Method of extracting charged particles from accelerator, and accelerator capable of carrying out the method, by shifting particle orbit

• US 5,285,166 A
• Filed: 03/26/1992
• Issued: 02/08/1994
• Est. Priority Date: 10/16/1991
• Status: Expired due to Term

• Current Assignee: Director General Of National Institute Of Radiological Sciences, Hitachi, Ltd.
• Original Assignee: Director General Of National Institute Of Radiological Sciences, Hitachi, Ltd.
• Inventors: Itano, Akifumi, Hiramoto, Kazuo, Nishi, Masatsugu
• Primary Examiner(s): Yusko, Donald J.
• Assistant Examiner(s): Giust, John
• Application Number:
  US07/857,660
• Time in Patent Office: 684 Days
• Field of Search: 328/235, 328/233, 328/237
• US Class Current: 315/507
• CPC Class Codes: A61N 2005/1087 Ions; Protons
• CPC Class Codes: A61N 5/1077 Beam delivery systems
• CPC Class Codes: H05H 7/10 Arrangements for ejecting particles from orbits

Abstract

A method of extracting a strong, charged particle beam, that is, a large current from an accelerator, and an accelerator capable of carrying out the method utilizes charged particles which are extracted from the accelerator. The equilibrium orbit of charged particles in one of a bending magnet and a magnet having multipole components greater than sextuple components, is shifted by a constituent element of the accelerator other than these magnets, to change the tune of charged particles. The adjustment of this tune based upon the shift of the equilibrium orbit in the above magnet for extracting charged particles, can keep the gradient of orbit of the extracted beam substantially constant. Accordingly, beam extraction is readily controlled, and a large current can be extracted from the accelerator.

Claims

1. A method of extracting a charged particle beam from an accelerator by exciting a betatron oscillation of charged particles to a specified resonance, comprising a step of changing a resonant state of the betatron oscillation by shifting an equilibrium orbit of the charged particles in one of a bending magnet and a magnet having multipole components greater than six poles, the magnets being included in the accelerator.

2. A method according to claim 1, wherein said accelerator is circular and includes:

a plurality of bending magnets;

a plurality of bumping magnets;

a plurality of quadrupole magnets;

a plurality of magnets having multipole components higher than a sextupole component;

a radio frequency accelerating cavity; and

a deflector for the extraction by exciting the specified resonance to the betatron oscillations.

3. A method of extracting a charged particle beam from an accelerator by exciting an betatron oscillation of charged particles to a specified resonance comprising a step of changing a size of a region indicative of a stable limit at a time when the betatron oscillation is excited to the specified resonance, by shifting an equilibrium orbit of charged particles in one of a bending magnet and a magnet having multipole components greater than six poles, the magnets being included in the accelerator.

4. A method according to claim 3, wherein said accelerator is circular and includes:

a plurality of bending magnets;

a plurality of bumping magnets;

a plurality of quadrupole magnets;

a plurality of magnets having multipole components higher than a sextupole component;

a radio frequency accelerating cavity; and

a deflector for the extraction by exciting the specified resonance to the betatron oscillations.

5. A method of extracting a charged particle beam from an accelerator in such a manner that a betatron oscillation of charged particles is excited to a specified resonance and a region indicative of a stable limit at a time when the betatron oscillation is excited to the specified resonance, is gradually reduced in a period from an initial stage of the extraction of the charged particle beam to a last stage of the extraction of the charged particle beam, the method comprising a step of shifting an equilibrium orbit of charged particles in one of a bending magnet and a magnet having multipole components greater than six poles, to change a tune of the charged particles, thereby decreasing a region indicative of the stable limit at a time when the betatron oscillation is excited to the specified resonance, gradually in the period from the initial stage of extraction of the charged particle beam to the last stage of the extraction of the charged particle beam.

6. A method according to claim 5, wherein the equilibrium orbit in one of the magnets is greatly shifted in the initial stage of the extraction of the charged particle beam and is slightly shifted in the last stage of the extraction of the charged particle beam, to make the tune gradually approach a value at the specified resonance.

