There is described a device for controlling an amount of current within a power distribution network by manipulating the amount of magnetic flux in the device and thus the impedance experienced by the power distribution network across the device. This is achieved by winding a plurality of coils about a magnetically permeable core and by providing the device with a magnetically permeable bridge element that is movable between a fully-open position at which the net magnetic flux generated in the core by alternating currents in each coil is zero, and a fully-closed position at which a net magnetic flux is present in the core.

There is provided an electrical switch comprising a length of superconducting material. In some forms the electrical switch is configured to be controlled between a low-resistance state and a higher-resistance state by the selective application of one or more switching mechanisms. In the higher-resistance state, current flowing through the length of superconducting material may approach the critical current of the length of superconducting material, may be substantially equal to the critical current or may be greater than the critical current. In some forms, the length of superconducting material is a length of high temperature superconducting material. The switching mechanisms may comprise: heating the length of superconducting material; applying a magnetic field to the length of superconducting material; applying a time-varying magnetic field to create dynamic resistance and/or heat; and/or applying a time-varying magnetic field to a loop of superconducting material to create a screening current around the loop.

A monolithic radio frequency (RF) power limiter for protecting sensitive superconductor receiver components from high-power microwave signals is disclosed. In some embodiments, two low-Tc superconductor (LTS) microstrip lines; one of which is coupled with an array of RF superconducting quantum interference devices (rf-SQUIDs); are combined with a pair of hybrid couplers to provide the power limiting operation at very low RF power levels. A microstrip line coupled to an array of rf-SQUIDs behaves as a power dependent phase shifter and its phase can be controlled by the input RF power. In one embodiment, a monolithically integrated wideband hybrid coupler is used as it dictates the bandwidth of the overall device.

A monolithic radio frequency (RF) power limiter for protecting sensitive superconductor receiver components from high-power microwave signals is disclosed. In some embodiments, two low-Tc superconductor (LTS) microstrip lines; one of which is coupled with an array of RF superconducting quantum interference devices (rf-SQUIDs); are combined with a pair of hybrid couplers to provide the power limiting operation at very low RF power levels. A microstrip line coupled to an array of rf-SQUIDs behaves as a power dependent phase shifter and its phase can be controlled by the input RF power. In one embodiment, a monolithically integrated wideband hybrid coupler is used as it dictates the bandwidth of the overall device.

A persistent current switch includes a superconducting wire including a substrate and a superconducting layer disposed on the substrate, and a heater. The superconducting wire includes a surface including a first portion and a second portion that are disposed apart from each other along a longitudinal direction of the superconducting wire. The first portion and the second portion face each other. The heater is sandwiched between the first portion and the second portion.

A superconducting magnet includes a cooling tank containing a cooling medium and at least one superconducting circuit configured for generating a magnetic field. The superconducting magnet further includes a power supply connected to the superconducting circuit(s) for energizing the superconducting circuit(s) and a superconducting switch electrically connected across ends of the superconducting circuit(s). The superconducting switch includes a superconducting winding and a thermal conduction member having a first end thermally coupled to the superconducting winding and a second end thermally coupled to the cooling medium within the cooling tank. The thermal conduction member includes, at least, a first layer and a second layer. The first layer is constructed of a metal material having a first thermal conductivity. The second layer supports the first layer and is constructed of a material having a second thermal conductivity that is lower than the first thermal conductivity.

An object of the present invention is to provide a persistent current switch with high heating efficiency by simplifying the configuration of the persistent current switch and reducing the heat capacity. To achieve the object, a superconducting magnet in accordance with the present invention includes a superconducting coil, a persistent current switch, and one of an alternating-current power supply, a pulsed power supply, or a charge/discharge circuit. The one of the alternating-current power supply, the pulsed power supply, or the charge/discharge circuit is connected to a loop circuit of the superconducting coil and the persistent current switch such that it is in parallel with the persistent current switch.

There is provided a rectifier of an alternating input current, which may comprise: an electrical switch comprising a length of HITS material to carry an alternating switch current, the HITS material having a critical current: a magnetic field generator to apply a magnetic field to the HTS material: a control mechanism to control the magnetic field generator to switch the switch between a low-resistance state when a magnitude of the magnetic field is relatively low and a higher-resistance state when a magnitude of the magnetic field is relatively high, the relatively high magnitude being sufficient to reduce the critical current so that, for a part of the alternating switch current cycle, the current approaches the critical current, is substantially equal to the critical current or is greater than the critical current. There is further provided an electrical switch having two strands of superconducting material arranged in a bifilar arrangement.

A technical problem is to turn a persistent current switch on and off at high speed with less heat input. The invention relates to a conductive cooling-type persistent current switch, including: a superconductive wire 1 through which a current is passed; a cooling stage 9 which cools the superconductive wire; and a heater 8 which heats the superconductive wire, wherein the superconductive wire is placed between faces which are each formed by the cooling stage and the heater, a core of the superconductive wire is magnesium diboride 6, and a base material 5 placed around an outer periphery of the core is a material having a resistivity of 10 cm or more at 40 K.

A coil device with at least one electrical coil winding with superconducting conductor material and a vacuum container is described in which the vacuum container surrounds the coil winding. The coil winding is part of a self-contained circuit for the formation of a continuous current. The closed circuit has a switchable conductor section, the conductor of which can be switched between a superconducting state and a normally conducting state by a magnetic device. The magnetic device has an internal part arranged inside the vacuum container and an external part arranged outside the vacuum container.