Linear accelerators including offset charged particle emitter

Abstract

Linear accelerators including an accelerating waveguide and an electron gun and methods of accelerating charged particles are disclosed. A linear accelerator can include an accelerating waveguide and an electron gun. The electron gun can be configured to emit an electron beam into the accelerating waveguide such that an axis of the electron beam is angled relative to an axis of the accelerating waveguide.

Description

Attorney Docket No. P323377.WO.01Client Docket No. 2024-022- WO1LINEAR ACCELERATORS INCLUDING OFFSET CHARGED PARTICLE EMITTERCROSS-REFERENCE TO RELATED APPLICATION(S)

[0001] This application claims priority to U.S. Provisional Patent Application No. 63 / 789,680 filed 16 April 2025, the entire disclosure of which is hereby incorporated by reference.FIELD

[0002] The described embodiments relate generally to linear accelerators, and more particularly, to linear accelerators including an offset charged particle emitter and methods of accelerating charged particles.BACKGROUND

[0003] Linear accelerators (also referred to as “LINACS”) can be used to accelerate electrons, ions, or other charged particles by subjecting them to oscillating electric potentials in a series of chambers or cavities. LINACs are widely used for a variety of tasks in a broad range of applications, including radiotherapy (RT). industrial applications such as non-destructive testing (NDT), security inspection (SI), electron beam processing (e.g, sterilization, polymer curing, and the like), and the like. In an X-ray application, a LINAC can generate an accelerated electron beam, which can strike a conversion target at the end of an accelerating channel to produce X-rays. LINACs can be used for many other applications including, but not limited to, electronic chip manufacturing and the like. The present disclosure focuses on electron beam LINACs. However, the teachings of the present disclosure can be used with LINACs for accelerating any charged particles for any application.14917-1653-5176' 1Attorney Docket No. P323377.WO.01Client Docket No. 2024-022- WO1SUMMARY

[0004] An aspect of the present disclosure relates to a linear accelerator, the linear accelerator including an accelerating waveguide and an electron gun. The electron gun can be configured to emit an electron beam into the accelerating waveguide such that an axis of the electron beam is angled relative to an axis of the accelerating waveguide.

[0005] In one or all examples, the axis of the electron beam can be angled relative to the axis of the accelerating waveguide by 5° or less. In one or all examples, the axis of the electron beam can be angled relative to the axis of the accelerating waveguide by 1° or more.

[0006] In one or all examples, the linear accelerator can further include a lens. The lens can include a magnetic coil. The magnetic coil can be configured to align the electron beam with the axis of the accelerating waveguide. In one or all examples, the lens can be disposed between the electron gun and the accelerating waveguide. In one or all examples, the lens can include anon-magnetic tube. The magnetic coil can be wrapped around the non-magnetic tube. In one or all examples, the lens can be a focusing lens. In one or all examples, the focusing lens can be configured to focus the electron beam.

[0007] In one or all examples, the axis of the electron beam can be angled relative to the axis of the accelerating waveguide such that a back-streaming electron beam is directed towards an anode of the electron gun.

[0008] Another aspect of the present disclosure relates to a linear accelerator including an electron source and an accelerating structure. The electron source can include a cathode configured to emit an electron beam, and an anode including an opening through which the electron beam can be directed. The accelerating structure can be configured to accelerate the electron beam. The electron source and the accelerating structure can be positioned such that the electron beam can be emitted through the opening into the accelerating structure and a back-streaming electron beam emitted from the accelerating structure can be directed towards the anode outside of the opening.

[0009] In one or all examples, the anode can include a sensor. The sensor can be configured to measure characteristics of the back-streaming electron beam. In one or all examples, the anode can be configured to be convectively cooled.

[0010] In one or all examples, the linear accelerator can further include a lens. The lens can include a steering coil which can be configured to align the electron beam emitted by the24917-1653-5176' 1Attorney Docket No. P323377.WO.01Client Docket No. 2024-022- WO1electron source with an axis of the accelerating structure. In one or all examples, the lens can be between the electron source and a buncher of the accelerating structure.

[0011] In one or all examples, the electron beam can be angled relative to an axis of the accelerating structure at an angle in a range from 1° to 5°.

[0012] In yet another aspect of the present disclosure, a method of accelerating charged particles includes emitting charged particles in a first direction parallel to a first axis, steering the charged particles to a second direction parallel to a second axis, the second axis extending at an angle oblique to the first axis, accelerating the charged particles, and directing the charged particles at a target. At least a portion of the charged particles can back-stream in a third direction opposite the second direction and parallel to the second axis.

[0013] In one or all examples, the charged particles can be emitted through an opening in an anode of an electron source and the portion of the charged particles that back-stream in the third direction can be directed toward the anode outside the opening.

[0014] In one or all examples, the method can further include actively cooling the anode of the electron source.

