Programmable radio frequency waveform generator for a synchrocyclotron

Abstract

A synchrocyclotron comprises includes 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 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.

What is claimed is: 
     
       1. A synchrocyclotron comprising:
 a magnetic field generator to produce a magnetic field; 
 a resonant circuit, comprising:
 electrodes, disposed within a cavity between magnetic poles, having a gap therebetween across a the magnetic field; and 
 a variable reactive element in circuit with the electrodes to vary a resonant frequency of the resonant circuit; and 
 
 an extraction channel to receive charged particles from the cavity and to output a particle beam from the synchrocyclotron; 
 a sensor to measure a voltage in the resonant circuit; and  
 a voltage input generator to provide adjust a frequency of a voltage input to the resonant circuit based on an intensity of the particle beam output by the synchrocyclotron and a frequency of the voltage measured in the resonant circuit, the voltage input being an oscillating voltage that varies in frequency over a time of acceleration of the charged particles. 
 
     
     
       2. The synchrocyclotron as claimed in  claim 1  wherein an amplitude of the voltage input is varied. 
     
     
       3. The synchrocyclotron of  claim 1  further including an ion source for injecting charged particles into the synchrocyclotron. 
     
     
       4. The synchrocyclotron of  claim 1  further including an extraction electrode disposed between the magnetic poles for extracting a the particle beam from the synchrocyclotron. 
     
     
       5. The synchrocyclotron of  claim 1  further including a wherein the sensor is for detecting resonant conditions in the resonant circuit. 
     
     
       6. The synchrocyclotron of  claim 5  further including means for adjusting at least one of a the frequency of the voltage input, reactance of the variable reactive element, and resonant frequency of the resonant circuit based on the resonant conditions. 
     
     
       7. The synchrocyclotron of  claim 1  further including a beam monitor for detecting a particle beam extracted from the synchrocyclotron. 
     
     
       8. The synchrocyclotron of  claim 7  wherein the beam monitor is configured to measure at least one of particle beam intensity, particle beam timing, and spatial distribution of the particle beam. 
     
     
       9. The synchrocyclotron as claimed in  claim 1  further including wherein the voltage input generator comprises a programmable digital waveform generator for generating the oscillating voltage. 
     
     
       10. The synchrocyclotron of  claim 9  wherein the programmable waveform generator is configured to compensate for at least one of variations in resonant conditions of the resonant circuit and variations in a the particle beam extracted from the synchrocyclotron. 
     
     
       11. A method of accelerating particles in a synchrocyclotron, comprising:
 providing particles in a cavity of the synchrocyclotron; 
 providing a resonant circuit in the cavity, the resonant circuit comprising accelerating electrodes having a gap therebetween across a magnetic field; and 
 using a sensor to measure a voltage in the resonant circuit;  
 withusing a voltage input generator, applying an oscillatingadjusting, based on an intensity of a particle beam output by the synchrocyclotron and a frequency of a voltage measured in the resonant circuit, a frequency of a voltage input that varies in frequency during acceleration of the particles to the resonant circuit, the oscillating voltage input creating an oscillating electric field across the gap that accelerates the particles in the synchrocyclotron cavity; and 
 receiving the particles from the cavity in an extraction channel and outputting a particle beam from the extraction channel. 
 
     
     
       12. The method as in  claim 11 , further including generating the oscillating voltage input. 
     
     
       13. The method of  claim 11 , further including varying an amplitude of the oscillating voltage input. 
     
     
       14. The method of  claim 11 , wherein providing particles includes injecting particles into the synchrocyclotron. 
     
     
       15. The method of  claim 11 , further including detecting resonant conditions in the resonant circuit. 
     
     
       16. The method of  claim 15 , further including adjusting at least one of a frequency of the oscillating voltage input, a reactance of a variable reactive element, and a resonant frequency of the resonant circuit based on the resonant conditions. 
     
     
       17. The method of  claim 11 , further including extracting accelerated particles from the synchrocyclotron to form a the particle beam. 
     
     
       18. The method as in  claim 17 , further including detecting variations in the particle beam. 
     
     
       19. The method as in  claim 18 , wherein the variations include variations in at least one of particle beam intensity, particle beam timing, and spatial distribution of the particle beam. 
     
