A cryocooler includes: a housing internally defining a low-pressure gas chamber; a valve stator defining a variable pressure zone and a high-pressure zone between the housing and the valve stator; a valve rotor, a first seal member disposed adjacent to the high-pressure zone to seal the high-pressure zone and encompassing a first surface area; a second seal member disposed adjacent to the variable pressure zone to seal the variable pressure zone, and encompassing a second surface area that is larger than the first surface area; and a third seal member disposed adjacent to the variable pressure zone to seal the variable pressure zone, and encompassing a third surface area that is larger than the second surface area.

A cryocooler includes a second-stage cooling stage, a second cylinder which includes the second-stage cooling stage on a terminal of the second-stage cylinder, a second-stage displacer which includes a magnetic regenerator material and is accommodated in the second-stage cylinder so as to be able to reciprocate in the second-stage cylinder, and a tubular magnetic shield which is installed on the second-stage cooling stage and extends along the second-stage cylinder outside the second-stage cylinder. The magnetic shield is formed of a normal conductor and a product of an electrical conductivity in a temperature range of 10 K (Kelvin) or less and a thickness of the tubular magnetic shield is 60 MS (Mega-Siemens) to 1980 MS.

A cryogenic refrigerator includes a displacer that is reciprocably mounted within a cylinder; a spool valve that is connected to the compressor and performs switching between an intake mode where a high-pressure refrigerant gas is supplied from the compressor to the cylinder and an exhaust mode where a low-pressure refrigerant gas within the cylinder is made to flow back to the compressor; and a drive unit that drives the spool valve. The spool valve has a valve body, and a drive rod that moves relative to the valve body and is integrated with the spool. The drive unit performs driving so that the magnitude of a speed when the drive rod moves from a top dead center to a bottom dead center is different from the magnitude of a speed when the drive rod moves from the bottom dead center to the top dead center, at the same displacement position.

A system includes a cryocooler configured to cool an object, a sensor configured to measure a temperature of the object, and a controller configured to generate an actuator drive signal to control the cryocooler based on at least one temperature measurement from the sensor. The cryocooler includes a heat exchanger and a needle configured to control flow of coolant gas through the heat exchanger. The cryocooler also includes a motion rod configured to move the needle and an actuator assembly configured to move the motion rod to thereby move the needle. The actuator could include a motor and a gear head configured to rotate a lead screw and a lead screw nut located around the lead screw and configured to translate rotational motion of the lead screw into linear motion. The actuator could also include a piezoelectric actuator or a linear actuator.

A mechanical system, such as cryogenic refrigerator system, is described. The system comprises two or more axial moving elements generating two or more cyclic forces along parallel axes and a vibration attenuation unit. The cyclic forces are provided with common frequency and certain phase difference between them. The vibration attenuation unit is configured for attenuating vibrations corresponding to two or more modes of vibrations characterized by a frequency corresponding to operation frequency of said two or more cyclic forces.

A Gifford-McMahon cryogenic refrigerator comprises a reciprocating displacer within a refrigeration volume. The displacer is pneumatically driven by a drive piston within a pneumatic drive volume. Pressure in the pneumatic drive volume is controlled by valving that causes the drive piston to follow a programmed displacement profile through stroke of the drive piston. The drive valving may include a proportional valve that provides continuously variable supply and exhaust of drive fluid. In a proportionally controlled feedback system, the valve into the drive volume is controlled to minimize error between a displacement signal and a programmed displacement profile. Valving to the warm end of the refrigeration volume may also be proportional. A passive force generator such as a mechanical spring or magnets may apply force to the piston in opposition to the driving force applied by the drive fluid.

A cryocooler includes a second-stage cooling stage, a second cylinder which includes the second-stage cooling stage on a terminal of the second-stage cylinder, a second-stage displacer which includes a magnetic regenerator material and is accommodated in the second-stage cylinder so as to be able to reciprocate in the second-stage cylinder, and a tubular magnetic shield which is installed on the second-stage cooling stage and extends along the second-stage cylinder outside the second-stage cylinder. The magnetic shield is formed of a normal conductor and a product of an electrical conductivity in a temperature range of 10 K (Kelvin) or less and a thickness of the tubular magnetic shield is 60 MS (Mega-Siemens) to 1980 MS.

A Gifford-McMahon cryogenic refrigerator comprises a reciprocating displacer within a refrigeration volume. The displacer is pneumatically driven by a drive piston within a pneumatic drive volume. Pressure in the pneumatic drive volume is controlled by valving that causes the drive piston to follow a programmed displacement profile through stroke of the drive piston. The drive valving may include a proportional valve that provides continuously variable supply and exhaust of drive fluid. In a proportionally controlled feedback system, the valve into the drive volume is controlled to minimize error between a displacement signal and a programmed displacement profile. Valving to the warm end of the refrigeration volume may also be proportional. A passive force generator such as a mechanical spring or magnets may apply force to the piston in opposition to the driving force applied by the drive fluid.

A Stirling cooler structure having multiple cooling modules includes at least one power unit, a pipeline, a plurality of Stirling cooling modules, and at least one piezoresistive unit. The power unit includes a cylinder and a piston. The pipeline is connected to the cylinder. The Stirling cooling modules each include a pipe and a passive displacer. The passive displacer is reciprocally, movably disposed in the pipe to partition the pipe into a cold end and a hot end. The hot end is connected to the pipeline. The piston is driven by an electric motor for a compressed air to flow through the pipeline to the hot end and then flow to the cold end through the passive displacer, such that the cold end absorbs ambient heat. The piezoresistive unit is selectively disposed between the Stirling cooling modules and the cylinder.

Cryocooler health monitoring systems and methods are provided. In one example, a method includes determining, for each setpoint temperature of a plurality of setpoint temperatures, a respective power applied to a cryocooler to set a cold tip of the cryocooler to the setpoint temperature. The method further includes determining a first load line associated with the cold tip based on the plurality of setpoint temperatures and the respective powers applied to the cryocooler. The method further includes determining a health metric associated with the cold tip based on the first load line and a reference load line associated with the cryocooler. Related devices and systems are also provided.