[0015] In one or all examples, the steering of the charged particles to the second direction can include angling the charged particles in a range from 1° to 5°. In one or all examples, the charged particles can be steered to the second direction after being emitted and before being accelerated.

[0016] In one or all examples, the method can further include measuring the portion of the charged particles that back-stream in the third direction.

[0017] In a still further aspect of the present disclosure, a bracket can include a first surface, and a second surface angled relative to the first surface. The first surface can be configured to be coupled to a charged particle source. The second surface can be configured to be coupled to an accelerator section.

[0018] In one or all examples, the second surface can be angled relative to the first surface in a range from 1° to 5°. The bracket can be configured to maintain an evacuated enclosure between the charged particle source and the accelerator section. The bracket can be configured to house a charged particle steering magnet.34917-1653-5176' 1Attorney Docket No. P323377.WO.01Client Docket No. 2024-022- WO1BRIEF DESCRIPTION OF THE DRAWINGS

[0019] The disclosure will be readily understood by the following detailed description in conjunction with the accompanying drawings, wherein like reference numerals designate like structural elements, and in which:

[0020] FIG. l is a schematic view of a linear accelerator.

[0021] FIG. 2 is a schematic view of a portion of a linear accelerator.

[0022] FIG. 3A is a cross-sectional view of a portion of a linear accelerator.

[0023] FIG. 3B is a cross-sectional view of a portion of the linear accelerator of FIG. 3 A.

[0024] FIG. 4 is a schematic view of a linear accelerator including a bracket between a charged particle source and accelerator sections.44917-1653-5176' 1Attorney Docket No. P323377.WO.01Client Docket No. 2024-022- WO1DETAILED DESCRIPTION

[0026] Reference will now be made in detail to representative embodiments illustrated in the accompanying drawings. The following descriptions are not intended to limit the embodiments to one preferred embodiment. To the contrary, it is intended to cover alternatives, modifications, and equivalents as can be included within the spirit and scope of the described embodiments as defined by the appended claims.

[0027] The following disclosure relates to linear accelerators that can be used to accelerate electrons, ions, or other charged particles. Linear accelerators can be used to generate high-energy beams of charged particles. In one or all examples, the linear accelerators can be used in X-ray systems, such as X-ray sources used to generate X-rays. Representative applications for X-ray sources and systems include, but are not limited to, imaging, medicine, diagnostics, radiology, radiotherapy, radiography and tomography, and a range of industrial X-ray technologies. The present disclosure focuses on electron beam LINACs, which can be used in X-ray systems. However, the teachings of the present disclosure can be used with LINACs for accelerating any charged particles for any applications.

[0028] Conventional linear accelerators can produce back-streaming electron beams, which travel back through an accelerating waveguide. The back-streaming electron beams can strike an electron source. Electrons within the back-streaming electron beam can bombard the cathode, cause additional, excessive heating of the cathode, and can in some instances cause material of the cathode to evaporate, which can lead to performance issues and can cause failures in the electron source and / or the linear accelerator.

[0029] The present disclosure relates to linear accelerators, charged particle systems, and methods of accelerating charged particles that include an offset charged particle emitter configured to reduce or prevent back-streaming electron beams from hitting components of the charged particle emitter, such as a cathode. The linear accelerators, charged particle systems, and methods of accelerating charged particles of the present disclosure can improve the efficiency and effectiveness of linear accelerators and can increase the longevity and durability of the charged particle emitter and the linear accelerators.

[0030] In order to realize these and other advantages, in one or all examples, a linear accelerator can include an accelerating waveguide and a charged particle source coupled together. The charged particle source can be configured to emit a beam of charged particles (e.g., an electron beam) into the accelerating waveguide such that an axis of the charged54917-1653-5176'1Attorney Docket No. P323377.WO.01Client Docket No. 2024-022- WO1particle beam is angled relative to an axis of the accelerating waveguide. The charged particle beam can be accelerated by the accelerating waveguide into a target surface. For example, in an X-ray application, the charged particle beam can include an electron beam, which is accelerated by the accelerating waveguide towards an X-ray target to generate an X-ray beam. As the charged particles contact the target surface, at least a portion of the charged particle beam can backstream into the accelerating waveguide towards the charged particle source. By angling the charged particle source relative to the accelerating waveguide, the portion of back-streaming charged particles that strike the charged particle source can be reduced or eliminated. This reduces heating and damage to components of the charged particle source caused by the back-streaming charged particle beam, and can improve the functioning, durability, and longevity of the charged particle source and the linear accelerator.

