Rotating dipole mode ion cyclotron auto-resonance accelerator

Abstract

Apparatuses and methods for accelerating charged particles include an accelerator. The accelerator includes a cavity comprising a chamber and conductive walls enclosing the chamber, and having one or more inlets and one or more outlets, an electro-magnet substantially surrounding at least a portion of the cavity; two or more rods disposed predominantly longitudinally within the chamber; and one or more RF couplers. The RF couplers are configured to generate a rotating or non-rotating dipole radio frequency field within the cavity by exciting the RF couplers in phase to accelerate the charged particles entering the cavity through the one or more inlets. The radio frequency field operates predominantly in transverse electromagnetic mode.

Description

100648.00046ROTATING DIPOLE MODE ION CYCLOTRON AUTO¬RESONANCE ACCELERATOR

[0001] The Government has rights in this invention pursuant to a USER Agreement between Particle Accelerator Research Foundation (PARF) and BROOKHAVEN SCIENCE ASSOCIATES, LLC, which manages and operates Brookhaven National Laboratory for the US Department of Energy under Contract No. DE-SC0012704.CROSS REFERENCE TO RELATED APPLICATIONS

[0002] This application claims priority to U.S. Provisional Application No. 63 / 707,636 filed October 15, 2024, and U.S. Provisional Application No. 63 / 752,313 filed January 31, 2025, both of which are incorporated herein in their entireties.TECHNICAL FIELD

[0003] Aspects of the present disclosure generally relate to apparatuses and methods for accelerating ions, protons, electrons, and / or other charged particles.BACKGROUND

[0004] Energetic charged particles have many usage applications in the fields of medicine, nuclear energy including transmutation of used nuclear fuel and accelerator driven systems, testing, experimental research, national security, etc. Examples of energetic charged particles include ions, protons, electrons, and positrons. Conventional equipment used in producing energetic charged particles may require high investment costs and large facilities or real estate, while limiting the mobility of the equipment. Therefore, there continue to be unmet needs for improvements in the production of energetic charged particles.SUMMARY

[0005] This summary is provided to introduce a selection of concepts in a simplified form that are further described below in the DETAILED DESCRIPTION. This summary is not intended to identify key features of the claimed subject matter, nor is it intended to be used as an aid in determining the scope of the claimed subject matter.AFSDOCS:303954570.2100648.00046

[0006] In some aspects, the techniques described herein relate to a device, including: an accelerator including: a cavity having a chamber, and conductive walls enclosing the chamber, one or more inlets and one or more outlets, two or more rods disposed longitudinally within the chamber; one or more RF couplers , the RF couplers being configured to generate a rotating (or non-rotating) dipole radio frequency field within the cavity by exciting each of the RF couplers with a phase difference to accelerate the charged particles entering the cavity through the one or more inlets, wherein the radio frequency field operates in predominantly transverse electromagnetic mode. It may also include one or more charged particle sources configured to provide charged particles entering the cavity through the one or more inlets. It may also include an electro-magnet substantially surrounding at least a portion of the cavity. It may also include a rf source configured to provide the radio frequency power through the RF couplers to the cavity.

[0007] Additional advantages and novel features of these aspects will be set forth in part in the description that follows, and in part will become more apparent to those skilled in the art upon examination of the following or upon learning by practice of the disclosure.BRIEF DESCRIPTION OF THE DRAWINGS

[0008] The features of various aspects of the disclosure are set forth in the appended claims. In the description that follows, like parts are marked throughout the specification and drawings with the same or similar numerals, respectively. The drawing figures are not necessarily drawn to scale, and certain figures may be shown in exaggerated or generalized form in the interest of clarity and / or conciseness. The disclosure itself, however, as well as a preferred mode of use, further advantages thereof, will be best understood by reference to the following detailed description of illustrative aspects of the disclosure when read in conjunction with the accompanying drawings, wherein:

[0009] FIG. 1 illustrates a schematic view of an example system of a charged particles accelerator, for use in accordance with aspects of the present disclosure;

[0010] FIG. 2 illustrates an example of a computer system for implementing a method of exchanging products in accordance with aspects of the present disclosure;

[0011] FIG. 3 illustrates a block diagram of various exemplary system components, in accordance with aspects of the present disclosure;

[0012] FIG. 4 illustrates a side view of an example of a charged particles accelerator, in accordance with aspects of the present disclosure;AFSDOCS:303954570.2100648.00046

[0013] FIG. 5 illustrates a cross-sectional view of the charged particles accelerator shown in FIG. 4, in accordance with aspects of the present disclosure;

[0014] FIG. 6 illustrates a cross-sectional view with example dimensions of the charged particles accelerator shown in FIG. 4, in accordance with aspects of the present disclosure;

[0015] FIG. 7A illustrates a top view of an example cavity, in accordance with aspects of the present disclosure;

[0016] FIG. 7B illustrates a cross-sectional view of the example cavity shown in FIG. 11 A in accordance with aspects of the present disclosure;

[0017] FIG. 8 illustrates a side view of an example beam tracking simulation of the charged particles accelerator shown in FIG. 4, in accordance with aspects of the present disclosure;

[0018]

[0019] FIG. 9 illustrates a perspective view of the example beam tracking simulation shown in FIG. 8, in accordance with aspects of the present disclosure;

[0020] FIG. 10 illustrates a top view of a cavity portion of the example beam tracking simulation shown in FIG. 8, in accordance with aspects of the present disclosure;

[0021] FIG. 11 illustrates examples of a rotating dipole radio frequency field generated in a cavity, in accordance with aspects of the present disclosure;

[0022]

[0023] FIG. 12 illustrates a superposition of simulated traces injected at all RF phases, in accordance with aspects of the present disclosure;

[0024] FIG. 13 illustrates an example of a half-wave resonator, in accordance with aspects of the present disclosure.

