Left-right canted-cosine-theta magnets
Disclosed herein are superconducting gantry magnets that include multiple quadrupole winding sections placed in sequence on a curve such that the effective current direction is reversed between sections. This produces alternating quadrupole field regions along the length of the bend whose individual integral strengths can be tuned by the location of the current polarity transitions. A simple transition scheme to reverse the current between sections can be implemented to allow for the use of one continuous winding and power supply. Dipole windings can be included in the superconducting gantry magnets so that the magnets produce superposed dipole and alternating quadrupole fields. The disclosed design for the windings and transition scheme to reverse current polarity can be implemented for higher order multipoles as well.
1. A superconducting gantry magnet comprising:
a pair of quadrupole layers configured to provide an alternating quadrupole field in a bore of the superconducting gantry magnet, each quadrupole layer comprising:
a mandrel comprising ribs forming a helical conductor channel comprising an undulating canted pattern around a bore axis of the superconducting gantry magnet;
a plurality of transition locations formed by the conductor channel configured to change a direction of winding around the mandrel while maintaining the same undulating canted pattern; and
a superconductor cable wound around the mandrel within the conductor channel such that each quadrupole layer includes at least two sections of the superconductor cable having the same cant and opposite winding directions about the bore axis;
a pair of dipole layers configured to provide a dipole field in the bore of the superconducting gantry magnet, each dipole layer comprising:
a mandrel comprising ribs forming a helical conductor channel comprising a canted pattern around a bore axis of the superconducting gantry magnet; and
a superconductor wire or cable wound around the mandrel within the conductor channel,
wherein the respective mandrels are configured to nest within one another around the bore axis, and
wherein the quadrupole layers are nested inside the dipole layers and have outer diameters smaller than inner diameters of the dipole layers, or the dipole layers are nested inside the quadrupole layers and have outer diameters smaller than inner diameters of the quadrupole layers.
2. The superconducting gantry magnet of claim 1 further comprising a quadrupole power supply configured to provide electrical power to the superconductor wires or cables of the quadrupole layers and a dipole power supply configured to provide electrical power to the superconducting wires or cables of the dipole layers.
3. The superconducting gantry magnet of claim 1 , wherein the alternating quadrupole field is configured to alternate between focusing and de-focusing sections.
4. The superconducting gantry magnet of claim 3 , wherein the alternating quadrupole field includes at least three alternating sections.
5. The superconducting gantry magnet of claim 3 , wherein the alternating quadrupole field includes at least five alternating sections.
6. The superconducting gantry magnet of claim 1 , wherein the dipole field has a strength that is at least about 2 T and the quadrupole field has a strength that is at least about 20 T/m within the bore.
7. The superconducting gantry magnet of claim 1 , wherein the superconducting gantry magnet is substantially achromatic over a range of energies of about ±20%.
8. The superconducting gantry magnet of claim 1 further comprising a pair of sextupole layers configured to provide an alternating sextupole field in the bore of the superconducting gantry magnet, each sextupole layer comprising:
a mandrel comprising ribs forming a helical conductor channel comprising an undulating canted pattern around a bore axis of the superconducting gantry magnet;
a plurality of transition locations formed by the conductor channel configured to change a direction of the winding around the mandrel while maintaining the same undulating canted pattern; and
a superconductor wire or cable wound around the mandrel within the conductor channel.
9. The superconducting gantry magnet of claim 1 , wherein the respective mandrels form a portion of a torus.