X-ray source with rotating liquid metal target

Abstract

The X-ray beam is generated in the interaction zone of the electron beam and the target, which is an annular layer of molten fusible metal in the annular channel of the rotating anode assembly. The channel has a surface profile that prevents the molten metal from tilting in the radial direction and in two directions along the axis of rotation. The liquid metal target forms a cylindrical surface due to the centrifugal force acting on it. The linear speed of the target is preferably higher than 80m / s; in the vacuum chamber, a variable membrane made of carbon nanotubes is installed in the X-ray beam path, and a protective screen with holes for the electron beam to enter and the X-ray beam to exit is arranged around the interaction zone. The technical result is that the X-ray source has increased power, brightness, life and ease of use.

Description

Technical Field

[0001] The present invention relates to a powerful high-brightness X-ray source with a liquid metal target and to a method for generating X-ray radiation based on electron deceleration. Background Art

[0002] High-intensity X-ray sources are used in fields such as microscopy, materials science, biomedicine and medical diagnostics, materials testing, crystal and nanostructure analysis, atomic physics, etc. They provide the analytical basis for modern high-tech manufacturing and are an important tool for the development of new materials and products.

[0003] In order to realize X-ray diagnostic methods, compact, powerful, high-brightness X-ray sources are required that are characterized by reliability and long lifetime.

[0004] According to a method known from patent RU2068210 published on October 20, 1996, the X-ray source is based on a decelerated beam of accelerated electrons focused on a rotating anode. The electron beam direction approaches the direction of the centrifugal force acting on the focusing anode. At the same time, the focusing temperature is maintained at a level above the melting point of the anode material. The device and method are intended to increase the power and brightness of the X-ray source.

[0005] However, the material of the rotating anode itself acts as a liquid metal target, which solidifies as it leaves the electron beam focus. Due to various forces acting on the melt, including gravity and surface tension, the shape of the rotating anode surface in the focus path region changes at a fairly rapid rate, which greatly limits the X-ray source lifetime.

[0006] This disadvantage is overcome by the method for generating X-ray radiation known from patent US6185277 published on February 6, 2001, which method comprises electron bombardment of a liquid metal target through a thin window in a closed loop through which the liquid metal circulates. The method and device for generating X-ray radiation allow to ensure that if the flow of the target in the region of the closed loop thin window is turbulent, contamination of the vacuum chamber is prevented. In addition, the possibility of using liquid metals is achieved, without being limited to using only those metals with a low saturation vapor pressure, which allows to optimize the target material to increase the X-ray radiation yield, David B et al. (2004) Liquid-metalanode x-ray tube SPIE 5196, 432-443, in: Laser-Generated and Other Laboratory X-Ray and EUV Sources, Optics, and Applications; (G Kyrala et al.; Eds.)

[0007] However, the flow system with MHD pumps that must provide head pressures in excess of 50 atm and target velocities of 40 m / s, and the closed-loop thin (thickness of a few microns), preferably diamond, windows add to the complexity of the device. Furthermore, the windows through which the electron bombardment occurs are exposed to mechanical, thermal and radiation loads, which limits the application of high-density electron beam currents on the target and the realization of high brightness of the X-ray source.

[0008] The method and device for generating X-ray radiation known from patent application US20020015473 published on February 7, 2002, using a liquid metal anode target in the form of a jet, largely overcomes this disadvantage.

[0009] X-ray sources of this type are characterized by compact dimensions and high stability of the X-ray radiation. Due to the large contact area between the liquid metal and the cooling surface of the heat exchange device, a faster reduction of the target temperature is achieved. In this way, it is possible to obtain a high-density electron beam energy flux on the target and ensure a very high spectral brightness of the X-ray source. The brightness of an X-ray source with a liquid metal jet target is therefore approximately one order of magnitude higher than an X-ray source with a solid rotating anode, as is known, for example, from patent US7697665 published on April 13, 2010, in which the liquid metal is used for heat transfer and as a hydrodynamic bearing.

[0010] However, the circulation system for spraying the liquid metal target is quite complex, including the gas pressure part and the high-pressure pump system for pumping the liquid metal. In addition, the problem of X-ray window contamination is a typical problem in the radiation source. The main sources of contamination are the nozzle and the trap of the liquid metal jet, from which the mist composed of droplets of target material spreads. This usually leads to a faster power drop of the radiation source, the higher the electron beam power.

[0011] The high brightness X-ray source known from patent US8681943 published on March 25, 2014 partially overcomes this disadvantage, wherein the X-ray beam generated by the electron bombardment of a jet liquid metal target leaves the vacuum chamber through an X-ray window. As target material, preferably low melting point metals are used, such as indium, tin, gallium, lead or bismuth or alloys thereof. The X-ray window, which is preferably made of beryllium foil, is provided with a protective film element and its evaporation cleaning system. This solution allows to increase the maintenance intervals of the X-ray source, which are required for replacing the X-ray window.