[0025] FIG. 14 illustrates a flow chart of an example of a method for accelerating charged particles, in accordance with aspects of the present disclosure.DETAILED DESCRIPTION

[0026] The following includes definitions of selected terms employed herein. The definitions include various examples and / or forms of components that fall within the scope of a term and that may be used for implementation. The examples are not intended to be limiting.AFSDOCS:303954570.2100648.00046

[0027] A “processor,” as used herein, processes signals and performs general computing and arithmetic functions. Signals processed by the processor may include digital signals, data signals, computer instructions, processor instructions, messages, a bit, a bit stream, or other computing that may be received, transmitted and / or detected.

[0028] A “memory,” as used herein may include volatile memory and / or non-volatile memory. Non-volatile memory may include, for example, ROM (read only memory), PROM (programmable read only memory), EPROM (erasable PROM) and EEPROM (electrically erasable PROM). Volatile memory may include, for example, RAM (random access memory), synchronous RAM (SRAM), dynamic RAM (DRAM), synchronous DRAM (SDRAM), double data rate SDRAM (DDR SDRAM), and / or direct RAM bus RAM (DRRAM).

[0029] An “operable connection,” as used herein may include a connection by which entities are "operably connected", is one in which signals, physical communications, and / or logical communications may be sent and / or received. An operable connection may include a physical interface, a data interface and / or an electrical interface.

[0030] High intensity neutron sources may have broad applications in fundamental research, nuclear energy, isotope production, medical therapy, material analysis and imaging. Particularly with great scientific impact, low-energy precision experiments using neutrons and decay nuclei may provide critical tests of the Standard Model. Neutron sources have become a desirable tool in discovering the violation of fundamental symmetry in electronic dipole moments, for example.

[0031] Aspects of the present disclosure may include an accelerator operating in predominately TEM mode. The accelerator may include one or more couplers in the TEM cavity that delivers a continuous or pulsed wave to accelerate charged particles injected into the cavity. The TEM cavity may be sufficiently compact to fit into a commercial medical magnetic resonant imaging (MRI) magnet and operated using a RF power source delivering sufficient power to accelerate the charged particles to desired particles energy and power, for example. The accelerator may include a magnet that maintains a cyclotron resonance condition inside the cavity. The cyclotron resonance condition, as known to one skilled in the art, may cause charged particles to gyrate in a substantially circular or elliptical path and accelerate under a continuous or pulsed oscillating electric field tuned to the resonance. The electric field may add kinetic energy to the charged particles.AFSDOCS:303954570.2100648.00046

[0032] Turning to FIG. 1, in some implementations, a schematic view of a nonlimiting example of a cyclotron auto-resonance system 100 for accelerating charged particles may include a charged particles source 102, various features of which may be usable in accordance with aspects of the present disclosure. The charged particles source 102 may provide charged particles using electron ionization, electron capture ionization, chemical ionization, charge exchange ionization, chemi-ionization, associative ionization, Penning ionization, ion attachment, inductively coupled plasma ionization, micro-wave plasma ionization, electron-cyclotron resonance ionization, glow discharge ionization, plasma afterglow ionization, spark ionization, and / or photoionization as known in the art. The particle source may operate in a pulsed mode to deliver bunched particle beams, or in a continuous wave mode (CW) to deliver unbunched particle beams. The cyclotron auto-resonance system may operate in a pulsed mode or in a CW mode.

[0033] In some examples, the charged particles source 102 may emit one or more charged particles, such as deuterons, protons, electrons, ions, and / or other particles carrying positive or negative electrical charges. The charged particles may be emitted by the charge particles source 102 into an optional low energy beam transport (LEBT) 104. The optional LEBT 104 may receive the charged particles from the charged particles source 102 and generate one or more beams of charged particles having energy levels of 10 kilo electron-volt (keV), 20 keV, 30 keV, 50 keV, 80 keV, 100 keV, 200 keV, 500 keV, or 1 MeV. Other energy levels are possible.

[0034] In certain implementations, the cyclotron auto-resonance system 100 may include an accelerator 106. The accelerator 106 may receive the one or more beams of charged particles from the LEBT 104 (optional). In certain examples, the optional LEBT 104 may guide the one or more beams of charged particles from the charged particles source 102 into the accelerator 106. The accelerator 106 may apply a radio frequency (RF) electro-magnetic wave (e.g., microwave) in predominantly TEM mode within the accelerator 106. The applied RF wave may accelerate the charged particles by inputting electro-magnetic energy into the charged particles. The one or more beams of charged particles may accelerate to energy levels (e.g., average) of 10 keV, 20 keV, 50 keV, 100 keV, 200 keV, 500 keV, 1 mega electron-volt (MeV), 2 MeV, 3 MeV, 5 MeV, 8 MeV, 10 MeV, 12 MeV, 15 MeV, 20 MeV, 30 MeV, 50 MeV, 100 MeV, 200 MeV, and / or 500 MeV. Other energy levels are possible.AFSDOCS:303954570.2100648.00046

[0035] In an aspect, the present disclosure provides an ion cyclotron auto-resonance accelerator, which may be referred to by the acronym iCARA. In some implementations, the iCARA may be configured to accelerate deuterons (i.e., deuterium ions) and may be referred to by the acronym dCARA.