     
       20. The method as in  claim 18 , further including compensating for detected variations in the particle beam. 
     
     
       21. A particle accelerator configured to generate a particle beam, the particle accelerator comprising:
 an ion source to provide pulses of charged particles that are accelerated in a cavity to form the particle beam;   a beam monitor to obtain information about the particle beam, the information comprising information about an intensity of the particle beam; and   a waveform generator comprising a controller to receive the information about the intensity and to write data to memory, the waveform generator comprising a driver to provide voltage to the cavity to accelerate the charged particles; and   circuitry to control operation of the ion source based on the information about the intensity so that the pulses are provided at timed instances in synchronism with a sweep of a frequency of the voltage that accelerates the charged particles.   
     
     
       22. The particle accelerator of claim 21, further comprising:
 magnetic pole pieces that border the cavity, the cavity housing at least part of the ion source;   wherein the voltage comprises an oscillating voltage having a frequency that varies over a time to accelerate the charged particles.   
     
     
       23. The particle accelerator of claim 21, wherein the voltage comprises an oscillating voltage having a frequency that varies over a time to accelerate the charged particles. 
     
     
       24. The particle accelerator of claim 21, further comprising:
 magnetic pole pieces that border the cavity, the cavity housing at least part of the ion source;   wherein the voltage comprises an oscillating voltage having a frequency that varies over a time to accelerate the charged particles; and   wherein the ion source is controlled to provide pulses of charged particles at a same point in each cycle of the oscillating voltage.   
     
     
       25. The particle accelerator of claim 21, wherein the operation of the ion source is controlled by turning the ion source on and off during a time interval in order to obtain a desired beam current. 
     
     
       26. The particle accelerator of claim 21, wherein the operation of the ion source is controlled by selecting a time interval and by dropping a number of pulses that occur during the time interval to obtain a desired beam current. 
     
     
       27. The particle accelerator of claim 21, wherein the particle accelerator comprises a synchrocyclotron. 
     
     
       28. The particle accelerator of claim 21, wherein the waveform generator comprises digital circuitry, the digital circuitry comprising a digital-to-analog converter (DAC) to generate an analog signal based on the data, the analog signal for controlling the ion source. 
     
     
       29. A particle accelerator configured to generate a particle beam, the particle accelerator comprising:
 an ion source to inject charged particles into a resonant cavity;   magnetic pole pieces that border the resonant cavity, the resonant cavity having a radio frequency (RF) voltage to accelerate the charged particles to produce the particle beam;   a feedback system to provide at least one property of the particle beam; and   circuitry to receive an injection control pulse that extends over multiple cycles of the RF voltage and to control, based on the at least one property, the injection control pulse based on cycles of the RF voltage so that charged particles are injected continuously over at least some of the multiple cycles.   
     
     
       30. The particle accelerator of claim 29, wherein the at least one property comprises an intensity of the particle beam. 
     
     
       31. The particle accelerator of claim 29, wherein the at least one property comprises a spatial distribution of the particle beam. 
     
     
       32. The particle accelerator of claim 29, wherein the at least one property comprises a timing associated with the particle beam. 
     
     
       33. The particle accelerator of claim 29, wherein the injection control pulse controls operation of the ion source by turning the ion source on and off during a time interval in order to maintain a beam current. 
     
     
       34. The particle accelerator of claim 29, wherein the injection control pulse controls operation of the ion source by selecting a time interval and wherein the circuitry is configured to drop a number of pulses that occur during the time interval to maintain a beam current. 
     
     
       35. The particle accelerator of claim 29, wherein the particle accelerator comprises a synchrocyclotron. 
     
     
       36. The particle accelerator of claim 29, wherein the feedback system comprises a beam monitor to monitor the particle beam to obtain the at least one property. 
     
