Abstract: A superconducting magnet comprising a field coil comprising high temperature superconducting material and having a joint; a bypass resistance comprising a non-superconducting conductive material, wherein the bypass resistance is electrically connected to the field coil on both sides of the joint; wherein the joint is openable to break the field coil such that current flowing in the superconductor flows though the bypass resistance in order to dump energy from the field coil, and wherein the superconducting magnet is configured to open the joint in response to detection of a quench in the magnet.

Abstract: A high temperature superconducting, HTS, magnet system. The HTS magnet system comprises an HTS field coil, a temperature control system, a power supply, and a controller. The HTS field coil comprises a plurality of turns comprising HTS material; and a resistive material electrically connecting the turns, such that current can be shared radially between turns via the resistive material. The temperature control system is configured to control the temperature of the coil, the temperature control system comprising at least a cryogenic cool system configured to keep the coil below a self-field critical temperature of the HTS material. The power supply is configured to supply current to the HTS field coil. The controller is configured to cause the power supply to provide a current greater than a critical current of all of the HTS material.

Abstract: A superconductor magnet system including a superconductor magnet including a plurality of field coils connected in series, each field coil having a plurality of turns including superconductor material. The system also includes a primary electric current source connected across the plurality of the field coils for supplying a DC electric current to the field coils to generate a magnetic field. The system further includes a secondary electric current source connected in parallel with the primary electric current source across a subset of the field coils for supplying an additional DC electric current to the or each field coil in the subset to modify or correct the magnetic field.

Abstract: There is described a central column for a toroidal field coil of a tokamak plasma chamber. The central column comprises a support member extending vertically along a central axis of the central column made from material with high compressive strength, and current carrying elements located radially outward of the support member. The support member is in structural contact with the current carrying elements so as to support them radially against compressive Lorentz stress.

Abstract: A cable for carrying electrical current in a coil of a magnet. The magnet comprises an HTS transport tape and a shunt assembly comprising two or more HTS shunt tapes arranged side-by-side across a face of the transport tape. Each of the transport and shunt tapes comprises a substrate layer and an HTS layer of high temperature superconductor (HTS) material, the layers of the shunt tapes extending parallel to the layers of the transport tape.

Abstract: A method of quenching a non-insulated or partially insulated high-temperature superconductor (HTS) magnet. A first current is provided to the HTS magnet to operate the HTS magnet. The magnet is quenched by either of: applying a second current to the HTS magnet, the second current in the opposite direction to the first current; or applying a second current to the HTS magnet, the second current in the same direction as the first current and less than the first current. Also provided are an HTS magnet system and a further method of quenching an HTS magnet using an AC current.

Abstract: A cable for carrying electrical current in a coil of a magnet. The cable comprises a stack of tape assemblies. Each tape assembly has a length and a width, such that the length is much larger than the width, and each tape assembly comprises an HTS layer of anisotropic high temperature superconductor. HTS material, wherein a c-axis of the HTS layer is at a non-zero angle to a vector perpendicular to the plane of the HTS layer. The tape assemblies are stacked as a series of pairs, each pair comprising first and second HTS tape assemblies and a copper layer therebetween. The tape assemblies in each pair are arranged such that the c-axis of the HTS layer of the first HTS tape assembly of each pair have reflective symmetry to the c-axis of the HTS layer of the second HTS tape assembly of each pair about a plane which is parallel to and equidistant from each HTS layer.

Abstract: A method of energizing or de-energizing a high temperature superconducting, HTS, coil, from an initial transport current to a final transport current. The HTS coil comprises a plurality of turns of HTS material. A transport current is supplied to the HTS coil, the transport current starting at the initial transport current and varying over time to the final transport current. Cooling is applied to the HTS coil. An operating condition of the HTS coil is monitored, wherein the operating condition is indicative of a ratio I/Ic of the transport current, I, to a critical current, Ic, of the HTS material in at least a part of the HTS coil. One or both of the transport current applied to the coil and a net cooling applied to the coil are controlled in a feedback loop responsive to the operating condition, in order to maintain the operating condition in a desired range during energisation or de-energisation, such that the indicated ratio I/Ic is maintained above a threshold ratio (e.g. 0.7).

Abstract: A high temperature superconducting, HTS, cable. The HITS cable comprises a channel, HITS material, and an insulating layer. The channel is formed from conductive material, and has a groove extending along the length of the HTS cable. The HTS material is located within the groove, such that when the HTS material is in a superconducting state the HTS material forms a superconducting current path along the cable, and the HTS material is electrically connected to the channel. The insulating layer is located on a surface of the channel. The channel has a plurality of recesses, each recess containing a electrical assembly comprising a conductive path and/or one or more electrical components, and further containing insulation which separates the electrical assembly from the channel.

Abstract: A method of manufacturing an HTS coil is provided. The method comprises winding an HTS coil cable to produce a coil having a plurality of turns. During winding of a turn of the coil, one or more HTS shunt cables are placed adjacent to the previous turn of the coil along a first arc of the coil, and then the turn is wound such that the HTS shunt cable is sandwiched between the turn and the previous turn of the coil such that current can be shared between the HTS shunt cable and the HTS coil cable.

