Multi-stage cavity cyclotron resonance accelerator

• US 6,914,396 B1
• Filed: 07/31/2001
• Issued: 07/05/2005
• Est. Priority Date: 07/31/2000
• Status: Expired due to Fees

• Current Assignee: L-3 Communications Corporation (L3Harris Technologies, Inc.), Yale University
• Original Assignee: L-3 Communications Corporation (L3Harris Technologies, Inc.), Yale University
• Inventors: Wang, Changbiao, Hirshfield, Jay L., Symons, Robert Spencer
• Primary Examiner(s): Lee, Wilson
• Application Number:
  US09/921,529
• Time in Patent Office: 1,435 Days
• Field of Search: 315500-507, 315/4, 315/5, 315/5.41, 315/5.42, 250/290, 250/292, 250/423.R
• US Class Current: 315/500
• CPC Class Codes: H05H 7/18 Cavities; Resonators travelling-wave tubes H01J23/18; hyperfrequency cavities in general H01P7/04, H01P7/06
• CPC Class Codes: H05H 9/00 Linear accelerators

Abstract

A high-current, high-gradient, high-efficiency, multi-stage cavity cyclotron resonance accelerator (MCCRA) provides energy gains of over 50 MeV/stage, at an acceleration gradient that exceeds 20 MeV/m, in room temperature cavities. The multi-stage cavity cyclotron resonance accelerator includes a charged particle source, a plurality of end-to-end rotating mode room-temperature cavities, and a solenoid coil. The solenoid coil encompasses the cavities and provides a substantially uniform magnetic field that threads through the cavities. Specifically, the MCCRA is provided with a constant magnetic field sufficient to produce a cyclotron frequency a little higher than the RF of the accelerating electric field. A plurality of input feeds, each of which respectively coupled to a cavity, are also provided. According to an embodiment of the invention, the beam from the first cavity passes through a cutoff drift tube and is accelerated further with a cavity supporting a still lower radio-frequency electric field. This embodiment yields a several-milliampere one-gigavolt proton beam efficiently. The single cavity transfers about 70% of the radio-frequency energy to the beam. A multiple-cavity accelerator using a constant or slightly decreasing static magnetic field along its length and using cutoff drift tubes between the cavities operating at progressively lower frequencies, each somewhat lower than the local relativistic cyclotron frequency of the beam in that cavity, provides an extremely-efficient, compact, continuously-operating, medium-energy accelerator. In another embodiment of the invention, the progressively lower frequencies are selected to decrease in substantially equal increments corresponding to a difference frequency. The charged particles are emitted in pulses in correspondence with the difference frequency.

Claims

1. A high-current, high-gradient, high-efficiency, multi-stage cavity cyclotron resonance accelerator (MCCRA) for accelerating charged particles, comprising:

a charged particle source for emitting pulses of said charged particles;

a plurality of successive rotating mode cavities extending in an axial direction and coupled to said charged particle source, wherein each successive cavity resonates at a progressively-lower RF resonance frequency to maintain approximate resonance of said pulses of charged particles, with the respective RF resonance frequency of each said successive cavity decreasing in substantially equal increments corresponding to a difference frequency, and said pulses of said charged particles being emitted in correspondence with said difference frequency; and

at least one solenoid coil coaxially disposed about said cavities, said solenoid coil proving a substantially uniform magnetic field along an axial extent of said plurality of successive cavities.

2. The MCCRA of claim 1, further comprising a coaxial dielectric liner disposed in at least one of said plurality of cavities.

3. The MCCRA of claim 1, further comprising a plurality of radial vanes disposed in at least one of said plurality of cavities.

4. The MCCRA of claim 3, wherein said plurality of radial vanes further comprise four radial vanes adapted to provide a radio-frequency double-dipole (RFDD).

5. The MCCRA of claim 1, wherein said charged particles are selected from a group consisting of ions, electrons, protons, and muons.

6. The MCCRA of claim 1, wherein each of said plurality of cavities resonates in a TE₁₁₁ mode.

7. A method of accelerating charged particles, comprising the steps of:

emitting said charged particles in pulses from a charged particle source;

transmitting said charged particle in an axial direction through a plurality of successive rotating mode cavities extending in an axial direction;

providing a substantially uniform magnetic field along an axial extent of said plurality of successive cavities; and

operating each successive cavity at a progressively-lower RF resonance frequency to maintain approximate resonance of said pulses of charged particles with the respective RF frequency of each said successive cavity decreasing in substantially equal increments corresponding to a difference frequency, and said pulses of said charged particles being emitted in correspondence with said difference frequency.

8. The method of claim 7, wherein the emitting step further comprises emitting said pulses of said charged particles at time intervals corresponding to an inverse of said difference frequency.

9. The method of claim 7, further comprising the step of capacitively loading at least one of said plurality of cavities.

10. The method of claim 7, wherein said charged particles are selected from a group consisting of ions, electrons, protons, and muons.

11. The method of claim 7, wherein said operating step further comprises resonating each of said plurality in a TE₁₁₁ mode.

12. A system for accelerating charged particles, comprising:

means for emitting pulses of said charged particles;

means for transmitting said charged particle in an axial direction through a plurality of successive rotating mode cavities extending in an axial direction;

means for providing a substantially uniform magnetic field along an axial extent of said plurality of successive cavities; and

means for operating each successive cavity at a progressively-lower RF frequency to maintain approximate resonance of said charged particle with the respective RF frequency of each said successive cavity decreasing in substantially equal increments corresponding to a difference frequency, and said pulses of said charged particles being emitted in correspondence with said difference frequency.

13. The system of claim 12, wherein each of said plurality of cavities resonates in a TE₁₁₁ mode.

14. The system of claim 12, further comprising means for reducing cutoff frequency for desired dipole modes.

15. The system of claim 12, wherein said charged particles are selected from a group consisting of ions, electrons, protons, and muons.

16. The system of claim 12, further comprising means for controlling an amount of power supplied to each one of said plurality of successive cavities.