TRAVELING WAVE LINEAR ACCELERATOR COMPRISING A FREQUENCY CONTROLLER FOR INTERLEAVED MULTI-ENERGY OPERATION

• US 20100188027A1
• Filed: 10/16/2009
• Published: 07/29/2010
• Est. Priority Date: 01/26/2009
• Status: Active Grant

• Current Assignee: Accuray Incorporated
• Original Assignee: Accuray Incorporated
• Inventors: Miller, Roger Heering, Wang, Juwen, Treas, Paul Dennis
• Granted Patent: US 8,232,748 B2
• Time in Patent Office: Days
• US Class Current: 315/505
• CPC Class Codes: H05H 7/02 Circuits or systems for supplying or feeding radio-frequency energy radio-frequency generators H03B
• CPC Class Codes: H05H 7/12 Arrangements for varying final energy of beam
• CPC Class Codes: H05H 9/02 Travelling-wave linear accelerators travelling-wave tubes H01J25/34

Abstract

An electromagnetic wave having a phase velocity and an amplitude is provided by an electromagnetic wave source to a traveling wave linear accelerator. The traveling wave linear accelerator generates a first output of electrons having a first energy by accelerating an electron beam using the electromagnetic wave. The first output of electrons can be contacted with a target to provide a first beam of x-rays. The electromagnetic wave can be modified by adjusting its amplitude and the phase velocity. The traveling wave linear accelerator then generates a second output of electrons having a second energy by accelerating an electron beam using the modified electromagnetic wave. The second output of electrons can be contacted with a target to provide a second beam of x-rays. A frequency controller can monitor the phase shift of the electromagnetic wave from the input to the output ends of the accelerator and can correct the phase shift of the electromagnetic wave based on the measured phase shift.

Claims

1. A traveling wave linear accelerator comprising:

an accelerator structure having an input and an output;

an electromagnetic wave source coupled to the accelerator structure to provide an electromagnetic wave to the accelerator structure; and

a frequency controller interfaced with the input and output of the accelerator structure to compare the phase of the electromagnetic wave at the input of the accelerator structure to the phase of the electromagnetic wave at the output of the accelerator structure to detect a phase shift of the electromagnetic wave,

wherein the frequency controller transmits a signal to an oscillator, and wherein the oscillator causes the electromagnetic wave source to generate a subsequent electromagnetic wave at a modified frequency based on the magnitude of the phase shift detected by the frequency controller.

2. The traveling wave linear accelerator of claim 1, wherein the frequency controller is operably connected to the oscillator, wherein the frequency controller transmits the signal to adjust the frequency settings of the oscillator, and wherein the oscillator generates a frequency signal that causes the electromagnetic wave source to generate the subsequent electromagnetic wave at the modified frequency.

3. The traveling wave linear accelerator of claim 2, wherein the frequency signal from the oscillator is amplified by an amplifier, and wherein the amplifier supplies the amplified frequency signal to the electromagnetic wave source.

4. The traveling wave linear accelerator of claim 1, further comprising an electron gun coupled to the input of the accelerator structure to provide one or more electron beams to the accelerator structure.

5. The traveling wave linear accelerator of claim 1, wherein the electromagnetic wave source is a klystron.

6. The traveling wave linear accelerator of claim 1, wherein the accelerator structure accelerates a first electron beam from the electron gun to a first energy using a first electromagnetic wave provided by the electromagnetic wave source, the first electromagnetic wave having a first amplitude and a first frequency in the accelerator structure,

wherein the frequency controller monitors a first phase shift of the first electromagnetic wave, and transmits a first signal to the oscillator based on the magnitude of the first phase shift,

wherein the accelerator structure accelerates a second electron beam from the electron gun to a second energy using a second electromagnetic wave provided by the electromagnetic wave source, the second electromagnetic wave having a second amplitude and a second frequency in the accelerator structure, and

wherein the frequency controller monitors a second phase shift of the second electromagnetic wave, and transmits a second signal to the oscillator based on the magnitude of the second phase shift.

7. The traveling wave linear accelerator of claim 6, wherein the first energy and the second energy are interleaved.

8. The traveling wave linear accelerator of claim 6, wherein the second amplitude is different from the first amplitude and the second frequency is different from the first frequency in the accelerator structure, and the second energy is different from the first energy.

