Abstract: A refrigerator 1 of the present disclosure includes: at least two compressors, namely, a low-stage compressor C1 and a high-stage compressor C3; an expander T; a cooling part 2 for cooling a cooling object R2 with a refrigerant R1 expanded by the expander T; a refrigerant circulation line 8 for circulating the refrigerant; a bypass line 31 connected to a high-pressure line and a low-pressure line of the refrigerant circulation line 8; a bypass valve 32; a first temperature sensor 33 for detecting a temperature of the refrigerant R1 on an inlet side of the expander T or a second temperature sensor 34 for detecting the temperature of the refrigerant R1 on an outlet side of the expander T; and a controller 40 for controlling an opening degree of the bypass valve 32 and a rotation speed of the refrigerator 1 based on a detection result of the first temperature sensor 33 or the second temperature sensor 34.

Abstract: A low-cost and space-saving cooling apparatus for a superconductor that prevents a function of the superconductor being compromised when a refrigerator is faulty. A cooling apparatus for a superconductor forms a circulation path in which a coolant, having been used for cooing the superconductor, is pumped by a circulation pump to a heat exchanger unit so that the coolant is cooled by a refrigerator, and the coolant is supplied to the superconductor.

Abstract: A low-cost and space-saving cooling apparatus for a superconductor that prevents a function of the superconductor being compromised when a refrigerator is faulty. A cooling apparatus for a superconductor forms a circulation path in which a coolant, having been used for cooing the superconductor, is pumped by a circulation pump to a heat exchanger unit so that the coolant is cooled by a refrigerator, and the coolant is supplied to the superconductor.

Abstract: A high relative-permittivity B-staged sheet obtained by incorporating an insulating inorganic filler having a relative permittivity of at least 500 at room temperature into a solvent-less resin component so as to have an insultaing inorganic filler content of 80 to 99% by weight, a high relative-permittivity prepreg obtained from the above high relative-permittivity B-staged sheet, a process for the production of the high relative-permittivity prepreg, and a printed wiring board obtained from any one of the above high relative-permittivity B-staged sheet and the high relative-permittivity prepreg.