7. A method according to claim 5, wherein a period when the charged particle beam is extracted from the accelerator, is controlled by changing a speed, at which the equilibrium orbit in one of the magnets is shifted.

8. A method according to claim 5, wherein said accelerator is circular and includes:

a plurality of bending magnets;

a plurality of bumping magnets;

a plurality of quadrupole magnets;

a plurality of magnets having multipole components higher than a sextupole component;

a radio frequency accelerating cavity; and

a deflector for the extraction by exciting the specified resonance to the betatron oscillations.

9. A method of extracting a charged particle beam from an accelerator in such a manner that a betatron oscillation of charged particles is excited to a specified resonance and a region indicative of a stable limit at a time when the betatron oscillation is excited to the specified resonance, is gradually reduced in a period from an initial stage of the extraction of the charged particle beam to a last stage of the extraction of the charged particle beam, the method comprising a step of maintaining a gradient of orbit of the extracted beam substantially constant.

10. A method according to claim 9, wherein an equilibrium orbit of charged particles is shifted so that the gradient of orbit of the extracted beam is kept substantially constant.

11. A method according to claim 9, wherein said accelerator is circular and includes:

a plurality of bending magnets;

a plurality of bumping magnets;

a plurality of quadrupole magnets;

a plurality of magnets having multipole components higher than a sextupole component;

a radio frequency accelerating cavity; and

a deflector for the extraction by exciting the specified resonance to the betatron oscillations.

12. A method of extracting a charged particle beam from an accelerator by exciting a betatron oscillation of charged particles to a specified resonance, comprising steps of:

forming a bumped orbit of charged particles in one of a bending magnet and a magnet having multipole components greater than six poles, the magnets being included in the accelerator; and

shifting the bumped orbit to change a resonant state of the betatron oscillation.

13. A method according to claim 12, wherein said accelerator is circular and includes:

a plurality of bending magnets;

a plurality of bumping magnets;

a plurality of quadrupole magnets;

a plurality of magnets having multipole components higher than a sextupole component;

a radio frequency accelerating cavity; and

a deflector for the extraction by exciting the specified resonance to the betatron oscillations.

14. An accelerator for extracting a charged particle beam therefrom by exciting a betatron oscillation of charged particles to a specified resonance, comprising:

a bending magnet for making charged particles travel along a circular orbit;

an extraction point where the charged particles are extracted from the circular orbit;

a resonance exciter magnet for exciting the betatron oscillation to the specified resonance; and

means for shifting the equilibrium orbit of charged particles in one of the bending magnet and a magnet having multiple components greater than six poles to change a tune of the charged particles.

15. An accelerator according to claim 14, further comprising:

a plurality of bending magnets;

a plurality of resonance exciter magnets; and

a plurality of magnets having multipole components higher than a sextupole component.

16. An accelerator for extracting a charged particle beam therefrom by exciting a betatron oscillation of charged particles to a specified resonance, comprising:

a bending magnet for making charged particles travel along a circular orbit;

an extraction point where the charged particles are extracted from the circular orbit;

a resonance exciter magnet for exciting the betatron oscillation to the specified resonance; and

means for shifting the equilibrium orbit of charged particles in one of the bending magnet and a magnet having multiple components greater than six poles, to change a tune of the charged particles.

17. An accelerator according to claim 16, further comprising:

a plurality of bending magnets;

a plurality of resonance exciter magnets;

a plurality of magnets having multipole components higher than a sextupole component; and

a plurality of magnets for shifting the equilibrium orbit of the charged particles.

18. An accelerator for extracting a charged particle beam therefrom by exciting a betatron oscillation of charged particles to a specified resonance, comprising:

a bending magnet for making charged particles travel along a circular orbit;

a sextuple magnet for exciting the betatron oscillation to the specified resonance;

an extraction point where the charged particles are extracted from the circular orbit; and

a magnet for shifting an equilibrium orbit of charged particles in one of the bending magnet and a sextuple magnet other than the resonance-exciting sextuple magnet, to change the tune of the charged particles.

