses. This control is achieved because tailoring the spatial and temporal characteristics of the electron pulses, was found by the present inventors to influence and shape the spatiotemporal

[0050]

[0051] profile of the resulting X-ray pulses. For instance, an example embodiment can create X-ray pulse trains where pulses arrive at regular intervals, or an example embodiment can be designed for more complex patterns, such as alternating long-duration and short-duration pulses. Additionally, an example embodiment can temporally shape the electron pulses to produce a variety of waveform patterns, such as chirped pulses, where the frequency changes over time; Gaussian pulses, which have a bell-shaped intensity profile; soliton pulses, which maintain their shape over long distances; square pulses, which have a constant intensity over their duration; triangular pulses, which linearly rise and fall; sine pulses, which have a characteristic oscillatory pattern; and even more intricate forms like double pulses, pulse bursts, and modulated pulses with varying amplitude or phase, which have been recognized by the present inventors to be exploitable for control of the X-ray emission characteristics. In the domain of spatially shaped electron pulses for use in example embodiments, all types of shaped beams can be used, such as Bessel electron waveforms, Laguerre-Gaussian beams, Hermite-Gaussian beams, Airy beams, Mathieu beams, Ince-Gaussian beams, vortex beams, optical bottle beams, Pearcey beams, and even more exotic forms like caustic beams, accelerating beams, and nondiffracting beams.

[0052] An example embodiment of an X-ray generation method allows the user to tune the X-ray photon energy in real-time, generating monochromatic ultrafast X-ray pulses across a wide energy range, from soft X-rays to the hard X-ray regime. While example embodiments may primarily utilize vdW crystals and their heterostructures, example embodiments are also applicable to other layered structures, including conventional crystals and nanostructured layered materials, such as two- and three-dimensional photonic crystals.

[0053] Achieving ultrafast pulsed X-rays according to example embodiments

[0054] Ultrafast X-ray Generation via Characteristic Radiation

[0055] By directing ultrafast electron beams at target materials, comprising crystalline materials such as conventional crystals, van der Waals (vdW) crystals and their heterostructures, as well as amorphous substances in solid or molten liquid form, an example embodiment generates X-rays through characteristic radiation (see FIG. 1A). When an incident electron e.g. 100 in an electron beam 103 from an electron gun 101 knocks out a shell electron 102 in a low energy level (e.g. K-shell) of the target atom 106, it creates a “hole.” An electron 108 from a higher energy shell (e.g. L-shell) then transitions to fill this vacancy, releasing an X-ray photon 112 with an energy characteristic of the specific atomic structure of the target material, detectable in an X-ray detector 114. This process under ultrafast electron beam excitation produces ultrafast characteristic X-ray pulses with fixed (non-tunable) photon energies, emitted isotropically. These X-rays pulses have narrow linewidths, down to a few electron volts (eV), useful for precise ultrafast diffraction experiments36.

[0056] Ultrafast X-ray generation via Bremsstrahlung Radiation

[0057] Bremsstrahlung radiation occurs when incident electrons are decelerated or deflected by the electric fields of atomic nuclei. As the electrons lose energy during this interaction, X-ray

[0058]

[0059] photons are emitted. This mechanism generates a continuous spectrum of X-rays, making bremsstrahlung radiation inherently broadband.

[0060] In an example embodiment, ultrafast electron pulses interact with the target material to produce broadband ultrafast X-ray pulses. In preferred embodiments high atomic number (Z) elements are used for bremsstrahlung radiation, such as tungsten (W), Molybdenum (Mo), as their intensity is higher than low Z elements. Although bremsstrahlung radiation is inherently broadband, the emitted X-ray pulses can be filtered or monochromatized using energy-selective X-ray optics, such as monochromators or zone plates, allowing for the generation of monochromatic X-ray pulses tailored to specific application needs.

