Systems, Devices, and Methods for Ion Beam Modulation

Abstract

System, device, and method embodiments relate to an ion beam source system. The ion source is configured to provide a beam of negative ions to a tandem accelerator system downstream of the ion source, and a modulator system connected to an extraction electrode of the ion source is configured to bias the extraction electrode for a duration sufficient to maintain acceleration voltage stability of the tandem accelerator system. In one embodiment, the ion source is configured to generate negative hydrogen ions.

Description

Technical Field

[0001] (Cross - Reference to Related Applications) This application claims priority to U.S. Provisional Application No. 63 / 044,314, filed Jun. 25, 2020, entitled “SYSTEMS, DEVICES, AND METHODS FOR ION BEAM MODULATION,” the contents of which are incorporated herein by reference in their entirety. (Technical Field)

[0002] The subject matter described herein generally relates to systems, devices, and methods for modulating a beam for use in a beam system.

Background Art

[0003] Boron neutron capture therapy (BNCT) is a modality for the treatment of various types of cancer, including some of the most difficult types. BNCT is a technique that uses boron compounds to selectively target tumor cells for treatment while avoiding normal cells. A boron - containing substance is injected into the bloodstream, and the boron concentrates within the tumor cells. The patient then undergoes radiation therapy using neutrons (e.g., in the form of a neutron beam). The neutrons react with the boron, killing the tumor cells without harming normal cells. Long - term clinical studies have demonstrated that neutron beams with an energy spectrum within 3 - 30 kiloelectron volts (keV) are preferred for achieving more efficient cancer treatment while reducing the radiation burden on the patient. This energy spectrum or range is frequently referred to as epithermal.

[0004] Most conventional methods for the generation of epithermal neutrons (e.g., epithermal neutron beams) are based on nuclear reactions of protons (e.g., proton beams) with either beryllium or lithium (e.g., beryllium targets or lithium targets).

[0005] A tandem accelerator is a type of electrostatic accelerator that can employ two-stage acceleration of ion particles using a single high-voltage terminal. The high voltage is used, for example, to form a gradually increasing positive gradient that is applied to an incoming negative beam to accelerate it. At that point, the tandem accelerator converts the negative beam into a positive beam. Then, the high voltage is used again to form a reversed, gradually decreasing positive gradient that accelerates (e.g., pushes) the positive beam out of the tandem accelerator. Since the high voltage can be used twice, the generation of a proton beam with a particle energy of 3 MeV typically requires only an accelerating voltage of 1.5 MV, which is within the scope of modern electrical insulation technology. Additionally, the ion source of a tandem accelerator is installed at ground potential, which makes it easier to control and maintain the ion source.

[0006] The proton beam provided by a tandem accelerator for the purpose of boron neutron capture therapy (BNCT) has favorable energy levels for therapeutic efficacy and use with downstream equipment (e.g., for efficient generation of neutrons on a lithium (Li) target). Over a reasonably short treatment time, a specific beam density threshold is required, and such an essential threshold results in a minimum proton beam current. The power density associated with such a proton beam greatly exceeds the safety limits for the materials used in the components of the neutron beam system.

[0007] Conventional approaches to protecting beam equipment involve aligning a high-power beam at a significantly reduced beam current. Beam alignment can function well for beams with relatively low currents when the shape and position of the beam do not depend on the beam's self-space charge. However, for a tandem accelerator where the beam parameters include much higher beam currents (and the self-space charge has a significant impact on the beam shape), beam alignment at a reduced current is difficult.

[0008] Conventional approaches to protecting beam equipment further include beam modulation for accelerator types such as radio frequency quadrupole (RFQ) accelerators or linear accelerators (e.g., not tandem accelerators). Beam modulation is used in such applications to reduce the average beam power when the beam current cannot be reduced. The method can be very suitable for accelerator types such as RFQ or linear accelerators ("linacs") because the beam current is in a bunched form. However, with respect to DC accelerators such as tandem accelerators, modulation has not been applicable because the load of the DC accelerator cannot be changed from zero to the nominal value and back within a short amount of time.

[0009] For these and other reasons, there is a need for improved efficient and compact systems, devices, and methods for modulating an ion beam source so that the beam power can be reduced for the safety and preservation of neutron beam system equipment while maintaining the therapeutic efficacy. SUMMARY OF THE INVENTION MEANS FOR SOLVING THE PROBLEM

[0010] Embodiments of the system, device, and method relate to a beam source system capable of modulating a charged particle beam. The ion source is configured to provide a negative ion beam to a tandem accelerator system downstream of the ion source, and a modulator system connected to the extraction electrode of the ion source is configured to bias the extraction electrode for a sufficient duration to maintain the acceleration voltage stability of the tandem accelerator system.