     
       37. The particle accelerator of claim 29, wherein the circuitry comprises a digital waveform generator. 
     
     
       38. A synchrocyclotron comprising:
 magnetic pole pieces that border a cavity;   an ion source to provide, to the cavity, ions that are accelerated to form a particle beam;   a voltage generator to provide voltage to the cavity, the voltage comprising an oscillating voltage having a frequency that varies over a time of acceleration of the ions;   a sensor to measure the oscillating voltage in the cavity; and   a control circuit to control, based on the oscillating voltage measured by the sensor, a timing at which ions are provided by the ion source, the timing being controlled so that ions are provided into the cavity for a limited time and at a same point in each of multiple frequency sweeps of the oscillating voltage, at least part of the control circuit comprising digital circuitry, the digital circuitry comprising an interface that provides a data link to a computer.   
     
     
       39. The synchrocyclotron of claim 38, further comprising:
 a beam monitor to provide information about the particle beam, the information comprising information based on an intensity of the particle beam;   wherein the control circuit is configured to control the timing based also on the information based on the intensity.   
     
     
       40. The synchrocyclotron of claim 38, further comprising:
 a beam monitor to provide information about the particle beam, the information comprising information based on a spatial distribution of the particle beam;   wherein the control circuit is configured to control the timing based also on the information based on the spatial distribution.   
     
     
       41. The synchrocyclotron of claim 38, further comprising:
 a beam monitor to provide information about the particle beam, the information comprising information based on a timing of the particle beam;   wherein the control circuit is configured to control the timing based also on the information based on a timing of the particle beam.   
     
     
       42. The synchrocyclotron of claim 38, wherein the at least part of the control circuit comprises a programmable processor. 
     
     
       43. The synchrocyclotron of claim 38, wherein the control circuit is configured to control the timing so as to cause the ion source to provide particles into the cavity over a number of cycles of the oscillating voltage. 
     
     
       44. The synchrocyclotron of claim 38, wherein the control circuit is configured to control the timing by turning the ion source on and off during a time interval in order to maintain a beam current. 
     
     
       45. The synchrocyclotron of claim 38, wherein the digital circuitry comprises a programmable processor. 
     
     
       46. The synchrocyclotron of claim 38, wherein voltage generator comprises a digital waveform generator that includes the control circuit. 
     
     
       47. A synchrocyclotron comprising:
 a particle source to provide charged particles into a cavity having a magnetic field;   a voltage circuit to cause acceleration of the charged particles in the cavity via an oscillating electric field, the oscillating electric field to vary over a time of acceleration of the charged particles, the voltage circuit comprising a resonant circuit that comprises accelerating electrodes having a gap therebetween across the magnetic field and a driver to drive an oscillating voltage input to produce the oscillating electric field across the gap, the oscillating voltage input to vary over the time of acceleration of the charged particles; and   a control circuit to control the particle source to provide the charged particles for a limited time during each of multiple frequency sweeps of the oscillating electric field across the gap, the limited time synchronizing with an acceptance phase angle of the synchrocyclotron, at least part of the control circuit comprising digital circuitry, the digital circuitry comprising an interface that provides a data link to a computer.   
     
     
       48. The synchrocyclotron of claim 47, further comprising:
 a beam monitor to provide information about a particle beam, the information comprising information based on an intensity of the particle beam;   wherein the control circuit is configured to control the particle source based also on the information based on the intensity.   
     
     
       49. The synchrocyclotron of claim 47, further comprising:
 a beam monitor to provide information about a particle beam, the information comprising information based on a spatial distribution of the particle beam;   wherein the control circuit is configured to control the particle source based also on the information based on the spatial distribution.   
     
     
       50. The synchrocyclotron of claim 47, further comprising:
 a beam monitor to provide information about a particle beam, the information comprising information based on a timing of the particle beam;   wherein the control circuit is configured to control the particle source based also on the information based on a timing of the particle beam.   
     
     
       51. The synchrocyclotron of claim 47, wherein the control circuit is configured to control the particle source based on variations of the oscillating electric field over time. 
     
     
       52. The synchrocyclotron of claim 47, wherein the control circuit is configured to control the particle source so as to cause the particle source to inject particles at a same point in each cycle of the oscillating electric field. 
     
     
       53. The synchrocyclotron of claim 47, wherein the control circuit is configured to control the particle source by turning the particle source on and off during a time interval in order to obtain a desired beam current. 
     