[0061] Tunable Ultrafast X-ray Generation via Parametric X-ray Radiation (PXR)

[0062] In an example embodiment, the interaction between ultrafast electron pulses and crystalline materials, such as vdW heterostructures, is used to produce coherent ultrafast X-rays through parametric X-ray radiation (PXR)25,37process (see FIG. IB). By adjusting the incident electron pulse energy in the electron beam 120 and / or tilting the vdW crystal 122, the energy of the emitted X-ray pulses 124 can be precisely controlled in real time24,25. Additionally, the energy of the X-ray pulse 124 can be tuned by varying the interlayer spacing of the crystal 122. Changing interlayer spacing can be achieved by various methods, such as during fabrication, by applying external pressure, or by altering the crystal's 122 temperature in real time.

[0063] As mentioned above, in an example embodiment the X-rays 124 produced from a single free electron emitting via parametric X-ray radiation are coherent. In another example embodiment, the X-rays 124 produced by multiple / many free electrons emitting via parametric X-ray radiation are also coherent as long as the free electrons are bunched with densities that contain periodicities that are an integer multiple or a fraction of the interlayer spacing of the target material, or / and are an integer multiple or a fraction of the structure parameter of the target material such as the thickness, density gradient, refractive index.

[0064] In an example embodiment, incorporating vdW heterostructures as target materials, enables the emission of coherent, multicolor, ultrafast X-ray pulses. These multicolor pulses are particularly valuable for X-ray pump-probe experiments, offering a powerful tool for studying the dynamic properties of materials38. Traditionally, multicolor ultrafast X-ray pulses have only been produced in large-scale synchrotrons and free-electron laser facilities, where gigaelectron volt electrons interact with two undulators to emit two-color X-rays3'41. An example embodiment offers the first continuously tunable, coherent, ultrafast, multicolor X-ray source in a compact, tabletop system.

[0065] Enhancement of X-ray Emission through Edge Configuration

[0066] In an example embodiment, an edge configuration20is used for electron interaction with vdW heterostructures to optimize the ultrafast X-ray pulse generation. In this configuration, electrons graze the edge of the crystal (similar to Smith-Purcell radiation42,43), which extends the interaction length while minimizing electron scattering and X-ray absorption, as illustrated

[0067]

[0068] in FIG. 1C. By applying electron wave-shaping techniques in an example embodiment, a pulsed flat electron beam 140 is precisely directed to interact with the crystal 122 edge, generating X-rays 142 via electromagnetic field interactions. This approach in an example embodiment amplifies the brightness of parametric X-ray radiation (PXR) by over 1,000 times and increases the photon flux by over 100 times, resulting in a brightness of about 1013Photons / (sec mm2mrad20.1% BW) and a flux of about 1010Photons / sec, comparable to values achieved in some of the large-scale facilities like FELs. Moreover, with negligible electron scattering under the edge configuration, an example embodiment can achieve a spectral linewidth over 100 times narrower compared to electrons penetrating through the vdW crystals 122, reaching resolutions in the tens of millielectronvolts. These enhancements are advantageous for maximizing the performance of the compact, coherent, ultrafast X-ray source according to an example embodiment.

[0069] In example embodiments, coincidence detection at the detector 114 can play a critical role in identifying correlated events between emitted X-rays and incident electrons. This technique can be essential for enhancing data quality by significantly improving the signal-to-noise ratio (SNR), thereby enabling more accurate and precise measurements of the X-ray 112, 124, 142 pulses. To achieve this, example embodiments can employ various coincidence detection techniques tailored to specific application needs, including time-of-flight detection, which measures the time difference between the emission and detection of particles; correlated photon counting, which detects simultaneous photon events to reduce background noise; and electronphoton coincidence detection, which correlates the detection of electrons 103, 120, 140 from the electron gun 101 and X-rays 112, 114, 142 to preferably ensure high-fidelity data acquisition with high SNR.