[0011] Other systems, devices, methods, features, and advantages of the subject matter described in this specification will be apparent to those skilled in the art upon consideration of the following figures and detailed description, or will become apparent. All such additional systems, methods, features, and advantages are intended to be included within this description, are within the scope of the subject matter described in this specification, and are protected by the accompanying claims. Even if a specific listing of those features is absent from the claims, in no way should the features of the exemplary embodiments be construed as limiting the appended claims. The present invention provides, for example, the following. (Item 1) An ion beam source system, wherein the ion beam source system comprises an ion source configured to provide a negative ion beam to a tandem accelerator system downstream of the ion source, and a modulator system connected to an extraction electrode of the ion source and the modulator system is configured to bias the extraction electrode for a sufficient duration to achieve steady-state ion extraction and maintain the acceleration voltage stability of the tandem accelerator system, the ion beam source system. (Item 2) The ion beam source system according to item 1, wherein the ion source is configured to generate negative hydrogen ions. (Item 3) The ion beam source system according to item 1, wherein the duration is less than 10 milliseconds (msec). (Item 4) The ion beam source system according to item 1, wherein the duration is in the range of 0.5 to 1.0 milliseconds (msec). (Item 5) The ion beam source system according to item 1, wherein the modulator system comprises a switch. (Item 6) The ion beam source system according to item 1, wherein the modulator system comprises a DC power supply. (Item 7) The ion beam source system according to item 1, wherein the acceleration voltage stability is partially based on a capacitive discharge associated with a plurality of capacitors of the tandem accelerator system. (Item 8) The ion beam source system according to item 1, wherein one of the electrodes or a plurality of electrodes of the tandem accelerator system is biased using a DC power supply. (Item 9) The ion beam source system according to item 8, wherein the DC power supply responds to a feedback loop based on a capacitive discharge associated with a plurality of capacitors within the tandem accelerator system. (Item 10) The ion beam source system according to item 8, wherein the DC power supply comprises an extra-low voltage (ELV) DC power supply. (Item 11) The ion beam source system according to item 9, wherein the duration is less than the response time of the feedback loop. (Item 12) The ion beam source system according to item 1, wherein the ion source comprises an acceleration electrode. (Item 13) The ion beam source system according to item 12, wherein the acceleration electrode is continuously biased using a first power supply. (Item 14) The ion beam source system according to item 1, wherein the ion source comprises a plasma electrode. (Item 15) The ion beam source system according to item 14, wherein the plasma electrode is continuously biased using a second power supply. (Item 16) The ion beam source system according to items 13 and 15, wherein the first power supply, the second power supply, and the third power supply of the modulator system are independent of each other. (Item 17) The ion beam source system according to item 1, wherein the negative ion beam passes through a pre-accelerator system downstream from the ion beam source system before reaching the tandem accelerator system. (Item 18) The ion beam source system according to item 17, wherein the duration is short enough to avoid beam-induced damage to components of the pre-accelerator system or the tandem accelerator system. (Item 19) The ion beam source system according to item 1, wherein the duration is sufficient to enable the provision of a proton beam having a beam energy of 2.5 mega electron volts (MeV). (Item 20) The ion beam source system according to item 1, wherein the duration is sufficient such that less than 15% of the capacitive discharge in the tandem accelerator system occurs as a result of the introduction of the negative ion beam. (Item 21) The ion beam source system according to item 1, wherein the duration is sufficient such that less than 6% of the capacitive discharge in the tandem accelerator system occurs as a result of the introduction of the negative ion beam. (Item 22) The ion beam source system according to item 1, wherein the duration is long enough to enable steady-state ion extraction from the ion source. (Item 23) The ion beam source system according to item 22, wherein the steady-state ion extraction ramp-up time for the ion source is 0.1 to 0.3 milliseconds (msec). (Item 24) The ion beam source system according to item 1, wherein the tandem accelerator system includes a plurality of input electrodes, a charge exchange device, and a plurality of output electrodes. (Item 25) The ion beam source system according to item 24, wherein the plurality of input electrodes are configured to accelerate a negative ion beam from a pre-accelerator system, the charge exchange device is configured to convert the negative ion beam into a positive beam, and the plurality of output electrodes are configured to accelerate the positive beam. (Item 26) The target device downstream from the tandem accelerator system is the ion beam source system according to item 25, which is configured to form a neutral beam from the positive beam received from the tandem accelerator system. (Item 27) The ion beam source system according to item 26, wherein the duration is short enough to avoid beam-induced damage to the target device. (Item 28) A method of beam modulation, the method comprising: biasing the extraction electrode of the ion source over a certain duration, the duration being sufficient to maintain the acceleration voltage stability of a tandem accelerator system configured such that the ion source provides a negative ion beam. (Item 29) The method according to item 28, wherein the ion source is configured to generate negative hydrogen ions. (Item 30) The method according to item 28, further comprising biasing the extraction electrode for less than 10 milliseconds (ms). (Item 31) The method according to item 28, further comprising biasing the extraction electrode for 0.5 to 1 millisecond (ms). (Item 32) The method according to item 28, further comprising measuring the acceleration voltage stability based at least in part on a capacitive discharge associated with a plurality of capacitors of the tandem accelerator system. (Item 33) The method according to item 28, further comprising biasing one of the electrodes or a plurality of electrodes of the tandem accelerator system using a DC power supply. (Item 34) The method according to item 33, wherein the DC power supply responds to a feedback loop based on a capacitive discharge associated with a plurality of capacitors within the tandem accelerator system. (Item 35) The method according to item 34, further comprising biasing the extraction electrode for a duration less than the response time of the feedback loop. (Item 36) The method according to item 28, wherein the ion source comprises an acceleration electrode. (Item 37) The method according to item 36, further comprising continuously biasing the acceleration electrode using a first power supply. (Item 38) The method according to item 28, wherein the ion source comprises a plasma electrode. (Item 39) The method according to item 38, further comprising continuously biasing the plasma electrode using a second power supply. (Item 40) The method according to item 28, wherein the negative ion beam passes through a pre-accelerator system downstream from the ion source before reaching the tandem accelerator system. (Item 41) The method according to item 40, wherein the duration is short enough to avoid beam-induced damage to components of the pre-accelerator system or the tandem accelerator system. (Item 42) The method according to item 28, wherein the duration is sufficient to enable the provision of a proton beam having a beam energy of 2.5 megaelectron volts (MeV). (Item 43) The method according to item 28, wherein the duration is sufficient such that a capacitive discharge within the tandem accelerator system of 6% or less occurs as a result of the introduction of the negative ion beam. (Item 44) The method according to item 28, wherein the ion source comprises a non-cesium-added ion source. (Item 45) The method according to item 28, wherein the duration is long enough to enable steady-state ion extraction from the ion source. (Item 46) The method according to item 45, wherein the steady-state ion extraction ramp-up time for the ion source is from 0.1 millisecond (msec) to 0.3 millisecond (msec). (Item 47) A beam system, the beam system comprising: A source comprising an extraction electrode, the source being configured to generate a charged particle beam; and A modulator system connected to the extraction electrode of the source, the modulator system being configured to modulate the charged particle beam; and An accelerator configured to accelerate the modulated charged particle beam The beam system. (Item 48) The beam system according to item 47, wherein the modulator system is configured to modulate the charged particle beam into a plurality of pulses, each pulse having a duration sufficient to achieve steady-state particle extraction. (Item 49) The beam system according to either item 47 or 48, wherein the accelerator comprises one or more capacitors, and the modulated beam does not discharge the one or more capacitors by more than a threshold amount. (Item 50) The beam system according to item 49, wherein the threshold amount is 15% or less of the full charge of the one or more capacitors. (Item 51) The beam system according to item 49, wherein the threshold amount is 6% or less of the full charge of the one or more capacitors. (Item 52) The beam system according to item 48, wherein the duration is less than 10 milliseconds (ms), and the duty cycle is 0.1 to 10%. (Item 53) The beam system according to item 48, wherein the duration is within the range of 0.5 to 1.0 millisecond (ms). (Item 54) The beam system according to item 47, wherein the modulator system is configured to modulate the charged particle beam and maintain the acceleration voltage stability of the accelerator. (Item 55) The beam system according to item 54, wherein the acceleration voltage stability is at least partially based on the capacitive discharge associated with a plurality of capacitors of the accelerator. (Item 56) The beam system according to item 47, wherein one of the electrodes of the accelerator or a plurality of electrodes is biased using a DC power supply. (Item 57) The beam system according to item 56, wherein the DC power supply responds to a feedback loop based on the capacitive discharge associated with a plurality of capacitors within the accelerator. (Item 58) The beam system according to item 57, wherein the duration is less than the response time of the feedback loop. (Item 59) The beam system according to item 58, wherein the accelerator is a tandem accelerator. (Item 60) The charged particle beam is a negative ion beam, and the accelerator is configured to convert the negative ion beam into a proton beam, and each pulse has a duration sufficient to enable the provision of the proton beam having a beam energy of 1.9 to 3.0 megaelectron volts (MeV). The beam system according to item 47. (Item 61) The beam system according to item 47, wherein the modulation system is configured to modulate the charged particle beam such that the capacitive discharge within the accelerator does not exceed 15% during the acceleration of the modulated charged particle beam. (Item 62) The beam system according to item 47, wherein the modulation system is configured to modulate the charged particle beam such that the capacitive discharge within the accelerator does not exceed 6% during the acceleration of the modulated charged particle beam. (Item 63) The beam system according to item 61 or 62, wherein the accelerator is a tandem accelerator including a plurality of nested shells and one or more capacitors electrically coupled between adjacent shells, and the capacitive discharge is the discharge of the one or more capacitors. (Item 64) The accelerator is a tandem accelerator including a plurality of input electrodes, a charge exchange device, and a plurality of output electrodes, and the beam system according to item 47. (Item 65) The charged particle beam is a negative ion beam, the tandem accelerator is configured to accelerate the negative ion beam using the plurality of input electrodes, the charge exchange device is configured to convert the negative ion beam into a positive beam, and the tandem accelerator is configured to accelerate the positive beam using the plurality of output electrodes, and the beam system according to item 64. (Item 66) The beam system according to item 65, further including a target device downstream from the tandem accelerator, the target device being configured to form a neutral beam from the positive beam. (Item 67) The modulator system is configured to modulate the charged particle beam into a plurality of pulses, each pulse having a duration limited to avoid thermal damage to the target device, and the beam source system according to item 26.

Brief Description of the Drawings

[0012] Details of the subject matter described in this specification regarding both its structure and operation may be apparent from a review of the accompanying figures in which like reference numerals refer to like parts. The components in the figures are not necessarily to scale; rather, emphasis has been placed on illustrating the principles of the subject matter. Further, all illustrations are intended to convey concepts, and relative sizes, shapes, and other detailed attributes may be illustrated diagrammatically rather than literally or precisely.