[0031] In one or all examples, a linear accelerator can include an electron source and an accelerating structure. The electron source can include a cathode and an anode, the cathode can be configured to emit an electron beam. The anode can include an opening (e.g., the anode can have a washer-like shape) through which the electron beam is directed towards the accelerating structure. The accelerating structure can be configured to accelerate the electron beam. The electron source and the accelerating structure can be positioned such that the electron beam can be emitted through the opening in the anode into the accelerating structure and a back-streaming electron beam emitted from the accelerating structure can be directed towards the anode outside of the opening. In other words, the opening in the anode can selectively allow a forward-streaming beam of electrons from the electron source to enter the accelerating structure, without allowing the back-streaming beam of electrons from the accelerating structure to enter the electron source. The positioning of the electron source at an angle relative to the accelerating structure is configured to allow the back-streaming electron beam to strike the anode outside the opening of the anode. The anode can act as a net capturing the electrons within the back-streaming beam to prevent electrons from unintentionally striking components of the electron source, such as the cathode. This prevents the cathode from overheating, evaporating, and the like, which improves the functioning, durability, and longevity of the electron source and the linear accelerator.

[0032] In one or all examples, a method of accelerating charged particles can include emitting charged particles, steering the charged particles, accelerating the charged particles, and directing the charged particles at a target. The charged particles can be emitted in a first direction parallel to a first axis. The charged particles can be steered from the first direction to 64917-1653-5176'1Attorney Docket No. P323377.WO.01Client Docket No. 2024-022- WO1a second direction parallel to a second axis. The second axis can extend at an angle oblique to the first axis. In an X-ray application, the charged particles can include electrons, and directing the charged particles at the target can produce X-rays. At least a portion of the charged particles can back-stream in a third direction opposite the second direction and parallel to the second axis after the charged particles contact the target. Steering the charged particles allows for the first axis (e.g., an axis of a charged particle source) to be offset from the second axis (e.g., an axis of an accelerating waveguide), which can prevent the back-streaming charged particles from heating and / or damaging components of the charged particle source. This reduces heating and damage to components of the charged particle source caused by the back-streaming charged particles, and can improve the functioning, durability, and longevity of a charged particle source and a linear accelerator using the method of the present disclosure.

[0033] These and other examples are discussed below with reference to FIGS. 1 through 4. However, those skilled in the art will readily appreciate that the detailed description given herein with respect to these figures is for explanatory purposes only and should not be construed as limiting. Furthermore, as used herein, a system, a method, an article, a component, a feature, or a sub-feature including at least one of a first option, a second option, or a third option should be understood as referring to a system, a method, an article, a component, a feature, or a sub-feature that can include one of each listed option (e.g., only one of the first option, only one of the second option, or only one of the third option), multiple of a single listed option (e.g., two or more of the first option), two options simultaneously (e.g., one of the first option and one of the second option), or combination thereof (e.g., two of the first option and one of the second option).

[0034] FIG. 1 is a schematic view of a linear accelerator 100. The linear accelerator 100 can generate and accelerate charged particles, such as electrons, ions, or the like. The linear accelerator 100 can include a radio frequency (RF) source 102 coupled to accelerator sections 103 (e.g., an accelerator section 110 and a buncher 116) by a waveguide 104, a circulator 106, and an input RF coupler 108. The RF power source 102 can be a magnetron, a klystron, or the like. The waveguide 104 can be an RF transmitting waveguide. The circulator 106 can be a high power circulator and can prevent reflected power from propagating in a direction back towards the RF source 102. The input RF coupler 108 can supply RF power to the accelerator sections. The input RF coupler 108 can match an impedance of an external and internal RF circuit to minimize power reflections at an operating RF frequency. The waveguide 104 can include multiple sections and can couple the RF source 102 to the circulator 106 and couple 74917-1653-5176' 1Attorney Docket No. P323377.WO.01Client Docket No. 2024-022- WO1the circulator 106 to the input RF coupler 108. The RF source 102 can provide RF power through the waveguide 104. the circulator 106, and the input RF coupler 108 to the accelerator sections of the linear accelerator 100.

[0035] In the example illustrated in FIG. 1, the linear accelerator 100 includes two accelerator sections 103, an accelerator section 110 and a buncher 116. The accelerator section 110 can be a standing wave accelerator. The buncher 116 can accelerate and bunch incident charged particles. Charged particles from the buncher 116 can be provided to the accelerator section 110, which can provide further acceleration and energy to the charged particles.

[0036] The linear accelerator 100 can further include a charged particle source 112. The charged particle source 112 can be positioned at an end of the linear accelerator 100, such as adjacent to the buncher 116. In one or all examples, the charged particle source 112 can emit electrons. However, the charged particle source 112 can emit ions or other charged particles. The charged particle source 112 can be an electron gun, an electron emitter, or the like. The charged particle source 112 can be configured to emit an electron beam 114 into the buncher 116. The electrons emitted by the charged particle source 112 forming the electron beam 114 may be focused, bunched, and accelerated by the buncher 116. The bunched and accelerated electrons of the electron beam can then be further accelerated and energized by the accelerator section 110. The accelerator section 110 can emit the electron beam 114 toward a conversion target 118. The electron beam 114 striking the conversion target 118 can produce X-rays in one or all examples.