9. The traveling wave linear accelerator of claim 6, wherein the first electron beam is emitted from the output of the accelerator structure at the first energy and is contacted with a target to produce a first beam of x-rays at a first range of x-ray energies.

10. The traveling wave linear accelerator of claim 6, wherein the second electron beam is emitted from the output of the accelerator structure at the second energy and is contacted with a target to produce a second beam of x-rays at a second range of x-ray energies.

11. A method of operating a traveling wave linear accelerator, comprising:

coupling a first electromagnetic wave having a first amplitude and a first frequency in an accelerator structure of the traveling wave linear accelerator from an electromagnetic wave source to an input of the accelerator structure;

generating a first output of electrons having a first energy from an output of the accelerator structure by accelerating a first electron beam using the first electromagnetic wave; and

monitoring a first phase shift of the first electromagnetic wave using a frequency controller interfaced with the input and the output of the accelerator structure,

wherein the frequency controller compares a phase of the first electromagnetic wave at the input of the accelerator structure to a phase of the first electromagnetic wave near the output of the accelerator structure,

wherein the frequency controller transmits a first signal to an oscillator based on the first phase shift, and

wherein the oscillator causes the electromagnetic wave source to generate a second electromagnetic wave having a second frequency in the accelerator structure based on the magnitude of the first phase shift of the first electromagnetic wave.

12. The method of claim 11, further comprising contacting the first output of electrons with a target to produce a first beam of x-rays at a first range of x-ray energies.

13. The method of claim 11, further comprising generating a second output of electrons having a second energy from the output of the accelerator structure by accelerating a second electron beam using the second electromagnetic wave.

14. The method of claim 13, wherein the second energy is the same as the first energy.

15. The method of claim 13, wherein the second frequency is different from the first frequency and the second energy is different from the first energy.

16. The method of claim 13, wherein the first energy and the second energy are interleaved.

17. The method of claim 11, wherein the electromagnetic wave source is a klystron.

18. The method of claim 11, further comprising:

coupling a third electromagnetic wave having a third amplitude and a third amplitude in the accelerator structure from the electromagnetic wave source to the input of the accelerator structure;

generating a third output of electrons having a third energy, different from the first energy, by accelerating a third electron beam using the third electromagnetic wave; and

monitoring a third phase shift of the third electromagnetic wave using the frequency controller,

wherein the frequency controller compares a phase of the third electromagnetic wave at the input of the accelerator structure to a phase of the third electromagnetic wave at the output of the accelerator structure,

wherein the frequency controller transmits a third signal to the oscillator based on the third phase shift, and

wherein the oscillator causes the electromagnetic wave source to generate a fourth electromagnetic wave having a fourth frequency in the accelerator structure based on the magnitude of the phase shift of the third electromagnetic wave.

19. The method of claim 18, further comprising contacting the third output of electrons with the target to produce a third beam of x-rays at a third range of x-ray energies.

20. The method of claim 18, further comprising generating a fourth output of electrons having a fourth energy from the output of the accelerator structure by accelerating a fourth electron beam using the fourth electromagnetic wave.

21. The method of claim 20, wherein the fourth energy is the same as the third energy.

22. The method of claim 20, wherein the third energy and the fourth energy are interleaved.

23. The traveling wave linear accelerator of claim 18, wherein the first energy and the third energy are interleaved.

24. A method of operating a traveling wave linear accelerator, comprising:

coupling an electromagnetic wave having a first frequency and a first amplitude from an electromagnetic wave source to an input of an accelerator structure of the traveling wave linear accelerator;

accelerating a first electron beam injected by an electron gun into the accelerator structure to a first energy using the electromagnetic wave; and

monitoring a first phase shift of the electromagnetic wave using a frequency controller interfaced with the input and an output of the accelerator structure,

wherein the frequency controller compares a phase of the electromagnetic wave at the input of the accelerator structure to a phase of the electromagnetic wave at the output of the accelerator structure to monitor the first phase shift,

wherein the frequency controller transmits a first signal to a first oscillator based on the first phase shift, and

wherein the first oscillator causes the electromagnetic wave source to generate a subsequent electromagnetic wave at a corrected frequency based on the magnitude of the first phase shift of the electromagnetic wave.

25. The method of claim 24, further comprising emitting the first electron beam from the output of the accelerator structure at the first energy and contacting the first electron beam with a target to produce a first beam of x-rays at a first range of x-ray energies.