[0012] However, the temperature required for evaporative cleaning is high, for example, about 1000°C or higher for the evaporation of Ga and In, which makes the device more complicated. Summary of the invention

[0013] The technical problem to be solved by the present invention is to produce an X-ray source which does not have the above-mentioned disadvantages, has high power and brightness and is able to deeply suppress the contamination particles flowing out from the interaction zone of the electron beam and the target.

[0014] These objectives can be accomplished using an X-ray source comprising a vacuum chamber having an X-ray window for outputting an X-ray beam generated in the interaction region of an electron beam with a liquid metal target.

[0015] The X-ray source is characterized in that the liquid metal target is an annular layer of molten fusible metal located in an annular groove implemented in the rotating anode assembly, and the annular groove has a surface profile that prevents material of the liquid metal target from being ejected in both radial directions and along the rotation axis (10) of the rotating anode assembly.

[0016] Preferably, the annular layer of molten meltable metal is formed by centrifugal force on the surface of the annular groove, which surface faces the axis of rotation.

[0017] Preferably, the liquid metal target has a cylindrical surface whose axis of symmetry coincides with the axis of rotation, or has a surface slightly different from said surface, due to the effect of centrifugal forces.

[0018] Preferably, the target material is selected from fusible metals belonging to the group Sn, Li, In, Ga, Pb, Bi, Zn and / or alloys thereof.

[0019] Preferably, the temperature of the liquid metal target is lower than the melting point of the recess material.

[0020] Preferably, the linear velocity of the target is greater than 80 m / s.

[0021] Embodiments of the invention also include a membrane made of carbon nanotubes CNTs mounted in a vacuum chamber in the path of the X-ray beam.

[0022] Preferably, the CNT film is coated on the side out of the line of sight of the interaction zone.

[0023] Embodiments of the present invention also include a unit for replacing a CNT film that does not require depressurization of the vacuum chamber.

[0024] In an embodiment of the invention, further comprising a debris shield rigidly mounted around the interaction zone, the shield comprising a first opening for entry of the electron beam and a second opening for exit of the X-ray beam.

[0025] In an embodiment of the present invention, a slit gap separates the debris shield (27) from the rotating anode assembly.

[0026] In an embodiment of the invention, the debris shield is positioned opposite an angular sector of the target near the interaction zone.

[0027] Preferably, the debris shield (27) is circular.

[0028] In an embodiment of the invention, the rotating anode assembly is provided with a liquid cooling system.

[0029] In another embodiment, the size of the interaction region or the focal spot of the electron beam on the target is less than 50 μm.

[0030] Preferably, the axis of rotation can have any direction.

[0031] A method for generating X-ray radiation comprises bombarding a liquid metal target on the surface of a rotating anode assembly with electrons, and outputting an X-ray beam generated in an interaction region between the electron beam and the liquid metal target through an X-ray window of a vacuum chamber, the method comprising: forming the target into an annular layer of molten fusible metal on the surface of an annular groove implemented in the rotating anode assembly by centrifugal force, and preventing the molten fusible metal from being ejected in both radial directions and directions along the axis of rotation by a selected profile of the surface of the annular groove.

[0032] Preferably, the liquid metal target rotates at a linear speed greater than 80 m / s.

[0033] In an embodiment of the present invention, the X-ray window is protected from debris generated by X-ray radiation in the interaction zone by means of a CNT film installed in front of the X-ray window, and the CNT film is replaced as needed.

[0034] In an embodiment of the invention, debris particles are additionally inhibited from leaving the interaction zone by means of a debris shield rigidly mounted around the interaction zone, the shield having a first opening formed for entry of the electron beam and a second opening formed for exit of the X-ray beam.

[0035] Preferably, the rotating anode assembly is cooled by a liquid cooling system.

[0036] In an embodiment of the present invention, the method further comprises: terminating the electron bombardment of the liquid metal target before the rotation is slowed down or stopped, and cooling the target to a solid state.

[0037] In an embodiment of the present invention, the initial melting of the target is performed by electron bombardment and / or induction heating.

[0038] The technical result of the present invention is that the liquid metal target forming system is simplified, the possibility of using a higher power electron beam by increasing the target speed in the interaction zone is provided, the target material is optimized, the contamination of the exit window is eliminated, and on this basis, the possibility of improving the brightness, life and ease of operation of the X-ray source is realized.

[0039] The above and other objects, advantages and features of the present invention will become more apparent from the following non-limiting description of embodiments thereof provided by way of example with reference to the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0040] The essence of the invention is explained in the accompanying drawings, in which:

[0041] Figure 1 , Figure 2 , Figure 3 is a schematic diagram of an X-ray source according to an embodiment of the present invention.