     
       54. The synchrocyclotron of claim 47, wherein the digital circuitry comprises a programmable processor. 
     
     
       55. The synchrocyclotron of claim 47, wherein voltage circuit and the control circuit are components of a digital waveform generator. 
     
     
       56. A particle accelerator comprising:
 a cavity having a magnetic field;   an ion source to provide charged particles to the cavity;   a digital waveform generator to apply an oscillating voltage input to a resonant circuit that comprises accelerating electrodes having a gap therebetween across the magnetic field to drive an oscillating electric field across the gap and accelerate the charged particles within the cavity;   a beam monitor to measure a property of a particle beam comprised of the charged particles that have been accelerated;   wherein the digital waveform generator is configured to control the oscillating voltage input and the ion source to compensate for variations in the property of the particle beam; and   a programmable processor to control at least part of the digital waveform generator.   
     
     
       57. The particle accelerator of claim 56, wherein digital waveform generator is configured to vary an amplitude of the oscillating voltage input. 
     
     
       58. The particle accelerator of claim 56, wherein digital waveform generator is configured to vary a frequency of the oscillating voltage input. 
     
     
       59. The particle accelerator of claim 56, wherein digital waveform generator is configured to vary an amplitude and a frequency of oscillating voltage input. 
     
     
       60. The particle accelerator of claim 59, wherein digital waveform generator is configured to vary a frequency of the oscillating voltage input in order to maintain resonant conditions in the cavity. 
     
     
       61. The particle accelerator of claim 60, further comprising:
 a variable reactive element in circuit with the oscillating voltage input and the accelerating electrodes.   
     
     
       62. The particle accelerator of claim 56, wherein the property comprises particle beam timing. 
     
     
       63. The particle accelerator of claim 56, wherein the property comprises spatial distribution of the particle beam. 
     
     
       64. A particle accelerator comprising
 magnetic pole pieces that border a cavity;   a voltage generator to provide voltage to the cavity, the voltage comprising an oscillating voltage having a frequency that varies over a time of acceleration of charged particles;   an ion source that is controllable to output, over a period of time, pulses of charged particles that are accelerated in the cavity based on the oscillating voltage to form a particle beam;   control circuitry to regulate a current of the particle beam by controlling the ion source so as not to output at least some of the pulses during the period of time; and   a beam monitor to obtain at least one property of the particle beam;   wherein the control circuitry is configured to control a timing at which some of the pulses are output based on the oscillating voltage and an acceptance phase angle of the synchrocyclotron and to control, based on the at least one property, the ion source so as to change a number of the pulses that are not output during the period of time across different cycles of the voltage.   
     
     
       65. The particle accelerator of claim 64, wherein the at least one property comprises an intensity of the particle beam. 
     
     
       66. The particle accelerator of claim 64, wherein the at least one property comprises a timing associated with the particle beam. 
     
     
       67. The particle accelerator of claim 64, wherein the at least one property comprises a spatial distribution of the particle beam. 
     
     
       68. The particle accelerator of claim 64, further comprising:
 a resonant circuit, comprising:
 electrodes, disposed between magnetic pole pieces, having a gap therebetween across the magnetic field; and 
 a variable reactive element in circuit with the electrodes to vary a resonant frequency of the resonant circuit; and 
   wherein the voltage generator is configured to provide the voltage to the resonant circuit.   
     
     
       69. The particle accelerator of claim 68, wherein the voltage generator is digitally controllable to change an amplitude of the voltage. 
     
     
       70. The particle accelerator of claim 69, wherein the control circuit is configured to regulate the current based on the at least one property. 
     
     
       71. A particle accelerator configured to generate a particle beam, the particle accelerator comprising:
 an ion source to provide charged particles into a resonant cavity;   electrodes in the resonant cavity, the electrodes being separated by a gap;   a voltage circuit to output a radio frequency (RF) voltage to at least one of the electrodes to produce an oscillating electric field across the gap, the RF voltage having a frequency that varies to accelerate the charged particles to form the particle beam; and   a feedback system to detect information about the frequency of the oscillating electric field, and to adjust a timing of operation of the voltage circuit and the ion source based on the information so that the charged particles are provided to the resonant cavity in synchronism with a variation in the frequency of the RF voltage.   
     
