CABLE DESIGN IN HTS TOKAMAKS
There is described a cable for carrying electrical current in a coil of a magnet. The cable comprises a stack of tape assemblies, each tape assembly comprising a high-strength metal substrate layer, and an HTS layer of high temperature superconductor material. The tape assemblies are stacked as a series of type 0 pairs such that the HTS layers of a type 0 pair face each other and the substrate layers of the type 0 pair are separated by the HTS layers.
1 . A cable for carrying electrical current in a coil of a magnet, comprising:
a stack of tape assemblies, each tape assembly comprising a high-strength metal substrate layer, and an HTS layer of high temperature superconductor, HTS, material;
wherein the tape assemblies are stacked as a series of type 0 pairs such that the HTS layers of a type 0 pair face each other and the substrate layers of the type 0 pair are separated by the HTS layers.
2 . The cable of claim 1 , wherein there is an internal layer of copper of thickness between about 20 μm and about 400 μm in each type 0 pair, the internal layer placed between the tape assemblies of the type 0 pair.
3 . The cable of claim 1 , wherein the internal layer of copper of each type 0 pair overhangs the edges of the tape for electrical connection to an adjacent type 0 pair in the stack.
4 . The cable of claim 3 , wherein a connection of the overhanging copper layers between type 0 pairs is a pressed, crimped or soldered connection.
5 . The cable of claim 1 , wherein stacks of type 0 tape pairs are arranged side-by-side with thermally and electrically conductive segments between the stacks.
6 . The cable of claim 5 , wherein some or all of the thermally conductive segments contain channels for the flow of cryogenic coolant.
7 . The cable of claim 1 , wherein the tape assemblies are incorporated in a copper matrix.
8 . The cable of claim 1 , wherein the tape assemblies are incorporated in a high strength structural jacket formed from material such as stainless steel or inconel.
9 . The cable of claim 1 , wherein there is at most 50 μm of copper between adjacent type 0 pairs of tape assemblies in the stack.
10 . The cable of claim 1 , wherein there is no copper between adjacent type 0 pairs of tape assemblies in the stack.
11 . The cable of claim 1 , wherein each HTS layer comprises ReBCO material.
12 . A cable for carrying electrical current in a coil of a magnet, comprising:
a stack of tape assemblies and copper layers, each tape assembly comprising a substrate layer and an HTS layer of HTS material;
wherein the tape assemblies are stacked such that there is a layer of copper of thickness at least 100 μm, preferably at least 200 μm, more preferably at least 400 μm facing the HTS layer of each tape assembly.
13 . A cable for carrying electrical current in a coil of a magnet, comprising:
a stack of tape assemblies, each tape assembly comprising a high-strength metal substrate layer, and an HTS layer of high temperature superconductor, HTS, material;
wherein the tape assemblies are stacked as a series of type 2 pairs such that the substrate layers of a type 2 pair face each other and the HTS layers of the type 2 pair are separated by the substrate layers.
14 . The cable of claim 13 , further comprising a layer of copper of thickness at least 40 μm, preferably at least 100 μm, more preferably at least 200 μm, more preferably at least 400 μm between each type 2 pair.
15 . The cable of claim 1 , configured to carry electrical current between joints with further cables.
16 . The cable of claim 1 , wherein the number of tape assemblies in the stack varies along the length of the cable.
17 . The cable of claim 1 , wherein each tape includes a silver layer adjacent to the HTS layer.
18 . The cable of claim 1 , wherein the width of the tape assemblies varies along the length of the cable.
19 . The cable of claim 1 , wherein the substrate does not contain nickel.
20 . The cable of claim 1 , wherein the stack is located within a pre-formed slot in a housing.
21 . The cable of claim 20 , wherein the housing is formed from thermally and electrically conductive material, optionally copper or stainless steel.
22 . The cable of claim 20 , further comprising a coolant channel in the slot adjacent the stack of tape assemblies.
23 . A field coil comprising two or more cables according to claim 1 electrically connected at respective ends by a joint.
24 . The field coil of claim 23 , wherein the joint is a praying hands joint.
25 . The field coil of claim 23 , wherein the joint is a scarfed joint.
26 . The field coil of claim 23 , wherein a copper lamination between tape assemblies in a pair of tape assemblies is replaced in the joint by a pair of HTS tape assemblies.
27 . The field coil of claim 23 , wherein a copper lamination between tape assemblies in a pair of tape assemblies extends continuously into the joint.
28 . The field coil of claim 23 , wherein each pair of tape assemblies is terminated with a copper jointing piece to enable the cables to be pressed together.
29 . A nuclear fusion reactor comprising a plasma vessel and a set of field coils for generating magnetic field, the field coils being field coils according to claim 23 .