[0036] U.S. Patent 10,492,287 entitled “Apparatus and method for isotope production based on a charged particle accelerator” describes a class of ion accelerator cavity structures that operate in a predominantly transverse electric-magnetic (TEM) mode. In this previous patent, continuous acceleration occurs in a dCARA coaxial TEM-mode cavity, where the ion beam traverses an annulus between an inner cylinder and an outer cylinder along an axis nearly parallel to, but displaced from the cavity axis. This structure, including two smooth coaxial cylinders with planar end plates, is immersed in a strong axial static magnetic field. The continuous (unbunched) deuterons injected at all RF phases undergo gyration motion while continuously being accelerated by the RF transverse electric field. A downstream beam manipulation system can be used to focus the accelerated beam; otherwise, the beam will raster along a spreading circular path as the magnetic field diverges. This configuration suffers from two deviations from ideal cyclotron auto-resonance acceleration since the RF fields in the coaxial structure are not rotating, resulting in an inherent (albeit small) ion energy spread and a sideways drift in the accelerated ion beam.

[0037] The iCARA of the present disclosure does not suffer from these deviations and thus can be said to conform ideally to the cyclotron auto-resonance concept. In an aspect, the present disclosure provides a TEM cavity structure that generates a rotating (or non-rotating) dipole mode whose RF electric and magnetic fields, together with a static axial magnetic field (B) provided by external coils, allow continuous (unbunched) acceleration of ions when the frequency of the applied RF fields is close to the ion cyclotron frequency f = QBI'ITIIV where Q and AT are the charge and mass of the ion. The rotating dipole mode structure includes two or more symmetrically-disposed rods within the chamber of the cavity. The RF fields are generated by feeding power into the structure using two or more symmetrically-disposed RF couplers that are driven with successive phase differences. In some implementations, the structure may include a resonant quarterwave cavity by choosing its length ( / .) to be approximately one-quarter of a free-space wavelength, i.e., L = c / f where c is the speed of light. In some implementations, the length may vary by 1%, 2%, or up to 5%. Other rotating-dipole configurations areAFSDOCS:303954570.2100648.00046 possible, including a half-wave resonator with L = c / 2f, multiple symmetrically-disposed conductors within the chamber of the cavity having a number M of circular or other crosssection shapes; and / or multiple symmetrically-disposed RF power couplers, including but not limited to loops, with a number N that are driven with successive phase differences of 360 / N degrees. The number N of loops may be equal to the number M of rods.

[0038] In a non-limiting example, the cyclotron auto-resonance system 100 may include an optional high energy beam transport (HEBT) 108. The optional HEBT 108 may guide the accelerated one or more beams of charged particles exiting the accelerator 106 into a target 110. The accelerated particles collide with the target nuclei, producing a shower of secondary particles for subsequent analysis or application. In some implementations, the optional HEBT 108 may focus the accelerated one or more beams of charged particles into a concentrated area on the target 110. In other implementations, the optional HEBT 108 may guide the accelerated one or more beams of charged particles into the distributed areas on the target 110. The target 110 may include a high-density supersonic helium jet gas target, a liquid / solid lithium target, a solid target, a cylindrical or spherical target, a copper target, a scandium target, and / or a rhenium target. As discussed further below, the target 110 may be selected by one skilled in the art, for example, depending on the desired application, including nuclear physics, medical imaging, national security, etc.

[0039] In some examples, the cyclotron auto-resonance system 100 may include an RF power source 112 that provides electrical power to the accelerator 106. The RF power source 112 may provide a continuous or pulsed wave operating at 10 megahertz (MHz), 20 MHz, 30 MHz, 50 MHz, 70 MHz, 100 MHz, 150 MHz, 200 MHz, or 500 MHz. Other frequencies are possible. The RF power source 112 may be able to supply 10 kilowatt (kW), 20 kW, 30 kW, 50 kW, 70 kW, 100 kW, 200 kW, 500 kW of electrical power. Other power levels are possible. In some implementations, the frequency of the wave may be matched to the cyclotron resonant frequency (described below).

[0040] Still referring to FIG. 1, the cyclotron auto-resonance system 100 may include a computer system 200 configured to automatically control the generation of accelerated charged particles and / or various other features of the system 100, such as those used for one or more accelerated beams of charge particles, via communication links 150. The communication links 150 may be wired and / or wireless couplings, including WI-FI ® links, BLUTOOTH ® links, General Purpose Interface Bus (GPIB) links, Parallel links,AFSDOCS:303954570.2100648.00046Serial links, Universal Serial Bus (USB) links, Peripheral Component Interconnect (PCI) link, or other suitable communication couplings.

[0041] In an aspect of the present disclosure, features are directed toward one or more computer systems capable of carrying out the functionality described herein. An example of such the computer system 200 is shown in FIG. 2. The computer system 200 may include one or more processors, such as the processor 204. The processor 204 is connected to a communication infrastructure 206 (e.g., a communications bus, cross-over bar, or network). Various software aspects are described in terms of this example computer system. After reading this description, it will become apparent to a person skilled in the relevant art(s) how to implement aspects of the disclosure using other computer systems and / or architectures.

