Superconductor electromagnet
An electromagnet comprising having one or more channels. Each channel has provided therein a conductor element comprising one or more layers of superconductor material for conducting electrical current along an axis of the channel. The conductor element is arranged to contact sidewalls of the channel through first and second wedge surfaces that are inclined with respect to one another such that a force biasing the conductor element in a direction perpendicular to the axis generates opposing contact forces on the wedge surfaces that act to compress the conductor element along a direction with a component perpendicular to the force.
1 . An electromagnet comprising one or more channels, each channel having provided therein:
a conductor element including one or more layers of superconductor material for conducting electrical current along an axis of the channel, the conductor element being arranged to contact first and second sidewalls of the channel through respective first and second wedge surfaces that are inclined with respect to one another such that a Lorentz force biasing the conductor element in a direction perpendicular to the axis generates opposing contact forces on the first and second wedge surfaces that act to compress the conductor element along a direction with a component perpendicular to the Lorentz force.
2 . An electromagnet according to claim 1 , wherein each conductor element includes one or more stacks of High Temperature Superconductor, HTS, tapes, each HTS tape including a layer of HTS material extending along the axis of the channel.
3 . An electromagnet according to claim 2 , wherein the HTS material is ReBCO.
4 . An electromagnet according to claim 2 , wherein each conductor element includes a first wedge member provided between the stack of HTS tapes and one of the sidewalls of the channel, the first wedge surface being provided on the first wedge member.
5 . An electromagnet according to claim 4 , wherein the first wedge member is fixed to the stack of HTS tapes.
6 . An electromagnet according to claim 4 , wherein the first wedge member includes a surface in contact with the stack that is substantially perpendicular to the layers of HTS material.
7 . An electromagnet according to claim 6 , wherein, for one or more of the conductor elements, an acute angle between the first wedge surface and the surface in contact with the stack is greater than 1 degree.
8 . An electromagnet according to claim 7 , wherein each conductor element includes a second wedge member attached to the one or more stacks of HTS tapes, the second wedge surface being provided on the second wedge member.
9 . An electromagnet according to claim 1 , wherein a static friction coefficient between each of the wedge surfaces of the conductor element and the sidewalls of the channel is greater than 0.1.
10 . An electromagnet according to claim 1 , wherein each of the conductor elements is potted.
11 . An electromagnet according to claim 1 , further includes a support member, the channels being provided in the support member, the support member includes one or more through holes extending in a direction having a component parallel to one or more of the channels.
12 . An electromagnet according to claim 11 , wherein the one or more holes are located adjacent one or more of the sidewalls of the channel.
13 . A central column for a toroidal field coil of a tokamak plasma chamber, the central column includes a plurality of electromagnets according to claim 1 , the channels being spaced around a central axis and the one or more layers of superconductor material being arranged for conducting electrical current parallel to the central axis, wherein the Lorentz force is a radial force biasing the conductor element towards the central axis.
14 . A central column according to claim 13 , wherein the channels are provided in a single support member.
15 . A central column according to claim 13 , includes one or more holes through the or each support member, each hole extending parallel to the central axis.
16 . A central column according to claim 15 , wherein the one or more holes are located radially outwards of a radially inner edge of the conductor element.
17 . T A central column according to claim 13 , wherein the or each support member includes one or more removable angular segments, each angular segment includes one or more of the plurality of channels.
18 . A central column for a toroidal field coil of a tokamak plasma chamber, the central column comprising a support member having a plurality of channels spaced around a central axis, each channel having provided therein a conductor element including one or more layers of superconductor material for conducting electrical current parallel to the central axis, the conductor element being arranged to contact first and second sidewalls of the channel through respective first and second wedge surfaces that are inclined with respect to one another such that a radial force biasing the conductor element towards the central axis generates opposing contact forces on the first and second wedge surfaces that act to compress the conductor element along a direction with a component perpendicular to the radial force.
19 . A toroidal field coil for a tokamak, the toroidal field coil includes a central column according to claim 13 .
20 . A tokamak includes a toroidal field coil according to claim 19 .