Abstract: A method of removing heat due to compression of a working gas from a linear cryocooler is disclosed. The cryocooler includes a sealed housing, a displacer including a displacer piston and a displacer cylinder, and a compressor all arranged within the housing. The compressor includes a compressor piston that is movable within a compression chamber. The method includes providing a port in the compression chamber to remove heat from the compression chamber due to the compression of the working gas to the housing prior to entering the displacer piston.

Abstract: According to certain embodiments, monitoring the health of a cryocooler includes monitoring physical properties of the cryocooler to obtain failure precursor parameters that indicate cryocooler health. A health fingerprint of the cryocooler is accessed. The health fingerprint associates the failure precursor parameters with a health level of the cryocooler. The health of the cryocooler is estimated in accordance with the health level.

Abstract: A thermal-cycle cryocooler, such as a Stirling-cycle cryocooler, has a single working volume that is utilized by both the compressor and the displacer. The compressor and the displacer have respective movable parts, one of which is surrounded by the other. One of the parts may be a piston, a portion of which moves within a central bore or opening in a cylinder that is the other movable part. The piston may be a component of the compressor and the cylinder may be a component of the displacer, or vice versa. The working volume is located in part in a bore of the cylinder, between the piston and a regenerator that is coupled to the cylinder. Movements of either the piston or the cylinder can directly (i.e. without the use of a gas transfer line or flow passage) cause compression or expansion of the working gas in the working volume.

Abstract: In one embodiment, a compressor includes a motor assembly configured to compress a gas within a compression volume, the motor assembly including: a stationary coil assembly; a moving assembly having at least one magnet, and a gap located between the stationary coil assembly and the moving assembly; wherein the moving assembly is configured to reciprocate axially with respect to the stationary coil assembly when electrical current is applied to the stationary coil assembly, and to change the width of the gap between the stationary coil assembly and the moving assembly so as to provide magnetic axial stiffness against motion of the moving assembly. One or more embodiments may be used in a cryocooler assembly.

Abstract: An inertance tube and a surge volume for a pulse tube refrigerator system may be integrally coupled together, such as by the inertance tube being at least in part a channel in a wall of the surge volume. The surge volume may have a helical channel in an outer wall that forms part of the inertance tube. The surge volume tank may be surrounded by a cover that closes off the channel to form the inertance tube as an integral part of the surge volume. The inertance tube may have a non-circular cross section shape, such as a square shape or non-square rectangular shape. The channel may be tapered, perhaps changing aspect ratio. Alternatively, the inertance tube may be a separate tube having a non-circular shape, which may be wrapped around at least part of the surge volume.

Abstract: In one embodiment, a compressor includes a moving assembly configured to compress a gas within a compression volume; a guide rod connected to the moving assembly which reciprocates axially with the moving assembly; and a bellows seal positioned between the moving assembly and a stationary housing which at least partially defining the compression volume. In another embodiment, a compressor includes a motor assembly configured to compress a gas within a compression volume, the motor assembly including: a stationary coil assembly; a moving assembly having at least one magnet, and a gap located between the stationary coil assembly and the moving assembly; wherein the moving assembly is configured to reciprocate axially with respect to the stationary coil assembly when electrical current is applied to the stationary coil assembly, and to change the width of the gap between the stationary coil assembly and the moving assembly so as to provide magnetic axial stiffness against motion of the moving assembly.

Abstract: A multi-stage cryocooler has three or more stages, including an active first stage and passive second and third stages. The active stage may include a Stirling expander, and the passive second and third stages may be pulse tube coolers. The cryocooler may provide cooling at three different temperatures. The coldest cooling temperature may be at or below 10 K, and may be at or below 5 K. The system may provide cooling at such low temperatures while still operating at a relatively high frequency, for example, at a frequency of at least about 20 Hertz.

Abstract: A method of removing heat due to compression of a working gas from a linear cryocooler is disclosed. The cryocooler includes a sealed housing, a displacer including a displacer piston and a displacer cylinder, and a compressor all arranged within the housing. The compressor includes a compressor piston that is movable within a compression chamber. The method includes providing a port in the compression chamber to remove heat from the compression chamber due to the compression of the working gas to the housing prior to entering the displacer piston.

