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.

Abstract: A cooling system for use in a superconducting magnet comprising a high temperature superconductor, HTS, coil. The cooling system comprises a refrigeration unit, one or more coolant channels, and a pumping unit. The refrigeration unit is configured to cool a gas, wherein the gas is hydrogen or helium. The one or more coolant channels are configured to be placed in thermal contact with components of the superconducting magnet and to carry said gas. The pumping unit is configured to pump said gas through the coolant channels. The refrigeration unit and pumping unit are configured to maintain the gas at a pressure and temperature such that a Joule-Thompson coefficient of the gas is positive, and the coolant channel is configured to reduce the pressure of gas as it flows through the channel by one or more of a throttle, a valve, and choice and/or variance of a cross section of the coolant channel.

Abstract: There is described neutron shielding for a nuclear fusion reactor. The neutron shielding includes a cemented carbide or boride comprising a binder and an aggregate, the aggregate comprising particles of a carbide or boride compound.

Abstract: A tokamak comprising a toroidal containment vessel and a plasma initiation system. The toroidal containment vessel is configured to contain a plasma. The plasma initiation system comprises upper and lower poloidal field, PF, coil sets. Each PF coil set comprises at least one inner PF coil located outside of the containment vessel, an outer PF coil located inside the containment vessel, and shielding located between the outer PF coil and a location of the plasma during operation of the tokamak and configured to protect the outer PF coil from heat emitted by the plasma. The inner and outer PF coils are configured so as to form a PF null within the containment vessel between the inner and outer PF coils, such that the upper and lower PF coil pairs are operable to initiate a plasma in the containment vessel via double null merging.

Abstract: A toroidal field coil for generating a toroidal magnetic field in a nuclear fusion reactor comprising a toroidal plasma chamber having a central column. The toroidal field coil comprises a portion passing through the central column. The portion passing through the central chamber comprises: ?a low temperature superconductor, LTS, layer (21) formed from LTS; ?a high temperature superconductor, HTS, layer (22) formed from HTS and located radially outward of the LTS layer. ?a non-superconducting conductive layer (23) formed from electrically conducting, non-superconducting material and located radially outward of the HTS and LTS layers.

Abstract: A toroidal field coil for generating a toroidal magnetic field in a nuclear fusion reactor includes a toroidal plasma chamber having a central column. The toroidal field coil has a plurality of windings configured to pass through the central column and around the outside of the plasma chamber. Each winding includes a cable having a plurality of stacked high temperature superconductor (HTS) tapes, each HTS tape including one or more layers of a high temperature superconductor material. With the toroidal field coil in place in the reactor, a face of each HTS tape is substantially perpendicular to a direction of maximal neutron flux during reactor operation as the cable passes through the center column.

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: 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: An efficient compact nuclear fusion reactor for use as a neutron source or energy source is described. The reactor comprises a toroidal plasma chamber and a plasma confinement system arranged to generate a magnetic field for confining a plasma in the chamber. The plasma confinement system is configured so that a major radius of the confined plasma is 1.5 m or less. The reactor is constructed using high temperature superconducting toroidal magnets, which may be operated at low temperature (77K or lower) to provide enhanced performance. The toroidal magnetic field can be increased to 5 T or more giving significant increases in fusion output, so that neutron output is very efficient and the reactor can produce a net output of energy.

Abstract: An efficient compact nuclear fusion reactor for use as a neutron source or energy source includes a toroidal plasma chamber and a plasma confinement system arranged to generate a magnetic field for confining a plasma in the chamber, where the plasma confinement system is configured so that a major radius of the confined plasma is 1.5 m or less and the toroidal magnetic field is operated 5 T or less and the plasma current is 5 MA or less, yet a-particles generated are confined in the plasma.