[0042] Identical device elements are provided with the same reference numerals in the figures.

[0043] These drawings do not cover and otherwise do not limit the full scope of embodiments of the technical concept; they are merely provided as supporting material to demonstrate specific examples of its implementation. DETAILED DESCRIPTION

[0044] exist Figure 1 In the schematically illustrated embodiment of the present invention, the X-ray source comprises a vacuum chamber 1 having an X-ray window 2 for outputting an X-ray beam 3 generated in an interaction region 4 between an electron beam 5 and a target 6 due to electron bombardment.

[0045] The vacuum chamber 1 may be provided with a vacuum pump system, or be sealed.

[0046] The pressure-tight X-ray window 2 is preferably made of a thin film. Requirements for the exit window material include high transparency to the X-ray beam, i.e. low atomic number, and sufficient mechanical strength to separate the vacuum from the ambient pressure. Beryllium is widely used for such windows.

[0047] The X-ray source is characterized in that the target 6 is an annular layer of molten metal formed by the action of centrifugal force, located in an annular groove 7 implemented in the rotating anode assembly 8 of the electron gun 9. The annular groove 7 has a surface profile that prevents the material of the liquid metal target 6 exposed to the centrifugal force from being ejected in both radial directions and along the rotation axis 10.

[0048] The anode assembly 8, mounted on a shaft 11 having a stable axis of rotation 10, is rotated by an electric motor or another drive.

[0049] According to the invention, due to sufficiently high centrifugal forces, the target 6 has an axis of symmetry with Figure 1 The cylindrical or similar surface of the target is coincident with the rotation axis 10. At the same time, the material volume of the liquid metal target 6 does not exceed the volume of the annular groove 7.

[0050] To form the target 6, a portion of the rotating anode assembly is preferably implemented as a disk 12 having a peripheral portion in the form of an annular shield 13 or shoulder. At the same time, an annular groove 7 is implemented on the surface of the annular shield 13 facing the rotation axis 10.

[0051] like Figure 1 As shown, the surface of the groove 7 may be formed by a cylindrical surface facing the rotation axis 10 and two radial surfaces, without being limited to this option.

[0052] The melting point of the groove material is higher than the temperature of the liquid metal target, and the material of the liquid metal target preferably belongs to the group of non-toxic fusible metals, including Sn, Li, In, Ga, Pb, Bi, Zn and / or their alloys. Metals and their alloys with low vapor pressure are preferred, such as Ga and Sn and their alloys.

[0053] For example, a Galinstan alloy including 68.5 wt% Ga, 21.5 wt% In and 10 wt% Sn, having a melting point and a freezing point of -19°C, and being in a liquid state during the entire operation time can be used as the material of the target 6. A preferred material for the target may be an alloy including 95 wt% Ga and 5 wt% In, and having a melting point of 25°C and a freezing point of about 16°C.

[0054] For the operation of the X-ray source and its storage and transportation, the preferred target material may be solid in the non-operating state and needs to be heated, for example by the electron beam 5 itself, to be converted into the operating state. The following can be used as such a target material: Sn / In alloy with a melting point of 125°C, the alloy contains 66% In and 34% Bi, and the melting point and freezing point are about 72°C, but it is not limited to the above materials.

[0055] In order to increase the yield of X-ray radiation, it is preferred to use a target material with a high atomic number, such as a lead-based alloy.

[0056] In general, the proposed design of the rotating anode assembly provides a wide range of options for optimizing the target material.

[0057] In order to transform the target material into a molten state, the X-ray source may be provided with a compact induction heating system 14 to start melting the target material. The induction heating system 14 may be implemented to be able to stabilize the temperature of the target material within a predetermined optimal temperature range.

[0058] The rotary drive may be implemented as an electric motor, wherein the cylindrical rotor 15 is located in the vacuum chamber 1 and the rotary drive 11 and the stator 16 are located outside the vacuum chamber 1 .

[0059] In other embodiments of the present invention, the rotation drive may be implemented in the form of magnetic coupling, with an external drive half coupling and an internal idle half coupling.

[0060] In order to increase the magnetic adhesion, a portion of the vacuum chamber wall between the inner and outer parts 15, 16 of the rotary drive must be sufficiently thin and its material must have high electrical resistance and minimum magnetic permeability. Dielectric or stainless steel can be used as such a material. In the latter case, the wall thickness can be about 0.5 mm.

[0061] In a specific embodiment of the present invention, Figure 1The rotating anode assembly 8 with the rotor 15 is supported by a liquid metal hydrodynamic bearing. The bearing comprises a fixed shaft 17 and a liquid metal layer 18, such as gallium or its alloys, such as gallium indium tin (GaInSn), characterized by low viscosity and low melting point.