19. An accelerator according to claim 18, further comprising:

a plurality of bending magnets;

a plurality of resonance exciter magnets;

a plurality of magnets having multipole components higher than a sextupole component; and

a plurality of magnets for shifting the equilibrium orbit of the charged particles.

20. An accelerator for extracting a charged particle beam therefrom by exciting a betatron oscillation of charged particles to a specified resonance, comprising:

a bending magnet for making charged particles travel along a circular orbit;

an octupole magnet for exciting the betatron oscillation to the specified resonance; and

an extraction point where the charged particles are extracted from the circular orbit;

a magnet for shifting an equilibrium orbit of charged particles in one of the bending magnet and a magnet which has multipole components greater than six poles and is different from the octupole magnet, to change the tune of the charged particles.

21. An accelerator according to claim 20, further comprising:

a plurality of bending magnets;

a plurality of octupole magnets;

a plurality of magnets which have multipole components higher than a sextupole component; and

a plurality of magnets for shifting the equilibrium orbit.

22. An accelerator for extracting a charged particle beam therefrom by exciting a betatron oscillation of charged particles to a specified resonance, comprising:

a multiplicity of bending magnets for making charged particles travel along a circular orbit;

a multiplicity of focusing quadrupole magnets and defocusing quadrupole magnets for focusing and defocusing the charged particle beam, respectively, each of the quadrupole magnets being devoid of a supplementary coil for beam extraction; and

means for extracting charged particles from the circular orbit.

23. An accelerator according to claim 22, wherein said means for extracting charged particles from the circular orbit, shifts and equilibrium orbit.

24. An accelerator for extracting a charged particle beam therefrom by exciting a betatron oscillation of charged particles to a specified resonance, comprising:

a multiplicity of magnets for making charged particles travel along a circular orbit; and

extraction means for extracting the charged particles from the circular orbit, the extraction means being provided with means for keeping a gradient of orbit of the extracted beam substantially constant.

25. An accelerator for extracting a charged particle beam therefrom by exciting a betatron oscillation of charged particles to a specified resonance, comprising:

a bending magnet for making charged particles travel along a circular orbit;

extraction means for extracting the charged particles from the circular orbit, the extraction means being provided with means for keeping a gradient of orbit of the extracted beam substantially constant;

a resonance exciter magnet for exciting the betatron oscillation to the specified resonance; and

means for shifting an equilibrium orbit of charged particles in one of the bending magnet and a magnet having multipole components greater than six poles, the change the tune of the charged particles.

26. An accelerator according to claim 25, further comprising:

a plurality of bending magnets;

a plurality of resonance exciter magnets; and

a plurality of magnetic having multipole components higher than a sextupole component.

27. An accelerator for extracting a charged particle beam therefrom by exciting a betatron oscillation of charged particles to a specified resonance, comprising:

an extractor for extracting charged particles;

a bending magnet;

a resonance exciter magnet for exciting the betatron oscillation to the specified resonance; and

means for shifting an equilibrium orbit of charged particles in one of the bending magnet and the resonance exciter magnet.

28. An accelerator according to claim 27, further comprising:

a plurality of bending magnets; and

a plurality of resonance exciter magnets.

29. An apparatus for extracting a charged particle beam from an accelerator by exciting a betatron oscillation of charged particles to a specified resonance, comprising:

an extractor including an extraction point for extracting the charged particles; and

means for maintaining a gradient of orbit of the extracted beam at the extraction point substantially constant.

30. An apparatus according to claim 29, wherein said accelerator is circular and includes:

a plurality of bending magnet;

a plurality bumping magnets;

a plurality of quadrupole magnets;

a plurality of magnets having multipole components higher than sextupole component;

a radio frequency accelerating cavity; and

a deflector for the extraction by exciting the specified resonance of the betatron oscillations.