26. The method of claim 24, further comprising:

coupling a modified electromagnetic wave having a second frequency and a second amplitude from the electromagnetic wave source to the input of the accelerator structure;

accelerating a second electron beam injected by the electron gun into the accelerator structure to a second energy, different from the first energy, using the modified electromagnetic wave; and

monitoring a second phase shift of the modified electromagnetic wave using the frequency controller,

wherein the frequency controller compares the phase of the modified electromagnetic wave at the input of the accelerator structure to the phase of the modified electromagnetic wave at the output of the accelerator structure to monitor the second phase shift,

wherein the frequency controller transmits a second signal to the second oscillator based on the second phase shift, and

wherein the second oscillator causes the electromagnetic wave source to generate a subsequent modified electromagnetic wave at a corrected frequency based on the magnitude of the second phase shift.

27. The method of claim 26, wherein the first energy and the second energy are interleaved.

28. The method of claim 26, further comprising emitting the second electron beam from the output of the accelerator structure at the second energy and contacting the second electron beam with a target to produce a second beam of x-rays at a second range of x-ray energies.

29. A traveling wave linear accelerator comprising:

an accelerator structure having an input and an output;

an electromagnetic wave source coupled to the accelerator structure to provide an electromagnetic wave to the accelerator structure;

an electron energy spectrum monitor positioned near the output of the accelerator structure, wherein the electron energy spectrum monitor provides (a) an indication of a first energy spectrum of a first output of electrons from the output of the accelerator structure, wherein the first output of electrons was accelerated in the accelerator structure using a first electromagnetic wave having a first amplitude and a first frequency, and (b) an indication of a second energy spectrum of a second output of electrons from the output of the accelerator structure, wherein the second output of electrons was accelerated in the accelerator structure using a second electromagnetic wave having a second amplitude and a second frequency, wherein the second amplitude has about the same magnitude as the first amplitude, and wherein the second frequency has a different magnitude than the first frequency; and

a frequency controller interfaced with the electron energy spectrum monitor,

wherein the frequency controller compares the indication of the first energy spectrum to the indication of the second energy spectrum and transmits a signal to an oscillator based on the comparison,

wherein the oscillator causes the electromagnetic wave source to generate a third electromagnetic wave at a third frequency and a third amplitude to stabilize an energy spectrum of a third output of electrons accelerated using the third electromagnetic wave, and

wherein the third amplitude has about the same magnitude as the first amplitude.

30. A traveling wave linear accelerator comprising:

an accelerator structure having an input and an output;

an electromagnetic wave source coupled to the accelerator structure to provide an electromagnetic wave to the accelerator structure;

an x-ray yield monitor positioned near the output of the accelerator structure, wherein the x-ray yield monitor provides (a) an indication of a first yield of a first beam of x-rays at the output of the accelerator structure, wherein the first beam of x-rays is generated using a first set of electrons that is accelerated in the accelerator structure by a first electromagnetic wave having a first amplitude and a first frequency, and (b) an indication of a second yield of a second beam of x-rays at the output of the accelerator structure, wherein the second beam of x-rays is generated using a second set of electrons that is accelerated in the accelerator structure by a second electromagnetic wave having a second amplitude and a second frequency, wherein the second amplitude has about the same magnitude as the first amplitude, and wherein the second frequency has a different magnitude than the first frequency; and

a frequency controller interfaced with the x-ray yield monitor,

wherein the frequency controller compares the indication of the first yield of the first beam of x-rays to the indication of the second yield of the second beam of x-rays and transmits a signal to an oscillator based on the comparison, and

wherein the oscillator causes the electromagnetic wave source to generate a third electromagnetic wave at a third frequency and a third amplitude to maximize a yield of a third beam of x-rays generated using a third set of electrons that is accelerated in the accelerator structure by the third electromagnetic wave, wherein the third amplitude has about the same magnitude as the first amplitude.

31. A method of tuning a traveling wave linear accelerator, comprising:

providing a carrier wave having a phase velocity and an amplitude;

generating a first X-ray beam having a first energy level by accelerating an electron beam using the carrier wave;

modifying the carrier wave by adjusting the amplitude and the phase velocity; and

generating a second X-ray beam having a second energy level by accelerating the electron beam using the modified carrier wave.