An alternative approach to flux pumping in superconducting devices is described for fast and extremely precise tuning of the current during persistent mode operation. Rather than bringing in new flux from outside the circuit, the alternative approach stores a small flux in a tunable inductor (also referred to herein as a “flux bank”) at the initial point of powering. Flux can be transferred back and forth from this bank to the main coil by simply changing the inductance of the bank. This allows for fine and fast adjustments of the persistent current without the use of thermal switches found in other approaches (which limit the adjustment speed and accuracy).

The present invention is intended to increase the critical current density of a wire rod having a shape with good symmetry such as a round wire or a square wire by making use of mechanical milling method. The production method of the present invention for the MgB.sub.2 superconducting wire rod comprises a mixing process of preparing a powder by adding a solid organic compound to a magnesium powder and a boron powder and then applying an impact to the powder to prepare a mixture of the powder in which boron particles are dispersed inside magnesium particles, a filling process of filling a metal tube with the mixture, an elongation process of elongating the metal tube filled with the mixture and a heat treatment process of heat-treating the metal tube to synthesize MgB.sub.2.

A superconducting current pump arranged to cause a DC electrical current to flow through a superconducting circuit accommodated within a cryogenic enclosure of a cryostat comprises a rotor external to the cryogenic enclosure and a stator within the cryogenic enclosure, the rotor and stator separated by a gap through which passes a thermally insulating wall of the cryogenic enclosure, the rotor and the stator comprising at least in part a ferromagnetic material to concentrate magnetic flux in a magnetic circuit across the gap between the rotor and the stator and through the wall, so that movement of the rotor external to the cryogenic enclosure relative to the stator within the cryogenic enclosure induces a DC transport current to flow around the superconducting circuit within the cryogenic enclosure. There is no coupling between a drive motor external to the cryogenic enclosure and an internal rotor which may introduce a path for heat leakage into the cryostat, in turn increasing the heat load and thus increasing the cooling power required to maintain the cold components within the cryogenic enclosure at the low operating temperature required.

Systems and methods for superconducting magnets are disclosed, such systems and methods comprising a primary coil and short-circuited secondary coil. The secondary coil can be made from a stack of superconducting tapes having longitudinal cuts forming closed superconductor loops without splices. The primary coil is used to pump the current into the secondary coil where it circulates continuously generating a permanent magnetic field.

A system for energizing a main coil of superconducting magnet in a magnetic resonance imaging (MRI) system includes a cryostat comprising a housing. A first coil is positioned within the housing of the cryostat. Alternatively, the first coil may be positioned external to the housing of the cryostat. A second coil is coupled to the first coil and positioned external to the housing of the cryostat. The second coil is configured to inductively couple to the main coil. A controller is coupled to the first coil and the second coil and is configured to control the first coil and the second coil to induce current in the main coil.

A superconductor magnet system (2) includes a cryostat (4), a superconductor bulk magnet (5), and a cryogenic cooling system (12). The bulk magnet (5) has at least N axially stacked bulk sub-magnets (6a-6c), with N≥3. Between each two axially neighboring bulk sub-magnets, an intermediate body (7a-7b) is arranged. The intermediate bodies (7a-7b) are made from a non-metallic thermal insulator material. The cryogenic cooling system (12) is adapted for independently controlling the temperature of each bulk sub-magnet (6a-6c), and has, for each bulk sub-magnet, a temperature sensor (16a-16c) for sensing the temperature of the respective bulk sub-magnet and an adjustment unit (13a-13c) for adjusting a heating power and/or a cooling power at the respective bulk sub-magnet.

A superconductor magnet system (2) includes a cryostat (4), a superconductor bulk magnet (5), and a cryogenic cooling system (12). The bulk magnet (5) has at least N axially stacked bulk sub-magnets (6a-6c), with N≥3. Between each two axially neighboring bulk sub-magnets, an intermediate body (7a-7b) is arranged. The intermediate bodies (7a-7b) are made from a non-metallic thermal insulator material. The cryogenic cooling system (12) is adapted for independently controlling the temperature of each bulk sub-magnet (6a-6c), and has, for each bulk sub-magnet, a temperature sensor (16a-16c) for sensing the temperature of the respective bulk sub-magnet and an adjustment unit (13a-13c) for adjusting a heating power and/or a cooling power at the respective bulk sub-magnet.

A method for charging a superconductor bulk magnet includes: step a) charging the magnet charger system so as to generate a first magnetic field in the sample volume, the superconductor bulk magnet having a temperature T>T.sub.c (300); step b) cooling the superconductor bulk magnet to a temperature T<T.sub.c (400); step c) discharging the magnet charger system, which inductively charges the superconductor bulk magnet, such that the superconductor bulk magnet traps a second magnetic field in the sample volume (500). In step a), the field adjustment unit is set such that the first magnetic field generated by the magnet charger system in the sample volume includes a homogeneous magnetic field component and at least one non-homogeneous magnetic field component (300). The non-homogeneous field component is chosen so that the second magnetic field of step c) has a higher homogeneity than the first magnetic field of step a) in the sample volume.

In one or more embodiments, a system for operation in a generator mode comprises a cryocooler to cool a superconducting coil. The system further comprises a flux pump to provide flux to the superconducting coil. Also, the system comprises a shaft of a prime mover to receive torque to rotate a rotor. In addition, the system comprises the superconducting coil to electrically interact with a main stator coil through a rotating magnetic field. Further, the system comprises a control stator coil to receive a current from a controller and to electrically interact with a non-superconducting coil. In one or more embodiments, a magnitude, phase, and/or frequency of rotating magnetic fields of the superconducting coil and the non-superconducting coil is varied in comparison to a magnitude, phase, and/or frequency of the magnetic field produced by the superconducting coil alone to control a magnitude, phase, and/or frequency of an output voltage.

In one or more embodiments, a system for operation in a generator mode comprises a cryocooler to cool a superconducting coil. The system further comprises a flux pump to provide flux to the superconducting coil. Also, the system comprises a shaft of a prime mover to receive torque to rotate a rotor. In addition, the system comprises the superconducting coil to electrically interact with a main stator coil through a rotating magnetic field. Further, the system comprises a control stator coil to receive a current from a controller and to electrically interact with a non-superconducting coil. In one or more embodiments, a magnitude, phase, and/or frequency of rotating magnetic fields of the superconducting coil and the non-superconducting coil is varied in comparison to a magnitude, phase, and/or frequency of the magnetic field produced by the superconducting coil alone to control a magnitude, phase, and/or frequency of an output voltage.