[0037] The accelerator sections 103 (including the buncher 116 and the accelerator section 110) can define an acceleration axis for the electron beam 114. The charged particle source 112 can emit charged particles with an axis that is offset or angled relative to the acceleration axis of the accelerator sections 103. As will be discussed in detail below, this offset or relative angle can prevent back-streaming charged particles, such as particles reflected after impacting the conversion target 118, from entering the charged particle source 112 and damaging components of the charged particle source 112, such as a cathode. This configuration can improve the functioning, durability, and longevity of the charged particle source 112 and the linear accelerator 100.

[0038] The linear accelerator 100 can further include an external magnetic system 120. The external magnetic system 120 can be or can include a focusing solenoid and / or a permanent periodic magnet (PPM) system. The external magnetic system 120 can further include steering coils, bending magnets, etc., for correction of beam positioning inside the linear accelerator 84917-1653-5176' 1Attorney Docket No. P323377.WO.01Client Docket No. 2024-022- WO1100, or at its exit via an electron beam window or towards the conversion target 118. The linear accelerator 100 can be a standing wave linear accelerator system in which the external magnetic system 120 can generally be omitted, or a traveling wave linear accelerator system in which the external magnetic system 120 can generally be included.

[0039] FIG. 2 is a schematic view of a portion of a linear accelerator 200. The linear accelerator 200 can be the same as. or similar to, the linear accelerator 100 discussed above with respect to FIG. 1. In one or all examples, the linear accelerator 200 can include a portion of the linear accelerator 100, such as a portion of the linear accelerator 1 0 that produces charged particles, which are sent to the accelerator sections 103 (<?.g, the charged particle source 112 and related components). FIG. 2 illustrates a portion of the linear accelerator 100, 200 in which an electron beam 214 is generated by a charged particle source 212 and directed towards accelerating sections, such as the buncher 116.

[0040] The linear accelerator 200 can include a charged particle source 212. The charged particle source 212 can include an electron gun, an electron emitter, or the like. Although the charged particle source 212 is discussed in the context of emitting electrons, the charged particle source 212 can emit ions or other charged particles. The charged particle source 212 may be configured to emit an electron beam 214 through an opening 226 in a steering magnet 228 and through a lens 220 to an accelerating structure, such as the buncher 116 discussed above in reference to FIG. 1. A portion of the charged particles within the electron beam 214 can be rebounded for a variety of reasons (e.g., by a collision with a target surface, such as the conversion target 118), creating a back-streaming beam 224 of charged particles.

[0041] In one or all examples, the charged particle source 212 can emit charged particles within the electron beam 214 in a first direction parallel to a first axis. The electron beam 214 can travel downstream through the opening 226 in the steering magnet 228. The steering magnet 228 can include steering coils that can steer the charged particles in the electron beam 214 from the first direction to a second direction parallel to a second axis. The steering coils of the steering magnet 228 can generate a magnetic field, which can steer the charged particles of the electron beam 214. The second axis can extend at an angle oblique to the first axis. The first axis can be an axis of the charged particle source 212 and the second axis can be an axis of, or parallel to, the steering magnet 228 (e.g., the second axis can be parallel to an axial axis of the steering magnet 228), the accelerator sections 103 (e.g, the second axis can be parallel acceleration axes or longitudinal axes of the buncher 116 and the accelerator section 110), or the like.94917-1653-5176' 1Attorney Docket No. P323377.WO.01Client Docket No. 2024-022- WO1

[0042] The steering magnet 228 can redirect the electron beam 214 such that the first axis of the electron beam 214 exiting the charged particle source 212 is angled relative to the second axis of the electron beam 214 exiting the steering magnet 228 and entering the accelerator sections (e.g., the buncher 116). The first axis and the second axis can be angled relative to one another at an angle of about 0.5° or more, about 1° or more, about 2° or more, about 3° or more, about 15° or less, about 10° or less, about 6° or less, about 5° or less, about 4° or less, in a range from about 0.5° to about 15°, in a range from about 2° to about 10°. in a range from about 1° to about 5°, in a range from about 0.5° to about 6°, or the like.

[0043] After striking the target, a portion of the charged particles of the electron beam 214 can rebound, creating the back-streaming beam 224. The back-streaming beam 224 can travel in a third direction opposite the second direction. The third direction of the back-streaming beam 224 can be parallel to the second axis (e.g, parallel to an axial axis of the steering magnet 228, parallel to acceleration axes or longitudinal axes of the buncher 116 and the accelerator section 110, or the like).