[0062] The rotor 15 is provided with an annular sliding seal 19 which surrounds a portion of the side surface of the fixed shaft 17 with a gap therebetween. The size of the gap between the sliding seal 19 and the fixed shaft 17 ensures that the shaft 11 with the rotor 15 rotates without leakage of the liquid metal 18. For this purpose, the gap width is 500 μm or less. Figure 1 The sliding seal 19 in the embodiment has a plurality of annular channels in which the liquid metal 18 accumulates. Like this, the sliding seal 19 plays the effect of a labyrinth seal ring.

[0063] The hydrodynamic bearing with liquid metal can withstand very high temperatures without vacuum contamination. The large contact area of ​​the bearing and the liquid metal lubrication ensures efficient heat dissipation from the rotating anode assembly 8 by means of a liquid coolant 20 (e.g. water) or by means of a coolant with a higher boiling point. For the liquid coolant 20 flowing through the heat exchanger of the cooling system (not shown), an inlet channel 21 and an outlet channel 22 are provided in the fixed shaft 17, wherein the flow direction of the coolant 20 is determined by Figure 1 The arrows in the figure indicate the

[0064] Therefore, in a preferred embodiment of the present invention, the rotating anode assembly 8 is provided with a liquid cooling system 20 .

[0065] exist Figure 1 In the illustrated embodiment of the invention, the liquid metal layer 18 serves as a sliding electrical contact between the rotating anode assembly 8 and the power supply 23 of the electron gun, as well as for heat transfer from the rotating target 6 to the liquid coolant 20 .

[0066] In other embodiments of the invention, liquid coolant 20 may be supplied directly into the rotating anode assembly 8. Magnetic fluid seals and / or sliding sleeves may be used to ensure the sealing of the rotating components. Various types of rolling element bearings may be used to support the rotating anode assembly.

[0067] Compared to X-ray sources with jet liquid metal anodes, the level of debris generated in the proposed design is significantly reduced, since it eliminates dense sources, such as nozzles and liquid metal jet traps, from which the mist consisting of target material droplets diffuses. Therefore, there is no need for a complex exit window evaporation cleaning system and its relatively frequent replacement. As a result, the proposed invention significantly improves the reliability and ease of operation of liquid metal target X-ray sources. The possibility of operation without additional debris suppression devices is realized.

[0068] However, during long-term operation of the liquid metal target X-ray source, the transparency of the X-ray window 2 may deteriorate due to vapor and clusters of target material deposited on its surface. Therefore, in order to ensure the longest possible operating period without complicated maintenance, a device for suppressing debris and protecting the X-ray window 2 may be additionally introduced.

[0069] exist Figure 2 , an embodiment of an X-ray source is schematically shown, wherein a film 24 made of carbon nanotubes, ie a CNT film, is installed in a vacuum chamber 1 in the path of an X-ray beam 3 .

[0070] The CNT film 24 is an optical element, preferably in the form of a free-standing CNT film, mounted on a frame or in a housing, 200 to 20 nm thick without being limited to this range, with low absorption of X-ray radiation, which may have coatings and / or fillers to extend its lifetime or impart other properties. Thus, the CNT film can be used as a solid substrate, onto which a coating is applied, such as a metal foil used as a spectral filter in the X-ray range.

[0071] Studies have shown that CNT films are not wetted by the target material and absorb it to a much lesser extent than most coating materials. Therefore, the CNT film can be applied, but preferably on the side out of sight of the interaction zone 4, i.e. less exposed to debris. At the same time, the CNT film 24 is preferably mounted flush with the X-ray window 2 to fully protect the X-ray window and the side of the CNT film 24 facing it from debris.

[0072] The CNT film 24, characterized by its high electrical conductivity, is preferably grounded to drain its static charge, which reduces the amount of debris deposited on the film.

[0073] In an embodiment of the present invention, in the X-ray tube 1, a compact unit 25 is installed to replace the CNT film after the transparency of the CNT film deteriorates to a predetermined value. Preferably, the unit 25 for replacing the CNT film does not require decompression of the vacuum chamber 1. For example, the unit 25 for replacing the CNT film of a rotary type can be started from the outside of the vacuum chamber 1, such as by driving via magnetic coupling, or by a gland, or by a micro-stepping motor installed in the vacuum chamber, but is not limited to these options.

[0074] It should be noted that for a long service life of the CNT film, the linear velocity of the target should be high enough, greater than 20 m / s, preferably greater than 80 m / s, so that the droplet fraction of the contaminating particles is mainly directed tangentially rather than towards the CNT film.

[0075] exist Figure 2 In the embodiment, the axis of rotation 10 is perpendicular to the drawing plane. The rotating anode assembly 8 with the target 6 is electrically connected to the power supply 23 of the electron gun via a sliding electrical contact 26 preferably located on the axis of rotation. Figure 1 ) in which the same equipment components are Figure 2 have the same item numbers as in the examples, their detailed descriptions are omitted.