Abstract: A toroidal field coil for a tokamak plasma chamber having a central column. The toroidal field coil comprises first and second high temperature superconductor. HITS, assemblies comprising a respective one or more HITS tapes for conducting electrical current parallel to an axis of the central column. Each of the HITS tapes comprises HITS material having an associated critical current that is dependent on a magnetic field at the HITS tape when the central column is in use. The central column further comprises a cooling mechanism configured to preferentially cool the first HITS assembly relative to the second HTS assembly to reduce or eliminate a difference in the critical current of the or each HITS tape of the first HITS assembly relative to the critical current of the or each HITS tape of the second HITS assembly.

Abstract: A method of manufacturing an HTS coil is provided. The method comprises winding an ITS coil cable to produce a coil having a plurality of turns. During winding of a turn of the coil, one or more HTS shunt cables are placed adjacent to the previous turn of the coil along a first arc of the coil, and then the turn is wound such that the HTS shunt cable is sandwiched between the turn and the previous turn of the coil such that current can be shared between the HTS shunt cable and the HTS coil cable.

Abstract: A superconducting magnet comprising a field coil comprising high temperature superconducting material and having a joint; a bypass resistance comprising a non-superconducting conductive material, wherein the bypass resistance is electrically connected to the field coil on both sides of the joint; wherein the joint is openable to break the field coil such that current flowing in the superconductor flows though the bypass resistance in order to dump energy from the field coil, and wherein the superconducting magnet is configured to open the joint in response to detection of a quench in the magnet.

Abstract: A high temperature superconductor, HTS, field coil having turns comprising HTS material wound about an axis of the coil. The turns are separated from one another along a direction perpendicular to the axis by a layer of insulator material having a first resistivity at a temperature less than a generation temperature of the HTS material and a lower, second resistivity at a second temperature greater than the generation temperature of the HTS material. The HTS field coil further comprises one or more electrical conductor elements arranged to provide one or more electrically conductive pathways extending from one turn to an adjacent turn and through the layer of insulator material. In response to a voltage difference generated across the one or more electrically conductive pathways, electrical current is driven through the one or more electrical conductor elements to heat the layer of insulator material.

Abstract: A method of manufacturing a High Temperature Superconductor, HTS, field coil from one or more HTS tapes. Each HTS tape comprises an HTS material layer. The method comprises: winding the one or more HTS tapes about an axis to form a field coil comprising windings of HTS tape; and removing material from an axial edge of the one or more of the HTS tapes around at least a part of one or more of the windings to reduce the extent of the one or more HTS tapes along the axis of the field coil.

Abstract: A superconducting magnet comprising: a field coil comprising high temperature superconducting material and having a joint; a bypass resistance comprising a non-superconducting conductive material, wherein the bypass resistance is electrically connected to the field coil on both sides of the joint; wherein the joint is openable to break the field coil such that current flowing in the superconductor flows though the bypass resistance in order to dump energy from the field coil, and wherein the superconducting magnet is configured to open the joint in response to detection of a quench in the magnet.

Abstract: A method of detecting pre-quench conditions in a superconducting magnet comprising an HTS field coil. The field coil comprises a plurality of turns comprising HTS material and metallic stabilizer; and conductive material connecting the turns such that current can be shared radially between turns via the conductive material. Strain is monitored for the HTS field coil and/or support structures of the HTS field coil. The monitored strain is compared to an expected strain during normal operation of the magnet. In response to the comparison, it is determined whether the field coil is in pre-quench conditions. A similar method is provided where the magnetic field of the HTS field coil is monitored to detect pre-quench conditions, instead of the strain.

Abstract: A first wall structure for a plasma chamber (200). The first wall structure comprises and inner wall (201) and a solid deposit (202). The inner wall is formed from a refractory metal or an alloy or composite thereof and has a plurality of pores. The solid deposit in thermal contact with the inner wall, such that the plurality of pores provide a passage from an exterior of the first wall structure to the deposit. The deposit consists of a material having a boiling point less than a melting point of the refractory metal. The first wall structure is configured such that at a normal operating temperature of the first wall structure, the deposit is solid.

Abstract: A method of detecting pre-quench conditions in a superconducting magnet comprising an HTS field coil. The field coil comprises a plurality of turns comprising HTS material and metallic stabilizer; and conductive material connecting the turns such that current can be shared radially between turns via the conductive material. Strain is monitored for the HTS field coil and/or support structures of the HTS field coil. The monitored strain is compared to an expected strain during normal operation of the magnet. In response to the comparison, it is determined whether the field coil is in pre-quench conditions. A similar method is provided where the magnetic field of the HTS field coil is monitored to detect pre-quench conditions, instead of the strain.

Abstract: A device comprising a high temperature superconductor, HTS, circuit; wherein the HTS circuit comprises: a quenchable section comprising HTS material and connected in series to other elements of the HTS circuit, the HTS material comprising a stack of HTS takes comprising at least one HTS tape; the device further comprising: a quenching system configured to quench the HTS material in the quenchable section; a quench protection system configured to detect temperature rises in the HTS circuit and, in response to detection of a temperature rise, cause the quenching system to quench the superconducting material in the quenchable section in order to dump stored magnetic energy from the HTS circuit into the quenchable section; wherein the HTS circuit is configured such that, when in use, the magnetic field on the or each HTS tape is substantially parallel to a a-b plane of the HTS tape, and the quenching system is configured to quench the HTS material by producing an additional magnetic field along the length of the