[0044] By angling the first axis relative to the second axis, the charged particle source 212 can be offset from the back-streaming beam 224. As described above, the back-streaming beam 224 can include a portion of the charged particles electron beam 214 that rebounds through the accelerator sections after impacting a target surface. If the back-streaming beam 224 enters the charged particle source 212, the back-streaming beam 224 can damage components of the charged particle source 212 (e.g.. a cathode of the charged particle source 212). As illustrated in FIG. 2, the back-streaming beam 224 can be directed towards a back-streaming beam collector 230. In one or all examples, the back-streaming beam collector 230 can be omitted, and the back-streaming beam 224 can be directed towards portions of the charged particle source 212 outside of an opening through which the electron beam 214 exits. For example, the back-streaming beam 224 can be directed towards portions of an anode of the charged particle source 212 outside of an opening in the anode through which the electron beam 214 passes. As such, damage to the charged particle source 212 can be prevented, improving the functioning, durability, and longevity of the charged particle source 212 and the linear accelerator 200. By steering the electron beam 214 with the steering magnet 228. the electron beam 214 can be directed into an accelerating structure at an appropriate angle for accelerating the electron beam 214.

[0045] In one or all examples, the linear accelerator 200 can further include a lens 220. The lens 220 can be a focusing lens. In one or all examples, the lens 220 can be configured to focus 104917-1653-5176'1Attorney Docket No. P323377.WO.01Client Docket No. 2024-022- WO1the electron beam 214. The lens 220 can be positioned between the charged particle source 212 and a downstream accelerating structure (e.g., the accelerating sections 103, discussed with respect to FIG. 1). The lens 220 can be positioned in any appropriately effective position in the system including between the steering magnet 228 and the accelerating structure, between the charged particle source 212 and the steering magnet 228, or the like. The lens 220 can be optional and can be omitted in one or all examples. The lens can be coupled to any of the charged particle source 212, the steering magnet 228. or the accelerating structure.

[0046] In one or all examples, the linear accelerator 200 can include a back-streaming beam collector 230. The back-streaming beam collector 230 can be positioned in-line with an axis of the back-streaming beam 224 such that the back-streaming beam collector 230 can collect the charged particles from the back-streaming beam 224. The back-streaming beam collector 230 can measure a current of the back-streaming beam 224. The back-streaming beam collector can further prevent damage to the charged particle source 212 by preventing the charged particles in the back-streaming beam 224 from striking the charged particle source 212. The back-streaming beam collector 230 can be placed in a position outside of, or offset from, the first axis so that the back-streaming beam collector 230 does not block the electron beam 214 emitted by the charged particle source 212.

[0047] The steering magnet 228 can have dimensions and can be positioned relative to components of the linear accelerator 200 (e.g., the lens 220) to provide sufficient steering of the electron beam 214. A distance 232 between a surface of the steering magnet 228 distal the lens 220 and proximal the charged particle source 212 can be in a range from about 1.8 inches to about 2.7 inches, in a range from about 2 inches to about 2.5 inches, or about 2.25 inches. The steering magnet 228 can have a length 234 in a direction parallel to the second axis (e.g., in a longitudinal or axial direction of the steering magnet 228) in a range from about 1.6 inches to about 2.4 inches, in a range from about 1.8 inches to about 2.2 inches, or about 2 inches.

[0048] FIGS. 3 A and 3B are cross-sectional views of portions of a linear accelerator 300. The linear accelerator 300 can be the same as, or similar to, the linear accelerators 100, 200, discussed above with respect to FIGS. 1 and 2. In one or all examples, the linear accelerator 300 can include a portion of the linear accelerator 100, such as a portion of the linear accelerator 100 that produces charged particles, which are sent to the accelerator sections 103 (e.g., the charged particle source 112 and related components). FIG. 3 illustrates a portion of the linear accelerator 100, 200, 300 in which an electron beam 314 is generated by a charged particle source 312 and directed towards accelerating sections, such as the buncher 116.114917-1653-5176' 1Attorney Docket No. P323377.WO.01Client Docket No. 2024-022- WO1

[0049] The linear accelerator 300 can include a charged particle source 312. The charged particle source 312 can include an electron gun, an electron emitter, or the like. Although the charged particle source 312 is discussed in the context of emitting electrons, the charged particle source 312 can emit ions or other charged particles. The charged particle source 312 can be configured to emit an electron beam 314. The charged particle source 312 can include a cathode 332 and an anode 334. A high voltage can be applied between the cathode 332 and the anode 334 such that an electron beam 314 is emitted by the cathode 332 towards the anode 334. The anode 334 can, in some or all examples, include an opening through which the electron beam 314 is directed. In one or all examples, the anode 334 can have a washer-like shape. For example, the anode 334 can include a flat plate with a hole or opening in the middle of the anode 334. The charged particle source 312 can emit the forward electron beam 314 in a first direction parallel to a first axis. The first axis can be a first axis of the charged particle source 312, can be parallel to a longitudinal axis of the charged particle source 312, or can be defined by a line between the cathode 332 and a center of the anode 334 (e.g., a center of the opening in the anode 334).

[0050] The electron beam 314 emitted by the charged particle source 312 can travel downstream from the charged particle source 312 through an opening 326 in a steering magnet 328. The steering magnet 328 can steer the charged particles in the electron beam 314, for example, by applying a magnetic field to the charged particles. Thus, the charged particles of the electron beam 314 traveling in the first direction emitted from the charged particle source 312 can be steered to a second direction parallel to a second axis 340. The second axis 340 can extend at an angle 342 oblique to the first axis. In one or all examples, the second axis 340 can be parallel to a longitudinal or axial axis of the steering magnet 328.