[0070] Example embodiments can be extended into full imaging systems. With reference to FIG. 2, in one non-limiting example embodiment of such a system, generally indicated at numeral 200, the sample 201 to be imaged is positioned on a multi-degree of freedom sample holder 215 within the path of the emitted X-ray pulses 202 from the target materials 214 supported on a multi-degree of freedom target holder 216 and / or the scattered electron pulses 203. Additional components, such as monochromators 204, X-ray focusing elements 205, or apertures 206, can be integrated to refine the imaging process, as is understood by a person skilled in the art. Furthermore, the X-ray detector 207 can be replaced by a high-resolution CCD camera in an example embodiment, either single -pixel or multi-pixel, to capture detailed images. If the sample 201 is placed on a multi-degree of freedom sample holder 215 in the path of the scattered electron pulses 203, electron detector 208 such as electron energy spectrometer or fluorescent screen can be used to capture electrons reflected or transmitted through the sample 201. In the example embodiment, an electron gun 210 is used to generate and direct / focus the beam 212 of electron pulses. The electron gun 210 in an example embodiment comprises collimators, bunchers, chicanes, magnetostatic fields, electrostatic fields, time-varying electromagnetic fields, laser pulses, apertures, slits, biprisms, solenoids, quadrupoles, and diffracting crystals for spatiotemporally shaping the electron pulses. One or more of those

[0071]

[0072] elements may alternatively or additionally be provided external to the electron gun 210 in the path of the beam of electron pulses 12, together function as the electron source for generating and directing the beam 212 of electron pulses.

[0073] A compact, coherent ultrafast X-ray sources according to an example embodiment is designed to capture rapid electronic dynamics at petahertz (PHz) and higher frequencies. By synchronizing ultrafast X-ray pulses with electronic processes in PHz materials, the system can capture these rapid dynamics. In particular, the PHz material can be pumped with an ultrafast optical pulse and probed with a synchronized X-ray pulse, derived from the same ultrafast pulse, enabling observing electronic dynamics at PHz frequencies.

[0074] An example embodiment comprises a vacuum chamber equipped with X-ray detectors, X-ray reflective optics like monochromators, and a compact tabletop ultrafast electron gun capable of generating a pulsed electron beam. The electron gun is designed to spatiotemporally shape the electron beam pulse, allowing for precise control over the beam’s characteristics. For instance, the electron gun could include a cathode whose electron discharge is triggered by a picosecond or femtosecond laser pulse, resulting in the generation of a picosecond and femtosecond electron pulse from the cathode respectively. Before hitting the cathode, the laser pulse may have been spatiotemporally shaped by adding optical elements including but not limited to spatial light modulators, temporal light shapers and lenses. After leaving the cathode, the free electron pulse may be further spatiotemporally shaped by adding electron-shaping elements, including but not limited to collimators, bunchers, chicanes, magnetostatic fields, electrostatic fields, time-varying electromagnetic fields, laser pulses (single or multiple; such as counter-propagating linearly-polarized laser pulses of different central frequencies), apertures and slits, biprisms, solenoids, quadrupoles, and diffracting crystals. The target stage, which holds the target crystal, is aligned with the focused electron beam and equipped with rotational and tilting capabilities, enabling nanometer-scale precision in the x, y, and z axes. Varying input parameters such as the electron beam energy, crystal tilt angle, and varying the crystal properties allows adjusting the X-ray photon energy in real-time. To refine the emitted X-rays further, X-ray reflective optics such as monochromators can be used to filter the X-ray energies produced, enabling the generation of highly monochromatic X-rays pulses. An X-ray detector within the chamber monitors the emitted X-ray pulses, while coincidence detection can help identify correlated X-ray and electron events, further improving data quality and SNR. Various types of X-ray detectors can be used, such as charge coupled device (CCD) cameras, Gas ionization chambers, Energy-Dispersive X-ray Spectroscopy (EDS) detector, Wavelength-Dispersive X-ray Spectroscopy (WDS) detector, Soft X-ray Emission Spectrometer (SXES), Scintillation detectors, Photodiodes, etc. Tn an example embodiment, employing advanced techniques such as electron wave-shaping and edge configuration can enhance the brightness, coherence, and flux of the X-ray pulses, making the system comparable to large-scale facilities like free-electron lasers (FELs) but with reduced size and cost. The compact size, combined with its high performance, makes example embodiment suitable for a wide range of applications, including medical imaging, semiconductor inspection, security scanning, and materials characterization.