[0042] The computer system 200 may include a display interface 202 that forwards graphics, text, and other data from the communication infrastructure 206 (or from a frame buffer not shown) for display on a display unit 230. Computer system 200 also includes a main memory 208, preferably random-access memory (RAM), and may also include a secondary memory 210. The secondary memory 210 may include, for example, a hard disk drive 212, and / or a removable storage drive 214, representing a floppy disk drive, a magnetic tape drive, an optical disk drive, a universal serial bus (USB) flash drive, etc. The removable storage drive 214 reads from and / or writes to a removable storage unit 218 in a well-known manner. Removable storage unit 218 represents a floppy disk, magnetic tape, optical disk, USB flash drive etc., which is read by and written to removable storage drive 214. As will be appreciated, the removable storage unit 218 includes a computer usable storage medium having stored therein computer software and / or data.

[0043] Alternative aspects of the present disclosure may include secondary memory 210 and may include other similar devices for allowing computer programs or other instructions to be loaded into computer system 200. Such devices may include, for example, a removable storage unit 222 and an interface 220. Examples of such may include a program cartridge and cartridge interface (such as that found in video game devices), a removable memory chip (such as an erasable programmable read only memory (EPROM), or programmable read only memory (PROM)) and associated socket, and other removable storage units 222 and interfaces 220, which allow software and data to be transferred from the removable storage unit 222 to computer system 200.AFSDOCS:303954570.2100648.00046

[0044] Computer system 200 may also include a communications interface 224. Communications interface 224 allows software and data to be transferred between computer system 200 and external devices. Examples of communications interface 224 may include a modem, a network interface (such as an Ethernet card), a communications port, a Personal Computer Memory Card International Association (PCMCIA) slot and card, etc. Software and data transferred via communications interface 224 are in the form of signals 228, which may be electronic, electromagnetic, optical or other signals capable of being received by communications interface 224. These signals 228 are provided to communications interface 224 via a communications path (e.g., channel) 226. This path 226 carries signals 228 and may be implemented using wire or cable, fiber optics, a telephone line, a cellular link, an RF link and / or other communications channels. In this document, the terms “computer program medium” and “computer usable medium” are used to refer generally to media such as a removable storage unit 218, a hard disk installed in hard disk drive 212, and signals 228. These computer program products provide software to the computer system 200. Aspects of the present disclosure are directed to such computer program products.

[0045] Computer programs (also referred to as computer control logic) are stored in main memory 208 and / or secondary memory 210. Computer programs may also be received via communications interface 224. Such computer programs, when executed, enable the computer system 200 to perform the features in accordance with aspects of the present disclosure, as discussed herein. In particular, the computer programs, when executed, enable the processor 204 to perform the features in accordance with aspects of the present disclosure. Accordingly, such computer programs represent controllers of the computer system 200.

[0046] In an aspect of the present disclosure where the method is implemented using software, the software may be stored in a computer program product and loaded into computer system 200 using removable storage drive 214, hard drive 212, or communications interface 220. The control logic (software), when executed by the processor 204, causes the processor 204 to perform the functions described herein. In another aspect of the present disclosure, the system is implemented primarily in hardware using, for example, hardware components, such as application specific integrated circuits (ASICs). Implementation of the hardware state machine so as to perform the functions described herein will be apparent to persons skilled in the relevant art(s).AFSDOCS:303954570.2100648.00046

[0047] FIG. 3 illustrates a block diagram of various example system components for use with implementations in accordance with an aspect of the present disclosure. FIG. 3 shows a communication system 300 usable in accordance with aspects of the present disclosure. The communication system 300 includes one or more accessors 360, 362 (also referred to interchangeably herein as one or more “users”) and one or more terminals 342, 366. In one aspect, data for use in accordance with aspects of the present disclosure may, for example, be input and / or accessed by accessors 360, 362 via terminals 342, 366, such as personal computers (PCs), minicomputers, mainframe computers, microcomputers, telephonic devices, or wireless devices, such as personal digital assistants (“PDAs”) or a hand-held wireless devices coupled to a server 343, such as a PC, minicomputer, mainframe computer, microcomputer, or other device having a processor and a repository for data and / or connection to a repository for data, via, for example, a network 344, such as the Internet or an intranet, and couplings 345, 346, 364. The couplings 345, 346, 364 include, for example, wired, wireless, or fiberoptic links. In another example variation, the method and system in accordance with aspects of the present disclosure operate in a stand-alone environment, such as on a single terminal. In some aspects, the cyclotron auto-resonance system 100 may be connected to the network 344 via a coupling 352. The data from the cyclotron auto-resonance system 100 may be accessed via the network 344 by, for example, the terminals 342, 366. The cyclotron auto-resonance system 100 may also access data from, for example, the server 343 via the network 344.

[0048] FIG. 4 illustrates a side view of an example of a charged particles accelerator 400. The accelerator 400 includes a cavity 410 having a chamber 422 and conductive walls 420 enclosing the chamber. The cavity 410 includes one or more inlets 412 for receiving one or more streams of charged particles (e.g., ion source 414). In some implementations, the present disclosure allows a single inlet within the rotating dipole cavity 410. Whereas previous accelerator designs include a central conductor, in the present disclosure the rods 416 may be located off axis inside the chamber 422 of the cavity, leaving an open space in the cavity. The shape of the rods may be cylinder, and the cross section of the rods may be circular, elliptical, or of a different shape, and the cross section of the rods may change along the longitudinal location of the rods. The RF couplers between the rods may be phased to create a rotating dipole field. That is, each of the RF couplers may be excited with a phase difference between successive loops. TheAFSDOCS:303954570.2100648.00046RF couplers may also be phased to create a non-rotating dipole field. At the end of the rods 416 is an RF cutoff section 424. The RF field is not applied in the RF cutoff section 424, but the particles continue through the outlets 440.