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DETAILED DESCRIPTION OF THE INVENTION

[0027] Before the subject matter is described in detail, it is to be understood that the present disclosure is not limited to the particular embodiments being described, and as such can, of course, vary. It is also to be understood that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting, since the scope of the present disclosure will be limited only by the appended claims.

[0028] The term "particle" is used herein in a broad sense and can be used to describe electrons, protons (or H+ ions), or neutrons, and species having two or more electrons, protons, and / or neutrons (e.g., other ions, atoms, and molecules), unless otherwise limited.

[0029] Exemplary embodiments of systems, devices, and methods for a beam source system for use with a beam system (e.g., including a particle accelerator) are described herein. The embodiments described herein can be used with any type of particle accelerator or in any particle accelerator application involving the generation of a charged particle beam at a defined energy for supply to a particle accelerator.

[0030] Embodiments of the present ion beam source system are particularly suitable for providing an ion beam, such as a negative particle beam, to a tandem accelerator (which also cooperates with a front-end accelerator system). Such systems can be used in a number of applications, an example of which is as a neutron beam system for the generation of a neutron beam for use in boron neutron capture therapy (BNCT). For ease of explanation, many of the embodiments described herein will be done so in the context of a neutron beam system for use in BNCT, but the embodiments are not limited to only neutron beams or BNCT applications.

[0031] The embodiments described herein reduce the average beam power of a particle accelerator system such that a proton beam with parameters suitable for a source of thermal neutrons can be provided for boron neutron capture therapy (BNCT) using a lithium (Li) or beryllium (Be) target. That is, embodiments of the present disclosure overcome some of the disadvantages associated with the limitations introduced by equipment and safety in the context of a neutron beam system. The proton beam provided by a tandem accelerator for the purposes of boron neutron capture therapy (BNCT) has a preferred energy level for therapeutic efficacy and use with downstream equipment (e.g., for efficient generation of neutrons on a lithium (Li) target). For example, the proton beam can preferably have an energy of 1.9 - 3.0 megaelectron volts (MeV). Over a reasonably short treatment time, a specific beam density threshold is desired, and such a desired threshold results in a minimum proton beam current (e.g., higher than 5 milliamperes (mA)). The power density associated with such a proton beam (e.g., having an energy of 1.9 - 3.0 MeV and a current higher than 5 mA) greatly exceeds the safety limits regarding the materials used in components of the neutron beam system (e.g., neutron generation targets, etc.).

[0032] As a further example, in an exemplary nominal setting of 2.5 MeV beam energy and 10 mA beam current, the beam power is 25 kilowatts (kW). Given such a large power, it is important to avoid situations where the beam can become misaligned. For a proton beam focused to a location (e.g., a circular or elliptical spot) having a diameter of less than 10 millimeters (mm) with a power exceeding 10 kW, the power density is likely to substantially exceed the safety limits regarding the materials used in the tandem accelerator (and the neutron beam system as a whole). Any slight deflection of the beam can cause its contact with elements of the beam duct (e.g., within the tandem accelerator), almost immediate damage, and perhaps destruction of the elements by the beam.

[0033] Advantageously, embodiments of the present disclosure enable modulation of a negative ion beam in an ion beam source by modulating the ion extraction voltage. Such modulation results in a limited pulse duration of the negative ion beam such that the average beam power is reduced to a safe level with respect to the materials of the beam system, while at the same time a detectable steady state ion beam is provided to the tandem accelerator without affecting the voltage stability of the tandem accelerator. Thus, a proton beam of the requisite beam energy and current is provided to downstream components without adversely affecting the components of the neutron beam system as a whole (e.g., a beam duration of 10 milliseconds (ms) to 100 ms can result in damage to the neutron generation target downstream from the tandem accelerator).

[0034] The desired pulse duration of the negative ion beam (e.g., the length of time the extraction electrode of the ion beam source should be biased) can be based on several factors. Embodiments will vary, but generally it is desirable that the pulse duration be (1) long enough to reach steady state extraction of negative hydrogen ions (H - -) from the plasma of the ion source and (2) short enough to avoid interference with the voltage stabilization system of the tandem accelerator. In some embodiments, the pulse is short enough in duration to avoid discharging more than 10 - 15%, more preferably more than 5 - 6% of the total capacitors within the tandem accelerator. Thus, the energy stability of the beam passing through the tandem accelerator is maintained while the equipment is protected.

[0035] (1) Regarding the pulse being long enough as described above, in some embodiments, the time to reach steady-state extraction of negative hydrogen ions for a non-cesium-added (e.g., without cesium (Cs)) ion source is 0.1 to 0.3 milliseconds. In some embodiments, the tandem accelerator has a capacitor installed at the output of the high-voltage rectifier section. (2) Regarding the pulse being short enough as described above, in such embodiments, when the tandem accelerator is at a nominal 2.5 MeV beam particle energy, the discharge capacitance due to the propagation of a beam with a current of 10 mA and a duration of 1 millisecond is preferably not more than 6%.

[0036] Certain embodiments described herein can achieve a desired pulse duration of 0.5 to 1.0 milliseconds at a frequency of 10 Hz or a duty cycle of 0.5 to 1%. The duty cycle (active time / total period) will vary based on the operating parameters of the beam system as implemented. For example, the duty cycle can range from 0.1% to 10%. In some embodiments, the duty cycle is 1% or less, in other embodiments, the duty cycle is 2% or less, in other embodiments, the duty cycle is 5% or less, and in still other embodiments, the duty cycle is 10% or less.

[0037] Preferably, such beam modulation: (a) does not significantly disrupt the voltage stabilization of the tandem accelerator; (b) does not discharge the capacitor in the tandem accelerator above a threshold amount (e.g., 15% or less); (c) provides a beam with a constant maximum output value (e.g., a flat or substantially flat top) over a threshold time amount that is long enough (e.g., 2 msec) for typical time resolution for most of the beam diagnostics; (d) reduces the average beam power to a substantially safe level for most of the materials used in the beam system compared to the unmodulated beam. In some embodiments, this reduction can be on the order of about 100-fold (down to a level of about 250 watts (W)). In addition to maintaining the functionality of the beam system, the beam modulation according to the embodiments described herein leads to greater long-term integrity and reliability of the beam system materials and components. (Exemplary BNCT applications)

[0038] Turning to the figures in detail, FIG. 1A is a schematic diagram of an exemplary embodiment of a beam system 10 for use with embodiments of the present disclosure. In FIG. 1A, the beam system 10 includes a source 12, a low energy beam line (LEBL) 14, an accelerator 16 coupled to the low energy beam line (LEBL) 14, and a high energy beam line (HEBL) 16 extending from the accelerator 16 to a target 100. The LEBL 14 is configured to transport the beam from the source 22 to the input of the accelerator 16, and the accelerator 16 is then configured to generate the beam by accelerating the beam transported by the LEBL 14. The HEBL 18 transfers the beam from the output of the accelerator 16 to the target 100. The target 100 can be a structure configured to produce a desired result in response to a stimulus applied by the incident beam, or can modify the properties of the beam. The target 100 can be a component of the system 10 or can be a workpiece at least partially conditioned or manufactured by the system 10.

[0039] Figure 1B is a schematic diagram illustrating another exemplary embodiment of a neutron beam system 10 for use in boron neutron capture therapy (BNCT). Here, the source 12 is an ion source and the accelerator 16 is a tandem accelerator. The neutron beam system 10 includes a front-end accelerator system 20 that serves as a charged particle beam injector, a high voltage (HV) tandem accelerator 16 coupled to the front-end accelerator system 20, and a HEBL 18 extending from the tandem accelerator 16 to a neutron target assembly 200 that stores a target 100 (not shown). In this embodiment, the target 100 is configured to generate neutrons in response to the impact of protons of sufficient energy and can be referred to as a neutron generating target. The neutron beam system 10 and the front-end accelerator system 20 can also be used for other applications such as those described in other examples herein and are not limited to BNCT.