     
       72. The particle accelerator of claim 71, wherein the feedback system comprises a voltage sensor configured to measure the oscillating electric field across the gap. 
     
     
       73. The particle accelerator of claim 71, wherein the feedback system comprises a digital control circuit configured to write data based on the information to memory, and to output data from memory to generate one or more waveforms upon which future outputs of the RF voltage are based. 
     
     
       74. The particle accelerator of claim 71, wherein the feedback system comprises:
 a beam monitor to detect an intensity of the particle beam; and   a control circuit to control operation of the ion source based on the intensity detected.   
     
     
       75. The particle accelerator of claim 72, wherein the particle accelerator is a synchrocyclotron. 
     
     
       76. The particle accelerator of claim 71, wherein the timing of operation of the voltage circuit is varied to compensate for physical features of the particle accelerator. 
     
     
       77. The particle accelerator of claim 71, wherein the information comprises a peak resonant condition of the resonant cavity; and
 wherein the feedback system is configured to control the timing of operation of the voltage circuit based on the peak resonant condition.   
     
     
       78. The particle accelerator of claim 77, wherein the timing of operation of the voltage circuit is controlled so that the RF voltage output matches a voltage of the resonant circuit corresponding to the peak resonant condition. 
     
     
       79. The particle accelerator of claim 71, wherein the feedback system comprises a programmable processor to control the timing of operation of at least one of the voltage circuit or the ion source based on the information. 
     
     
       80. A synchrocyclotron configured to output a particle beam, the synchrocyclotron comprising:
 an ion source to provide charged particles to a resonant cavity for orbital acceleration to form the particle beam, the particle beam comprising multiple pulses;   a voltage source to provide a radio frequency (RF) voltage to the resonant cavity, the voltage source comprising an amplifier to change an amplitude of the RF voltage before providing the RF voltage to the resonant cavity;   a control system to control operation of the ion source in order to control intensities of individual pulses among the multiple pulses comprising the particle beam, the control system comprising a programmable processor to control the operation of the ion source based on a frequency of the RF voltage in the resonant cavity; and   a beam monitor to detect an intensity of the particle beam;   wherein the programmable processor is configured to control operation of the ion source based also on information about the detected intensity.   
     
     
       81. The synchrocyclotron of claim 80, wherein the operation of the ion source is controlled by turning the ion source on and off during a time interval. 
     
     
       82. The synchrocyclotron of claim 80, wherein the operation of the ion source is controlled by selectively providing charged particles from the ion source over a number of cycles of the frequency of the RF voltage. 
     
     
       83. The synchrocyclotron of claim 80, wherein the operation of the ion source is controlled to control a timing at which the charged particles are provided. 
     
     
       84. The synchrocyclotron of claim 80, wherein the operation of the ion source is controlled to inject the charged particles at a same time relative to each cycle among multiple cycles of the frequency of the RF voltage. 
     
     
       85. The synchrocyclotron of claim 80, wherein the operation of the ion source is controlled to inject the charged particles continuously over multiple cycles of the frequency of the RF voltage. 
     
     
       86. The synchrocyclotron of claim 80, further comprising:
 magnetic pole pieces that border the resonant cavity in which the charged particles accelerate; and   a resonant circuit to control a resonant frequency within the resonant cavity;   wherein the voltage source is configured to provide the RF voltage to the resonant circuit, the RF voltage comprising an oscillating voltage that varies over a time of acceleration of the charged particles; and   wherein the voltage source comprises a digital waveform generator that includes the control system.   
     
     
       87. The synchrocyclotron of claim 80, wherein the operation of the ion source is controlled to inject the charged particles so as to compensate for detected variations of the particle beam. 
     
     
       88. The synchrocyclotron of claim 80, wherein the operation of the ion source is controlled to inject the charged particles periodically. 
     
     
       89. The synchrocyclotron of claim 80, wherein controlling intensities of individual pulses comprises controlling pulse widths of the individual pulses. 
     
