Method and apparatus for intensity control of a charged particle beam extracted from a synchrotron
View Patent ↗The invention comprises intensity control of a charged particle beam acceleration, extraction, and/or targeting method and apparatus used in conjunction with charged particle beam radiation therapy of cancerous tumors. Particularly, intensity of a charged particle stream of a synchrotron is described. Intensity control is described in combination with turning magnets, edge focusing magnets, concentrating magnetic field magnets, winding and control coils, and extraction elements of the synchrotron. The system reduces the overall size of the synchrotron, provides a tightly controlled proton beam, directly reduces the size of required magnetic fields, directly reduces required operating power, and allows continual acceleration of protons in a synchrotron even during a process of extracting protons from the synchrotron.
1. An apparatus for controlling intensity of charged particles extracted from a circulating charged particle beam path in a synchrotron, said apparatus comprising:
a radio-frequency field generator, wherein during use said radio-frequency generator applies a radio-frequency field to the circulating charged particles yielding betatron oscillating charged particles;
an extraction material, wherein during use at least a portion of the betatron oscillating charged particles pass through said extraction material resulting in a secondary emission electron flow using electrons originating from the extraction material and without loss of electrons from the betatron oscillating charged particles;
an intensity sensor, said intensity sensor configured to determine a measure of the electron flow; and
a feedback control loop comprising an intensity controller, said intensity controller configured to provide the measure of electron flow as a feedback to said radio-frequency generator,
said feedback control loop configured to control intensity of charged particles extracted from said synchrotron via control of said radio-frequency generator,
wherein intensity comprises a number of the charged particles extracted as a function of time.
2. The apparatus of claim 1 , further comprising:
a target signal, wherein said intensity controller calculates a difference between said measure of said electron flow and said target signal, wherein said intensity controller alters amplitude of said radio-frequency field based upon said difference.
3. The apparatus of claim 1 , wherein said extraction material consists essentially of atoms having six or fewer protons.
4. The apparatus of claim 1 , wherein said extraction material comprises a foil of about thirty to one hundred micrometers thickness, said foil comprising any of:
beryllium;
lithium hydride; and
carbon.
5. The apparatus of claim 1 , further comprising:
at least a one kilovolt direct current field applied across a pair of extraction blades; and
a deflector,
wherein said at least a portion of the betatron oscillating charged particles passing through said extraction material yield reduced energy charged particles,
wherein the reduced energy charged particles pass between said pair of extraction blades, and
wherein said direct current field redirects the reduced energy charged particles through said deflector yielding intensity controlled extracted charged particles.
6. The apparatus of claim 1 , further comprising at least one turning magnet, wherein said turning magnet comprises a magnetic field concentrating first magnet, wherein said first magnet comprises:
a gap circumferentially encompassing the circulating charged particle beam path;
a first cross-section diameter not in contact with said gap; and
a second cross-sectional diameter proximate said gap, wherein said second cross-section diameter is less than seventy percent of said first cross-sectional diameter,
wherein a magnetic field passing through said first cross-sectional diameter concentrates in said second cross-sectional diameter before crossing said gap.
7. A method for controlling intensity of charged particles extracted from a circulating charged particle beam path in a synchrotron, said method comprising the steps of:
generating a radio-frequency field using a radio-frequency field generator, wherein said radio-frequency generator applies the radio-frequency field across the circulating charged particle beam path yielding oscillating charged particles;
traversing at least a portion of the oscillating charged particles through an extraction material yielding a secondary emission electron flow, the secondary emission electron flow using electrons originating from the extraction material without substantial loss of electrons from the betatron oscillating charged particles;
determining a measure of the electron flow using an intensity sensor; and
providing the measure of the electron flow to an intensity controller via a feedback control loop,
wherein said intensity controller controls intensity of charged particles extracted from said synchrotron via control of said radio-frequency generator,
wherein intensity comprises a number of the charged particles extracted as a function of time.
8. The method of claim 7 , further comprising the step of:
determining a difference between a target signal and said measure of electron flow, wherein said intensity controller alters amplitude of said radio-frequency field based upon said difference.