[0040] The front-end accelerator system 20 is configured to transport an ion beam from the ion source 12 to the input (e.g., input aperture) of the tandem accelerator 16 and thus also serves as the LEBL 14. The tandem accelerator 16 is powered by a high voltage power supply 42 coupled thereto, and the tandem accelerator 16 can generate a proton beam with an energy equal to approximately twice the voltage applied to the acceleration electrodes located generally within the accelerator 16. The energy level of the proton beam can be achieved by accelerating a beam of negative hydrogen ions from the input of the accelerator 16 to the innermost high potential electrode, stripping two electrons from each ion, and then accelerating the resulting protons downstream by the same applied voltage.

[0041] HEBL18 can transfer a proton beam from the output of accelerator 16 to a target within neutron target assembly 200 located at the end of beam line branch 70 that extends into the patient treatment rooms. System 10 can be configured to direct the proton beam to any number of one or more targets and associated treatment areas. In this embodiment, HEBL18 includes three branches 70, 80, and 90 that can extend into three different patient treatment rooms, each branch terminating at target assembly 200 and a downstream beam shaping device (not shown). HEBL18 can include pump chamber 51, quadrupole magnets 52 and 72 to prevent beam defocusing, dipole or bending magnets 56 and 58 to steer the beam into the treatment rooms, beam corrector 53, diagnostics such as current monitors 54 and 76, fast beam position monitor 55 section, and scanning magnet 74.

[0042] The design of HEBL18 depends on the configuration of the treatment facility (e.g., a single-story treatment facility, a multi-story treatment facility, etc.). The beam can be delivered to target assembly 200 (e.g., located near the treatment rooms) by use of bending magnet 56. Quadrupole magnet 72 can then be included to focus the beam to a certain size at the target. The beam then passes through one or more scanning magnets 74, which provide lateral movement of the beam on the target surface in a desired pattern (e.g., spiral, curved, stepped in rows and columns, combinations thereof, and others). Beam lateral movement can help achieve a smooth and uniform time-averaged distribution of the proton beam on the lithium target, prevent overheating, and make neutron generation as uniform as possible within the lithium layer.

[0043] After being incident on the scanning magnet 74, the beam can be delivered into the current monitor 76, which measures the beam current. The target assembly 200 can be physically separated from the HEBL volume using the gate valve 77. The main function of the gate valve is the separation of the target from the vacuum volume of the beam line during target loading and / or during replacement of the used target with a new one. In an embodiment, the beam may not be bent 90 degrees by the bending magnet 56; rather, it proceeds straight to the right of FIG. 1B and then is incident on the quadrupole magnet 52 located within the horizontal beam line. The beam can subsequently be bent by another bending magnet 58 to the required angle, depending on the building and room configuration. Otherwise, the bending magnet 58 can be replaced with a Y-shaped magnet for splitting the beam line in two directions for two different treatment rooms located on the same floor.

[0044] FIG. 2 illustrates an example of a pre-accelerator system or ion beam injector for use with an embodiment of the present disclosure. In this example, the pre-accelerator system 20 (e.g., LEBL 14) includes an Einzel lens 30 (invisible in FIG. 2 but depicted in FIGS. 3A - 3B), a pre-accelerator tube 26, and a solenoid 510, and is configured to accelerate a negative ion beam injected from the ion source 12. The pre-accelerator system 20 provides acceleration of the beam particles to the energy required for the tandem accelerator 16 and provides an overall convergence of the negative ion beam to match the input aperture area at the input aperture or entrance of the tandem accelerator 16. The pre-accelerator system 20 is further configured to minimize or defocus backflow when the tandem accelerator 16 passes through the pre-accelerator system, in order to reduce the possibility of damage to the ion source 12 and / or of backflow reaching the filament of the ion source.

[0045] In an embodiment, the ion source 12 can be configured to provide a negative ion beam upstream of the Einzel lens 30, and the negative ion beam continues to pass through the front - stage accelerator tube 26 and the magnetic focusing device (e.g., solenoid) 510. The solenoid 510 can be positioned between the front - stage accelerator tube 26 and the tandem accelerator 16 and can be electrically coupled to a power supply. The negative ion beam passes through the solenoid 510 up to the tandem accelerator 16.

[0046] The front - stage accelerator system 20 can include an ion - source vacuum box 24 for removing gas and a pump chamber 28, which, together with the front - stage accelerator tube 26 and the other elements described above, are part of a relatively low - energy beam line leading to the tandem accelerator 16. The ion - source vacuum box 24, where the Einzel lens 30 can be positioned, extends from the ion source 12. The front - stage accelerator tube 26 can be coupled to the ion - source vacuum box 24 and the solenoid 510. The vacuum pump chamber 28 for removing gas can be coupled to the solenoid 510 and the tandem accelerator 16. The ion source 12 serves as a source of charged particles, which, when accelerated, conditioned, and finally delivered to a neutron - generating target, can be used to generate neutrons. The exemplary embodiment will be described herein with reference to an ion source that generates a negative hydrogen ion beam, but the embodiments are not limited to such, and other positive or negative particles can also be generated by the source.

[0047] The front - stage accelerator system 20 can have zero, one, or more magnetic elements for purposes such as focusing the beam and / or adjusting its alignment. For example, any such magnetic element can be used to align the beam with the beam - line axis and the acceptance angle of the tandem accelerator 16. The ion vacuum box 24 can have an ion - optical system positioned therein.

[0048] Generally, there are two types of negative ion sources 12, which differ in the mechanism of negative ion generation: surface type and volume type. The surface type generally requires the presence of cesium (Cs) on a specific internal surface. The volume type relies on the formation of negative ions within the volume of a high-current discharge plasma. Both types of ion sources can deliver the desired negative ion current for applications related to tandem accelerators, but the surface type of negative ion source is undesirable for modulation. That is, for the modulation of the negative ion beam in the embodiments described herein, a volume type of negative ion source (e.g., without employing cesium (Cs)) is preferred.

[0049] Turning to FIG. 3A, the ion source vacuum box 24 of the ion beam injector 20 includes an Einzel lens 30 positioned therein. As shown in detail in FIG. 3B, the Einzel lens 30 mounted downstream of the ground lens 25 of the ion source 12 within the vacuum box 24 includes a mounting plate 32, two grounded electrodes 34 mounted on the mounting plate 32 and coupled to each other in a spaced relationship using mounting rods 35, and a powered (biased) electrode 38 positioned between the two grounded electrodes 34. The electrodes 34 and 38 are fabricated in the form of cylindrical apertures and assembled to have an axial axis that coincides with the beam path. The powered electrode 38 is supported by an insulator / isolator 36 that extends between the grounded electrodes or apertures 34.

[0050] The standoff isolator 36 can include a geometric design configured to prevent the development of electron avalanches and suppress streamer formation and propagation (typically ending in flashover formation). The geometric design of the standoff isolator 36 can partially screen the external electric field (which drives electron avalanches and effectively increases the path length) on the insulator surface. Additionally, the material of the insulator / isolator 36 tends to reduce the formation of conductive coatings on the insulator / isolator surface that lead to sputtering effects, loss of negative ions on the surface, volume contamination, and reduction of electrical strength.

[0051] Functionally, the action of the Einzel lens 30 on the beam of charged particles advancing from the ion source 12 is similar to the action of an optical focusing lens on a beam of light. That is, the Einzel lens 30 focuses an incoming parallel beam into a spot at the focal plane. However, here, the electric field formed between the pair of the powered electrode 38 and the two grounded electrodes 34 determines the focusing intensity (focal length) of the Einzel lens.

[0052] By mounting the Einzel lens 30 downstream of the ion source ground lens 25, it reduces the beam free space transport in which the beam is exposed to divergence due to its own space charge.

