Superconducting medical cyclotron

• US 4,641,104 A
• Filed: 04/26/1984
• Issued: 02/03/1987
• Est. Priority Date: 04/26/1984
• Status: Expired due to Term

• Current Assignee: Board of Trustees East Lansing Michigan A Constitutional Corporation Operating Michigan
• Original Assignee: The Board of Trustees of Michigan State University (Michigan State University)
• Inventors: Jemison, Emanuel B., Burleigh, Richard J., Blosser, Henry G., Blosser, Gabe F.
• Primary Examiner(s): Moore, David K.
• Assistant Examiner(s): WIEDER, KENNETH A
• Application Number:
  US06/604,089
• Time in Patent Office: 1,013 Days
• Field of Search: 328/234, 313/35, 313/62, 250/492.1, 250/497.1, 250/498.1, 250/493.1, 165/58, 165/60, 174/15 R, 174/15 CA, 174/15 S, 335/216, 376/112
• US Class Current: 315/502
• CPC Class Codes: A61N 2005/1087 Ions; Protons
• CPC Class Codes: A61N 5/1081 Rotating beam systems with a specific mechanical construction, e.g. gantries
• CPC Class Codes: H05H 13/00 Magnetic resonance accelerators; Cyclotrons strophotrons, turbine tubes H01J25/62
• CPC Class Codes: H05H 7/20 with superconductive walls
• CPC Class Codes: Y10S 505/88 Inductor

Abstract

An improved superconducting cyclotron (10) particularly useful for medical or therapeutic purposes is described. The vessel (105) for liquified gas surrounding superconducting coils (101, 101a) is provided with a capillary tube (200) joined to a semi-circular tube (123) leading into an exit tube (201) from the vessel which provides Joule-Thompson effect cooling upon flow of a portion of the liquified gas in the vessel into the semi-circular tube. The cooling maintains the liquified gas in the vessel in a subcooled condition to prevent boiling. The liquified gas from the exit tube can be used to cool the magnetic poles (103, 104) and then can be vented to the atmosphere or recycled. A special external magnetic yoke (102) configuration for weight reduction is described. Also described is a flexible hose (37) for supplying the liquified gas to and from the cyclotron which is mounted in a helical coil so as to allow up to a 360° of rotation of the cyclotron. Finally a movable floor (27) around the cyclotron is described.

Claims

1. In a superconducting cyclotron apparatus which generates a beam of high velocity particles comprising atomic particles and subparticles thereof to be directed at an object to be irradiated from spirally accelerated charged particles around a cyclotron axis which form the beam or which impinge upon a target to produce the beam and including inlet and outlet conduit means for supplying and removing liquified gas to and from a vessel around superconducting coils supplied by electrical leads inside the vessel which pass around spaced apart iron poles so as to generate a magnetic field between the poles when current is supplied to the coils and which function to produce the spirally accelerated charged particles with an oscillatory electrical field, the improvement which comprises:

a Joule-Thompson effect constricted capillary tube leading to a semi-circular tube adjacent to and in heat transfer relationship with both coils and the liquified gas in the vessel, with the semi-circular tube connected to an exit tube from the vessel and cyclotron, wherein in operation of the cyclotron liquified gas is at an elevated pressure P₁ in the vessel and a portion of the liquified gas in the vessel flows through the capillary tube and expands into the semi-circular tube at a pressure P₂ lower than P₁ thus cooling the semicircular tube and thus the liquified gas in the vessel and the coils and then the liquified gas is removed through the exit tube, and wherein the cooled semi-circular tube subcools the liquified gas in the coil vessel thus preventing the formation of bubbles in this vessel due to heat flowing into the liquified gas in the vessel along the electrical leads supplying current to the coils.

2. The superconducting cyclotron of claim 1 wherein the cyclotron is mounted on a rotatable support structure with a counterweight for the cyclotron on the support structure opposite the cyclotron, wherein the support structure is rotatable on a rotation axis between the cyclotron and counterweight for changing the angle of the beam in an arc defining a plane about the axis so that an object positioned at the axis can be irradiated.

3. The superconducting cyclotron of claim 2 wherein the rotatable support structure is a balance bar having two segments joined to a pivot means along the rotation axis and defining the rotation axis intermediate to opposite ends of the bar and wherein the cyclotron and counterweight are positioned on opposite ends of the balance bar.

4. The superconducting cyclotron of claim 3 wherein the segments of the balance bar are mounted on either side of the pivot means along the rotation axis.