[0076] exist Figure 3 , an X-ray source is schematically shown, wherein for additional suppression of debris particles leaving the rotating anode assembly, a debris shield 27 is introduced, which is rigidly mounted around the interaction zone 4. The debris shield comprises a first opening 28 formed for the electron beam 5 to enter the target 6 and a second opening 29 formed for the X-ray beam 3 to exit from the interaction zone 4 to the X-ray window 2.

[0077] The introduction of the debris shield 27 leads to a strong suppression of the debris particle flow from the interaction zone of the electron beam and the target. For a deeper debris suppression, the shield 12 is separated from the rotating anode assembly 8 by a slit gap. In this case, the focal spot is located in a substantially closed cavity formed by the groove 7 and the surface of the debris shield 27. It is possible for the debris particles (vapors, ions, clusters of the target material) generated by the X-ray radiation in the interaction zone 3 to leave from the cavity only through two small openings 28, 29, which ensures a low level of contamination in the X-ray source.

[0078] according to Figure 3 In the illustrated embodiment of the invention, the debris shield 12 may be located adjacent the interaction zone 4 opposite an angular sector of the target 3 and may be separated therefrom by a slit gap at the end.

[0079] In another embodiment, the debris shield 27 may be circular.

[0080] The first and second openings 28 , 29 in the shield 27 may be conical, which allows minimizing their cross-sectional area in order to more effectively retain the debris in the cavity between the debris shield 27 and the annular groove 7 .

[0081] For the same purpose, in an embodiment of the invention, the electron beam 5 and the X-ray beam 3 are oriented so that in the interaction zone 4 the direction of the linear velocity vector of the target which determines the main direction of the discharged droplets and fragment cluster portions is significantly different from the direction towards the openings 28, 29 in the shield 27.

[0082] The X-ray source with liquid metal target realized according to the invention has the advantages of modern cyclically operated X-ray tubes for tomography. The latter are characterized by a rotating anode with a heat capacity of about 5 MJ and an effective focal spot area of ​​less than 1 mm. 2 High (up to 100kW) operating power is achieved under the condition of

[0083] At the same time, the X-ray source realized according to the present invention has the advantages of an X-ray source with a jetted liquid metal anode, which allows operation with very small focal spot sizes, since there are no restrictions related to target melting. According to the above, in a preferred embodiment of the present invention, the high-brightness X-ray source is microfocused. In these embodiments of the present invention, an electrostatic and / or magnetic lens system located at the outlet of the electron gun 9 is used to form the electron beam 5, and the focal spot on the liquid metal target 6 has a size of 50 to 5 μm. Typically, focal spots with a size of less than 1 μm can be obtained. It should be noted that the presence of an electrostatic and / or magnetic lens system for microfocusing of the electron beam leads to larger cross-sectional dimensions of the electron gun 9, such as Figure 3 Shown schematically.

[0084] In an embodiment of the present invention, the linear velocity of the target is greater than 80 m / s, which is higher than known analogs. Higher target velocity allows operation at high (kW) levels of electron beam power and ensures more efficient dissipation of the power input into the target.

[0085] Due to the centrifugal force, the rotating target surface is stable and resilient to disturbances introduced by the electron beam. If the rotation speed is high enough, the electron beam interacts with the undisturbed "fresh" surface of the target, which ensures high spatial and energetic stability of the X-ray source. The higher the stability of the target surface, the higher the speed of the liquid metal target.

[0086] The proposed design of the anode assembly allows to achieve rotation frequencies of up to 200-400 rpm. This allows to achieve values ​​of liquid metal target linear velocity of up to 100-200 m / s in the interaction zone of the electron beam. At the same time, no high-pressure pump systems used in known analogues are required. This greatly simplifies the design of high-brightness and high-power X-ray sources.

[0087] The method of generating X-ray radiation is carried out as follows. The vacuum chamber 1 is evacuated to a temperature below 10°C using an oil-free pump system. -5 …10 -8 bar. In other embodiments, the vacuum chamber 1 may be sealed. The anode assembly 8 is rotated, for example, by a drive consisting of a stator 16 and a rotor 15. In an embodiment of the present invention, a fluid dynamic bearing is used for rotation, which includes a fixed shaft 17 and a liquid metal layer 18. Figure 1 .

[0088] Under the action of centrifugal force, the target 6 is formed as a molten metal layer belonging to the group Sn, Li, In, Ga, Pb, Bi, Zn and / or alloys thereof on the surface of the annular groove 7 of the rotating anode assembly 8 facing the rotation axis 10.

[0089] If necessary, the target material is pre-melted using a stationary induction heating system 14 .

