Abstract: A method of controlling a plasma in a nuclear fusion reactor. The nuclear fusion reactor comprises sensors and plasma control inputs. An initial control model is provided, relating readings of at least a subset of the sensors to control of the plasma control inputs. A control loop is performed, comprising: operating the plasma control inputs in dependence upon the sensors according to the control model; determining correlations between readings of each of the sensors, and/or between readings of the sensors and states of the plasma control inputs; and adjusting the control model based on the determined correlations.

Abstract: A segment of a field coil, a toroidal field coil, and a method of manufacturing is provided. The segment of a field coil is for use in a superconducting electromagnet. The segment includes an assembly for carrying electrical current in a coil of a magnet. The assembly includes a pre-formed housing comprising a channel configured to retain high temperature superconductor (HTS) tape, the channel including at least one pre-formed curved section. The assembly further includes a plurality of layers of HTS tape fixed within the channel. Wherein the pre-formed curved section has a radius of curvature which is less than a total thickness of the layers of HTS tape in that section divided by twice a maximum permitted strain of the HTS tape.

Abstract: A method of protecting a superconducting magnet from quenches, the superconducting magnet having at least one primary coil comprising high temperature superconductor, HTS, material. A secondary HTS tape is provided, the secondary HTS tape being in proximity to and electrically insulated from the primary coil, and being configured to cease superconducting at a lower temperature than the primary coil during operation of the magnet. A loss of superconductivity in the secondary HTS tape is detected. In response to said detection, energy is dumped from the primary coil into an external resistive load.

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

Abstract: A method of operating a nuclear fusion device. The nuclear fusion device comprises a toroidal plasma chamber and has poloidal field coils configured to form a plasma within the plasma chamber by one of merging compression and double null merging. A varying current is provided to the poloidal field coils. The varying current comprises a plurality of pulses. Each pulse comprises a plasma formation period having a rate of change of current which is opposite in sign to the current; and a merging period following the plasma formation period and having a current sufficiently low in magnitude as to allow plasmas within the chamber to merge into a single plasma. The current during the plasma formation period is varied such that the energy density of the single plasma immediately after merging is sufficient for fusion to occur.

Abstract: A poloidal field coil assembly for use in a tokamak. The poloidal field coil assembly comprises inner and outer poloidal field coils and a controller. The inner poloidal field coil is configured for installation inside a toroidal field coil of the tokamak. The outer poloidal field coil is configured for installation outside the toroidal field coil. The controller is configured to cause current to be supplied to the inner and outer poloidal field coils such that the combined magnetic field produced by the inner and outer poloidal field coils has a null at the toroidal field coil.

Abstract: A partially insulating layer for use in an HTS magnet coil. The partially insulating layer comprises an insulating body 401 having within it a set of linking tracks and a set of pickup tracks. Each linking track is electrically conductive and is electrically connected to first and second surfaces of the partially insulating layer, in order to provide an electrical path between said first and second surfaces. Each pickup track is electrically conductive and is inductively coupled to a respective linking track, and electrically isolated from the first and second surfaces. Each of the pickup tracks is configured for connection to a current measuring device in order to measure a current induced in the pickup track by a change in current flowing in the respective linking track.

Abstract: A tokamak plasma vessel. The tokamak plasma vessel comprises a toroidal plasma chamber, a plurality of poloidal field coils, an upper divertor assembly, and a lower divertor assembly. The plurality of poloidal field coils are configured to provide a poloidal magnetic field having a substantially symmetric plasma core and an upper and lower null, such that ions in a scrape off lay outside the plasma core are directed by the magnetic field past one of the upper and lower nulls to divertor surfaces of the respective upper and lower divertor assembly. Each of the upper and lower divertor assembly comprises a liquid metal inlet and a liquid metal outlet located below the liquid metal inlet. Each of the upper and lower divertor assembly is configured such that in use liquid metal flows from the liquid metal inlet to the liquid metal outlet over at least one divertor surface of the divertor assembly.

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: There is described a magnet assembly comprising a superconducting coil, a cryogenic system, a DC voltage source, an SMPS, current leads, and a controller. The cryogenic system comprises a cryostat and is configured to maintain the superconducting coil at an operating temperature below the critical temperature of the superconductor. The DC voltage is source located outside the cryostat. The SMPS is located inside the cryostat and configured to supply power from the DC voltage source to the superconducting coil. The SMPS comprises a voltage step-down transformer having a primary and a secondary winding. The current leads connect the DC voltage source to the SMPS. The controller is configured to cause the SMPS to supply a first amount of power to the magnet in order to ramp up the magnet to operating current, and a second amount of power to the magnet during steady state operation of the magnet, wherein the first amount of power is greater than the second amount of power.

Abstract: A toroidal field coil comprising a central column, a plurality of return limbs, a quench protection system, and a cooling system. The central column comprises IITS material. Each return limb comprises a quenchable section, two IITS sections, and a quenching 5 system. The quenchable section comprises superconducting material, and is configured to contribute towards a magnetic field of the toroidal field coil. The IITS sections comprise IITS material. The IITS sections electrically connect the quenchable section to the central column and are in series with the central column and the quenchable section. The quenching system is associated with the quenchable section 10 and configured to quench the quenchable section.