[0049] In some implementations, the accelerator 400 may include a cavity 410, such as a TEM cavity. The cavity 410 may include an outer conductor (e.g., conductive walls 420 enclosing the chamber 422 of the cavity). The cavity 410 may apply a RF electromagnetic wave (e.g., radio wave or microwave) in predominantly TEM mode. Alternatively, the cavity may apply a RF wave operating in transverse electrical (TE) mode or transverse magnetic (TM) mode. In certain examples, the cavity 410 may function as a waveguide for the applied RF wave. The applied RF wave may accelerate the one or more streams of charged particles by inputting electro-magnetic energy into the charged particles. The energy of the charged particles in the one or more beams of charged particles may increase to energy levels of 500 keV, 1 mega electron-volt (MeV), 2 MeV, 3 MeV, 5 MeV, 8 MeV, 10 MeV, 12 MeV, 15 MeV, 20 MeV, and / or 30 MeV, for example. Other energy levels are possible.

[0050] In some examples, the length of the cavity 410 may be configured such that the cavity 410 operates as a half-wave resonator (HWR) for the applied RF wave (i.e., the length of the cavity is approximately one half of the wavelength of the applied RF wave). In other examples, the length of the cavity 410 may be configured such that the cavity operates as a quarter-wave resonator (QWR) for the applied RF wave (i.e., the length of the cavity is approximately 14 of the wavelength of the applied RF wave). In some examples, the length of the cavity may be configured to be multiples of a quarter of a wavelength of the applied RF wave.

[0051] In certain implementations, the accelerator 400 may include a magnet 430. The magnet 430 may be a superconducting electro-magnet, an electro-magnet, a permanent magnet, and / or an electro-permanent magnet. In some implementations, the magnet 430 includes one or more main coils 432, one or more compensating coils 434, and one or more canceling coils 436. The magnet 430 may be surrounded by a shield 438. Different configurations of the solenoids and the shield of the magnet may be possible. The magnet 430 may be cooled to a critical temperature, or below, as needed for use and / or operation of any superconducting materials inside the magnet. The magnet 430 may include materials such as niobium titanium, niobium tin, vanadium gallium, magnesium diboride, bismuth strontium calcium copper oxide, yttrium barium copperAFSDOCS:303954570.2100648.00046 oxide, and / or other suitable materials. The magnetic field strength of the magnet may be 1 Tesla, 2 Tesla, 5 Tesla, 7 Tesla, 10 Tesla, or other suitable field strength. In some examples, the magnet 430 may maintain a cyclotron resonant condition in the cavity. The cyclotron resonance condition, as known to one skilled in the art, may cause charged particles to gyrate in a substantially circular or elliptical path and accelerate under a continuous or pulsed oscillating electric field tuned to the resonance. The electric field may add kinetic energy to the charged particles. The magnet 430 may repel or otherwise operate to maintain the one or more streams of charged particles at a minimum distance from the inner wall (e.g., cylinder 420) and / or the rods 416 of the cavity. In a non-limiting example, the magnet 430 may prevent the one or more streams of charged particles from contacting an inner wall of the cavity.

[0052] Still referring to FIG. 4, the accelerator 400 may include one or more outlets 440. The one or more streams of charged particles may exit the cavity 410 via the one or more outlets 440. In some implementations, the accelerator 400 may have a single outlet 440 defined by the single beam pipe 420. The RF field is not applied in the outlet 440. In some implementations, additional static or oscillating electric fields, static or oscillating magnetic fields, or electromagnetic fields may be applied beyond the outlet 440 to manipulate the trajectories of the charged particles.

[0053] In some implementations, the accelerator 400 includes a high-energy beam transport (HEBT) 450. The HEBT 450 includes an expansion section 452 and a transport section 454. The expansion section 452 extends from the outlet 440 and increases in diameter. The transport section 454 extends from the expansion section and has a uniform diameter. A focusing solenoid 456 surrounds the transport section 454 near the expansion section 452. As the charged particles exit the cavity 410 via the outlet 440, the particles move in a helical path with an expanding radius. The focusing solenoid 456 generates a magnetic field that deflects the particles inwardly as the particles leave the expansion section 452. The transport solenoid 458 is located further downstream and may further deflect the particles inward to focus on a target. A plural of focusing solenoids or transport solenoids may be used.

[0054] FIG. 5 illustrates a cross-sectional view of the charged particles accelerator 400 shown in FIG. 4. Notably, as illustrated, the cavity 410 does not include a central conductor. Instead, the rods 416 are located within the chamber 422 of the cavity 410.AFSDOCS:303954570.2100648.00046

[0055] FIG. 6 illustrates a cross-sectional view with example dimensions of the charged particles accelerator shown in FIG. 4. The size of the accelerator 400 may be relatively small. For example, the length of the cavity 410 may be less than 5m, preferably less than 2 m. In the illustrated example, the length of the cavity is 1.58m. The cavity has an outer diameter of 0.72m measured at the inner wall of inner cylinder 420. The magnet 430 has a length of 2.5m and diameter of 2.0m. The transport section 454 has a length of 3.9m and a diameter of 1.3m. The focusing solenoid 456 has a width of 0.7m. As illustrated, the target would be located to the right of the HEBT 450.