[0090] The power supply 23 and liquid cooling system 20 of the electron gun are turned on. Using the power supply 23, a high voltage, typically between 40 kW and 160 kW, is applied between the cathode and anode located in the electron gun 9. This voltage potential is used to accelerate the electrons emitted by the cathode in the direction of the rotating anode assembly 8.

[0091] The electron beam 5 generated by the electron gun is used to electron bombard the liquid metal target 6. As a result of the electron bombardment, in the interaction zone 4 on the rotating liquid metal target 6, an X-ray beam 3 is generated which leaves the vacuum chamber through the X-ray window 2.

[0092] In order to achieve a high brightness of the X-ray source, the liquid metal target is bombarded with electrons using a micro-focusing electron gun, the size of the interaction zone or focal spot of which is in the range of 50 to 1 μm. In order to obtain a small size of the focal spot, focusing means in the form of electrostatic and / or magnetic and electromagnetic lenses are used in the cathode assembly 9 of the electron gun.

[0093] In order to reduce the hydrodynamic and thermal loads on the target surface in the interaction zone, it is rotated at a high linear speed of more than 80 m / s.

[0094] Preferably, heat from the rotating anode assembly 8 is dissipated using a liquid cooling system 20. In a particular embodiment of the invention, heat from the rotating anode assembly to the liquid coolant is transferred through the liquid metal layer 18 of the hydrodynamic bearing. Figure 1 .

[0095] In an embodiment of the present invention, heat dissipation may be achieved by radiation.

[0096] The X-ray source can be operated in a continuous or cyclic mode. In the latter case, the anode assembly 8 can be decelerated after each cycle to extend its life.

[0097] In an embodiment of the present invention, the electron bombardment of the target is terminated before the rotating anode assembly slows down or stops and the target cools to a solid state. This ensures easy operation of the X-ray source, in particular, it allows the rotation axis 10 of the anode assembly 8 to be freely oriented and the X-ray beam 3 to be output in any desired direction.

[0098] The next initial melting of the target is performed by electron bombardment and / or using an induction heating system.

[0099] During operation, the target temperature remains below the melting point of the annular groove material, which ensures long-term stable operation of the X-ray source.

[0100] When the CNT film transparency changes to a predetermined value, it is replaced using the replacement unit 25 .

[0101] In an embodiment of the method for generating X-ray radiation, debris particles are further inhibited from leaving the rotating anode assembly using a debris shield 27 rigidly mounted near the interaction zone 4. At the same time, the flow of debris particles from the interaction zone is restricted by the apertures of the two said openings.

[0102] Compared with X-ray sources that eject liquid metal anodes, the high-speed rotating liquid metal target produces much less debris. At the same time, the obvious benefit of the proposed design is that it does not require the use of highly complex evaporation X-ray window cleaning systems at temperatures of 1000°C or higher. All of this simplifies the design, increases the working life of the high-brightness X-ray source, and improves its maintenance and operating conditions.

[0103] The invention thus allows increasing the brightness of liquid metal target X-ray sources, simplifying their design, extending their lifetime and facilitating their operation.

[0104] Particular aspects of the subject matter disclosed herein are set forth in the following numbered clauses. Claims of the present disclosure or any divisional application may be directed to one or more of these aspects.

[0105] 1. An X-ray source, comprising a vacuum chamber having an X-ray window for outputting an X-ray beam generated in a focal spot of an electron beam on a liquid metal target, wherein the liquid metal target is a molten metal layer formed on a surface of an annular groove of a rotating anode assembly of an electron gun by centrifugal force (the surface facing the rotation axis).

[0106] 2. An apparatus according to clause 1, wherein the rotating anode assembly is a disk having a peripheral portion in the form of an annular barrier, whose inner surface faces the axis of rotation, and the annular groove has a surface profile that prevents material of the liquid metal target from being ejected in both radial directions and along the axis of rotation.

[0107] 3. Apparatus according to clause 1 or 2, wherein the rotating anode assembly is provided with a liquid cooling system.

[0108] 4. The device according to any of the preceding clauses, wherein the target material is selected from fusible metals belonging to the group Sn, Li, In, Ga, Pb, Bi, Zn and alloys thereof.

[0109] 5. Apparatus according to any of the preceding clauses, wherein the size of the electron beam focal spot on the target is less than 50 μm.

[0110] 6. The device according to any of the preceding clauses, wherein the linear velocity of the target is not less than 80 m / s,

[0111] 7. The device according to any of the preceding clauses, further comprising a film made of carbon nanotubes (CNT film) mounted in the vacuum chamber in the path of the outgoing X-ray beam.

[0112] 8. The apparatus of clause 7, wherein the CNT film is coated on a side outside the line of sight of the focal spot on the target.

[0113] 9. The device according to clause 7 or 8, further comprising a unit for replacing the CNT film, which does not require decompression of the vacuum chamber.