Abstract: A system and method for sensing position of an oscillating moving element. The inventive position sensor includes a first arrangement for sampling the position of the element at first positions thereof and providing samples in response thereto and a second arrangement for calculating other positions of the element using the sample of the first position. In the illustrative application, the first arrangement includes an LED and a photodiode and the moving element is a piston of a long-life cryogenic cooler. A processor receives samples from the photodiode and solves an equation of motion therefor. The equation of motion is P(t)=A·sin(?t+?)+B, where P(t)=the position of the element; A=position waveform amplitude; B=position waveform DC Offset; ?=angular frequency of operation; t=time; and ?=position waveform phase.

Abstract: According to certain embodiments, monitoring the health of a cryocooler includes monitoring physical properties of the cryocooler to obtain failure precursor parameters that indicate cryocooler health. A health fingerprint of the cryocooler is accessed. The health fingerprint associates the failure precursor parameters with a health level of the cryocooler. The health of the cryocooler is estimated in accordance with the health level.

Abstract: An inertance tube and a surge volume for a pulse tube refrigerator system may be integrally coupled together, such as by the inertance tube being at least in part a channel in a wall of the surge volume. The surge volume may have a helical channel in an outer wall that forms part of the inertance tube. The surge volume tank may be surrounded by a cover that closes off the channel to form the inertance tube as an integral part of the surge volume. The inertance tube may have a non-circular cross section shape, such as a square shape or non-square rectangular shape. The channel may be tapered, perhaps changing aspect ratio. Alternatively, the inertance tube may be a separate tube having a non-circular shape, which may be wrapped around at least part of the surge volume.

Abstract: A thermal-cycle cryocooler, such as a Stirling-cycle cryocooler, has a single working volume that is utilized by both the compressor and the displacer. The compressor and the displacer have respective movable parts, one of which is surrounded by the other. One of the parts may be a piston, a portion of which moves within a central bore or opening in a cylinder that is the other movable part. The piston may be a component of the compressor and the cylinder may be a component of the displacer, or vice versa. The working volume is located in part in a bore of the cylinder, between the piston and a regenerator that is coupled to the cylinder. Movements of either the piston or the cylinder can directly (i.e. without the use of a gas transfer line or flow passage) cause compression or expansion of the working gas in the working volume.

Abstract: A system and method for sensing position of an oscillating moving element. The inventive position sensor includes a first arrangement for sampling the position of the element at first positions thereof and providing samples in response thereto and a second arrangement for calculating other positions of the element using the sample of the first position. In the illustrative application, the first arrangement includes an LED and a photodiode and the moving element is a piston of a long-life cryogenic cooler. A processor receives samples from the photodiode and solves an equation of motion therefor. The equation of motion is P(t)=A·sin(?t+?)+B, where P(t)=the position of the element; A=position waveform amplitude; B=position waveform DC Offset; ?=angular frequency of operation; t=time; and ?=position waveform phase.

Abstract: A multi-stage cryocooler includes a concentric second-stage pulse tube expander in which a pulse tube is located within a second-stage regenerator. In one embodiment, an inner wall of the regenerator also functions as an outer wall of the pulse tube. In another embodiment, there is an annular gap between an inner wall of the regenerator and an outer wall of the pulse tube. The gap may be maintained at a low pressure, approaching a vacuum, by placing the gap in fluid communication with an environment around the cryocooler, such as the low-pressure environment of space. The integrated second-stage structure, with the pulse tube within the annular regenerator, provides several potential advantages over prior multi-stage cryocooler systems.

Abstract: A regenerative refrigeration system includes one or more control devices that utilize micro electro mechanical systems (MEMS) technology. Such MEMS devices may be small in size, on a scale such that it can be introduced into a refrigeration system, such as a cryocooler, without appreciably affecting the size or mass of the refrigeration system. Through the use of MEMS devices, dynamic control of the system may be achieved without need for disassembly of the system or making the system bulky. Suitable regenerative refrigeration systems for use with the MEMS devices include pulse tube coolers, Stirling coolers, and Gifford-McMahon coolers.

