Abstract: The present invention relates to valved cryogenic refrigerators, in particular, Gifford McMahon (GM) refrigerators, and GM type pulse tube refrigerators where gas is cycled between high and low pressures by a valve mechanism that connects to an expander. Input power is reduced by use of a buffer volume which stores gas that flows to and from the warm end of the regenerator through a valve that opens and closes during the periods when the main supply and return valves are closed and is closed when the main supply and return valves are open.

Abstract: A rotary valve unit which reduces the torque required to turn the valve disc, and the amount of wear dust that is blown into the cold head, using differential gas forces to keep the valve disc in contact with the valve seat, and which enables larger diameter valve discs to be utilized for multi-ported pulse tubes that have less force on the face of the valve disc, resulting in reduced torque and reduced wear rate.

Abstract: An improved method of reducing wear dust and torque required to turn a multi-port rotary disc valve utilizes a thrust bearing to hold the valve seat and/or valve disc such that they are not in contact with each other, or have light contact each other.

Abstract: Convection losses associated with different temperature profiles in the pulse tubes and regenerators of multi-stage pulse tubes mounted in helium gas in the neck tube of a MRI cryostat are reduced by providing one or more of thermal bridges, and/or insulating sleeves between one or more pulse tubes and regenerators, and/or spacers, and spacer tubes, in one or more pulse tubes and regenerators.

Abstract: A multi valve two-stage pulse tube type GM refrigerator having a rotary valve that comprises one track for flow to the regenerator and two tracks for flow to the pulse tubes where the valve has two high pressure ports to the pulse tubes located on a single track and two low pressure ports from the pulse tubes located on a separate single track and where there are two cooling cycles per revolution of the rotary face valve.

Abstract: A magnetic shield is mounted in its own vacuum enclosure in a regenerative type expander comprising a vacuum enclosure, magnetic material in a cold regenerator, and a magnetic shield, where the magnetic shield surrounds the magnetic material.

Abstract: This invention provides an improved means of quickly warming a pulse tube (165) by shifting the phase relation of flow to the warm end of the pulse tube relative to flow to the warm end (117) of the pulse tube relative to flow to the warm end of the regenerator (160) using a “four valve” concept and the “active buffer” concept. Several different pulse tube configurations and valve timing relations that are effective at reversing the cycle from the normal mode, which produces cooling at the pulse tube heat station, to a reverse mode that produces heating are disclosed.

Abstract: Disclosed is a two-stage pulse tube cryopump cooling system in which the pulse tubes and valves are inline, with the hot ends of the pulse tubes at the top and the valve mechanism is at the bottom and the hot ends and buffer volume are cooled by an inline coolant line from the compressor input to the compressor output and attached in heat exchange relationship with the buffer volume.

Abstract: Disclosed are two-stage inter-phasing pulse tube refrigerators with and without shared buffer volumes.

Abstract: A two-stage pulse tube refrigerator comprises a pressure wave generator-compressor, first stage and second stage regenerators, first stage and second stage pulse tubes, heat exchangers and a hybrid phase shift mechanism for the first and second stage pulse tubes. The second stage phase shift mechanism includes double fixed orifices while the first stage shifter is an arrangement including one of a) 4 valves, b) 5 valves c) 2 active buffers or d) 3 active buffers. The double fixed orifice phase shifter is located either at room temperature or is thermally connected with the first stage cold end. Two-stage pulse tube refrigerators with a hybrid phase shifter have increased second stage regenerator performance at lower temperature. Pressure drop through the valves and compressor power consumption are decreased, and losses from phase interaction between each stage are eliminated.

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.