5. The superconducting cyclotron apparatus of claim 2 wherein the rotatable support structure includes the cyclotron and counterweight both mounted on two spaced apart rings each having a center on the rotation axis and wherein each of the rings is mounted on rollers which provide rotation of the rings, cyclotron and counterweights around the rotation axis.

6. In a superconducting cyclotron apparatus which generates a beam of high velocity particles comprising atomic particles and subparticles thereof directed at an object to be irradiated by spirally accelerated charged particles around a cyclotron axis which impinge upon a target to produce the beam, with a window and a collimator on a first side of the cyclotron tangental to the spirally accelerated charged particles for defining the beam, including a support structure having a counterweight for the cyclotron so as to be rotatable on a rotation axis between the cyclotron and counterweight for changing the angle of the beam in an arc defining a plane around the rotation axis so that an object on the axis can be irradiated, and including inlet and outlet conduit means for supplying and removing a liquified gas to and from a vessel with superconducting coils in the vessel which pass around spaced apart iron poles so as to generate a magnetic field between the poles when current is supplied to the coils and with an iron yoke connecting the poles outside the coils so as to return the magnetic field between the poles, wherein the poles and coils function to produce the spirally accelerated charged particles with an oscillating electrical field produced by electrodes, the improvement in the yoke which comprises:

an iron or steel yoke having sections which are essentially the same in external configuration over an angle of 120°

around the cyclotron axis including

(a) three first flat exterior faces of the yoke which are parallel to the cyclotron axis and tangential to first radii from the cyclotron axis and symmetrical at equal arcs around the cyclotron axis and

(b) three second flat exterior faces of the yoke equal in number to the first faces which are parallel to the cylotron axis and tangential to second radii from the cyclotron axis shorter than the first radii and are tangential in an opposite direction from the first faces so that the flat faces intersect at a third radii from the cyclotron axis to form three lobes, wherein the first and second flat surfaces provide for mounting of electrical, target and liquified gas connections to the inlet conduit means to the cyclotron and reduce the weight of the cyclotron over a cyclotron having a cylindrically faced yoke with a diameter of the third radii.

7. The superconducting cyclotron apparatus of claim 6 wherein the window and collimator are mounted through one of the first flat faces of the yoke.

8. The superconducting cyclotron apparatus of claim 6 wherein coil retaining members are mounted through the yoke at equal arcs around the cyclotron axis and engage bobbins mounting the coils and forming part of the vessel through each of the first or second flat faces of the yoke.

9. The superconducting cyclotron apparatus of claim 6 wherein coil retaining members are provided through each first flat faces, wherein the window and collimator are provided through one first flat face, wherein electrical leads to the coils are provided through another first flat face 120°

from the initial first flat face and wherein a liquified gas inlet and outlet is provided through a final first flat face 240°

from the initial first flat face and wherein liquified gas safety vent is provided through a first or second flat face so that the weight and magnetic field around the cyclotron axis is equally distributed.

10. In a superconducting cyclotron apparatus which generates a beam of high velocity particles comprising atomic particles and subparticles thereof directed at an object to be irradiated by spirally accelerated charge particles around a cyclotron axis which impinge upon a target to produce the beam, with a window and a collimator on a first side of the cyclotron tangental to the spirally accelerated charged particles for defining the beam, including a support structure mounting a counterweight for the cyclotron and rotatable on a rotation axis between the cyclotron and counterweight for changing the angle of the beam in an arc defining a plane around the rotation axis so that an object on the axis can be irradiated and including inlet and outlet conduit means for supplying and removing a liquified gas to and from a vessel with superconducting coils in the vessel which pass around spaced apart iron poles which can generate a magnetic field between the poles when current is supplied to the poles and with an iron or steel yoke between the poles for returning the magnetic field between the poles, wherein the poles and coils function to produce the spirally accelerated charged particles with an oscillating electrical field produced by electrodes, the improvement which comprises:

a yoke having sections which are essentially the same in external configuration over an angle of 120°

around the cyclotron axis including

(a) three first flat exterior faces of the yoke which are parallel to the cyclotron axis and tangential to a first radius from the cyclotron axis and symmetrical at equal arcs around the cyclotron axis;

(b) three second flat exterior faces of the yoke equal in number to the first faces which are parallel to the cyclotron axis and tangential to second radii from the cyclotron axis shorter than the first radii and are tangential in an opposite direction from the first face so that the flat faces intersect at a third radii from the cyclotron axis to form three lobes, wherein the first and second flat faces provide for mounting of electrical, target and liquified gas connections to the inlet means to the cyclotron;

(c) retaining members for the coils mounted through the first faces of the yoke supporting both coils at angles of 120°

around the cyclotron axis, wherein, the window and the collimator are provided through one first flat face of the yoke, wherein electrical leads to the coils are provided through another first flat face 120°

from the first flat face, wherein the liquified gas inlet and outlet means is provided through a final first flat face 240°

.