[0075]

[0076] Figure 3 shows a flowchart 300 illustrating a method for generating X-ray emission, according to an example embodiment. At step 302, an electron beam comprising one or more electron pulses is generated using an electron source. At step 304, the electron beam is directed onto a target material. At step 306, coherent X-ray emission is generated as a result of the interaction between the one or more electron pulses and the target material, wherein the electron beam comprises free electrons bunched with densities that comprise periodicities that are an integer multiple or a fraction of an interlayer spacing of the target material, or / and are an integer multiple or a fraction of a structure parameter of the target material.

[0077] The method may further comprise generating X-ray emission by characteristic radiation. The method may further comprise generating X-ray emission by bremsstrahlung.

[0078] The generating of the coherent X-ray emission may be by parametric X-ray radiation or / and coherent bremsstrahlung, as a result of the interaction between the electron pulses and the target material. The electron beam may be directed to graze an edge of the target material for generating the coherent X-ray emission as a result of electromagnetic field interactions between the electron pulses and the edge of the target material.

[0079] The method may comprise tuning an energy of the coherent X-ray emission by controlling one or more of a group consisting of a tilt angle of the target material relative to the electron beam, a collection angle for extracting the coherent X-ray emission relative to the electron beam, the target material and its atomic composition, and an energy of the electron beam. The method may comprise tuning the energy of the coherent X-ray emission by simultaneously controlling at least two of the group.

[0080] The coherent X-ray emission may comprise one or more coherent X-ray emission pulses and the electron pulses and the coherent X-ray emission pulses may have a duration of milliseconds, nanoseconds, picoseconds, femtoseconds, or shorter.

[0081] The method may comprise spatiotemporally shaping the electron pulses controlling intensities and directionalities of the coherent X-ray emission. The spatiotemporally shaping may comprise using one or more of a group consisting of collimators, bunchers, chicanes, magnetostatic fields, electrostatic fields, time-varying electromagnetic fields, laser pulses, apertures, slits, biprisms, solenoids, quadrupoles, and diffracting crystals.

[0082] The method may comprise applying coincidence detection using an X-ray detector for the purpose of, but not limited to, reducing a signal-to-noise ratio in a measurement of the coherent X-ray emission pulses.

[0083] The method may comprise using the X-ray emission and / or the electron pulses scattered at the target material as a probing beam for analysis of a sample.

[0084] The method may comprise generating a plurality of the pulses of free electrons using the electron source; directing the plurality of the pulses of bunched free electrons onto the target

[0085]

[0086] material; and generating a plurality of the coherent X-ray emission pulses as a result of the interaction between the plurality of the pulses of bunched free electrons and the target material; wherein a periodicity of the plurality of pulses of bunched free electrons is equal to an integer multiple or a fraction of the interlayer spacing of the target material, or / and equal to an integer multiple or a fraction of the structure parameter of the target material.

[0087] In one embodiment, a system for generating a X-ray emission is provided, comprising a holder for a target material; an electron source for generating an electron beam comprising one or more electron pulses and for directing the electron beam onto the target material on the holder to generate coherent X-ray emission as a result of the interaction between the one or more electron pulses and the target material; wherein the electron source is configured such that the electron beam comprises free electrons bunched with densities that comprise periodicities that are an integer multiple or a fraction of an interlayer spacing of the target material, or / and are an integer multiple or a fraction of a structure parameter of the target material.

[0088] The electron source may be configured such that the bunched free electrons further generate X-ray emission by characteristic radiation. The electron source may be configured such that the bunched free electrons further generate X-ray emission by bremsstrahlung.

[0089] The electron source may be configured such that the bunched free electrons generate the coherent X-ray emission by parametric X-ray radiation or / and by coherent bremsstrahlung, as a result of the interaction between the electron pulses and the target material. The electron source may be configured such that the electron beam is directed to graze an edge of the target material for generating the coherent X-ray emission as a result of electromagnetic field interactions between the electron pulses and the edge of the target material.