[0056] FIG. 7A illustrates a top view 700 of an example cavity. FIG. 7B illustrates a cross sectional view 720 of the example cavity. The cavity includes a chamber and conductive walls enclosing the chamber. The chamber 422 may extend further than the conducting walls 420 through the inlets and outlets. The outlet 440 may form the RF cutoff section 424. The rods 416 are evenly spaced about the circumference within the chamber 420 and extend approximately the length of the chamber. For example, as illustrated, four rods 416 are spaced 90° apart. The rods 416 may be suspended from an upper end plate from one end wall of the chamber. The RF couplers 710 may be located at the end of the chamber 420 adjacent the inlet between the rods 416. Other locations of the couplers may be possible. As illustrated, the RF couplers 710 are also spaced evenly, (e.g., 90° apart). The illustrated example is for a quarter-wave cavity, so the rods 416 terminate before the end of the cavity, after which a cutoff beam pipe conveys the accelerated beam to the HEBT. In some implementations, the rods 416 are hollow and coupled to a coolant source to allow circulation of coolant because a major proportion of the Ohmic power losses in the cavity is on the rods, rather than on the surrounding cylinder. In some implementations, a greater number of rods and / or RF couplers may be used.

[0057] FIG. 8 illustrates a side view 800 of an example beam tracking simulation of the charged particles accelerator shown in FIG. 4. FIG. 9 illustrates a perspective view 900 of the example beam tracking simulation. FIG. 10 illustrates a top view 1010 of the cavity 410 in the example beam tracking simulation. The particles experience rapid cyclotronic acceleration within the cavity 410. Upon exiting the cavity, the accelerated particles are contained and directed within the expansion section 452 and the transport section 454. In FIG 8-1 IB, the particles are injected into the cavity at a single arbitrary phase of the RF field.AFSDOCS:303954570.2100648.00046

[0058] In the illustrated tracking simulation, particles of deuteron are injected at up to 250 mA and 40keV. The acceleration occurs within the cavity 410 such that the output is 40MeV.

[0059] The conceptual beam dynamics design was carried out using CST Studio Particle Tracking solver, and preliminarily tested using Particle-In-Cell (PIC) simulation. The simulated traces in FIGS. 7-9 portray dCARA performance. The deuterons move on helical orbits around a strong magnetic field, acquiring energy continuously and without bunching during many revolutions within the cavity, in synchronism with the rotating RF fields. Two static focusing magnets allow the diameter of the area swept by the deuteron beam to be adjusted to match the area of the breakup target as well as the incident angle to the target, which in turn can match the area for parts arrayed for used nuclear fuel (UNF) transmutation.

[0060] It is worth emphasizing that the tracking simulations of FIGs. 7-10 only depict the history of individual particle trajectories. There are actually no tightly adjacent simultaneous orbits as seemingly implied in FIGS. 7-10. The instantaneous spatial distribution of the continuous beam produces prolonged gyrating orbits, which make dCARA much more resilient to the beam halo effect and inter-orbit instability. The tracking simulation is subjected to the limitation that the RF fields in the dCARA cavity are prescribed in the tracking simulation where the fields are free of transients from initiation of pulses in the RF power, and free of distortions the beam itself might impose. Field distortions, and the alterations in orbits they cause, arise from space-charge and finite beam current; from parasitic mode excitation; and from wake fields. These can be sources for beam instabilities, including beam breakup and beam reflections. Instabilities are not in evidence in dCARA as seen in the continuous un-bunched nature of the beam. Accordingly, dCARA may provide improved beam stability. The PIC simulation can incorporate the excitation, distortions and transients of electromagnetic fields as well as space charge effect.

[0061] In the illustrations, acceleration of deuterons is shown from 40 keV to 40 MeV in a dCARA cavity less than 3 meters in length. The example is shown for the exceptionally high current up to 250 mA, which is possible in dCARA because of the absence of bunching, wherein highly concentrated charged particles create intense non- uniform fields that can lead to beam instability. Operation at high beam current is desirable for the isotope transmutation application in order to effect a transmutation rateAFSDOCS:303954570.2100648.00046 for the present stockpile of used nuclear fuel that can substantially reduce its long-term toxicity in a matter of decades, rather than centuries. The deuteron energy of 40 MeV is in a desirable range, since subsequent deuteron breakup will produce neutrons of energy about 16 MeV that can, either as is or by slowing, prove effectual in transmutation. The static magnetic field configuration needed for idealized cyclotron auto-resonance acceleration is produced by judicious selection of coils that surround the dCARA accelerator cavity. Further details should be self-explanatory through study of the illustrations.

[0062] FIG. 12 illustrates examples of a rotating dipole radio frequency field generated in a cavity. The operating mode utilized with a TEM quarter- wave cavity is the rotating dipole mode with a certain circular polarization, one among four neardegenerate modes which can be excited depending upon the relative phase of the RF fields driven at the four coupling loops. When only two loops opposing one another vertically (horizontally) are driven in phases 0 and 180°, a non-rotating stationary vertical (horizontal) dipole mode is excited.