11. The superconducting apparatus of claim 10 wherein the retaining members are circular cross-sectional folded support columns which engage bobbins supporting the coils as part of the vessel and wherein magnetic or non-magnetic structural support cores support the columns through the yoke.

12. In a superconducting cyclotron apparatus which generates a beam of high velocity particles comprising atomic particles and subparticles thereof to be directed at an object to be irradiated from spirally accelerated charged particles which impinge upon a target to produce the beam, with a window and a collimator on a first side of the cyclotron tangential to the spirally accelerated charged particles for defining the beam including a support structure having a counterweight for the cyclotron rotatable in two directions on a rotation axis between the counterweight and cyclotron for changing the angle of the beam in an arc defining a plane around the rotation axis so that an object on the axis can be irradiated and further including inlet and outlet conduit means for supplying and removing liquified gas to and from a vessel and with superconducting coils in the vessel which pass around spaced apart iron poles which can generate a magnetic field between the poles when current is supplied to the coils and which functions to produce the spirally accelerated charged particles with an oscillating electrical field, the improvement which comprises:

(a) flexible hose in the form of a helical coil defining a diameter about the pivot axis and attached at the inlet and outlet conduit means so that upon rotation of the cyclotron on the rotation axis the diameter of the coil increases in one direction and decreases in the opposite direction; and

(b) spring means attached to and supporting the helically coil hose.

13. The apparatus of claim 12 wherein the counterweight and cyclotron are mounted on a balance bar with a pivot means mounted on the bar between the counterweight and cyclotron.

14. The superconducting cyclotron apparatus of claim 12 wherein the counterweight and cyclotron are mounted 180°

apart between two spaced apart parallel rings and wherein the rings are mounted on rollers for rotation about the rotation axis.

15. The superconducting cyclotron apparatus of claim 12 wherein an essentially cylindrically shaped rotatable floor having a longitudinal axis of rotation is mounted adjacent to the support structure around the cyclotron and counterweight so that the longitudinal axis of the floor and rotation axis of the support structure are the same and so that the floor rotates with the support structure.

16. The superconducting cyclotron apparatus of claim 15 wherein the floor is composed of elongate sections joined together to articulate in the direction of rotation and wherein a horizontal flat floor surface is provided below the rotation axis of the support structure so that the elongate sections ride over the flat surface and flatten as the cyclotron is rotated.

17. In a superconducting cycltron apparatus which generates a beam of high velocity particles comprising atomic particles and subparticles thereof to be directed at an object to be irradiated from spirally accelerated charge particles which impinge upon a target to produce the beam, with a window and a collimator on a first side of the cyclotron tangential to the spirally accelerated charged particles for defining the beam including a support structure having a counterweight for the cyclotron rotatable in two directions on a rotation axis between the counterweight and cyclotron for changing the angle of the beam in an arc defining a plane around the rotation axis so that an object on the axis can be irradiated and further including inlet and outlet conduit means for supplying and removing liquified gas to and from a vessel and with superconducting coils in the vessel which pass around spaced apart iron poles which can generate a magnetic field between the poles when current is supplied to the coils and which functions to produce the spirally accelerated charged particles with an oscillating electrical field, the improvement which comprises:

(a) two elongate segments on either side of and along the rotation axis so as to be 180°

apart with ends on each segment including a counterweight at the end of one segment and a cyclotron at the end of the other segment opposite the counterweight, such that at the end of one segment and a cyclotron at the end of the other segment opposite the counterweight, such that the beam can be generated in a plane perpendicular to and in the direction of the rotation axis;

(b) pivot means supporting the segments at the rotation axis with the cyclotron balancing the counterweight and with the rotation axis providing a fulcrum such that the segments are rotatable in an arc in the plane perpendicular to the pivot axis;

(c) drive means for rotating the segments in the arc about the rotation axis and the pivot means as the beam is generated;

(d) flexible hose in a helical coil about the rotation axis attached at the inlet and outlet conduit means of the cyclotron for supplying and removing a liquified gas to and from the vessel and coils; and

(e) spring means supporting the hose in the helical coil.