[0051] The steering magnet 328 can redirect the electron beam 314 such that the first axis of the electron beam 314 exiting the charged particle source 312 is angled relative to the second axis 340 of the electron beam 314 exiting the steering magnet 328 and entering the accelerator sections (e.g., the buncher 116). The first axis and the second axis 340 can be angled relative to one another at an angle 342 of about 0.5° or more, about 1° or more, about 2° or more, about 3° or more, about 15° or less, about 10° or less, about 6° or less, about 5° or less, about 4° or less, in a range from about 0.5° to about 15°, in a range from about 2° to about 10°, in a range from about 1° to about 5°, in a range from about 0.5° to about 6°, or the like.124917-1653-5176' 1Attorney Docket No. P323377.WO.01Client Docket No. 2024-022- WO1

[0052] The steering magnet 328 can include a tube 327, which can be formed from a nonmagnetic material, and which defines the opening 326. Steering coils 329 can be coupled to the tube and can be formed from magnetic materials. In one or all examples, the steering coils 329 can include a number of turns in a range from about 16 to about 24, in a range from about 18 to about 22, or about 20. The steering coils 329 can operate at an amperage of about 16 mA or less, about 20 mA or less, 24 mA or less, or the like.

[0053] The linear accelerator 300 can include one or more lenses 320. The lenses 320 can be, for example, focusing lenses, which can focus the electron beam 314. As illustrated in FIGS.3A and 3B, the lenses 320 can be positioned adjacent to, outside of, or surrounding the steering magnet 328. The lenses 320 can encircle or surround at least a portion of the steering magnet 328. The lenses 320 can include a magnetic material and can apply a magnetic field or electrostatic field to the electron beam 314 to focus the electron beam 314. The linear accelerator 300 can include a dielectric core 336, which can be disposed between the lenses 320 and the steering magnet 328 (e.g., between the lenses 320 and each of the coils 329 and the tube 327). Outer surfaces of the steering magnet 328 can be coupled to inner surfaces of the dielectric core 336. In one or all examples, the lenses 320 can include one or more coils that include a number of turns in a range from about 120 to about 180, in a range from about 135 to about 165, or about 150. The coils of the lenses 320 can operate at an amperage of about 7 A or less, about 9 A or less, 11 A or less, or the like.

[0054] In one or all examples, the electron beam 314 travels downstream from the charged particle source 312 through the steering magnet 328. The electron beam 314 can continue to travel downstream through an accelerating structure (e.g., the accelerating sections 103, including the buncher 116 and the accelerating section 110, described above with respect to FIG. 1), which can be configured to accelerate the electron beam 314. The electron beam 314 can be emitted from the accelerating structure towards a target. After colliding with the target, at least a portion of the charged particles of the electron beam 314 can rebound creating a back-streaming electron beam 324. The back-streaming electron beam 324 can travel back through the accelerating structure towards the charged particle source 312 in a third direction parallel to the second axis 340. The third direction can be opposite the second direction and can be parallel to the second axis 340.

[0055] In one or all examples, the charged particle source 312 can be angled relative to the second axis 340 and axes of the accelerating structure (e.g., longitudinal or axial axes of the134917-1653-5176' 1Attorney Docket No. P323377.WO.01Client Docket No. 2024-022- WO1accelerating sections 103, including the buncher 116 and the accelerating section 110) such that the back-streaming electron beam 324 does not reenter the charged particle source 312. For example, the back-streaming electron beam 324 can be directed towards portions of the anode 334 of the charged particle source 312 outside the opening in the anode 334 through which the electron beam 314 is emitted. The charged particle source 312 can be positioned such that the back-streaming electron beam 324 strikes outside the opening within the anode 334 and is prevented from traveling through the opening of the anode 334 to strike the cathode 332. As such, damage to the charged particle source 312, such as the cathode 332, can be prevented, improving the functioning, durability, and longevity of the charged particle source 312 and the linear accelerator 300. By steering the electron beam 314 with the steering magnet 328, the electron beam 314 can be directed into an accelerating structure at an appropriate angle for accelerating the electron beam 314.

[0056] The back-streaming electron beam 324 can be directed towards the anode 334. The charged particles of the back-streaming electron beam 324 can heat the anode 334. As such, the anode 334 can include components to cool the anode 334. For example, the anode 334 can be actively cooled, such as through coolant supplied to the anode 334 through cooling channels. In one or all examples, the anode 334 can be convectively cooled. In one or all examples, the anode 334 can include a sensor configured to measure characteristics of the back-streaming electron beam 324, such as a current supplied by the back-streaming electron beam 324.

