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 high separation efficacy, compact, bulk oil separator oriented horizontally and used with a scroll-type oil-lubricated compressor unit adapted to compressing helium. The horizontal bulk oil separator contains an integral oil reservoir and removes more than 99.9% of the oil from the helium that exits. The bulk oil separator contains successive chambers where oil separates from the gas by impingement.

Abstract: The problems of reducing the torque required to turn the valve, eliminating wear dust, and extending the life of the valves in Gifford McMahon (G-M) type multi-port pulse tube refrigerators are solved by using a rotary spool valve having radial clearance to control flow to and from the regenerator, and using face seal ports on the end of the spool to control flow to and from the pulse tubes.

Abstract: An oil lubricated compressor which includes a bypass oil line connecting respective oil paths upstream and downstream of the motor. The bypass oil path permits oil to be detoured around the motor in a tube that is external to the compressor shell and flows back into the shell near the scroll inlet. The oil bypass line returns “excess” oil directly to sump 28, rather than having it flow from sump 27 to sump 28 through an air-gap, thereby reducing both the drag on the motor and the input power.

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 two-stage pulse tube refrigerator having a compact design, low vibration and low heat loss is provided where at least the 2nd stage is co-axial but preferably, both stages are co-axial with the second stage pulse tube being central and the first stage pulse tube occupying the annular space between the second stage pulse tube and the first stage regenerator. Convection losses associated with different temperature profiles in the pulse tubes and regenerators are minimized by shifting the thermal patterns in the pulse tubes relative to the regenerators by one or more of spacers in the regenerators, physical differences in length with gas channel connections, adjustment of dc flow, and thermal bridges.

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: The problems of reducing the torque required to turn the valve, eliminating wear dust, and extending the life of the valves in Gifford McMahon (G-M) type multi-port pulse tube refrigerators are solved by using a rotary spool valve having radial clearance to control flow to and from the regenerator, and using face seal ports on the end of the spool to control flow to and from the pulse tubes.

Abstract: A range of buffer volume/pulse tube volume ratios for two-stage hybrid GM type pulse tube cold-heads that are designed to produce refrigeration at 4 K are provided. The ranges of volume ratios for the first and second stages provides a good balance between the inefficiencies but compact size of a four-valve phase shifting mechanism and the better efficiency but larger size of a double-orifice phase shifting mechanism. The buffer volumes are small enough to be conveniently machined into the warm end housing, or as an option, one can be part of a valve disc housing. The drive motor for the valve disc is in an attached housing to make the valve disc readily accessible for service.

Abstract: A two-stage pulse tube refrigerator having a compact design, low vibration and low heat loss is provided where at least the 2nd stage is co-axial but preferably, both stages are co-axial with the second stage pulse tube being central and the first stage pulse tube occupying the annular space between the second stage pulse tube and the first stage regenerator. Convection losses associated with different temperature profiles in the pulse tubes and regenerators are minimized by shifting the thermal patterns in the pulse tubes relative to the regenerators by one or more of spacers in the regenerators, physical differences in length with gas channel connections, adjustment of dc flow, and thermal bridges.

Abstract: A direct current voltage to heat the sensor wire for powering and extracting a signal voltage from a thermocouple-type vacuum sensor. The direct current used produces a DC offset in the sensor output where the heating current flow is stopped for a short interval and the unbiased sensor voltage is then sampled and stored.

Abstract: A rotary disc valve unit and refrigerators containing a rotary disc valve unit that has multiple valves, in which at least one rotary valve has ports connecting to the regenerator and at least one rotary valve has ports connecting to the warm ends of one or more pulse tubes where the rotary valve with ports for the regenerator has lighter contact than the rotary valve with ports for the pulse tubes. The valve face is divided into an inner area with ports for the pulse tubes and an outer area with ports for the regenerator, the inner area having a greater sealing pressure than the outer area.

Abstract: A cryopump cooled by a GM type refrigerator is disclosed in which the cold (second stage) cryopanel(s) are in planes that are pitched parallel to the axis of the expander cylinder; the cold end of the first stage expansion space is close to the point where the expander cylinder enters the vacuum housing that contains the cryopanels; and a drain system removes all the liquid argon and water flowing out through a vent port for two orientations of the cryopump.

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: The present invention applies to single or two stage pulse tube refrigerators that have one or more passive orifices at the hot end(s) of the pulse tube(s) through which gas flows to achieve phase shifting and the phase shifting gas flow circulates to a remote heat sink by adding check valves and an appropriate piping circuit.

Abstract: Disclosed is a method of removing contaminants from a GM type cryogenic refrigerator that incorporates an oil lubricated compressor where such contaminants are introduced during servicing the refrigerator where at least some of the oil is replaced with clean oil.

Abstract: The pulse tubes (165, 175) and regenerators (160, 170) contained within a cryopump housing (210) are arranged in a way that facilitates the fabrication and installation of the cryopanels (265). The pulse tubes and regenerators are located in a common plane in the center of the cryopump housing and the cold (second stage) panels (265) that are pitched parallel to the plane with the tubes.

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: An integrated cryopump and 2 stage pulse tube refrigeration system (100) comprising a cryopump, a compressor for a pulse tube refrigerator, a pulse tube refrigerator located within the vacuum chamber of the cryopump where the hot ends of the pulse tubes (165,175) are connected to each other through a buffer volume (180), are integral to the cryopump vacuum chamber hosing, and a buffer volume (180) is connected to the hot ends (117,119) of the pulse tubes (165,175) through flow restrictors (145,150).

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.