18. In a superconducting cyclotron apparatus which generates a beam of high velocity particles comprising atomic particles and subparticles thereof to be directed at an object to be irradiated from spirally accelerated charged particles which impinge upon a target to produce the beam, with a window and a collimator on a first side of the cyclotron tangential to the spirally accelerated charged particles for defining the beam including a support structure having a counterweight for the cyclotron rotatable in two directions on a rotation axis between the counterweight and cyclotron for changing the angle of the beam in an arc defining a plane around the rotation axis so that an object on the axis can be irradiated and further including inlet and outlet conduit means for supplying and removing liquified gas to and from a closed vessel and with superconducting coils in the vessel which pass around spaced apart iron poles which can generate a magnetic field between the poles when current is supplied to the coils and which functions to produce the spirally accelerated charged particles with an oscillating electrical field, the improvment which comprises:

(a) dual space apart parallel rings each rigidly supporting the counterweight and cyclotron so as to be 180°

from each other such that the cyclotron can be rotated by the rings about the rotation axis which is defined by the centers of the rings;

(b) rollers mounting the rings for rotation of the rings about the rotation axis;

(c) drive means for rotating the rings;

(d) flexible hose in a helical coil about the rotation axis attached to the inlet and outlet of the conduit means for supplying and removing the liquid gas to and from the closed vessel and coils; and

(e) spring means attached to and supporting the hose in the helical coil.

19. In a superconducting cyclotron apparatus which generates a beam of high velocity particles comprising atomic particles and subparticles thereof to be directed at an object to be irradiated from spirally accelerated charged particles which impinge upon a target to produce the beam, with a window and a collimator on a first side of the cyclotron tangential to the spirally accelerated charged particles for defining the beam including a support structure having a counterweight for the cyclotron rotatable in two directions on a rotation axis between the counterweight and cyclotron for changing the angle of the beam in an arc defining a plane around the rotation axis so that an object on the axis can be irradiated and further including inlet and outlet conduit means for supplying and removing liquified gas to and from a closed vessel and with superconducting coils in the vessel which pass around spaced apart iron poles which can generate a magnetic field between the poles when current is supplied to the coils and which functions to produce the spirally accelerated charged particles with an oscillating electrical field, the improvement which comprises:

(a) dual spaced apart parallel rings each rigidly supporting the counterweight and cyclotron so as to be 180°

from each other such that the cyclotron can be rotated by the rings about a rotation axis defined by the centers of the rings;

(b) rollers mounting the rings for rotation of the rings about the rotation axis; and

(c) drive means for rotating the rings.

20. In a superconducting cyclotron apparatus which generates a beam of high velocity particles comprising atomic particles and subparticles thereof directed at an object to be irradiated by spirally accelerated charged particles around a cyclotron axis which impinge upon a target to produce the beam, with a window and a collimator on a first side of the cyclotron tangental to the spirally accelerated charged particles for defining the beam, including a support structure having a counterweight for the cyclotron so as to be rotatable on a rotation axis between the cyclotron and counterweight for changing the angle of the beam in an arc defining a plane around the rotation axis so that an object on the axis can be irradiated, and including inlet and outlet conduit means for supplying and removing a liquified gas to and from a vessel with superconducting coils in the vessel which pass around spaced apart iron poles so as to generate a magnetic field between the poles when current is supplied to the coils and with an iron or steel yoke connecting the pole outside the coils so as to return the magnetic field between the poles, wherein the poles and coils function to produce the spirally accelerated charged particles with an oscillating electrical field produced by electrodes, the improvement in the yoke which comprises:

a yoke with a number of flat surfaces, wherein the flat face are parallel to the cyclotron axis and having section which are essentially the same in external configuration over angles of 120°

around the cyclotron axis.

21. In a superconducting cyclotron apparatus which generates a beam of high velocity particles comprising atomic particles and subparticles thereof to be directed at an object to be irradiated from spirally accelerated charged particles which impinge upon a target to produce the beam, with a window and a collimator on a first side of the cyclotron tangential to the spirally accelerated charged particles for defining the beam including a support structure having a counterweight for the cyclotron rotatable in two directions on a rotation axis between the counterweight and cyclotron for changing the angle of the beam in an arc defining a plane around the rotation axis so that an object on the axis can be irradiated and further including inlet and outlet conduit means for supplying and removing liquified gas to and from a vessel and with superconducting coils in the vessel which pass around spaced apart iron poles which can generate a magnetic field between the poles when current is supplied to the coils and which functions to produce the spirally accelerated charged particles with an oscillating electrical field, the improvement which comprises:

an essentially cylindrically shaped rotatable floor of articulated slats having a longitudinal axis of rotation which is mounted adjacent to the support structure around the cyclotron and counterweight so that the longitudinal axis of the floor and rotational axis of the support structure are the same and so that the floor rotates with the support structure.