[0057] FIG. 3B is a cross-sectional view of a portion of the linear accelerator 300 taken along the axis 346 illustrated in FIG. 3 A. The cross-sectional view shows the electron beam 314 traveling downstream in the second direction from the charged particle source 312 towards the accelerating structure. Continuing with FIGS. 3A and 3B, the back-streaming electron beam 324, traveling in the third direction from the accelerating structure towards the charged particle source 312 is illustrated as being outside of and offset from the electron beam 314. Within the steering magnet 328, the electron beam 314 and the back-streaming electron beam 324 can be offset from one another, which allows the back-streaming electron beam 324 to strike the anode 334 outside the opening through which the electron beam 314 is emitted. Once the electron beam 314 passes through the steering magnet 328. the axes of the electron beam 314 and the back-streaming electron beam 324 can be parallel to one another and can be parallel to an axis of the steering magnet 328.144917-1653-5176' 1Attorney Docket No. P323377.WO.01Client Docket No. 2024-022- WO1

[0058] A vacuum or evacuated enclosure can be defined between the various components of the linear accelerator 300 and remaining portions of the accelerating structure. For example, the charged particle source 312 can be sealed to the steering magnet 328 (e.g., the tube 327 of the steering magnet 328), and the steering magnet 328 can be sealed to the accelerating structure (e.g., the buncher 116 or accelerating sections 103, discussed above with respect to FIG. 1 and not separately illustrated in FIGS. 3A and 3B). The linear accelerator 300 can include a flange 338, which can be used to seal the steering magnet 328 (e.g.. the tube 327 of the steering magnet 328) to the accelerating structure. This allows for a vacuum to be maintained between the portions of the linear accelerator 300 illustrated in FIGS. 3 A and 3B and remaining portions of the accelerating structure.

[0059] FIG. 4 is a schematic view of a linear accelerator 400 that includes a bracket 406 between a charged particle source 402 and accelerator sections 404. The linear accelerator 400 can be the same as, or similar to, the linear accelerators 100, 200, 300, discussed above with respect to FIGS. 1 through 3B, and can include the same or similar components to the linear accelerators 100, 200, 300. For example, the charged particle source 402 can be the same as or similar to the charged particle sources 112, 212, 312 and the accelerator sections 404 can be the same as or similar to the accelerator sections 103 (including the buncher 116 and the accelerator section 110). FIG. 4 specifically illustrates the bracket 406, which can be used in any of the examples described herein to control the relative positions of the charged particle source 402 and the accelerator sections 103.

[0060] As illustrated in FIG. 4, the bracket 406 can be positioned between the charged particle source 402 and the accelerator sections 404. The bracket 406 can be a fixture, shim, or any other feature attachable to the charged particle source 402 and the accelerator sections 404 to control positions of the charged particle source 402 relative to the accelerator sections 404. The bracket 406 can be used to angle the charged particle source 402 relative to the accelerator sections 404. For example, a surface of the bracket 406 proximal the charged particle source 402 can be angled relative to a surface of the bracket 406 proximal the accelerator sections 404. The surface of the bracket 406 proximal the charged particle source 402 can be angled relative to the surface of the bracket 406 proximal the accelerator sections 404 at an angle of about 0.5° or more, about 1° or more, about 2° or more, about 3° or more, about 15° or less, about 10° or less, about 6° or less, about 5° or less, about 4° or less, in a range from about 0.5° to about 15°, in a range from about 2° to about 10°, in a range from about 1° to about 5°, in a range from about 0.5° to about 6°, or the like. However, other angles are possible. The bracket 154917-1653-5176'1Attorney Docket No. P323377.WO.01Client Docket No. 2024-022- WO1406 can control both the spacing between the charged particle source 402 and the accelerator sections 404 and the relative angle between the charged particle source 402 and the accelerator sections 404. The bracket 406 can be replaceable, and different brackets 406 can be used to alter or adjust the spacing and angles between the charged particle source 402 and the accelerator sections 404.

[0061] The bracket 406 can be used to house various components of the linear accelerator 400, or the components can be housed within the charged particle source 402 and / or the accelerator sections 404. For example, one or more steering magnets (e.g., the steering magnets 228, 328), lenses (e.g., the lenses 220, 320), sensors (e.g., the back-streaming beam collector 230). or the like can be housed or positioned within the bracket 406.

[0062] The bracket 406 can be mountable to the charged particle source 402 and the accelerator sections 404. A vacuum or evacuated enclosure can be defined between the bracket 406 and each of the charged particle source 402 and the accelerator sections 404. This allows for a vacuum to be maintained between the charged particle source 402 and the accelerator sections 404. In one or all examples, the bracket 406 can include components the same as or similar to the flange 338, which can be used to seal the bracket 406 to the charged particle source 402 and the accelerator sections 404.

