Phase-Lock Loop Synchronization Between Beam Orbit And RF Drive In Synchrocyclotrons

• US 20140028220A1
• Filed: 07/24/2013
• Published: 01/30/2014
• Est. Priority Date: 07/27/2012
• Status: Active Grant

• Current Assignee: Massachusetts Institute of Technology
• Original Assignee: Massachusetts Institute of Technology
• Inventors: Bromberg, Leslie, Minervini, Joseph V., Radovinsky, Alexey L., Antaya, Timothy A., Le, Peisi, Michael, Phillip C.
• Granted Patent: US 9,603,235 B2
• Time in Patent Office: Days
• US Class Current: 315/502
• CPC Class Codes: H05H 13/005 Cyclotrons
• CPC Class Codes: H05H 13/02 Synchrocyclotrons, i.e. frequency modulated cyclotrons
• CPC Class Codes: H05H 2007/025 Radiofrequency systems
• CPC Class Codes: H05H 7/02 Circuits or systems for supplying or feeding radio-frequency energy radio-frequency generators H03B
• CPC Class Codes: H05H 7/10 Arrangements for ejecting particles from orbits

Abstract

The invention specifies the use of feedback in the radio frequency (RF) drive for a synchrocyclotron, controlling the phase and/or amplitude of the accelerating field as a means to assure optimal acceleration of the beam, to increase the average beam current and to alter the beam orbit in order to allow appropriate extraction as the beam energy is varied. The effect of space charge is reduced by rapid acceleration and extraction of the beam, and the repetition rate of the pulses can be increased. Several means are presented to monitor the phase of the beam in synchrocyclotrons and to adjust the phase and amplitude of the RF to optimize the acceleration of the beam and to adjust the extraction and injection of the beam. Also, the use of a pulsed ion source that matches the acceptance window of the synchrocyclotron is described.

Claims

1. A method of creating and extracting an ion beam having a predetermined energy from a cyclotron, comprising:

introducing ions into said cyclotron;

using a RF drive to accelerate the ions to move as an ion beam in said cyclotron;

sensing a position of said ion beam in said cyclotron during said acceleration;

using said position of said ion beam to alter said RF drive to maintain a desired acceleration; and

extracting said ion beam.

2. The method of claim 1, further comprising establishing a magnetic field in said cyclotron by applying a current to cyclotron coils, said magnetic field used to determine said predetermined energy of said ion beam.

3. The method of claim 1, wherein said RF drive comprises a frequency, a phase and an amplitude, and wherein said phase of said RF drive is altered.

4. The method of claim 1, wherein said RF drive comprises a frequency, a phase and an amplitude, and wherein said frequency of said RF drive is altered.

5. The method of claim 1, wherein said RF drive comprises a frequency, a phase and an amplitude, and wherein said amplitude of said RF drive is altered.

6. The method of claim 1, wherein said ion beam is extracted by actuating a non-axisymmetric pulsed magnetic field.

7. The method of claim 6, wherein said non-axisymmetric pulsed magnetic field is actuated when said ion beam reaches a predetermined position and velocity.

8. The method of claim 6, wherein said actuating is performed using open loop control.

9. The method of claim 8, where said open loop control utilizes information selected from the group consisting of ion mass, ion mass/charge ratio and desired ion beam energy, to actuate said magnetic field.

10. The method of claim 6, wherein said actuating is performed using phase locked loop control.

11. The method of claim 1, wherein said predetermined energy of said ion beam is used to determine how said RF drive is to be altered.

12. A cyclotron, comprising:

a beam detector disposed so as to detect the presence of an ion beam;

a beam sensor in communication with said beam detector;

a RF wave generator having a variable phase or frequency output;

said output defined as RF drive;

a RF cavity or dee in communication with said RF drive; and

an electronic control unit in communication with said beam sensor and having outputs in communication with said RF wave generator so as to control said RF drive, thereby controlling velocity and position of said ion beam.

13. The cyclotron of claim 12, further comprising a kicker coil to generate a non-axisymmetric pulsed magnetic field to extract said ion beam.

14. The cyclotron of claim 13, wherein said electronic control unit is in communication with said kicker coil, and actuates said kicker coil when said ion beam reaches a predetermined position and velocity.

15. The cyclotron of claim 14, wherein said electronic control unit utilizes open loop control to actuate said kicker coil to generate said magnetic field.

16. The cyclotron of claim 15, where said open loop control comprises information selected from the group consisting of ion mass, ion mass/charge ratio and desired ion beam energy.

17. The cyclotron of claim 14, wherein said electronic control unit utilizes information from said beam sensor to actuate said coil to generate said magnetic field.

18. The cyclotron of claim 12, where said beam detector is disposed at a location where a rate of change in said RF drive is a minimum.

19. The cyclotron of claim 12, where said beam detector is disposed at a location where said RF drive is a minimum.

20. The cyclotron of claim 13, further comprising a cyclotron coil used to generate a magnetic field so as to confine said ion beam and determine a final energy of said ion beam upon extraction, and a second kicker coil so that said kicker coil and said second kicker coil have zero mutual inductance to said cyclotron coil.