[0053] The dimensions of the axially symmetric design of the Einzel lens 30 are optimized to avoid the direct interaction between the extracted ions and the exposed surface of the Einzel lens 30.

[0054] During operation, the negative polarity bias of the Einzel lens 30 provides a higher focusing power than the positive bias polarity. Also, during operation, the method of power delivery to the Einzel lens 30 provides a gradual voltage build-up instead of an instantaneous voltage application, which reduces the growth rate (dE / dt) of the electric field at the micro protrusions present on the surface of the Einzel lens 30 (for example, involved in plasma formation by an explosion emission mechanism). The prevention of such plasma formation enhances the dielectric strength.

[0055] A negative bias potential for the Einzel lens within a high background pressure is usually impossible due to dielectric breakdown. The configuration of the exemplary embodiment of the Einzel lens provided herein enables the application of a negative bias voltage high enough for 100% current utilization without dielectric breakdown.

[0056] FIG. 4A illustrates an exemplary ion beam source system for use with embodiments of the present disclosure. In FIG. 4A, the ion source 12 is optionally housed within an ion source enclosure. The ion source 12 includes a plurality of electrodes such as a plasma electrode 320, an accelerator / acceleration electrode (e.g., or ground lens) 310, and an extraction electrode 330. Optionally, the ion source 12 is coupled with an Einzel lens 30, and a negative ion beam is injected or propagated from the ion source 12 through the Einzel lens 30, the front-end accelerator tube 26, and the solenoid 510 to the input aperture of the tandem accelerator 16.

[0057] Referring to FIG. 4B, the ion source 12 can be electrically coupled at the accelerator electrode 310 to a first terminal of a power supply PS3, which is then electrically coupled at a second terminal to the enclosure of the ion source 12. The bias of the ion source 12 at the accelerator electrode 310 configures the front-end accelerator system 20 for the maintenance and passage of a negative ion beam as such a beam passes from the ion source 12. In some embodiments, the power supply PS3 can provide a voltage of -30 kV.

[0058] The plasma electrode 320 of the ion source 12 can be electrically coupled to a power supply PS5, and the extraction electrode 330 of the ion source 12 can be electrically coupled to a modulator 350, which is then electrically coupled to a power supply PS4. The bias of the plasma electrode 320 enables it to be used for extraction into the negative ion beam when the ion source 12 maintains a plasma within the ion source 12 and the extraction electrode 330 is biased.

[0059] In some embodiments, the modulator 350 and the power supply PS4 can be combined within a single integrated regulator system. The modulator 350 includes switches that can be used to control the bias of the extraction electrode 330.

[0060] When the extraction electrode 330 is biased, a negative ion beam is passed or propagated from the ion source 12 along the tandem accelerator 16. When the extraction electrode 330 is not biased, the negative ion beam is not passed or propagated from the ion source 12 along the tandem accelerator 16.

[0061] As discussed above, the tandem accelerator 16 is powered by a high-voltage power supply 42 coupled thereto and can generally generate a proton beam with an energy equal to twice the voltage applied to the acceleration electrodes positioned within the accelerator 16. The tandem accelerator 16 can include any number of two or more nested shells, and the acceleration electrodes can be positioned at the left and right ends of each shell as shown in FIG. 4A. In this embodiment, the accelerator 16 includes an innermost shell labeled as a high-voltage (HV) chamber in addition to four shells G1, G2, G3, and G4. The power supply PS6 can be controlled by a feedback loop, whereby the voltage stability within the tandem accelerator 16 is maintained. That is, a measurement or control device 360 (e.g., a voltmeter) can monitor the voltage of a capacitor (C) installed at the output of the high-voltage rectifier section of the tandem accelerator 16. At least one capacitor can be connected between each shell and the shell immediately adjacent thereto. In this example, there are four capacitors connected across five shells. The operation of the beam through the accelerator 16 can lead to the discharge of the capacitor. Voltage stability requires that the discharge of the capacitor not exceed a threshold of a fully charged state in order to maintain the stability of the beam 620. In some embodiments, this threshold is 5%, in other embodiments, this threshold is 6%, in other embodiments, this threshold is 10%, and in still other embodiments, this threshold is 15%. In such an example, the measurement or control device 360 can provide a feedback signal indicating voltage instability to the power supply PS6, and the power supply PS6 interrupts biasing the tandem accelerator 16.

[0062] FIG. 5A illustrates an exemplary desired steady-state emission pulse of an ion beam source for use with embodiments of the present disclosure. FIG. 5B illustrates an exemplary undesired steady-state emission pulse of the ion beam source. As shown in FIG. 5A, the bias of the extraction electrode in the ion beam source results in a steady-state extraction of negative hydrogen ions from the plasma of the ion source within a short period, and otherwise, the generation of the ion beam is unsuccessful within the essential window for the protection of downstream components. FIG. 5B depicts an undesired ramp-up to the steady-state extraction.

[0063] FIG. 6A illustrates an exemplary capacitive discharge curve for use with embodiments of the present disclosure. FIG. 6B illustrates an exemplary desired current pulse curve for use with embodiments of the present disclosure. The desired ion beam pulse current signature is similar to an ideal step function with a minimum rise and fall gradient of the pulse and a constant value over the active duration as shown in FIG. 6B, leading to a capacitive discharge as shown in FIG. 6A, and the modulation does not lead to a capacitive discharge exceeding the threshold (e.g., the threshold can be about 5 - 6% in some embodiments). As discussed above, limiting the duration of the pulse of the negative ion beam 600 using the modulator 350 or modulation system that controls the bias (or lack of bias) of the extraction electrode 330 of the ion source 12 reduces the possibility that the discharge of a plurality of capacitors exceeds 5 - 6%, thereby reducing (or completely eliminating) the possibility that the power supply PS6 interrupts the power to the tandem accelerator 16.

[0064] The capacitance ratings of the plurality of capacitors can affect the limit for a normal beam pulse duration. That is, the larger the capacitor, the longer the beam pulse duration may be, however, this leads to a lack of flexibility when space and other design constraints would increase the capacitance in various beam systems.

[0065] FIG. 7 is a timing diagram showing examples of various parameters in their temporal relationship for use with embodiments of the present disclosure. In the top schematic of FIG. 7, an extraction bias is applied over a given duration (e.g., t pulse ) from t1 to t3 (e.g., U extraction ) to form an extraction pulse 700 that causes extraction of the beam from the particle source. As shown here, the extraction bias is applied in the shape of a step function or square wave, which is an idealized depiction, and one of ordinary skill in the art will recognize that some deviation will occur. The current (I beam ) of the extracted beam is depicted in the middle schematic. The current I beam rapidly increases from t1 until it reaches a constant or substantially constant magnitude at t2 in response to the extraction bias U extraction . This is depicted by the flat or substantially flat top contour of the current pulse 702. This region of stable magnitude can be referred to as the steady state of the current and persists for a duration (e.g., t flat top ) until the extraction bias is removed at t3. In some embodiments, the steady state duration from time t2 to t3 (e.g., t flat top ) is long enough for one or more measurements associated with the beam system to be acquired.

[0066] Prior to beam extraction (e.g., t0 to t1), the accelerator voltage U tandem is charged to a steady state level 704. In the embodiment of the tandem accelerator 16 described with respect to FIG. 4A, this steady state level can be a full charge to the capacitor (C) between respective acceleration electrodes. When beam extraction is initiated from the ion source at t1, discharge of these capacitors can occur. In these embodiments, the discharge is preferably maintained within a discharge threshold ΔU (e.g., 15% or less, 10% or less, 6% or less). In some embodiments, the modulation system can be set or programmed such that the duration of t pulse is the length of time to maintain the discharge amount within the threshold ΔU. In some embodiments, t pulseThe duration is such that the discharge amount is actively monitored by the modulation system (or by the control system described herein), and the extraction pulse ends before the discharge reaches the discharge threshold ΔU (or conversely, before U tandem decreases or drops below it). It can be controlled using a feedback loop. When the extraction pulse 700 ends at t3 so that the beam is no longer extracted from the exemplary ion source, the charge of the capacitor (e.g., U tandem ) returns to the nominal level 704. In an embodiment, the minimum period of the charge pulse (e.g., t1 - t4) is sufficient to exceed the duration for which the capacitor should be charged to return it to level 704.