[0063] The RF couplers may be excited in phase to generate the rotating (or nonrotating) dipole field. For example, in the example cavity 410 with 4 rods 416 and 4 coupling loops 710, each coupling loop 710 may have a phase offset by 90° from a previous coupling loop. For instance, phases of 0°, 90°, 180° and, 270° for the loop excitations moving clockwise around the end face of the cavity produce both horizontal and vertical dipole modes, but with the 90° phase shift between them, resulting in a clockwise rotating dipole mode. Similarly, for the same phases going counter-clockwise, a counter-clockwise rotating dipole mode is excited. The direction of rotation of the dipole fields must be the same as the direction of rotation of ions in the magnetic field, which in turn depends upon the charge on the ions and upon the direction of the magnetic field. Other scenarios are that a monopole mode is excited if all the loops are driven in phase, and an RF quadrupole mode is excited when phases are 0°, 180°, 360° and, 540°. The operating mode dominates other modes given the controlled phase and amplitude balance at each coupling port.

[0064] The cavity may apply a RF wave (originating from the RF power source) to the one or more streams of charged particles in the cavity via the RF couplers. Under the application of the electro-magnetic field by the RF wave, the charged particles in the one or more streams of charged particles may move in a direction away from the one or moreAFSDOCS:303954570.2100648.00046 inlets 412 toward the one or more outlets 440. Contemporaneously, the energy levels of the charged particles may increase as a result of the application of the RF wave. The energy of the charged particles in the one or more beams of charged particles may increase to energy levels of 500 keV, 1 mega electron-volt (MeV), 2 MeV, 3 MeV, 5 MeV, 8 MeV, 10 MeV, 12 MeV, 15 MeV, 20 MeV, 30 MeV and / or 40 MeV. Other energy levels may be possible.

[0065] In some implementations, magnetic coils inside the magnet 430 include wires of superconducting materials such as niobium titanium, niobium tin, vanadium gallium, magnesium diboride, bismuth strontium calcium copper oxide, yttrium barium copper oxide, and / or other suitable materials wound around or otherwise distributed within at least a portion of the cavity 410. In some examples, the magnetic coils and / or other features may be cooled by coolants (e.g., liquid helium or liquid nitrogen) disposed within or about the magnet. The magnetic coils may maintain the one or more streams of charged particles a minimum distance from an inner wall of the cavity 410. The magnetic field may have greatest strength in the area of the cavity. Active and passive shielding may be used to contain the magnetic field radially close to the accelerator. The magnetic field an axial magnetic field in the direction of the acceleration.

[0066] FIG. 12 illustrates a superposition of simulated traces injected at all RF phases. The path of each particle is based on the phase. Accordingly, injecting a continuous stream of particles as the phase cycles causes the accelerated particles to trace a circular path at a target. To compare, for a pulsed stream of particles, the trajectories of the accelerated particles are depicted in FIG 8-10.

[0067] FIG. 13 is a diagram 1300 illustrating an example of a cavity 1310 for a halfwave resonator. A length of the cavity 1310 is approximately one half of a wavelength of a radio frequency wave. The cavity 1310 is formed by a cylindrical wall 1320 forming a chamber. A charged particle source provides charged particles via an inlet 1314. In the illustrated example, the cavity 1310 has an end wall at the inlet end and an end wall at the outlet end.

[0068] The rods 1316 extend from the end wall of the cavity including the inlet to the end wall of the cavity including the outlet 1324. In some implementations, the rods 1316 are hollow. Coolant may be passed through the rods and / or around the cylindrical wall 1320 in a fluid circuit.AFSDOCS:303954570.2100648.00046

[0069] Turning now to FIG. 14, a flowchart of an example method 1900 for accelerating charged particles may be performed by the cyclotron auto-resonance system 100 of FIG. 1, for example.

[0070] At block 1402, the method 1400 may include receiving a plurality of charged particles via one or more inlets in a cavity of an accelerator. For example, the cavity of the accelerator 400 (FIG. 4) may receive a plurality of charged particles via one or more inlets.

[0071] At block 1404, the method 1400 may include applying a rotating dipole radio frequency wave in transverse electromagnetic mode via a plurality of RF couplers to accelerate the plurality of charged particles. For example, the coupling loops 710 and rods 416 in the cavity 410 may apply the rotating dipole radio frequency wave in transverse electromagnetic mode to accelerate the plurality of charged particles. For example, the coupling loops 710 may be excited in phase to generate the rotating dipole radio frequency wave. In some implementations, at sub-block 1406, the block 1404 may optionally include exciting the plurality of RF couplers with equal successive phase differences in a clockwise or counterclockwise direction around an end face of the cavity to excite the rotating dipole mode in a same direction as the phase differences.

[0072] At block 1408, the method 1400 includes maintaining a cyclotron resonance condition and / or preventing the plurality charged particles from contacting an inner wall of a cavity via an electro-magnet. For example, the magnet of the accelerator in FIG. 4 may maintain a cyclotron resonance condition and / or prevent the plurality of charged particles from contacting an inner wall of the cavity.

[0073] At block 1410, the method 1400 may optionally include supplying a coolant via the two or more rods and via the walls of the cavity. For example, a coolant supply (e.g., a water pipe) may supply a coolant via the two or more rods 416 and via the walls of the cavity. At 1412, the method 1400 may include emitting the plurality of accelerated charged particles via one or more outlets. For example, the cavity 410 of the accelerator 400 (FIG. 4) may emit the plurality of accelerated charged particles via one or more outlets 440.