[0090] The system may be configured for tuning an energy of the coherent X-ray emission by controlling one or more of a group consisting of a tilt angle of the target material relative to the electron beam, a collection angle for extracting the coherent X-ray emission relative to the electron beam, the target material and its atomic composition, and an energy of the electron beam. The system may be configured for tuning the energy of the coherent X-ray emission by simultaneously controlling at least two of the group.

[0091] The coherent X-ray radiation may comprise one or more coherent X-ray emission pulses and the electron source may be configured such that the electron pulses and the coherent X-ray emission pulses have a duration of milliseconds, nanoseconds, picoseconds, femtoseconds, or shorter.

[0092] The electron source may be configured for spatiotemporally shaping the electron pulses for controlling intensities and directionalities of the coherent X-ray emission pulses. The electron source may comprise one or more of a group consisting of collimators, bunchers, chicanes, magnetostatic fields, electrostatic fields, time-varying electromagnetic fields, laser pulses, apertures, slits, biprisms, solenoids, quadrupoles, and diffracting crystals for the spatiotemporally shaping the electron pulses.

[0093]

[0094] The system may comprise a coincidence detection unit with an X-ray detector for the purpose of, but not limited to, reducing a signal-to-noise ratio in a measurement of the coherent X-ray emission pulses.

[0095] The system may be configured for using the X-ray emission and / or the electron pulses scattered at the target material as a probing beam for analysis of a sample.

[0096] The electron source may configured for generating a plurality of the pulses of bunched free electrons and for directing the plurality of the pulses of bunched free electrons onto the target material on the holder for generating a plurality of coherent X-ray emission pulses as a result of the interaction between the plurality of the pulses of bunched free electrons and the target material; wherein a periodicity of the plurality of pulses of bunched free electrons is equal to an integer multiple or a fraction of the interlayer spacing of the target material, or / and equal to an integer multiple or a fraction of the structure parameter of the target material.

[0097] Commercial Applications of example embodiments

[0098] The commercial potential of a compact, coherent ultrafast X-ray source according to an example embodiment includes, but extends beyond, academic research in petahertz spectroscopy, impacting multiple high-demand sectors. For example, in medical imaging, an example embodiment offers high-resolution tunable X-ray imaging of soft tissues, cells, and viruses. The ultrafast nature of X-rays from a source according to an example embodiment allows to capture rapid dynamics inside the cell. For industrial and semiconductor inspection, an example embodiment’s high-brightness and coherence can enable precise non-destructive testing (NDT), crucial for identifying defects in manufacturing. In security scanning, an example embodiment can enhance the detection of concealed threats with high-resolution imaging. Additionally, for materials characterization, the tunable X-ray source according to an example embodiment supports advanced analysis of structural, electronic, and optical properties, driving innovations in nanotechnology and materials science. An example embodiment not only matches the capabilities of large-scale facilities like synchrotrons and FELs but does so in a compact, cost-effective, sustainable format, making cutting-edge X-ray science accessible to a broader range of industries and research institutions.

[0099] Aspects of the systems and methods described herein, such as the control of the electron gun, the X-ray detector, the target material orientation and of other components of the described example embodiments may be implemented on computing device(s), including cloud-based computing device(s) and / or Internet-of-Things computing device(s), for example as functionality programmed into any of a variety of circuitry, including programmable logic devices (PLDs), such as field programmable gate arrays (FPGAs), programmable array logic (PAL) devices, electrically programmable logic and memory devices and standard cell-based devices, as well as application specific integrated circuits (ASICs). Some other possibilities for

[0100]

[0101] implementing aspects of the system include: microcontrollers with memory (such as electronically erasable programmable read only memory (EEPROM)), embedded microprocessors, firmware, software, etc. Furthermore, aspects of the system may be embodied in microprocessors having software -based circuit emulation, discrete logic (sequential and combinatorial), custom devices, fuzzy (neural) logic, quantum devices, and hybrids of any of the above device types. Of course the underlying device technologies may be provided in a variety of component types, e.g., metal-oxide semiconductor field-effect transistor (MOSFET) technologies like complementary metal-oxide semiconductor (CMOS) ), fin field-effect transistor (FinFET), gate-all-around field-effect transistor GAAFET, bipolar technologies like emitter-coupled logic (ECL), polymer technologies (e.g., silicon-conjugated polymer and metal-conjugated polymer-metal structures), mixed analog and digital, etc.

