Adjusting energy of a particle beam

1. A particle accelerator comprising:

a coil to provide a magnetic field to a cavity;

a particle source to provide a plasma column to the cavity;

a voltage source to provide a radio frequency (RF) voltage to the cavity to accelerate particles from the plasma column, the magnetic field causing particles accelerated from the plasma column to move orbitally within the cavity;

an enclosure containing an extraction channel to receive the particles accelerated from the plasma column and to output the particles from the cavity; and

an actuator to change an energy level of the particles received by the extraction channel by physically changing a position of the coil.

2. The particle accelerator of claim 1 , wherein the coil is a first coil; and

wherein the particle accelerator further comprises:

a second coil to provide the magnetic field to the cavity; and

a cryostat comprising a first chamber for holding the first coil and a second chamber for holding the second coil; and

wherein the actuator is configured to move the cryostat, thereby changing a position of the first coil and a position of the second coil.

3. The particle accelerator of claim 2 , wherein the particle accelerator is subjected to movement that causes the first coil and the second coil to move in addition to the movement of the first coil and the second coil produced by virtue of being part of the particle accelerator; and

wherein the actuator is configured to move the cryostat to compensate for movement of the first coil and the second coil that is in addition to the movement of the first coil and the second coil produced by virtue of being part of the particle accelerator.

4. The particle accelerator of claim 2 , wherein the particle accelerator is subjected to movement that causes the first coil and the second coil to move in a first direction; and

wherein the actuator is configured to move the cryostat in a second direction that is opposite to the first direction.

5. The particle accelerator of claim 1 , further comprising:

a regenerator to provide a magnetic field bump within the cavity to affect orbits of the particles, thereby causing the particles to move towards the extraction channel;

wherein the position of the coil is changed relative to the regenerator.

6. The particle accelerator of claim 1 , further comprising:

a regenerator to provide a magnetic field bump within the cavity to affect orbits of the particles, thereby causing the particles to move towards the extraction channel;

wherein movement of the particle accelerator causes the coil to be out of alignment with the regenerator; and

wherein the position of the coil is changed to bring the coil back into alignment with the regenerator.

7. The particle accelerator of claim 6 , wherein the regenerator is movable within the cavity to selectively affect orbits of the particles.

8. The particle accelerator of claim 1 , further comprising

a cryostat comprising a chamber for holding the coil; and

straps that attached to the cryostat that restrict, but do not prevent, movement of the coil during movement of the magnet;

wherein the position of the coil is changed based on the movement of the coil during movement of the magnet.

9. The particle accelerator of claim 8 , wherein the position of the coil is changed to compensate for the movement of the coil during movement of the magnet.

10. The particle accelerator of claim 1 , wherein the particle accelerator is a synchrocyclotron that is capable of outputting particles having different energies.

11. A particle therapy system comprising:

the particle accelerator of claim 1 ;

a rotatable gantry on which the particle accelerator is mounted for rotation relative to a patient position; and

a computing device to control operation of the particle accelerator.

12. The particle therapy system of claim 11 , wherein the computing device is programmed to control the actuator to change the position of the coil based on a rotational position of the gantry.

13. A system comprising:

a magnet comprising one or more coils to conduct current to generate a magnetic field, the magnetic field to affect output of radiation to a target, the magnet being configured for movement relative to the target; and

one or more actuators that are controllable to move the one or more coils physically based on the movement of the magnet.

14. The system of claim 13 , further comprising:

a housing to hold the one or more coils;

wherein the one or more actuators are controllable to move the housing in order to move the one or more coils.

15. The system of claim 14 , wherein the housing comprises a cryostat having chambers, each of the chambers for holding a respective coil, the cryostat for maintaining the one or more coils at superconducting temperatures.

16. The system of claim 13 , further comprising:

a particle accelerator comprising the magnet, the magnetic field for accelerating particles in a cavity of the particle accelerator to produce a particle beam comprising the radiation for output to the target; and

a gantry on which the particle accelerator is mounted for movement relative to the target.

17. The system of claim 16 , wherein the gantry is configured to rotate the particle accelerator relative to the target in order to direct the particle beam to different points on the target.

18. The system of claim 13 , further comprising:

a housing to hold the one or more coils;

wherein the movement of the magnet causes the one or more coils to move relative to the housing; and

wherein the one or more actuators are controllable to move the one or more coils physically in order to compensate for the movement of the one or more coils to move relative to the housing.

19. The system of claim 13 , further comprising:

a particle accelerator comprising the magnet, the magnetic field for accelerating particles in orbits within a cavity of the particle accelerator to produce a particle beam comprising the radiation for output to the target, the particle accelerator comprising:

a regenerator comprising a ferromagnetic material to produce a magnetic field bump to affect an orbit of the particles within the cavity;

wherein the one or more actuators are controllable to move the one or more coils physically in order to align the one or more coils relative to the regenerator.

20. The system of claim 13 , further comprising:

a particle accelerator comprising the magnet, the magnetic field for accelerating particles in orbits within a cavity of the particle accelerator to produce a particle beam comprising the radiation for output to the target, the particle accelerator comprising:

a regenerator comprising a ferromagnetic material to produce a magnetic field bump to affect an orbit of the particles within the cavity;

wherein the movement of the magnet causes the one or more coils to move within the magnet, and the one or more actuators are controllable to move the one or more coils physically in order to move the one or more coils to an original position of the one or more coils within the magnet.

21. A particle accelerator comprising:

superconducting coils for conducting current to generate a magnetic field;

a cryostat for holding the superconducting coils, and for maintaining the superconducting coils at superconducting temperatures;

magnetic structures adjacent to the cryostat, the magnetic structures at least partly defining a cavity;

a particle source to provide a plasma column to the cavity;

a voltage source to provide a radio frequency (RF) voltage to the cavity to accelerate particles from the plasma column within the cavity, the magnetic field causing particles accelerated from the plasma column to move orbitally within the cavity;

an extraction channel to receive the particles from the cavity, and to direct the particles for output from the particle accelerator; and

one or more actuators that are controllable to move the cryostat physically.

22. The particle accelerator of claim 21 , wherein the particle accelerator is rotatable relative to a fixed position; and

wherein the particle accelerator further comprises a control system to control the one or more actuators based on a rotational position of the particle accelerator.

23. The particle accelerator of claim 22 , wherein the one or more actuators are controlled to control movement of the cryostat so as to compensate for effects of gravity on the superconducting coils.

24. The particle accelerator of claim 22 , further comprising:

a regenerator comprising a ferromagnetic material to produce a magnetic field bump to affect an orbit of the particles within the cavity;

wherein the one or more actuators are controllable to move the one or more coils physically so that the one or more coils reach predetermined positions relative to the regenerator.

25. The particle accelerator of claim 24 , wherein the regenerator is movable within the cavity.