[0114] 10. A method for generating X-ray radiation, comprising bombarding a liquid metal target with electrons and outputting an X-ray beam generated at a focal spot of the electron beam on the liquid metal target through an X-ray window of a vacuum chamber, characterized in that the liquid metal target is formed by centrifugal force as a molten metal layer belonging to the group Sn, Li, In, Ga, Pb, Bi, Zn and alloys thereof on the surface of an annular groove implemented in a rotating anode assembly, the surface facing the axis of rotation.

[0115] 11. The method according to clause 10, wherein the electron bombardment of the liquid metal target is performed with a focal spot size of less than 50 μm.

[0116] 12. The method according to clause 10 or 11, wherein the liquid metal target rotates at a linear speed greater than 80 m / s.

[0117] 13. The method according to any of clauses 10-12, wherein the rotating anode assembly is cooled by a liquid cooling system.

[0118] 14. The method according to any of clauses 10-13, further comprising: terminating the electron bombardment of the liquid metal target before the rotation is slowed down or stopped, and cooling the target to a solid state.

[0119] 15. A method according to any of clauses 10-14, wherein the X-ray window is protected from debris by means of a CNT film mounted in front of the X-ray window, and the CNT film is replaced as needed.

[0120] 16. A shortwave high brightness radiation source, comprising a vacuum chamber with a rotating target assembly, which introduces a target in the form of a molten metal layer into an interaction zone, the layer being formed by centrifugal force on an annular groove surface of the rotating target assembly, which surface faces the axis of rotation, an energy beam focusing on the target in the interaction zone, and a debris suppression device in the path of the shortwave radiation beam, characterized in that the debris suppression device comprises: rotating the target at a high linear speed of more than 20 m / s, determining the main direction of the debris droplet portion leaving the interaction zone, leaving the shortwave radiation beam in a direction different from the main direction of the leaving droplet portion of the debris, a replaceable membrane made of carbon nanotubes (CNT membrane) with a high transparency of more than 50% in the wavelength range shorter than 20 nm, an aperture mounted in the line of sight area of ​​the interaction zone and completely overlapping the shortwave radiation beam.

[0121] 17. Apparatus according to clause 16, wherein the energy beam is a pulsed laser beam and the short-wave radiation is generated by laser plasma of the target material in the extreme ultraviolet (EUV) and / or soft X-ray and / or X-ray range.

[0122] 18. Device according to clause 16 or 17, wherein additionally debris suppression devices such as electrostatic and magnetic fields, shielding gas flows and foil traps are used.

[0123] 19. A device according to any of clauses 16-18, wherein the thickness of the CNT film is in the range of 20 to 100 nm.

[0124] 20. The device according to clause 16, wherein the CNT film acts as a window between a high vacuum compartment and a medium vacuum compartment of the vacuum chamber.

[0125] 21. Apparatus according to any of clauses 16 to 20, wherein the energy beam is an electron beam, the rotating target assembly acts as a rotating anode of an electron gun, and the short wave radiation is X-ray radiation generated by electron bombardment of the target.

[0126] 22. A shortwave radiation source comprising a vacuum chamber and a debris suppression device, wherein the vacuum chamber has a rotating target assembly, which uses a focused laser beam to introduce a target in the form of a metal molten layer into an interaction zone, and the useful shortwave radiation beam leaves the interaction zone, characterized in that the debris shield is rigidly mounted to surround the interaction zone, and the shield includes a first opening and a second opening, the first opening forming an entrance for the focused laser beam to enter the interaction zone, and the second opening forming an exit for the useful shortwave radiation beam to leave the interaction zone.

[0127] 23. The radiation source of clause 22, wherein a slit gap separates the shield from the rotating target assembly.

[0128] 24. A radiation source according to clause 22 or 23, wherein the shield is circular.

[0129] 25. The radiation source of any of clauses 22-24, wherein at least one of the two openings in the shield is conical.

[0130] 26. The radiation source of any of clauses 22-25, wherein the axis of the shortwave radiation beam makes an angle greater than 45 degrees with the target assembly rotation plane.

[0131] 27. A radiation source according to any of clauses 22 to 26, wherein a main direction of debris particles leaving the interaction zone is significantly different from a direction of arrival at at least one of the two openings in the shield.

[0132] 28. The radiation source of clause 27, wherein the target linear velocity vector in the interaction zone and at least one of the two openings are located on different sides of a plane passing through the interaction zone and the axis of rotation of the target assembly.

[0133] 29. The radiation source of clause 27 or 28, wherein the axis of at least one of the two openings in the shield makes an angle of less than 45 degrees with the target plane.

[0134] Thus, embodiments of the present invention provide for the generation of X-ray sources with deep suppression of debris, highest brightness and power, long lifetime, and excellent ease of use.

