Magnet structure for particle acceleration
DCFirst Claim
1. A magnet structure for use in an ion accelerator comprising:
- a cold-mass structure including;
at least two coils that comprise a material that is superconducting at a nominal temperature of 4.5 K and that radially circumscribe an acceleration chamber and a segment of a central axis extending across the acceleration chamber, wherein a median acceleration plane extends orthogonally from the central axis across the acceleration chamber; and
a bobbin in which the coils are mounted, the bobbin including a pair of outer wings to support the coils in an outward radial direction and an inner wing between the coils and intersecting the median acceleration plane to support the coils in an inward axial direction;
a cryostat enclosing the cold-mass structure;
a dry cryocooler coupled with the cold-mass structure to cool the coils;
radial-tension links coupled with the bobbin and applying outward radial tension on the bobbin at a plurality of positions; and
a magnetic yoke wrapped around the cold-mass structure, circumscribing the segment of the central axis, and including a pair of poles having tapered inner surfaces that define a pole gap between the poles and across the acceleration chamber.
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Abstract
A magnet structure for particle acceleration includes at least two coils that include a continuous path of superconducting material [e.g., niobium tin (Nb3Sn) having an A15-type crystal structure] for electric current flow there through. The coils can be mounted in a bobbin, which together with the coils form a cold-mass structure. The coils are cooled to their superconducting temperatures via cryocoolers. Radial-tension members are coupled with the cold-mass structure to keep it centered, such that it remains substantially symmetrical about a central axis and is not pulled out of alignment by magnetic forces acting thereon. A wire can be wrapped around the coils, and a voltage can be applied thereto to quench the coils to prevent their operation of the coils in a partially superconducting condition, which may otherwise cause damage thereto. A magnetic yoke surrounds the cold-mass structure and includes a pair of poles that, in part, define an acceleration chamber there between. The inner surfaces of the poles have tapered profiles that establish a correct weak focusing requirement for ion and that reduce pole diameter by increasing energy gain versus radius. An integral magnetic shield is positioned about the yoke to contain magnetic fields emanating there from and can have a tortuous configuration to contain magnetic fields having a variety of orientations. The magnet structure can be very compact and can produce particularly high magnetic fields.
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Citations
27 Claims
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1. A magnet structure for use in an ion accelerator comprising:
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a cold-mass structure including; at least two coils that comprise a material that is superconducting at a nominal temperature of 4.5 K and that radially circumscribe an acceleration chamber and a segment of a central axis extending across the acceleration chamber, wherein a median acceleration plane extends orthogonally from the central axis across the acceleration chamber; and a bobbin in which the coils are mounted, the bobbin including a pair of outer wings to support the coils in an outward radial direction and an inner wing between the coils and intersecting the median acceleration plane to support the coils in an inward axial direction; a cryostat enclosing the cold-mass structure; a dry cryocooler coupled with the cold-mass structure to cool the coils; radial-tension links coupled with the bobbin and applying outward radial tension on the bobbin at a plurality of positions; and a magnetic yoke wrapped around the cold-mass structure, circumscribing the segment of the central axis, and including a pair of poles having tapered inner surfaces that define a pole gap between the poles and across the acceleration chamber. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14)
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15. A magnet structure for use in a synchrocyclotron comprising:
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a cold-mass structure including at least two superconducting coils, wherein the cold-mass structure is contained in a cryostat that circumscribes an acceleration chamber; a magnetic yoke wrapped around the cold-mass structure and including a pair of poles that define a pole gap between the poles and across the acceleration chamber, wherein the superconducting coils and the poles are structured to produce a radially decreasing combined magnetic field reaching at least 8 Tesla for synchrocyclotron acceleration in the acceleration chamber; and an integral magnetic shield surrounding the yoke in substantially all directions and positioned outside the contour of a 1,000 gauss magnetic flux density that can be generated by the magnet structure outside the yoke when a voltage is applied to the superconducting coils to generate the combined magnetic field of at least 8 Tesla inside the acceleration chamber. - View Dependent Claims (16, 17, 18, 19)
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20. A method for generating a magnetic field for ion acceleration comprising:
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providing a cold-mass structure in a cryostat that circumscribes an acceleration chamber, the cold-mass structure including at least two superconducting coils centered about a central axis, a cryocooler coupled with the cold-mass structure;
a magnetic yoke positioned about the cold-mass structure and including a pair of poles that define a tapered pole gap there between and across the acceleration chamber;cooling the superconducting coils to or below the critical temperature of the superconductor and applying a voltage to the cold-mass structure to generate a magnetic field of at least 8 Tesla within the pole gap; and injecting an ion into the acceleration chamber and accelerating the ion in an outward spiral in the acceleration chamber, wherein the ion is subjected to a radially decreasing magnetic field in the acceleration chamber as it is accelerated outward, and wherein a weak-focusing field index parameter, n, is in the range from 0 to 1 across the entire span of the spiral traversed by the ion, where n=−
(r/B)(dB/dr), and where B is the magnetic field, and r is the radius from the central axis. - View Dependent Claims (21, 22, 23, 24, 25, 26, 27)
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Specification