Compact cyclotron

Patent metadata

Field	Value
Publication number	US-9907153-B2
Application number	US-201715594538-A
Country	US
Kind code	B2
Filing date	May 12, 2017
Priority date	May 13, 2016
Publication date	Feb 27, 2018
Grant date	Feb 27, 2018

Abstract

The present disclosure relates to compact isochronous sector-focused cyclotrons having reduced dimensions and weight compared with state of the art cyclotrons of same energies. In one implementation, a cyclotron may include two pole magnets facing each other in a chamber defined by a yoke having base plates and flux return yokes forming a lateral wall of the chamber. The magnet poles may include between three and eight hill sectors alternating with a same number of valley sectors distributed about a central axis. The lip of the abyssal opening may be positioned at a distance from the corresponding valley peripheral edge. The flux return yoke may have a thickness in the portions facing valley sectors, such that the ratio of the product of the distance times the thickness to the square of the distance of the peripheral edge to the central axis is less than 5%.

First claim

The invention claimed is:

1. A cyclotron for accelerating a particle beam over a given path comprised within a gap, said cyclotron comprising:
a chamber defined within a yoke, wherein said yoke is formed by a first and second base plates normal to a central axis and separated from one another by a flux return yoke defining a lateral outer wall of the cyclotron; and
first and second magnet poles located in the chamber and symmetrically positioned opposite to one another with respect to a median plane normal to the central axis and separated from one another by said gap, and wherein each of the first and second magnet poles comprises:
at least three hill sectors having an upper surface and a same number of valley sectors comprising a bottom surface, said hill sectors and valley sectors being alternatively distributed around the central axis such that the gap separating the first and second magnet poles comprises hill gap portions defined between the upper surfaces of two opposite hill sectors and having an average hill gap height measured along the central axis, and valley gap portions defined between the bottom surfaces of two opposite valley sectors and having an average valley gap height measured along the central axis, with the average valley gap height exceeding the average gap hill height,
the bottom surfaces of each valley sector are defined by a valley peripheral edge, said valley peripheral edge being bounded by a first and a second lower distal ends and defined as the edge of the bottom surface located furthest from the central axis,
the bottom surfaces of each valley sector further comprise an abyssal opening extending through a thickness of the yoke base plates and defining an abyss gap portion having a height at least five times as large as the average hill gap height, said abyssal opening having a cross-section normal to the central axis defined by an abyss perimeter, which is separated from the valley peripheral edge by a shortest distance measured along an abyss radial axis intersecting perpendicularly the central axis, and wherein the valley peripheral edge is separated from the central axis by a distance measured along the abyss radial axis, and
the flux return yoke has a wall thickness varying with the angular position about the central axis, with a lowest wall thickness value measured along the abyss radial axis of each valley sector,

wherein a ratio of the product of the shortest distance times the flux return yoke thickness to the square of the distance of the valley peripheral edge to the central axis is less than 5%.

2. The cyclotron according to claim 1 , wherein the ratio is less than 3%.

3. The cyclotron according to claim 1 , wherein a ratio of a diameter of the abyssal opening to the distance of the valley peripheral edge to the central axis is between 45% and 60%.

4. The cyclotron according to claim 1 , wherein a ratio of a diameter of the abyssal opening to the distance between the central axis and a centre of an abyssal opening cross-section is at least 60%, and wherein the diameter between 240 and 300 mm.

5. The cyclotron according to claim 1 , wherein a ratio of the product of the average valley gap height times the flux return yoke thickness to the square of the distance of the valley peripheral edge to the central axis is less than 20%.

6. The cyclotron according to claim 1 , wherein a height ratio of the average hill gap height to the average valley gap height is between 8% and 20%.

7. The cyclotron according to claim 1 , wherein a ratio of the product of the average hill gap height times the average valley gap height to the square of the distance of the valley peripheral edge to the central axis is less than 5%.

8. The cyclotron according to claim 1 , wherein the average hill gap height is between 20 and 27 mm.

9. The cyclotron according to claim 1 , wherein the average valley gap height is between 100 and 500 mm.

10. The cyclotron according to claim 1 , wherein the first and second lower distal ends of the valley peripheral edge form, with the central axis, a valley azimuthal angle, such that a ratio of the average hill gap height to the tangent of the valley azimuthal angle is not larger than 30 mm.

11. The cyclotron according to claim 10 , wherein the valley azimuthal angle is greater than 35°, and is also more not more than 50.

12. The cyclotron according to claim 1 , further comprising four hill sectors and a same number of valley sectors, wherein the flux return yoke further comprises an inner surface facing the chamber, and an outer surface facing away from the chamber and separated from the inner surface by the wall thickness of the flux return yoke, wherein a cross-section of the inner surface normal to the central axis has a circular geometry concentric with the central axis, and wherein a cross-section of the outer surface normal to the central axis has a square geometry concentric with the central axis, whose edges are normal to the abyss radial axes of the four valley sectors, and whose corners are cut off.

13. The cyclotron according to claim 1 , wherein the base plates, magnet poles, and flux return yokes are all made of a same material, and wherein portions of the base plates and flux return yokes have a same height measured along the central axis.

14. The cyclotron according to claim 1 , wherein each of the first and second magnet poles is made of a single monobloc element comprising all the hill sectors and valley sectors thereof.

15. The cyclotron according to claim 1 , further comprising eight hill sectors and a same number of valley sectors, wherein the flux return yoke further comprises an inner surface facing the chamber, and an outer surface facing away from the chamber and separated from the inner surface by the wall thickness of the flux return yoke, wherein a cross-section of the inner surface normal to the central axis has a circular geometry concentric with the central axis, and wherein a cross-section of the outer surface normal to the central axis has a square geometry concentric with the central axis, whose edges are normal to the abyss radial axes of the eight valley sectors, and whose corners are cut off.

16. The cyclotron according to claim 4 , wherein the ratio of the diameter of the abyssal opening to the distance between the central axis and the centre of an abyssal opening cross-section is at least 70%.

17. The cyclotron according to claim 5 , wherein the ratio of the product of the average valley gap height times the flux return yoke thickness to the square of the distance of the valley peripheral edge to the central axis is less than 10%.

18. The cyclotron according to claim 7 , wherein the ratio of the product of the average hill gap height times the average valley gap height to the square of the distance of the valley peripheral edge to the central axis is less than 2%.

19. The cyclotron according to claim 9 , wherein the average valley gap height is between 200 and 250 mm.

20. The cyclotron according to claim 11 , wherein the valley azimuthal angle is greater than 42° and is also more not more than 45°.

Assignees

• Ion Beam Appl Sa
• Ion Beam Appl Sa

Inventors

• Abs Michel
• De Neuter Sebastien

Classifications

• H05H13/005

  Cyclotrons · CPC title

• H05H7/04 Primary

  Magnet systems {, e.g. undulators, wigglers (free-electron laser H01S3/0903)}; Energisation thereof · CPC title

• H01F7/20

  without armatures (cores H01F3/00; coils H01F5/00 {; shaping metal by applying magnetic forces B21D26/14; electromagnets specially adapted for NMR applications G01R33/381}) · CPC title

• H01F3/10

  Composite arrangements of magnetic circuits · CPC title

• H05H7/001

  Arrangements for beam delivery or irradiation (irradiation systems per se G21K5/00) · CPC title