Abstract: A monitoring device for use in a cryogenic system. The monitoring device comprises first and second conducting elements and a current detector. The first conducting element comprises high temperature superconducting, HTS, material and is configured for connection to a current source and insertion into the cryogenic system. The second conducting element comprises HTS material and is connected in parallel to the first conducting element by first and second joints. The current detector is configured to detect a current in the second conducting element. When the HTS material in each of the first and second conducting elements is in a superconducting state, the resistance, RT, of the first conducting element between the first and second joints, is less than the sum, RB, of the resistance of the second conducting element between the first and second joints and the resistances of the first and second joints.

Abstract: A high temperature superconductor, HTS, tape (100) for detecting a quench in a superconducting magnet. The HTS tape comprises an HTS layer (101) of HTS material supported by a substrate (102). The HTS layer is divided into a plurality of strips (104,105,107). The strips are connected (106) in series along an open path.

Abstract: A high temperature superconducting, HTS, field coil. The HTS field coil comprises a plurality of turns and a partially insulating layer. The plurality of turns comprises HTS material and metallic stabilizer. The partially insulating layer separates the turns, such that current can be shared between turns via the partially insulating layer. The partially insulating layer comprises an electrically conducting layer, and first and second insulating layers. The electrically conducting layer is coated on one side with the first insulating layer and on the other side with the second insulating layer. Each insulating layer has one or more windows through which electrical contact can be made between the turns and the electrically conducting layer. The windows in the first insulating layer are offset in the plane of the electrically conducting strip from the windows in the second insulating layer.

Abstract: An HTS assembly for use in a toroidal field coil having a central column is described. The HTS assembly comprises a plurality of parallel arrays of HTS tapes arranged to pass through the central column, each array comprising a plurality of HTS tapes arranged such that c-axes of all tapes in an array are parallel to each other, and such that planes of the HTS layers of the HTS tapes are perpendicular to a first radius of the central column. Each HTS tape has a c-angle which is an angle between a perpendicular to a plane of an HTS layer of the HTS tape and the c-axis of the tape. The plurality of arrays comprises first and second sets of arrays. Each array within the first set of arrays comprises HTS tapes of a first type having a first c-angle, and each array within the second set of arrays comprises HTS tapes of a second type having a second c-angle which is greater than the first c-angle. The first set of arrays are arranged closer to the first radius than the second set of arrays.

Abstract: There is disclosed a toroidal field coil for use in a spherical tokamak. The toroidal field coil comprises a central column and a plurality of return limbs. The central column comprises a plurality of exfoliated HTS tapes, and the return limbs comprise a plurality of substrated HTS tapes. Each exfoliated HTS tape comprises a ReBCO layer bonded to respective metal interface layers on each side of the ReBCO layer, each metal interface layer being bonded to a metal stabiliser layer. Each substrated HTS tape comprises a ReBCO layer bonded on one side to a metal interface layer and on the other side to an oxide buffer stack, the metal interface layer being bonded to a metal stabiliser layer and the oxide buffer stack being bonded to a substrate.

Abstract: There is disclosed an assembly for carrying electrical current in a coil of a magnet. The assembly comprises a pre-formed housing of thermally and electrically conductive material (e.g. copper) which comprises a channel configured to retain HTS tape. A plurality of layers of HTS tape are fixed within the channel. The channel has at least one pre-formed curved section.

Abstract: Neutron shielding for the central column of a tokamak nuclear fusion reactor. The neutron shielding comprises an electrically conductive neutron absorbing material. The neutron shielding is arranged such that the electrically conductive neutron absorbing material forms a solenoid for the initiation of plasma within the tokamak.

Abstract: According to a first aspect of the present invention, there is provided a method of forming a superconducting joint between ReBCO tapes. Two or more ReBCO tapes are provided, each having an exposed ReBCO region. A bridge is provided, comprising an exposed ReBCO layer and an oxygen-permeable backing on the exposed ReBCO layer. Each exposed ReBCO region is bonded to the exposed ReBCO layer of the bridge by heating to a first temperature (T1) in an environment where the partial pressure of oxygen is sufficiently low that the melting point of the ReBCO (TR) is less than the melting point of silver (TAg), the temperature (T1) being between the melting point of the ReBCO (TR) and the melting point of silver (TAg), (TR<T1<TAg). The resulting joint is annealed at a second temperature (T2) which is less than the melting point of ReBCO (TR) (T2<TR), for a time (t), in an environment where the partial pressure of oxygen is sufficient to reoxygenate the ReBCO at the second temperature (T2).

Abstract: An apparatus for protecting an interior surface of a fusion reactor vessel. The apparatus comprises a power supply operably connected to an electrode for insertion into the vessel. The apparatus supports a solid material within the vessel, and is configured such that power supplied to the electrode within the vessel causes a plasma located in proximity to the solid material to sputter the solid material in order to deposit a protective material on said interior surface.