Charging method for a superconductor magnet system with reduced stray field, weight and space includes: arranging the system within a charger magnet bore; with T.sub.main>T.sub.main.sup.crit and T.sub.shield>T.sub.shield.sup.crit, applying a current I.sub.charger to the charger magnet and increasing I.sub.charger to a first current I.sub.1>0; lowering a main superconductor bulk magnet temperature T.sub.main to an operation temperature T.sub.main.sup.op, with T.sub.main.sup.op<T.sub.main.sup.crit, while keeping T.sub.shield>T.sub.shield.sup.crit; lowering I.sub.charger to a second current I.sub.2<0, thereby inducing a persistent current IP.sub.main in the main magnet; lowering a shield magnet temperature T.sub.shield to an operation temperature T.sub.shield.sup.op, with T.sub.shield.sup.op<T.sub.shield.sup.crit; increasing I.sub.charger to zero, thereby inducing a persistent current IP.sub.shield in the shield magnet; removing the magnet system from the charger bore, and keeping T.sub.main≤T.sub.main.sup.op with T.sub.main.sup.op<T.sub.main.sup.crit and T.sub.shield≤T.sub.shield.sup.op with T.sub.shield.sup.op<T.sub.shield.sup.crit; where: T.sub.main.sup.crit: main magnet critical temperature and T.sub.shield.sup.crit: shield magnet critical temperature.

A superconductor magnetic field effect transistor. The superconductor magnetic field effect transistor may include a sheet of a superconducting material; and a solenoid. The sheet may be substantially flat, and the solenoid may include a plurality of turns, each of the turns being substantially parallel to the sheet. The superconducting material may be a type-II superconducting material.

A persistent current switch includes a superconducting wire, a heater, and an insulating member. The superconducting wire includes a substrate and a superconducting layer provided on the substrate. The superconducting layer includes a first principal surface facing the substrate and a second principal surface on an opposite side of the first principal surface. The heater is disposed only on the second principal surface side with respect to the superconducting layer. The insulating member is provided between the second principal surface of the superconducting layer and the heater.

A persistent current switch includes a superconducting wire, a heater, and an insulating member. The superconducting wire includes a substrate and a superconducting layer provided on the substrate. The superconducting layer includes a first principal surface facing the substrate and a second principal surface on an opposite side of the first principal surface. The heater is disposed only on the second principal surface side with respect to the superconducting layer. The insulating member is provided between the second principal surface of the superconducting layer and the heater.

A superconducting coil module includes: a superconducting coil configured by winding a superconducting wire a plurality of times; and a magnetic dam wound along a shape of the superconducting coil, and electromagnetically coupled. The magnetic dam may include a conductive structure device insulated from the superconducting coil, and implemented by a conductive wire wound along the shape of the superconducting coil a plurality of times, and a control circuit controlling current which flows to the magnetic dam during charging and discharging of the superconducting coil between both terminals of the conductive wire.

A superconducting coil module includes: a superconducting coil configured by winding a superconducting wire a plurality of times; and a magnetic dam wound along a shape of the superconducting coil, and electromagnetically coupled. The magnetic dam may include a conductive structure device insulated from the superconducting coil, and implemented by a conductive wire wound along the shape of the superconducting coil a plurality of times, and a control circuit controlling current which flows to the magnetic dam during charging and discharging of the superconducting coil between both terminals of the conductive wire.

A quench protection system for a superconducting machine, such as a superconducting generator having a plurality of series-arranged superconducting coils, includes at least one switch heater electrically coupled to each of the superconducting coils. A quench protection switch is provided in series with the coils, wherein each switch heater is in thermal contact with the quench protection switch. A heater network is configured in parallel with the quench protection switch and is in thermal contact with each of the coils. A quench of any one of the coils triggers a quench of the quench protection switch, wherein the heater network then triggers a quench of all of the remaining coils.

A quench protection system for a superconducting machine, such as a superconducting generator having a plurality of series-arranged superconducting coils, includes at least one switch heater electrically coupled to each of the superconducting coils. A quench protection switch is provided in series with the coils, wherein each switch heater is in thermal contact with the quench protection switch. A heater network is configured in parallel with the quench protection switch and is in thermal contact with each of the coils. A quench of any one of the coils triggers a quench of the quench protection switch, wherein the heater network then triggers a quench of all of the remaining coils.

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.

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.