Structures and methods enable emergency or rapid shutdown of an energized no-insulation (NI) superconducting magnet, without damage due to thermal effects of a quench. A resistive bypass wire is coupled between electrical terminals of the magnet coil, and does not pass significant current during normal magnet operation. When rapid shutdown is required, the bypass wire is cooled below its critical temperature, adding a superconducting current path in parallel with the magnet coil. A portion of the coil is then heated above its critical temperature, interrupting current flow through the coil. Hot spots near the coil leads are mitigated through the use of a conductive structure, such as copper cladding, that carries away excess heat due to the quench. This heat may be deposited in a resistive matrix, such as a steel plate, over a duration of seconds and without compromising other magnet design parameters.

A magnetic resonance imaging (MRI) system includes a set of magnet coils for generating a magnetic field. The set of magnet coils are composed of a superconducting material. The system further includes a mechanical cryocooler in thermal contact with the set of magnet coils and operable to reduce and maintain a temperature of the set of magnet coils below a transition temperature of the superconducting material, and an energy storage device coupled to the set of magnet coils. The energy storage device may be capable of receiving and storing energy dissipated from the set of magnet coils during rapid shutdown of the set of magnet coils. The system may also include a controller coupled to the energy storage device. The controller may be programmed to recharge the set of magnet coils using the energy stored in the energy storage device during the rapid shutdown of the set of magnet coils.

The present invention provides a rare earth cold accumulating material particle comprising a rare earth oxide or a rare earth oxysulfide, wherein the rare earth cold accumulating material particle is composed of a sintered body; an average crystal grain size of the sintered body is 0.5 to 5 μm; a porosity of the sintered body is 10 to 50 vol. %; and an average pore size of the sintered body is 0.3 to 3 μm. Further, it is preferable that the porosity of the rare earth cold accumulating material particle is 20 to 45 vol. %, and a maximum pore size of the rare earth cold accumulating material particle is 4 μm or less. Due to this structure, there can be provided a rare earth cold accumulating material having a high refrigerating capacity and a high strength.

Devices and methods are provided for shutting down a magnet system. The device includes a portable housing, a communication unit, and a switch on the portable housing. The portable housing encloses a field shutdown initiation circuitry. The communication unit is disposed at least partially in the portable housing and the communication unit is configured to establish communication between the field shutdown initiation circuitry and the magnet system. The switch is configured to turn on the field shutdown initiation circuitry to initiate a magnet field shutdown in the magnet system.

A refrigerator is provided, including rare earth cold accumulating material particles filled in a cold accumulating vessel. The rare earth cold accumulating material particles are a rare earth oxide or a rare earth oxysulfide. The rare earth cold accumulating material particles define a sintered body. An average crystal grain size of the sintered body is 0.5 to 5 μm, a porosity of the sintered body is 10 to 50 vol. %, and an average pore size of the sintered body is 0.3 to 3 μm. In an arbitrary cross-section of the rare earth cold accumulating material particles, a number of pores per a unit area of 10 μm×10 μm is 20 to 70.

A magnetic resonance imaging (MRI) system includes a set of magnet coils for generating a magnetic field. The set of magnet coils are composed of a superconducting material. The system further includes a mechanical cryocooler in thermal contact with the set of magnet coils and operable to reduce and maintain a temperature of the set of magnet coils below a transition temperature of the superconducting material, and an energy storage device coupled to the set of magnet coils. The energy storage device may be capable of receiving and storing energy dissipated from the set of magnet coils during rapid shutdown of the set of magnet coils. The system may also include a controller coupled to the energy storage device. The controller may be programmed to recharge the set of magnet coils using the energy stored in the energy storage device during the rapid shutdown of the set of magnet coils.

A magnetic resonance imaging (MRI) system includes a set of magnet coils for generating a magnetic field. The set of magnet coils are composed of a superconducting material. The system further includes a mechanical cryocooler in thermal contact with the set of magnet coils and operable to reduce and maintain a temperature of the set of magnet coils below a transition temperature of the superconducting material, and an energy storage device coupled to the set of magnet coils. The energy storage device may be capable of receiving and storing energy dissipated from the set of magnet coils during rapid shutdown of the set of magnet coils. The system may also include a controller coupled to the energy storage device. The controller may be programmed to recharge the set of magnet coils using the energy stored in the energy storage device during the rapid shutdown of the set of magnet coils.

The present invention provides a rare earth cold accumulating material particle comprising a rare earth oxide or a rare earth oxysulfide, wherein the rare earth cold accumulating material particle is composed of a sintered body; an average crystal grain size of the sintered body is 0.5 to 5 μm; a porosity of the sintered body is 10 to 50 vol. %; and an average pore size of the sintered body is 0.3 to 3 μm. Further, it is preferable that the porosity of the rare earth cold accumulating material particle is 20 to 45 vol. %, and a maximum pore size of the rare earth cold accumulating material particle is 4 μm or less. Due to this structure, there can be provided a rare earth cold accumulating material having a high refrigerating capacity and a high strength.

The present invention provides a rare earth cold accumulating material particle comprising a rare earth oxide or a rare earth oxysulfide, wherein the rare earth cold accumulating material particle is composed of a sintered body; an average crystal grain size of the sintered body is 0.5 to 5 μm; a porosity of the sintered body is 10 to 50 vol. %; and an average pore size of the sintered body is 0.3 to 3 μm. Further, it is preferable that the porosity of the rare earth cold accumulating material particle is 20 to 45 vol. %, and a maximum pore size of the rare earth cold accumulating material particle is 4 μm or less. Due to this structure, there can be provided a rare earth cold accumulating material having a high refrigerating capacity and a high strength.

The present invention provides a rare earth cold accumulating material particle comprising a rare earth oxide or a rare earth oxysulfide, wherein the rare earth cold accumulating material particle is composed of a sintered body; an average crystal grain size of the sintered body is 0.5 to 5 μm; a porosity of the sintered body is 10 to 50 vol. %; and an average pore size of the sintered body is 0.3 to 3 μm. Further, it is preferable that the porosity of the rare earth cold accumulating material particle is 20 to 45 vol. %, and a maximum pore size of the rare earth cold accumulating material particle is 4 m or less. Due to this structure, there can be provided a rare earth cold accumulating material having a high refrigerating capacity and a high strength.