[0135] Although specific embodiments are disclosed herein, various changes and modifications may be made without departing from the scope of the invention. The present embodiments are to be considered in all respects as illustrative and not restrictive, and all changes coming within the meaning and equivalency range of the appended claims are to be embraced therein.

[0136] Industrial Applicability

[0137] The proposed X-ray source is intended for use in many applications including microscopy, material science, X-ray inspection of materials, biomedicine, and medical diagnostics.

Claims

1. An X-ray source, comprising a vacuum chamber (1), the vacuum chamber having an X-ray window (2) for outputting an X-ray beam (3) generated in an interaction region (4) between an electron beam (5) and a liquid metal target (6), wherein: The liquid metal target (6) is an annular layer of molten fusible metal located in an annular groove (7) implemented in a rotating anode assembly (8), a part of which is made in the form of a disk (12), the disk (12) having a peripheral portion in the form of an annular shield (13), and the annular groove is implemented on the surface of the annular shield facing the rotation axis (10), and due to the effect of centrifugal force, the liquid metal target (6) has a cylindrical surface with a symmetry axis coinciding with the rotation axis (10); and the annular groove (7) has a surface profile that prevents the material of the liquid metal target (6) from being ejected in the radial direction and in two directions along the rotation axis (10) of the rotating anode assembly (8); Also included is a debris shield (27) rigidly mounted around the interaction zone (4), the shield comprising a first opening (22) for entry of the electron beam (5) and a second opening (28) for exit of the X-ray beam (3), with a slit gap separating the debris shield (27) from the rotating anode assembly, wherein The linear velocity vector of the target in the interaction zone and at least one of the two openings are located on opposite sides of a plane passing through the interaction zone (4) and the axis of rotation (10), and The linear velocity of the target is high enough so that the droplet portion of the debris particles leaving the interaction zone (4) is directed primarily tangentially to the target surface and not towards the openings (22), (28) in the debris shield (27).

2. The X-ray source according to claim 1, wherein: The annular layer of molten meltable metal is formed by centrifugal force on the surface of the annular groove, which surface faces the axis of rotation (10).

3. An X-ray source according to any one of the preceding claims, wherein: The target material is selected from fusible metals belonging to the group Sn, Li, In, Ga, Pb, Bi, Zn or alloys thereof.

4. An X-ray source according to any one of the preceding claims, wherein: The temperature of the liquid metal target is lower than the melting point of the groove material.

5. The X-ray source according to any of the preceding claims, further comprising an induction heating system (14) configured to initiate melting of the target material.

6. An X-ray source according to any one of the preceding claims, wherein: The linear velocity of the target is greater than 80 m / s.

7. X-ray source according to any of the preceding claims, further comprising a membrane (24) made of carbon nanotubes CNTs, mounted in the vacuum chamber in the path of the X-ray beam (3).

8. An X-ray source according to any one of the preceding claims, wherein: The rotating anode assembly (8) is equipped with a liquid cooling system (20).

9. A method for generating X-ray radiation, comprising bombarding a liquid metal target (6) on the surface of a rotating anode assembly (8) with electrons, and outputting an X-ray beam (3) generated in an interaction region (4) between the electron beam (5) and the liquid metal target through an X-ray window (2) of a vacuum chamber (1), the method comprising: By centrifugal force, the target (6) is formed as an annular layer of molten fusible metal on the surface of an annular groove (7) implemented in a rotating anode assembly (8), a part of which is made in the form of a disk (12) having a peripheral portion in the form of an annular shield (13), and the annular groove is implemented on the surface of the annular shield facing the rotation axis (10), By means of the selected profile of the annular groove surface, the molten melt is not ejected in the radial direction and in both directions along the axis of rotation (10), and being rigidly mounted around the interaction zone (4) for debris suppression by means of a debris shield (27), said shield having a first opening (28) forming the entry of the electron beam (5) and a second opening (29) forming the exit of the X-ray beam (3), The liquid metal target is rotated at a linear speed greater than 80 m / s, wherein The linear velocity vector of the target in the interaction zone and at least one of the two openings are located on opposite sides of a plane passing through the interaction zone (4) and the axis of rotation (10).

10. The method according to claim 9, wherein: The X-ray window (2) is protected from debris generated by X-ray radiation in the interaction zone (4) by means of a CNT film (24) mounted in front of the X-ray window, and the CNT film is replaced as needed.

11. The method according to claim 9, wherein: The rotating anode assembly is cooled by a liquid cooling system.

12. The method according to claim 9, further comprising: The electron bombardment of the liquid metal target is terminated before the rotation slows down or stops, and the target is cooled to a solid state.

13. The method according to claim 9, wherein: Initial melting of the target is carried out by electron bombardment and / or induction heating.

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