[0074] While the aspects described herein have been described in conjunction with the example aspects outlined above, various alternatives, modifications, variations, improvements, and / or substantial equivalents, whether known or that are or may be presently unforeseen, may become apparent to those having at least ordinary skill in theAFSDOCS:303954570.2100648.00046 art. Accordingly, the example aspects, as set forth above, are intended to be illustrative, not limiting. Various changes may be made without departing from the spirit and scope of the disclosure. Therefore, the disclosure is intended to embrace all known or later- developed alternatives, modifications, variations, improvements, and / or substantial equivalents.

[0075] Also, it will be appreciated that various implementations of the abovedisclosed and other features and functions, or alternatives or varieties thereof, may be desirably combined into many other different systems or applications. Also that various presently unforeseen or unanticipated alternatives, modifications, variations, or improvements therein may be subsequently made by those skilled in the art which are also intended to be encompassed by the following claims.AFSDOCS:303954570.2

Claims

100648.00046CLAIMSWHAT IS CLAIMED IS:

1. A device, comprising: an accelerator including: a cavity comprising a chamber and conductive walls enclosing the chamber, and having one or more inlets and one or more outlets; two or more rods disposed predominantly longitudinally within the chamber; one or more couplers being configured to generate a dipole radio frequency field within the cavity by exciting each of the RF couplers with a phase difference to accelerate the charged particles entering the cavity through the one or more inlets, wherein the radio frequency field operates in a predominantly transverse electromagnetic mode.

2. The device of claim 1, wherein the RF couplers are configured to generate a rotating dipole radio frequency field.

3. The device of claim 2, wherein the plurality of RF couplers are excited with equal successive phase differences in a clockwise or counterclockwise direction to excite a rotating dipole mode in a same direction as the phase differences.

4. The device of claim 1, wherein the RF couplers are configured to generate a nonrotating dipole radio frequency field.

5. The device of claim 1, wherein the one or more inlets comprise a single inlet located at an open space of the chamber between the cavity rods.

6. The device of claim 1, wherein the rods extend substantially a length of the chamber of the cavity, and the outlets extend past the chamber forming a radio frequency cutoff section.AFSDOCS:303954570.2100648.000467. The device of claim 1, wherein the cavity is a quarter-wave resonator having a length of approximately one quarter of a wavelength of a radio frequency wave applied via the plurality of RF couplers.

8. The device of claim 1, wherein the cavity is a half-wave resonator having a length of approximately one half of a wavelength of a radio frequency wave applied via the one or more RF couplers.

9. The device of claim 1, wherein the two or more rods are hollow and coupled to a supply of coolant.10 The device of claim 1, further comprising a beam transport comprising a cylindrical tube and one or more magnets surrounding the cylindrical tube and configured to guide an accelerated beam of charged particles exiting the accelerator toward a target.

11. The device of claim 7, further comprising the target, wherein the target will be illuminated by the accelerated charged particles.

12. The device of claim 1, further comprising a charged particle source configured to provide charged particles.

13. The device of claim 1 , further comprising a magnet substantially surrounding at least a portion of the cavity.

14. The device of claim 1, further comprising a radio frequency power source.

15. The device of claim 1, wherein the charged particles are particles of deuteron that are injected at approximately tens of mA and tens of keV and accelerated to between 100 keV and 50 MeV.

16. A method comprising: receiving a plurality of charged particles via one or more inlets in a cavity of an accelerator, the cavity comprising a chamber and conducting walls enclosing theAFSDOCS:303954570.2100648.00046 chamber, and two or more rods disposed predominantly longitudinally within the chamber; applying a radio frequency wave in transverse electromagnetic mode via one or more RF couplers to accelerate the plurality of charged particles; maintaining a cyclotron resonance condition within the cavity via an electromagnet; and emitting the plurality of accelerated charged particles via one or more outlets.

17. The method of claim 16, wherein the one or more inlets comprise a single inlet located at the open space of the chamber of the cavity.

18. The method of claim 16, wherein the rods extend substantially a length of the chamber of the cavity, and the outlets extend past the chamber forming a radio frequency cutoff section.

19. The method of claim 16, wherein applying the rotating dipole radio frequency wave in predominantly transverse electromagnetic mode comprises exciting the plurality of RF couplers with equal successive phase differences in a clockwise or counterclockwise direction to excite a rotating dipole mode in a same direction as the phase differences.

20. The method of claim 16, wherein the cavity is a quarter- wave resonator having a length of approximately one quarter of a wavelength of a radio frequency wave applied via the plurality of RF couplers, the cavity including two or more rods and one or more RF couplers.

21. The method of claim 16, wherein the two or more rods are hollow, further comprising supplying a coolant via the two or more rods.

22. The method of claim 10, further comprising guiding a beam of the accelerated charged particles exiting the accelerator toward a target via a beam transport comprising a cylindrical tube and one or more magnets surrounding the cylindrical tube.AFSDOCS:303954570.2100648.0004623. The method of claim 16, further comprising illuminating the target with the accelerated charged particles.

24. The method of claim 10, wherein the charged particles are particles of deuteron that are injected at tens of mA and tens of keV and accelerated to between 100 keV and 50 MeV.AFSDOCS:303954570.2

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