Interrupted Particle Source

• US 20090140672A1
• Filed: 11/30/2007
• Published: 06/04/2009
• Est. Priority Date: 11/30/2007
• Status: Active Grant

• Current Assignee: Mevion Medical Systems Incorporated
• Original Assignee: Mevion Medical Systems Incorporated
• Inventors: Zwart, Gerrit Townsend, Gall, Kenneth
• Granted Patent: US 8,581,523 B2
• Time in Patent Office: Days
• US Class Current: 315/502
• CPC Class Codes: H05H 13/02 Synchrocyclotrons, i.e. frequency modulated cyclotrons

Abstract

A synchrocyclotron includes magnetic structures to provide a magnetic field to a cavity, a particle source to provide a plasma column to the cavity, where the particle source has a housing to hold the plasma column, and where the housing is interrupted at an acceleration region to expose the plasma column, and a voltage source to provide a radio frequency (RF) voltage to the cavity to accelerate particles from the plasma column at the acceleration region.

Claims

1. A synchrocyclotron comprising:

magnetic structures to provide a magnetic field to a cavity;

a particle source to provide a plasma column to the cavity, the particle source having a housing to hold the plasma column, the housing being interrupted at an acceleration region to expose the plasma column; and

a voltage source to provide a radio frequency (RF) voltage to the cavity to accelerate particles from the plasma column at the acceleration region.

2. The synchrocyclotron of claim 1, wherein the magnetic field is above 2 Tesla (T), and the particles accelerate from the plasma column outwardly in spirals with radii that progressively increase.

3. The synchrocyclotron of claim 1, wherein the housing comprises two portions that are completely separated at the acceleration region to expose the plasma column.

4. The synchrocyclotron of claim 1, wherein the voltage source comprises a first dee that is electrically connected to an alternating voltage and a second dee that is electrically connected to ground;

and

wherein at least part of the particle source passes through the second dee.

5. The synchrocyclotron of claim 1, further comprising a stop in the acceleration region, the stop for blocking acceleration of at least some of the particles from the plasma column.

6. The synchrocyclotron of claim 5, wherein the stop is substantially orthogonal to the acceleration region and is configured to block certain phases of particles from the plasma column.

7. The synchrocyclotron of claim 1, further comprising:

cathodes for use in generating the plasma column, the cathodes being operable to pulse a voltage to ionize gas to generate the plasma column;

wherein the cathodes are not heated by an external heat source.

8. The synchrocyclotron of claim 7, wherein the cathodes are configured to pulse at voltages between about 1 kV to about 4 kV.

9. The synchrocyclotron of claim 7, further comprising:

a circuit to couple voltage from the RF voltage to the at least one of the cathodes.

10. The synchrocyclotron of claim 9, wherein the circuit comprises a capacitive circuit.

11. The synchrocyclotron of claim 1, wherein the magnetic structures comprise magnetic yokes, wherein the voltage source comprises a first dee that is electrically connected to an alternating voltage and a second dee that is electrically connected to ground, wherein the first dee and the second dee form a tunable resonant circuit, and wherein the cavity comprises a resonant cavity containing the tunable resonant circuit.

12. A particle accelerator comprising:

a tube containing a gas;

a first cathode adjacent to a first end of the tube; and

a second cathode adjacent to a second end of the tube, the first and second cathodes applying voltage to the tube to form a plasma column from the gas;

wherein particles are available to be drawn from the plasma column for acceleration; and

a circuit to couple energy from an external radio frequency (RF) field to at least one of the cathodes.

13. The particle accelerator of claim 12, wherein the tube is interrupted at an acceleration region at which the particles are drawn from the plasma column;

and

wherein the first cathode and the second cathode are not heated by an external source.

14. The particle accelerator of claim 12, wherein the first cathode is on a different side of the acceleration region than the second cathode.

15. The particle accelerator of claim 13, further comprising:

a voltage source to provide the RF field, the RF field for accelerating the particles from the plasma column at the acceleration region.

16. The particle accelerator of claim 15, wherein the energy comprises a portion of the RF field provided by the voltage source.

17. The particle accelerator of claim 13, wherein the circuit comprises a capacitor to couple the energy from the external field to at least one of the first cathode and the second cathode.

18. The particle accelerator of claim 13, wherein the tube comprises a first portion and a second portion that are completely separated at a point of interruption at the acceleration region.

19. The particle accelerator of claim 13, further comprising:

a stop at the acceleration region, the stop to block at least one phase of the particles from further acceleration.

20. The particle accelerator of claim 13, further comprising:

a voltage source to provide the RF field to the plasma column, the RF field for accelerating the particles from the plasma column at the acceleration region, wherein the RF field comprises voltage that is less than 15 kV; and

magnetic yokes to provide a magnetic field that crosses the acceleration region, the magnetic field being greater than about 2 Tesla (T).

21. A particle accelerator comprising:

a Penning ion gauge (PIG) source comprising a first tube portion and a second tube portion that are at least partially separated at an acceleration region, the first tube portion and the second tube portion for holding a plasma column that extends across the acceleration region; and

a voltage source to provide a voltage at the acceleration region, the voltage for accelerating particles out of the plasma column at the acceleration region.

22. The particle accelerator of claim 21, wherein the first tube portion and the second tube portion are completely separated from each other.

23. The particular accelerator of claim 21, wherein portions of the first tube portion are separated from corresponding portions of the second tube portion;

and

wherein the PIG source comprises a physical connection between a part of the first tube portion and the second tube portion, the physical connection enabling particles accelerating out of the plasma column to complete a first turn upon escaping from the plasma column without running into the physical connection.

24. The particle accelerator of claim 21, wherein the PIG source passes through a first dee that is electrically connected to ground, and wherein a second dee that is electrically connected to an alternating voltage source provides the voltage at the acceleration region.

25. The particle accelerator of claim 21, further comprising:

magnetic yokes that define a cavity containing the acceleration region, the magnetic yokes for generating a magnetic field across the acceleration region.

26. The particle accelerator of claim 25, wherein the magnetic field is at least 2 Tesla (T).

27. The particle accelerator of claim 26, wherein the magnetic field is at least 10.5 T.

28. The particle accelerator of claim 27, wherein the voltage comprises a radio frequency (RF) voltage that is less than 15 kV.

29. The particle accelerator of claim 21, further comprising one or more electrodes for use in accelerating the particles out of the particle accelerator.

30. The particle accelerator of claim 21, further comprising:

at least one cathode for use in generating the plasma column, the at least one cathode comprising a cold cathode; and

a capacitive circuit to couple at least some of the voltage to the at least one cathode.

31. The particle accelerator of claim 30, wherein the at least one cathode is configured to pulse voltage to generate the plasma column from gas in the first tube portion and the second tube portion.

32. The particle accelerator of claim 31, further comprising a structure that substantially encloses the PIG source.