[0067] FIG. 8 is a block diagram showing an exemplary system in which embodiments of the present disclosure can operate. For example, the exemplary system shown includes an ion beam source system 3001, one or more computing devices 3002, and a tandem accelerator system 3003. In an embodiment, the ion beam source system 3001 and the tandem accelerator system 3003 can collectively be part of an exemplary neutron beam system (e.g., system 10 above). In such an embodiment, the neutron beam system 10 can employ one or more control systems, and using them, one or more computing devices 3002 can communicate to interact with the systems and components of the neutron beam system 10. Each of these devices and / or systems is configured to communicate either directly with each other (not shown) or via a local network such as network 3004.

[0068] The computing device 3002 can be implemented by various user devices, systems, computing apparatuses, etc. For example, a first computing device 3002 can be a desktop computer associated with a specific user, while another computing device 3002 can be a laptop computer associated with a specific user, and yet another computing device 3002 can be a mobile device (e.g., a tablet or a smart device). Each of the computing devices 3002 can be configured to communicate with the ion beam source system 3001 and / or the tandem accelerator system 3003 through, for example, a user interface accessible via the computing device. For example, a user can execute a desktop application on the computing device 3002, which is configured to communicate with the ion beam source system 3001 and / or the tandem accelerator system 3003.

[0069] By using the computing device 3002 and communicating with one or more of the ion beam source system 3001 or the tandem accelerator system 3003, a user can provide operating parameters (e.g., operating voltage, etc.) for any of the systems according to the embodiments described herein. In an embodiment, the ion beam source system 3001 can include a control system 3001A, whereby the ion beam source system 3001 can receive and apply operating parameters from the computing device 3002. In an embodiment, the tandem accelerator system 3003 can include a control system 3003A, whereby the tandem accelerator system 3003 can receive and apply operating parameters from the computing device 3002.

[0070] The communication network 3004 can include any wired or wireless communication network, such as a wired or wireless local area network (LAN), personal area network (PAN), metropolitan area network (MAN), wide area network (WAN), etc., and any hardware, software, and / or firmware required to implement it (e.g., network routers, etc.). For example, the communication network 3004 can include 802.11, 802.16, 802.20, and / or WiMax networks. Further, the communication network 3004 can include a public network such as the Internet, a private network such as an intranet, or a combination thereof, and can utilize various networking protocols, including but not limited to TCP / IP-based networking protocols, that are currently available or developed later.

[0071] The computing device 3002 and the control systems 3001A and 3003A can be embodied by one or more computing systems, such as the device 3100 shown in FIG. 9. As shown in FIG. 9, the device 3100 can include a processor 3102, a memory 3104, an input and / or output circuitry 3106, and a communication device or circuitry 3108. It should also be understood that some of these components 3102 - 3108 may include similar hardware. For example, both of two modules can utilize the use of the same processor, network interface, storage medium, etc., so that duplicate hardware is not required for each device, and can implement their associated functions. The use of the terms "device" and / or "circuitry" as used herein with respect to the components of the device can thus include the specific hardware configured with software to implement the functions associated with that particular device, as described herein.

[0072] The terms "device" and / or "circuitry" should be understood broadly to include hardware, and in some embodiments, the device and / or circuitry may also include software for configuring the hardware. For example, in some embodiments, the device and / or circuitry can include a processing circuitry, a storage medium, a network interface, input / output devices, etc. In some embodiments, other elements of apparatus 3100 can provide or complement the functionality of a particular device. For example, processor 3102 can provide processing functionality, memory 3104 can provide storage functionality, a communication device or circuitry 3108 can provide network interface functionality, etc.

[0073] In some embodiments, processor 3102 (and / or a coprocessor or any other processing circuitry that assists or is otherwise associated with the processor) can communicate with memory 3104 via a bus to pass information between components of the device. Memory 3104 can be non-transitory and can include, for example, one or more volatile and / or non-volatile memories. In other words, for example, the memory can be an electronic storage device (e.g., a computer-readable storage medium). Memory 3104 can be configured to store information, data, content, applications, instructions, etc. to enable the device to perform various functions according to the exemplary embodiments of the present disclosure.

[0074] Processor 3102 can be embodied in several different ways and can include, for example, one or more processing devices configured to operate independently. Additionally or alternatively, the processor can include one or more processors configured to operate in concert via a bus and enable independent execution of instructions, pipelines, and / or multithreading. The use of the terms “processing device” and / or “processing circuitry” can be understood to include a single-core processor, a multi-core processor, multiple processors, and / or a remote or “cloud” processor within the device.

[0075] In an exemplary embodiment, processor 3102 can be configured to execute instructions stored in memory 3104 or otherwise accessible to the processor. Alternatively or additionally, the processor can be configured to execute hard-coded functionality. Thus, whether configured by hardware or software methods, or a combination of hardware and software, the processor can represent an entity that, while appropriately configured, is capable of performing operations in accordance with certain embodiments of the present disclosure (e.g., physically embodied within circuitry). Alternatively, as another example, when the processor is embodied as an executor of software instructions, the instructions can specifically configure the processor to perform the algorithms and / or operations described herein when the instructions are executed.

[0076] In some embodiments, the apparatus 3100 can include an input / output device 3106, which then communicates with the processor 3102 to provide output to the user and, in some embodiments, can receive input from the user. The input / output device 3106 can include a user interface and can include a device display such as a user device display that can include a web user interface, a mobile application, a client device, and the like. In some embodiments, the input / output device 3106 can also include a keyboard, a mouse, a joystick, a touch screen, a touch area, a soft key, a microphone, a speaker, or other input / output mechanisms. The processor and / or user interface circuitry including the processor can be configured to control one or more functions of one or more user interface elements through computer program instructions (e.g., software and / or firmware) stored on a memory accessible to the processor (e.g., memory 3104 and / or equivalents).

[0077] The communication device or network 3108 can be any means such as a device circuit network embodied in either hardware or a combination of hardware and software configured to receive data from and / or transmit to any other device or network that communicates with the network and / or device 3100. In this regard, the communication device or network 3108 can include, for example, a network interface to enable communication with a wired or wireless communication network. For example, the communication device or network 3108 can include one or more network interface cards, antennas, buses, switches, routers, modems, and support hardware and / or software, or any other device suitable for enabling communication over a network. Additionally, or alternatively, the communication interface can include circuitry for interacting with an antenna, causing transmission of signals via the antenna, or handling reception of signals received via the antenna. These signals can be transmitted by the device 3100 using any of several wireless personal area network (PAN) technologies, such as current and future Bluetooth (registered trademark) standards (including Bluetooth (registered trademark) and Bluetooth (registered trademark) Low Energy (BLE)), infrared wireless (e.g., IrDA), FREC, ultra-wideband (UWB), inductive wireless transmission, etc. Additionally, it should be understood that these signals can be transmitted using Wi-Fi, near field communication (NFC), Worldwide Interoperability for Microwave Access (WiMAX), or other proximity-based communication protocols.

[0078] As will be appreciated, any such computer program instructions and / or other types of code can be loaded onto the circuitry of a computer, processor, or other programmable device, and a computer, processor, or other programmable circuitry that executes the code on the machine can produce a machine that generates means for implementing various functions, including those described herein.

