METHOD AND APPARATUS FOR INTENSITY CONTROL OF A CHARGED PARTICLE BEAM EXTRACTED FROM A SYNCHROTRON

• US 20090314961A1
• Filed: 09/01/2009
• Published: 12/24/2009
• Est. Priority Date: 05/22/2008
• Status: Active Grant

• Current Assignee: Andrey Vladimirovich Balakin, Pavel Vladimirovich Balakin
• Original Assignee: Vladimir Balakin
• Inventors: Balakin, Vladimir
• Granted Patent: US 8,368,038 B2
• Time in Patent Office: Days
• US Class Current: 250/492.300
• CPC Class Codes: A61N 2005/1087 Ions; Protons
• CPC Class Codes: G21K 1/087 by electrical means
• CPC Class Codes: G21K 1/093 by magnetic means
• CPC Class Codes: H05H 7/04 Magnet systems , e.g. undulators, wigglers free-electron laser H01S3/0903; Energisation thereof
• CPC Class Codes: H05H 7/12 Arrangements for varying final energy of beam

Abstract

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.

Claims

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 at least a portion of the betatron oscillating charged particles pass through said extraction material resulting in a secondary emission electron flow;

an intensity sensor, said intensity sensor determining a measure of said electron flow; and

a feedback control loop comprising an intensity controller, wherein said intensity controller provides said measure of electron flow as a feedback to said radio-frequency generator,

wherein said feedback control loop 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.

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;

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.

9. An apparatus for extracting intensity controlled charged particles from charged particles circulating in a synchrotron of a charged particle cancer therapy system, comprising:

oscillation blades, said oscillation blades comprising a radio-frequency voltage across said blades during use, said radio-frequency inducing oscillating charged particles from the charged particles circulating in said synchrotron;

an extraction material in said synchrotron, wherein the oscillating charged particles traverse said extraction material during use generating both reduced energy charged particles and secondary emission electrons; and

extraction blades, said extraction blades extracting said reduced energy charged particles from said synchrotron.

10. The apparatus of claim 9, further comprising:

a feedback intensity controller, wherein said intensity controller generates a measure of the secondary emission electrons, wherein said intensity controller generates a comparison of said measure and a target signal, wherein said intensity controller adjusts amplitude of said radio-frequency voltage based on said comparison.

11. The apparatus of claim 10, wherein said extraction blades comprises an extraction field across said extraction blades, wherein the reduced energy charged particles, comprises movement along a radius of curvature passing through said extraction blades, wherein the reduced energy charge particles extract from said synchrotron after passing through said extraction field.

12. The apparatus of claim 9, further comprising a main controller, said main controller controlling:

acceleration of the circulating charged particles to a target energy level; and

intensity of said radio-frequency voltage yielding a target intensity level of the extracted charged particles.

13. A method for extracting intensity controlled charged particles from charged particles circulating in a synchrotron, comprising the steps of:

inducing oscillating charged particles from the charged particles circulating in said synchrotron using a radio-frequency voltage applied across a pair of oscillation blades,

traversing the oscillating charged particles through an extraction material in said synchrotron, said step of traversing generating both reduced energy charged particles and a current; and

extracting said reduced energy charged particles from said synchrotron by passing the reduced energy charged particles through an extraction field between two extraction blades.

14. The method of claim 13, further comprising the steps of:

generating a measure of the current;

generating a comparison of said measure and a target signal using an intensity controller; and

adjusting amplitude of said radio-frequency voltage based on said comparison.

15. The method of claim 14, wherein the reduced energy charged particles, comprises movement along a radius of curvature passing through said extraction blades,

wherein the reduced energy charge particles extract from said synchrotron after passing through said extraction field.

16. The method of claim 13, further comprising the step of:

controlling acceleration of the circulating charged particles to a target energy level of the extracted charged particles; and

controlling intensity of said radio-frequency voltage yielding a target intensity level of the extracted charged particles.

17. A method for extracting a circulating charged particle beam from a synchrotron, comprising the steps of:

transmitting the circulating charged particle beam through an extraction material, said extraction material yielding both;

a reduced energy charged particle beam; and

a secondary emission current;

applying a field of at least five hundred volts across a pair of extraction blades;

passing the reduced energy charged particle beam between said pair of extraction blades,

wherein said field redirects the reduced energy charged particle as an extracted charged particle beam.

18. The method of claim 17, further comprising the step of:

controlling intensity of the energy controlled extracted charged beam with an intensity controller.

19. The method of claim 18, wherein said step of controlling comprises the steps of:

inputting a feedback signal to said intensity controller, said secondary emission current converted to said feedback signal;

comparing said feedback signal to an irradiation plan intensity;

adjusting betatron oscillation with said intensity controller until said feedback signal proximately equals said irradiation plan intensity.