Abstract: A two-stage hybrid cryocooler includes a first-stage Stirling expander having a first-stage regenerator having a first-stage-regenerator inlet and a first-stage-regenerator outlet, and a second-stage pulse tube expander. The second-stage pulse tube expander includes a second-stage regenerator having a second-stage regenerator inlet in gaseous communication with the first-stage regenerator outlet, and a second-stage regenerator outlet, and a pulse tube having a pulse-tube inlet in gaseous communication with the second-stage regenerator outlet, and a pulse-tube outlet. The second-stage regenerator and the pulse tube together provide a first gas-flow path between the first-stage regenerator and the pulse-tube outlet. A pulse tube pressure drop structure has a pulse-tube-pressure-drop inlet in gaseous communication with the pulse-tube outlet, and a pulse-tube pressure-drop outlet, and a gas volume is in gaseous communication with the pulse-tube pressure-drop outlet.

Abstract: A cryogenic refrigeration system includes an expansion nozzle having a high-pressure nozzle inlet and a low-pressure nozzle outlet, and a compressor having a compression device, such as a pair of opposing pistons, operable to compress gas within a compression volume. The compression volume has an inlet port and an outlet port. A flapper inlet valve has an inlet valve inlet, and an inlet valve outlet in gaseous communication with the inlet port of the compression volume. The inlet valve opens when a gaseous pressure at the inlet valve inlet is sufficiently greater than a gaseous pressure in the compression volume to overcome a spring force of the flapper inlet valve. A flapper outlet valve has an outlet valve inlet in gaseous communication with the outlet port of the compression volume, and an outlet valve outlet in gaseous communication with the nozzle inlet.

Abstract: A two-stage cryocooler (10) includes an ambient temperature portion (12), a first-stage temperature portion (14), and a second-stage temperature portion (16). The ambient temperature portion includes a surge volume (44) that is coupled to and in communication with the first-stage temperature portion. The surge volume may be coupled to a first-stage interface (36) of the first-stage temperature portion by use of an inertance tube (42). Locating the surge volume in the ambient temperature portion may advantageously reduce size and mass of the first-stage temperature portion. Also, thermal losses may be reduced by maintaining the surge volume at ambient temperature. Space and structural requirements for maintaining the system may be met more easily with the surge volume maintained in the ambient temperature portion of the two-stage cooler. The surge volume may be a separate unit, or may be a plenum or other chamber within an expander in the ambient temperature portion.

Abstract: A cryogenic refrigeration system includes an expansion nozzle having a high-pressure nozzle inlet and a low-pressure nozzle outlet, and a compressor having a compression device, such as a pair of opposing pistons, operable to compress gas within a compression volume. The compression volume has an inlet port and an outlet port. A flapper inlet valve has an inlet valve inlet, and an inlet valve outlet in gaseous communication with the inlet port of the compression volume. The inlet valve opens when a gaseous pressure at the inlet valve inlet is sufficiently greater than a gaseous pressure in the compression volume to overcome a spring force of the flapper inlet valve. A flapper outlet valve has an outlet valve inlet in gaseous communication with the outlet port of the compression volume, and an outlet valve outlet in gaseous communication with the nozzle inlet.

Abstract: A high-frequency, low-temperature regenerator (12). The regenerator (12) includes a substrate (50) having rare earth material (52) disposed thereon. In a specific embodiment, the substrate (50) has channels or pores (54) therethrough or therein to facilitate gas flow through the regenerator (12). The substrate (50) is constructed from a material, such as polyimide, polyester, or stainless steel, which is sufficient to define the geometry of the regenerator (12). The rare earth material (52) is selected and deposited on the substrate (50) in a layer (52) having thermal penetration depth that is greater than the thickness of the layer (52). The thermal penetration depth is sufficiently high to enable all of the rare earth material (52) to contribute to thermal regeneration at an operating frequency of 30 Hz. In the illustrative embodiment, the thickness of the substrate (50) is less than or equal to approximately 0.001 inches. The layer of rare earth material (52) is approximately 0.0002 inches thick.