[0079] As described above and as will be appreciated based on the present disclosure, embodiments of the present disclosure can be configured as a system, method, mobile device, backend network device, etc. Thus, the embodiments can include various implementations including entirely hardware or any combination of software and hardware. Further, the embodiments can take the form of a computer program product on at least one non-transitory computer-readable storage medium having computer-readable program instructions (e.g., computer software) embodied therein. Any suitable computer-readable storage medium including a non-transitory hard disk, CD-ROM, flash memory, optical storage device, or magnetic storage device can be utilized.

[0080] The processing circuitry for use with embodiments of the present disclosure can include one or more processors, microprocessors, controllers, and / or microcontrollers, each of which can be on separate chips or can be distributed among several different chips (and portions thereof). The processing circuitry for use with embodiments of the present disclosure can include a digital signal processor that can be implemented in the hardware and / or software of the processing circuitry for use with embodiments of the present disclosure. The processing circuitry for use with embodiments of the present disclosure can be communicatively coupled to other components of the figures herein. The processing circuitry for use with embodiments of the present disclosure can execute software instructions stored in memory that cause the processing circuitry to perform a set of different actions and control other components in the figures herein.

[0081] The memory for use with embodiments of the present disclosure can be shared by one or more of the various functional units or can be distributed among two or more of them (e.g., as separate memories existing within different chips). The memory can also be its own separate chip. The memory can be non-transitory and can be volatile (e.g., RAM, etc.) and / or non-volatile memory (e.g., ROM, flash memory, F-RAM, etc.).

[0082] The computer program instructions for performing operations in accordance with the described subject matter can be written in any combination of one or more programming languages, including object-oriented programming languages such as Java®, Java® Script, Smalltalk, C++, C#, Transact-SQL, XML, PHP, etc., and conventional procedural programming languages such as the "C" programming language or similar programming languages.

[0083] Various aspects of the present subject matter are described below as a review of, and / or as complementary to, the embodiments described so far, and the interrelationships and interchangeability of the following embodiments are emphasized here. In other words, it is emphasized that each feature of an embodiment can be combined with any other feature unless explicitly stated otherwise or logically impossible.

[0084] In many embodiments, the ion beam system includes an ion source configured to provide a negative ion beam to a tandem accelerator system downstream of the ion source, and a modulator system connected to the extraction electrode of the ion source. In many of these embodiments, the modulator system is configured to bias the extraction electrode for a duration sufficient to achieve steady-state ion extraction and maintain the acceleration voltage stability of the tandem accelerator system.

[0085] In many of these embodiments, the ion source is configured to generate negative hydrogen ions.

[0086] In many of these embodiments, the duration is less than 10 milliseconds (ms). In many of these embodiments, the duration is in the range of 0.5 to 1.0 millisecond (ms).

[0087] In many of these embodiments, the modulator system includes a switch. In many of these embodiments, the modulator system includes a DC power supply.

[0088] In many of these embodiments, the acceleration voltage stability is based in part on the capacitive discharge associated with a plurality of capacitors in the tandem accelerator system.

[0089] In many of these embodiments, one of the electrodes of the tandem accelerator system or a plurality of electrodes is biased using a DC power supply. In many of these embodiments, the DC power supply responds to a feedback loop based on the capacitive discharge associated with a plurality of capacitors within the tandem accelerator system. In many of these embodiments, the DC power supply includes an extremely low voltage (ELV) DC power supply. In many of these embodiments, the duration is less than the response time of the feedback loop.

[0090] In many of these embodiments, the ion source includes an acceleration electrode. In many of these embodiments, the acceleration electrode is continuously biased using a first power supply.

[0091] In many of these embodiments, the ion source includes a plasma electrode. In many of these embodiments, the plasma electrode is continuously biased using a second power supply.

[0092] In many of these embodiments, the first power supply, the second power supply, and the third power supply of the modulator system are independent of each other.

[0093] In many of these embodiments, the negative ion beam passes through a pre-accelerator system downstream from the ion beam source system before reaching the tandem accelerator system. In many of these embodiments, the duration is short enough to avoid beam-induced damage to the components of the pre-accelerator system or the tandem accelerator system.

[0094] In many of these embodiments, the duration is sufficient to enable the provision of a proton beam having a beam energy of 2.5 megaelectron volts (MeV).

[0095] In many of these embodiments, the duration is sufficient such that less than 15% of the capacitive discharge within the tandem accelerator system occurs as a result of the introduction of the negative ion beam.

[0096] In many of these embodiments, the duration is sufficient such that a capacitive discharge within the tandem accelerator system of less than 6% occurs as a result of the introduction of the negative ion beam.

[0097] In many of these embodiments, the duration is long enough to enable steady-state ion extraction from the ion source. In many of these embodiments, the steady-state ion extraction ramp-up time for the ion source is 0.1 to 0.3 milliseconds (ms).

[0098] In many of these embodiments, the tandem accelerator system includes a plurality of input electrodes, a charge exchange device, and a plurality of output electrodes. In many of these embodiments, the plurality of input electrodes are configured to accelerate a negative ion beam from a pre-accelerator system, the charge exchange device is configured to convert the negative ion beam into a positive beam, and the plurality of output electrodes are configured to accelerate the positive beam. In many of these embodiments, a target device downstream from the tandem accelerator system is configured to form a neutral beam from the positive beam received from the tandem accelerator system. In many of these embodiments, the duration is short enough to avoid beam-induced damage to the target device.

[0099] In many embodiments, the method of beam modulation includes biasing the extraction electrode of the ion source for a duration sufficient to maintain the acceleration voltage stability of a tandem accelerator system configured such that the ion source provides a negative ion beam.

[0100] In many of these embodiments, the ion source is configured to generate negative hydrogen ions.

[0101] In many of these embodiments, the method includes biasing the extraction electrode over a period of less than 10 milliseconds (ms). In many of these embodiments, the method includes biasing the extraction electrode over a period of 0.5 to 1 millisecond (ms).

[0102] In many of these embodiments, the method includes, at least in part, measuring acceleration voltage stability based on a capacitive discharge associated with a plurality of capacitors of a tandem accelerator system.

[0103] In many of these embodiments, the method includes biasing one of the electrodes or a plurality of electrodes of the tandem accelerator system using a DC power supply.

[0104] In many of these embodiments, the DC power supply responds to a feedback loop based on a capacitive discharge associated with a plurality of capacitors within the tandem accelerator system.

[0105] In many of these embodiments, the method includes biasing the extraction electrode over a duration less than the response time of the feedback loop.

[0106] In many of these embodiments, the ion source includes an acceleration electrode. In many of these embodiments, the method includes continuously biasing the acceleration electrode using a first power supply.

[0107] In many of these embodiments, the ion source includes a plasma electrode. In many of these embodiments, the method includes continuously biasing the plasma electrode using a second power supply.

[0108] In many of these embodiments, the negative ion beam passes through a pre-accelerator system downstream from the ion source before reaching the tandem accelerator system. In many of these embodiments, the duration is short enough to avoid beam-induced damage to components of the pre-accelerator system or the tandem accelerator system.

[0109] In many of these embodiments, the duration is sufficient to enable the provision of a proton beam having a beam energy of 2.5 megaelectron volts (MeV).

[0110] In many of these embodiments, the duration is sufficient such that capacitive discharge within the tandem accelerator system is 6% or less as a result of the introduction of the negative ion beam.

[0111] In many of these embodiments, the ion source includes a non-cesium-added ion source.

[0112] In many of these embodiments, the duration is long enough to enable steady-state ion extraction from the ion source. In many of these embodiments, the steady-state ion extraction ramp-up time for the ion source is from 0.1 millisecond (ms) to 0.3 millisecond (ms).

[0113] In many embodiments, the beam system includes a source that includes an extraction electrode, the source being configured to generate a charged particle beam, and a modulator system connected to the extraction electrode of the source, the modulator system being configured to modulate the charged particle beam, and an accelerator configured to accelerate the modulated charged particle beam.