[0102] It will be appreciated by a person skilled in the art that numerous variations and / or modifications may be made to the present invention as shown in the specific embodiments without departing from the spirit or scope of the invention as broadly described. The present embodiments are, therefore, to be considered in all respects to be illustrative and not restrictive. Also, the invention includes any combination of features described for different embodiments, including in the summary section, even if the feature or combination of features is not explicitly specified in the claims or the detailed description of the present embodiments.

[0103] In general, in the following claims, the terms used should not be construed to limit the systems and methods to the specific embodiments disclosed in the specification and the claims, but should be construed to include all processing systems that operate under the claims. Accordingly, the systems and methods are not limited by the disclosure, but instead the scope of the systems and methods is to be determined entirely by the claims.

[0104] Unless the context clearly requires otherwise, throughout the description and the claims, the words "comprise," "comprising," and the like are to be construed in an inclusive sense as opposed to an exclusive or exhaustive sense; that is to say, in a sense of "including, but not limited to." Words using the singular or plural number also include the plural or singular number respectively. Additionally, the words "herein," "hereunder," "above," "below," and words of similar import refer to this application as a whole and not to any particular portions of this application. When the word "or" is used in reference to a list of two or more items, that word covers all of the following interpretations of the word: any of the items in the list, all of the items in the list and any combination of the items in the list.

[0105] References

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[0153]

Claims

CLAIMS1. A method for generating X-ray emission, comprising the steps of:generating an electron beam comprising one or more electron pulses using an electron source; directing the electron beam onto a target material; andgenerating coherent X-ray emission as a result of the interaction between the one or more electron pulses and the target material;wherein the electron beam comprises free electrons bunched with densities that comprise periodicities that are an integer multiple or a fraction of an interlayer spacing of the target material, or / and are an integer multiple or a fraction of a structure parameter of the target material.

2. The method of claim 1, further comprising generating X-ray emission by characteristic radiation.

3. The method of claim 2, further comprising generating X-ray emission by bremsstrahlung.

4. The method of any one of the preceding claims, wherein the generating of the coherent X-ray emission is by parametric X-ray radiation or / and coherent bremsstrahlung, as a result of the interaction between the electron pulses and the target material.

5. The method of claim 4, wherein the electron beam is directed to graze an edge of the target material for generating the coherent X-ray emission as a result of electromagnetic field interactions between the electron pulses and the edge of the target material.

6. The method of any one of the preceding claims, comprising tuning an energy of the coherent X-ray emission by controlling one or more of a group consisting of a tilt angle of the target material relative to the electron beam, a collection angle for extracting the coherent X-ray emission relative to the electron beam, the target material and its atomic composition, and an energy of the electron beam.

7. The method of claim 6, comprising tuning the energy of the coherent X-ray emission by simultaneously controlling at least two of the group.

8. The method of any one of the preceding claims, wherein the coherent X-ray radiation comprises one or more coherent X-ray emission pulses and the electron pulses and the coherent X-ray emission pulses have a duration of milliseconds, nanoseconds, picoseconds, femtoseconds, or shorter.

9. The method of any one of the preceding claims, comprising spatiotemporally shaping the electron pulses for controlling intensities and directionalities of the coherent X-ray emission.

10. The method of claim 9, wherein the spatiotemporally shaping comprises using one or more of a group consisting of collimators, bunchers, chicanes, magnetostatic fields, electrostatic fields, time-varying electromagnetic fields, laser pulses, apertures, slits, biprisms, solenoids, quadrupoles, and diffracting crystals.

11. The method of any one of the preceding claims, comprising applying coincidence detection using an X-ray detector for the purpose of, but not limited to, reducing a signal-to-noise ratio in a measurement of the coherent X-ray emission pulses.