     
       90. A synchrocyclotron comprising:
 magnetic pole pieces that border a cavity in which charged particles accelerate;   a resonant circuit to control a resonant frequency within the cavity;   a voltage circuit to provide voltage to the resonant circuit, the voltage comprising an oscillating voltage that varies over a time of acceleration of the charged particles; and   a feedback system to detect parameters based on operation of the resonant circuit, and to control the voltage circuit based on a least one of the parameters so as to maintain a resonant condition in the resonant circuit;   wherein the parameters comprises an amplitude of the voltage and a frequency of the voltage, and wherein the voltage circuit comprises an amplifier to change the amplitude of the voltage to maintain beam focusing.   
     
     
       91. The synchrocyclotron of claim 90, wherein the feedback system comprises a control circuit to control a property of the voltage based on the at least one parameter. 
     
     
       92. The synchrocyclotron of claim 91, wherein the control circuit is configured to control the property of the voltage by writing data about the property to memory. 
     
     
       93. The synchrocyclotron of claim 90, further comprising:
 an ion source to provide the charged particles to the cavity, the charged particles to accelerate in the cavity to form a particle beam;   an extraction channel to output the particle beam from the synchrocyclotron; and   a beam monitor to obtain information about a property of the particle beam;   wherein the feedback system is configured to receive the information about the property of the particle beam, and to use the information to control operation of the ion source.   
     
     
       94. The synchrocyclotron of claim 93, wherein the property of the particle beam is an intensity of the particle beam. 
     
     
       95. The synchrocyclotron of claim 93, wherein the property of the particle beam is particle beam timing or spatial distribution of the particle beam. 
     
     
       96. The synchrocyclotron of claim 90, wherein the resonant circuit comprises:
 electrodes in the cavity, the electrodes having a gap therebetween across a magnetic field in the cavity produced by the magnetic pole pieces; and   a variable reactive element in circuit with the electrodes to vary the resonant frequency.   
     
     
       97. The synchrocyclotron of claim 96, further comprising:
 an angular position sensor associated with the variable reactive element to output information about a position of the variable reactive element;   wherein at least one parameter comprises the information about the position.   
     
     
       98. The synchrocyclotron of claim 90, wherein at least part of the voltage circuit comprises digital circuitry. 
     
     
       99. The synchrocyclotron of claim 90, wherein at least one parameter comprises a timing parameter. 
     
     
       100. The synchrocyclotron of claim 93, wherein the feedback system is configured to use the information to generate, based on digital data, timing waveforms to control the voltage circuit. 
     
     
       101. The synchrocyclotron of claim 90, wherein the feedback system is adaptive. 
     
     
       102. A synchrocyclotron comprising:
 a magnetic field generator;   a resonant circuit comprising a variable reactive element to vary a resonant frequency of the resonant circuit;   a source to provide a voltage input to the resonant circuit, the voltage input being an oscillating voltage that varies over a time of acceleration of charged particles;   a feedback system to vary at least one property of the voltage input to the resonant circuit; and   one or more sensors to detect that there has been a deviation from a peak resonant condition in the resonant circuit;   wherein the voltage input is controlled by the feedback system based on the deviation in order to maintain the peak resonant condition.   
     
     
       103. The synchrocyclotron of claim 102, wherein the at least one property comprises amplitude of the voltage input. 
     
     
       104. The synchrocyclotron of claim 102, wherein the at least one property comprises frequency of the voltage input. 
     
     
       105. The synchrocyclotron of claim 102, wherein the at least one property comprises amplitude of the voltage input and frequency of the voltage input. 
     
     
       106. The synchrocyclotron of claim 102, wherein the feedback system is configured to maintain the peak resonant condition. 
     
     
       107. The synchrocyclotron of claim 102, further comprising:
 an ion source to provide the charged particles that form a particle beam following acceleration; and   a beam monitor to monitor the at least one property of the particle beam;   wherein the feedback system comprises control circuitry to receive the at least one property of the particle beam, and to control at least one of the voltage input or the ion source based on the at least one property to compensate for variations in the particle beam.   
     
     
       108. The synchrocyclotron of claim 107, wherein the at least one property comprises beam intensity, beam timing, or beam spatial distribution. 
     
     
       109. The synchrocyclotron of claim 107, wherein the voltage input is generated by a programmable digital waveform generator.