[0063] By including the bracket 406 between the charged particle source 402 and the accelerator sections 404, the charged particle source 402 can be angled relative to the accelerator sections 404. Specifically, an axis of the charged particle source 402 can be angled relative to an axis of the accelerator sections 404. This can be used to offset the charged particle source 402 from a back-streaming beam, preventing damage to the charged particle source 402 by the back-streaming beam, and improving the functioning, durability, and longevity of the charged particle source 402 and the linear accelerator 400.

[0064] The foregoing description, for purposes of explanation, used specific nomenclature to provide a thorough understanding of the described embodiments. However, it will be apparent to one skilled in the art that the specific details are not required in order to practice the described embodiments. Thus, the foregoing descriptions of the specific embodiments described herein are presented for purposes of illustration and description. They are not intended to be exhaustive or to limit the embodiments to the precise forms disclosed. It will be apparent to one of ordinary skill in the art that many modifications and variations are possible in view of the above teachings.164917-1653-5176' 1

Claims

Attorney Docket No. P323377.WO.01Client Docket No. 2024-022- WO1CLAIMSWhat is claimed is:

1. A linear accelerator comprising:an accelerating waveguide; andan electron gun configured to emit an electron beam into the accelerating waveguide such that an axis of the electron beam is angled relative to an axis of the accelerating waveguide.

2. The linear accelerator of claim 1, wherein the axis of the electron beam is angled relative to the axis of the accelerating waveguide by 5° or less.

3. The linear accelerator of claim 2, wherein the axis of the electron beam is angled relative to the axis of the accelerating waveguide by 1° or more.

4. The linear accelerator of claim 1, further comprising a lens comprising a magnetic coil configured to align the electron beam with the axis of the accelerating waveguide.

5. The linear accelerator of claim 4, wherein the lens is disposed between the electron gun and the accelerating waveguide.

6. The linear accelerator of claim 4, wherein:the lens comprises anon-magnetic tube; andthe magnetic coil is wrapped around the non-magnetic tube.

7. The linear accelerator of claim 4, wherein the lens is a focusing lens configured to focus the electron beam.

8. The linear accelerator of claim 1, wherein the axis of the electron beam is angled relative to the axis of the accelerating waveguide such that a back-streaming electron beam is directed towards an anode of the electron gun.

9. A linear accelerator comprising:an electron source comprising:174917-1653-5176' 1Attorney Docket No. P323377.WO.01Client Docket No. 2024-022- WO1a cathode configured to emit an electron beam; andan anode comprising an opening through which the electron beam is directed; andan accelerating structure configured to accelerate the electron beam;wherein:the electron source and the accelerating structure are positioned such that the electron beam is emitted through the opening into the accelerating structure and a back- streaming electron beam emitted from the accelerating structure is directed towards the anode outside of the opening.

10. The linear accelerator of claim 9, wherein the anode comprises a sensor configured to measure characteristics of the back-streaming electron beam.

11. The linear accelerator of claim 9, wherein the anode is configured to be convectively cooled.

12. The linear accelerator of claim 9, further comprising a lens comprising a steering coil configured to align the electron beam emitted by the electron source with an axis of the accelerating structure.

13. The linear accelerator of claim 12, wherein the lens is between the electron source and a buncher of the accelerating structure.

14. The linear accelerator of claim 9, wherein the electron beam is angled relative to an axis of the accelerating structure at an angle in a range from 1° to 5°.

15. A method of accelerating charged particles comprising:emitting charged particles in a first direction parallel to a first axis;steering the charged particles to a second direction parallel to a second axis, the second axis extending at an angle oblique to the first axis;accelerating the charged particles; and184917-1653-5176' 1Attorney Docket No. P323377.WO.01Client Docket No. 2024-022- WO1directing the charged particles at a target, wherein at least a portion of the charged particles back-stream in a third direction opposite the second direction and parallel to the second axis.

16. The method of claim 15, wherein:the charged particles are emitted through an opening in an anode of an electron source; andthe portion of the charged particles that back-stream in the third direction are directed toward the anode outside the opening.

17. The method of claim 15, further comprising actively cooling the anode of the electron source.

18. The method of claim 15, wherein steering the charged particles to the second direction comprises angling the charged particles in a range from 1° to 5°.

19. The method of claim 15, wherein the charged particles are steered to the second direction after being emitted and before being accelerated.

20. The method of claim 15, further comprising measuring the portion of the charged particles that back-stream in the third direction.

21. A bracket for a linear accelerator comprising:a first surface configured to be coupled to a charged particle source; anda second surface configured to be coupled to an accelerator section, wherein the second surface is angled relative to the first surface.

22. The bracket of claim 21, wherein the second surface is angled relative to the first surface in a range from 1° to 5°.

23. The bracket of claim 21, wherein the bracket is configured to maintain an evacuated enclosure between the charged particle source and the accelerator section.194917-1653-5176' 1Attorney Docket No. P323377.WO.01Client Docket No. 2024-022- WO124. The bracket of claim 21, wherein the bracket is configured to house a charged particle steering magnet.204917-1653-5176'1

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