Abstract: A pulse tube refrigerator which can generate cryogenic temperatures of below 10 K includes first and second refrigeration stages. Each stage includes a pulse tube and an associated regenerator provided at the low temperature side of the pulse tube. A pressure fluctuation generator having a compressor and a first to a fourth valve is provided at the high temperature side of each regenerator. The high temperature sides of each pulse tube are connected by a continuous channel while the high temperature side of each pulse tube and the high temperature side of each regenerator are connected by a by-pass channel. A magnetic material having a rare-earth element and a transition metal is used as a regenerative material for the regenerator. When pressure fluctuation is generated in each pulse tube at the phase difference angle of 180.degree.

Abstract: A multi-staged gas cycle refrigerator having a first stage regeneration part including a compression piston, a second stage regeneration part including a double inlet pulse tube and a buffer is described. Temperatures below 10K are achieved without leakage of refrigerant gas, this configuration resulting in the improvement of efficiency and reduction of cost.