12. The method of any one of the preceding claims, comprising using the X-ray emission and / or the electron pulses scattered at the target material as a probing beam for analysis of a sample.

13. The method of any one of the preceding claims, comprising:generating a plurality of the pulses of free electrons using the electron source;directing the plurality of the pulses of bunched free electrons onto the target material ; and generating a plurality of coherent X-ray emission pulses as a result of the interaction between the plurality of the pulses of bunched free electrons and the target material;wherein a periodicity of the plurality of pulses of bunched free electrons is equal to an integer multiple or a fraction of the interlayer spacing of the target material, or / and equal to an integer multiple or a fraction of the structure parameter of the target material.

14. A system for generating X-ray emission, comprising:a holder for a target material,an electron source for generating an electron beam comprising one or more electron pulses and for directing the electron beam onto the target material on the holder to generate coherent X-ray emission as a result of the interaction between the one or more electron pulses and the target material;wherein the electron source is configured such that the electron beam comprises free electrons bunched with densities that comprise periodicities that are an integer multiple or a fraction of an interlayer spacing of the target material, or / and are an integer multiple or a fraction of a structure parameter of the target material.

15. The system of claim 14, wherein the electron source is configured such that the bunched free electrons further generate X-ray emission by characteristic radiation.

16. The system of claim 15 , wherein the electron source is configured such that the bunched free electrons further generate X-ray emission by bremsstrahlung.

17. The system of any one of claims 14 to 16, wherein the electron source is configured such that the bunched free electrons generate the coherent X-ray emission by parametric X-rayradiation or / and by coherent bremsstrahlung, as a result of the interaction between the electron pulses and the target material.

18. The system of claim 17, wherein the electron source is configured such that the electron beam is directed to graze an edge of the target material for generating the coherent X-ray emission as a result of electromagnetic field interactions between the electron pulses and the edge of the target material.

19. The system of any one of claims 14 to 18, wherein the system is configured for tuning an energy of the coherent X-ray emission by controlling one or more of a group consisting of a tilt angle of the target material relative to the electron beam, a collection angle for extracting the coherent X-ray emission relative to the electron beam, the target material and its atomic composition, and an energy of the electron beam.

20. The system of claim 19, wherein the system is configured for tuning the energy of the coherent X-ray emission by simultaneously controlling at least two of the group.

21. The system of any one of claims 14 to 20, wherein the coherent X-ray radiation comprises one or more coherent X-ray emission pulses and the electron source is configured such that the electron pulses and the coherent X-ray emission pulses have a duration of milliseconds, nanoseconds, picoseconds, femtoseconds, or shorter.

22. The system of any one of claims 14 to 20, wherein the electron source is configured for spatiotemporally shaping the electron pulses for controlling intensities and directionalities of the coherent X-ray emission.

23. The system of claim 22, wherein the electron source comprises comprises one or more of a group consisting of collimators, bunchers, chicanes, magnetostatic fields, electrostatic fields, time-varying electromagnetic fields, laser pulses, apertures, slits, biprisms, solenoids, quadrupoles, and diffracting crystals for the spatiotemporally shaping the electron pulses.

24. The system of any one of claims 14 to 23, comprising a coincidence detection unit with an X-ray detector for the purpose of, but not limited to, reducing a signal-to-noise ratio in a measurement of the coherent X-ray emission pulses.

25. The system of any one of claims 14 to 24, configured for using the X-ray emission and / or the electron pulses scattered at the target material as a probing beam for analysis of a sample.

26. The system of any one of claims 14 to 25, wherein:the electron source is configured for generating a plurality of the pulses of bunched free electrons and for directing the plurality of the pulses of bunched free electrons onto the target material on the holder for generating a plurality of coherent X-ray emission pulses as a result of the interaction between the plurality of the pulses of bunched free electrons and the target material;wherein a periodicity of the plurality of pulses of bunched free electrons is equal to an integer multiple or a fraction of the interlayer spacing of tire target material, or / and equal to an integer multiple or a fraction of the structure parameter of the target material.

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