Programmable radio frequency waveform generatior for a synchrocyclotron

• US 20080218102A1
• Filed: 01/25/2008
• Published: 09/11/2008
• Est. Priority Date: 07/21/2004
• Status: Active Grant

• Current Assignee: Mevion Medical Systems Incorporated
• Original Assignee: Still River Systems Incorporated
• Inventors: Gall, Kenneth, Sliski, Alan
• Granted Patent: US 7,626,347 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 comprises a resonant circuit that includes electrodes having a gap therebetween across the magnetic field. An oscillating voltage input, having a variable amplitude and frequency determined by a programmable digital waveform generator generates an oscillating electric field across the gap. The synchrocyclotron can include a variable capacitor in circuit with the electrodes to vary the resonant frequency. The synchrocyclotron can further include an injection electrode and an extraction electrode having voltages controlled by the programmable digital waveform generator. The synchrocyclotron can further include a beam monitor. The synchrocyclotron can detect resonant conditions in the resonant circuit by measuring the voltage and or current in the resonant circuit, driven by the input voltage, and adjust the capacitance of the variable capacitor or the frequency of the input voltage to maintain the resonant conditions. The programmable waveform generator can adjust at least one of the oscillating voltage input, the voltage on the injection electrode and the voltage on the extraction electrode according to beam intensity and in response to changes in resonant conditions.

Claims

1. A synchrocyclotron comprising:

a magnetic field generator;

a resonant circuit, comprising;

electrodes, disposed between magnetic poles, having a gap therebetween across the magnetic field; and

a variable reactive element in circuit with the electrodes to vary the resonant frequency of the resonant circuit; and

a voltage input to the resonant circuit, the voltage input being an oscillating voltage that varies in amplitude or frequency over the time of acceleration of charged particles.

2. The synchrocyclotron as claimed in claim 1 wherein the amplitude of the voltage input is varied.

3. The synchrocyclotron as claimed in claim 1 wherein the frequency of the voltage input is varied.

4. The synchrocyclotron of claim 1 wherein the amplitude and the frequency of the voltage are varied.

5. The synchrocyclotron of claim 1 further including an ion source for injecting charged particles into the synchrocyclotron.

6. The synchrocyclotron of claim 5 further including an extraction electrode, disposed between the magnetic poles to extract a particle beam from the synchrocyclotron.

7. The synchrocyclotron of claim 6 further including a one or more sensors for detecting resonant conditions in the resonant circuit.

8. The synchrocyclotron of claim 7 wherein the frequency of the voltage input is adjusted to maintain the resonant conditions.

9. The synchrocyclotron of claim 8 further including means for controlling the reactance of the variable reactive element and adjusting the resonant frequency of the resonant circuit to maintain the resonant conditions.

10. The synchrocyclotron of claim 9 further including a beam monitor for measuring particle beam, at least one of the voltage input, the ion source and the extraction electrode being controlled to compensate for variations in the particle beam.

11. The synchrocyclotron of claim 10 wherein the beam monitor measures particle beam intensity.

12. The synchrocyclotron of claim 10 wherein the beam monitor measures particle beam timing.

13. The synchrocyclotron of claim 10 wherein the beam monitor measures spatial distribution of the particle beam.

14. The synchrocyclotron as claimed in claim 1 wherein the oscillating voltage input is generated by a programmable digital waveform generator.

15. The synchrocyclotron of claim 10 wherein at least one of the ion source and the extraction electrode is controlled by a programmable waveform generator to compensate for variations in the particle beam.

16. The synchrocyclotron of claim 1 further including a one or more sensors for detecting resonant conditions in the resonant circuit.

17. The synchrocyclotron of claim 1 further including a beam monitor for detecting variations in a particle beam.

18. The synchrocyclotron of claim 1 wherein the frequency of the voltage input is adjusted to maintain the resonant conditions.

19. The synchrocyclotron of claim 1 further including an ion source and an extraction electrode, wherein at least one of the ion source and the extraction electrode is controlled to compensate for variations-in a particle beam.

20. The synchrocyclotron of claim 19 further including one or more sensors for detecting resonant conditions in the resonant circuit.

21. The synchrocyclotron of claim 19 further including a beam monitor for detecting variations in a particle beam.

22. The synchrocyclotron of claim 19 wherein the frequency of the voltage input is adjusted to maintain the resonant conditions.

23. A method of producing a particle beam in a synchrocyclotron, comprising:

injecting charged particles into a synchrocyclotron by an ion source;

applying oscillating voltage input to a resonant circuit comprising accelerating electrodes having a gap therebetween across a magnetic field, to create an oscillating electric field across the gap and accelerating charged particles, the oscillating voltage input being controlled to vary in amplitude or frequency over the time of acceleration of the charged particles; and

extracting the accelerated charged particles by an extraction electrode to form a particle beam.

24. The method of claim 23 wherein the amplitude of the oscillating voltage input is varied.

25. The method of claim 23 wherein the frequency of the oscillating voltage input is varied.

26. The method of claim 23 wherein the amplitude and the frequency of the voltage are varied.

27. The method of claim 23 further including detecting resonant conditions in the resonant circuit.

28. The method of claim 27 wherein the frequency of the voltage input is adjusted to maintain the resonant conditions.

29. The method of claim 28 further including adjusting reactance of a variable reactive element in circuit with the oscillating voltage input and the accelerating electrodes to maintain the resonant conditions in the resonant circuit.

30. The method of claim 29 further including measuring particle beam intensity by a beam monitor;

and

controlling at least one of the oscillating voltage input, the ion source and the extraction electrode to compensate for variations in the particle beam.

31. The method of claim 30 wherein the beam monitor measures particle beam intensity.

32. The method of claim 30 wherein the beam monitor measures particle beam timing.

33. The method of claim 30 wherein the beam monitor measures spatial distribution of the particle beam.

34. The method of claim 23 wherein the oscillating voltage input is generated by a programmable digital waveform generator.

35. The method of claim 30 wherein at least one of the ion source and the extraction electrode is controlled by a programmable waveform generator to compensate for variations in the particle beam.

36. The method of claim 23 further including detecting resonant conditions in the resonant circuit.

37. The method of claim 23 further including detecting variations in a particle beam.

38. The method of claim 23 further including adjusting the frequency of the voltage input to maintain the resonant conditions.

39. The method of claim 23 further including controlling at least one of the ion source and the extraction electrode to compensate for variations in a particle beam.

40. A synchrocyclotron comprising:

injecting means for injecting charged particles into a synchrocyclotron;

accelerating means for accelerating the charged particles by an oscillating electric field, the oscillating electric field being varied over the time of acceleration of charged particles, the accelerating means including a resonant circuit that comprises accelerating electrodes having a gap therebetween across the magnetic field and an oscillating voltage input driving the oscillating electric field across the gap, the amplitude or the frequency of the voltage input being varied over the time of acceleration of the charged particles; and

extracting means for extracting the accelerated charged particles to form a particle beam.

42. The synchrocyclotron of claim 40 further including voltage controlling means for varying the oscillating voltage input over the time of acceleration of charged particles.

43. The synchrocyclotron of claim 42 further including monitoring means for monitoring the particle beam.

44. The synchrocyclotron of claim 43 further including resonant frequency controlling means in circuit with the oscillating voltage input and the accelerating electrodes for varying the resonant frequency of the resonant circuit.

45. The synchrocyclotron of claim 44 further including resonance detecting means for detecting resonance conditions in the resonant circuit.

41. (canceled)