[0114] In many of these embodiments, the modulator system is configured to modulate the charged particle beam into a plurality of pulses. In many of these embodiments, each pulse has a duration sufficient to achieve steady-state particle extraction.

[0115] In many of these embodiments, the accelerator includes one or more capacitors. In many of these embodiments, the modulated beam does not discharge more than a threshold amount into one or more capacitors. In many of these embodiments, the threshold amount is 15% or less of a full charge of the one or more capacitors. In many of these embodiments, the threshold amount is 6% or less of a full charge of the one or more capacitors.

[0116] In many of these embodiments, the duration is less than 10 milliseconds (ms), and the duty cycle is 0.1 to 10%.

[0117] In many of these embodiments, the duration is in the range of 0.5 to 1.0 millisecond (ms).

[0118] In many of these embodiments, the modulator system is configured to modulate a charged particle beam and maintain the acceleration voltage stability of the accelerator.

[0119] In many of these embodiments, the acceleration voltage stability is at least partially based on a capacitive discharge associated with a plurality of capacitors of the accelerator.

[0120] In many of these embodiments, one of the electrodes of the accelerator or a plurality of electrodes is biased using a DC power source. In many of these embodiments, the DC power source responds to a feedback loop based on a capacitive discharge associated with a plurality of capacitors within the accelerator. In many of these embodiments, the duration is less than the response time of the feedback loop. In many of these embodiments, the accelerator is a tandem accelerator.

[0121] In many of these embodiments, the charged particle beam is a negative ion beam, and the accelerator is configured to convert the negative ion beam into a proton beam, and each pulse has a duration sufficient to enable the provision of a proton beam having a beam energy of 1.9 to 3.0 megaelectron volts (MeV).

[0122] In many of these embodiments, the modulation system is configured to modulate the charged particle beam such that the capacitive discharge within the accelerator does not exceed 15% during the acceleration of the modulated charged particle beam.

[0123] In many of these embodiments, the modulation system is configured to modulate the charged particle beam such that the capacitive discharge within the accelerator does not exceed 6% during the acceleration of the modulated charged particle beam.

[0124] In many of these embodiments, the accelerator is a tandem accelerator including a plurality of nested shells and one or more capacitors electrically coupled between adjacent shells, and the capacitive discharge is the discharge of one or more capacitors.

[0125] In many of these embodiments, the accelerator is a tandem accelerator including a plurality of input electrodes, a charge exchange device, and a plurality of output electrodes. In many of these embodiments, the charged particle beam is a negative ion beam, the tandem accelerator is configured to accelerate the negative ion beam using the plurality of input electrodes, the charge exchange device is configured to convert the negative ion beam into a positive beam, and the tandem accelerator is configured to accelerate the positive beam using the plurality of output electrodes. In many of these embodiments, the beam system includes a target device downstream from the tandem accelerator. In many of these embodiments, the target device is configured to form a neutral beam from the positive beam.

[0126] In many of these embodiments, the modulator system is configured to modulate the charged particle beam into a plurality of pulses. In many of these embodiments, each pulse has a duration limited to avoid thermal damage to the target device.

[0127] Note that for any embodiment provided in this specification, all features, elements, components, functions, and steps described in relation to that embodiment are intended to be freely combinable and substitutable with those from any other embodiment. If a feature, element, component, function, or step is described in relation to only one embodiment, it is to be understood that that feature, element, component, function, or step can be used with all other embodiments described in this specification, unless explicitly stated otherwise. This paragraph thus serves as a premise for the introduction of claims and as a description aid for combining features, elements, components, functions, and steps from different embodiments or substituting features, elements, components, functions, and steps from one embodiment with those from another, and the following description applies even if it does not explicitly state in a particular case that such combination or substitution is possible. In particular, given that the permissibility of any such combination and substitution will be readily recognized by those skilled in the art, it is explicitly recognized that an explicit listing of all possible combinations and substitutions would be unduly burdensome.

[0128] To the extent that embodiments disclosed herein include, or operate in association with, a memory, a storage device, and / or a computer-readable medium, that memory, storage device, and / or computer-readable medium is non-transitory. Thus, to the extent that a memory, a storage device, and / or a computer-readable medium is covered by one or more claims, that memory, storage device, and / or computer-readable medium is only non-transitory.

[0129] As used in this specification and the appended claims, the singular forms "a", "an", and "the" include plural referents unless the context clearly dictates otherwise.

[0130] Embodiments are subject to various modifications and alternative forms, specific examples of which are shown in the drawings and described in detail herein. However, it should be understood that these embodiments are not limited to the specific forms disclosed, but rather, these embodiments cover all modifications, equivalents, and alternatives falling within the spirit of the present disclosure. Further, any feature, function, step, or element of an embodiment may be listed in or added to the claims, together with a negative limitation that defines the inventive scope of the claims by features, functions, steps, or elements that do not fall within its scope.

Claims

1. An ion beam source system, wherein the ion beam source system comprises: An ion source configured to provide a negative ion beam to a tandem accelerator system downstream of the ion source, the tandem accelerator system comprising a plurality of capacitors; and an ion source, A modulator system connected to an extraction electrode of the ion source, Comprising, The modulator system is configured to bias the extraction electrode for a duration sufficient to achieve steady-state ion extraction and sufficient to maintain the acceleration voltage stability of the tandem accelerator system. The ion beam source system, wherein the duration is sufficient such that a capacitance discharge within the tandem accelerator system of less than 15% of the total capacitance of the plurality of capacitors occurs as a result of the introduction of the negative ion beam.

2. The ion beam source system according to claim 1, wherein the ion source is configured to generate negative hydrogen ions.

3. The ion beam source system according to claim 1, wherein the duration is less than 10 milliseconds (ms).

4. The ion beam source system according to claim 1, wherein the duration is in the range of 0.5 milliseconds (ms) to 1.0 milliseconds (ms).

5. The ion beam source system according to claim 1, wherein the modulator system comprises a switch and a DC power supply.

6. The ion beam source system according to claim 1, wherein one of the electrodes or a plurality of electrodes of the tandem accelerator system is biased using a DC power supply.

7. The DC power supply responds to a feedback loop based on a capacitance discharge associated with the plurality of capacitors, and the duration is less than the response time of the feedback loop. The ion beam source system according to claim 6.

8. The ion beam source system according to claim 1, wherein the ion source comprises an acceleration electrode configured to be continuously biased using a first power supply.

9. The ion beam source system according to claim 8, wherein the ion source comprises a plasma electrode configured to be continuously biased using a second power supply.

10. The ion beam source system further comprises a pre-accelerator system downstream from the ion beam source system, and the pre-accelerator system is configured to propagate the negative ion beam towards the tandem accelerator system. The ion beam source system according to claim 1.

11. The ion beam source system according to claim 10, wherein the duration is short enough to avoid beam-induced damage to components of the pre-accelerator system or the tandem accelerator system.

12. The ion beam source system according to claim 1, wherein less than 6% of the capacitive discharge within the tandem accelerator system occurs during the propagation of the negative ion beam through the tandem accelerator system.

13. The ion beam source system according to claim 1, wherein the steady-state ion extraction ramp-up time for the ion source is from 0.1 millisecond (ms) to 0.3 millisecond (ms).

14. The tandem accelerator system comprises a plurality of input electrodes, a charge exchange device, and a plurality of output electrodes. The plurality of input electrodes are configured to accelerate the negative ion beam from the pre-accelerator system, the charge exchange device is configured to convert the negative ion beam into a positive beam, and the plurality of output electrodes are configured to accelerate the positive beam. The ion beam source system according to claim 1.

15. The ion beam source system according to claim 14, wherein a target device downstream from the tandem accelerator system is configured to form a neutral beam from the positive beam received from the tandem accelerator system.

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