A heat exchanger for use with a refrigeration device having a FPA disposed therein being comprised of a polymeric composite mesh material having a hot end and a cold end and defining an array of weft capillaries interwoven with a perpendicular array of warp strands. The array of weft capillaries may include a plurality of high pressure inlet capillaries for channeling and distributing high pressure gas from an inlet at the hot end to a Joule-Thomson orifice at the cold end, a plurality of low pressure outlet capillaries for channeling and distributing high pressure gas from a Joule-Thomson orifice to an outlet of the heat exchanger, and a plurality of low thermal conductivity fibers interspersed between the high pressure inlet capillaries and the low pressure outlet capillaries. In example embodiments. the array of warp strands comprises at least one or more of carbon fibers, copper fibers or glass fibers.

A cryostat for subcooled (<2.5 K) liquid helium includes two separate helium tanks. A Joule-Thomson cooling unit includes a heat exchanger in the lower part of the first helium tank and uses liquid stored in the second helium tank in order to cool the subcooled liquid helium stored in the lower part of the first helium tank. The Joule-Thomson cooling unit draws in liquid helium either directly from the second helium tank or from the first helium tank, which is replenished via the gas phase from the second helium tank. In this way, the subcooled liquid helium of the first helium tank can be cooled for a long time from a combined stock of liquid helium in the first helium tank and the second helium tank. The second helium tank may be arranged adjacent or surrounding the first helium tank to maintain a lower overall height of the cryostat.

A cryostat for subcooled (<2.5 K) liquid helium includes two separate helium tanks. A Joule-Thomson cooling unit includes a heat exchanger in the lower part of the first helium tank and uses liquid stored in the second helium tank in order to cool the subcooled liquid helium stored in the lower part of the first helium tank. The Joule-Thomson cooling unit draws in liquid helium either directly from the second helium tank or from the first helium tank, which is replenished via the gas phase from the second helium tank. In this way, the subcooled liquid helium of the first helium tank can be cooled for a long time from a combined stock of liquid helium in the first helium tank and the second helium tank. The second helium tank may be arranged adjacent or surrounding the first helium tank to maintain a lower overall height of the cryostat.

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 cryostat with improved accessibility for experiments includes a cooling device, a vacuum chamber and multiple cooling levels, heat shields and experimentation places. The cooling device is thermally coupled to cooling levels that have different temperatures. The experimentation places are at the temperatures of the cooling levels and are arranged side by side when viewed from above such that each experimentation place is accessible from above and from the side. Each cooling level has an associated heat shield that also encloses an experimentation place. The vacuum chamber encloses the cooling levels. The cold plate of a second cooling level is arranged above the cold plate of a first cooling level such that a portion of the first cold plate protrudes laterally from under the second cold plate. An experimentation place is disposed above the protruding portion of the first cold plate and is accessible from above and from the side.

A miniature Joule-Thomson cryocooler operating at liquid helium temperatures includes an integral structure formed by welding at least three base plates sequentially superposed, an outermost base plate in the at least three base plates is configured as a cover plate and configured to seal the rest of the at least three base plates, the rest of the at least three base plates is configured as a first-stage cooling circulator, a second-stage cooling circulator and a third-stage cooling circulator respectively, the first-stage cooling circulator, the second-stage cooling circulator and the third-stage cooling circulator have a first-stage working fluid, a second-stage working fluid and a third-stage working fluid respectively, the first-stage cooling circulator is configured to precool the second-stage working fluid and the third-stage working fluid through the first-stage working fluid, and the second-stage cooling circulator is configured to precool the third-stage working fluid through the second-stage working fluid.

A miniature Joule-Thomson cryocooler operating at liquid helium temperatures includes an integral structure formed by welding at least three base plates sequentially superposed, an outermost base plate in the at least three base plates is configured as a cover plate and configured to seal the rest of the at least three base plates, the rest of the at least three base plates is configured as a first-stage cooling circulator, a second-stage cooling circulator and a third-stage cooling circulator respectively, the first-stage cooling circulator, the second-stage cooling circulator and the third-stage cooling circulator have a first-stage working fluid, a second-stage working fluid and a third-stage working fluid respectively, the first-stage cooling circulator is configured to precool the second-stage working fluid and the third-stage working fluid through the first-stage working fluid, and the second-stage cooling circulator is configured to precool the third-stage working fluid through the second-stage working fluid.

A cryogenic cooling system is provided comprising: a mechanical refrigerator, a heat pipe and a heat switch assembly. The mechanical refrigerator has a first cooled stage and a second cooled stage. The heat pipe has a first part coupled thermally to the second cooled stage and a second part coupled thermally to a target assembly. The heat pipe is adapted to contain a condensable gaseous coolant when in use. The heat switch assembly comprises one or more gas gap heat switches, a first end coupled thermally to the second cooled stage and a second end coupled thermally to the target assembly. The cryogenic cooling system is adapted to be operated in a heat pipe cooling mode in which the temperature of the second cooled stage is lower than the first cooled stage and wherein the temperature of the target assembly causes the coolant within the second part of the heat pipe to be gaseous and the temperature of the second cooled stage causes the coolant in the first part of the heat pipe to condense. The target assembly is cooled by the movement of the condensed liquid coolant from the first part of the heat pipe to the second part of the heat pipe during the heat pipe cooling mode. The cryogenic cooling system is further adapted to be operated in a gas gap cooling mode in which the temperature of the second cooled stage causes freezing of the coolant. The heat switch assembly is adapted to provide cooling from the second cooled stage to the target assembly during the gas gap cooling mode via the one or more gas gap heat switches.

A cryogenic cooling system is provided comprising: a mechanical refrigerator, a heat pipe and a heat switch assembly. The mechanical refrigerator has a first cooled stage and a second cooled stage. The heat pipe has a first part coupled thermally to the second cooled stage and a second part coupled thermally to a target assembly. The heat pipe is adapted to contain a condensable gaseous coolant when in use. The heat switch assembly comprises one or more gas gap heat switches, a first end coupled thermally to the second cooled stage and a second end coupled thermally to the target assembly. The cryogenic cooling system is adapted to be operated in a heat pipe cooling mode in which the temperature of the second cooled stage is lower than the first cooled stage and wherein the temperature of the target assembly causes the coolant within the second part of the heat pipe to be gaseous and the temperature of the second cooled stage causes the coolant in the first part of the heat pipe to condense. The target assembly is cooled by the movement of the condensed liquid coolant from the first part of the heat pipe to the second part of the heat pipe during the heat pipe cooling mode. The cryogenic cooling system is further adapted to be operated in a gas gap cooling mode in which the temperature of the second cooled stage causes freezing of the coolant. The heat switch assembly is adapted to provide cooling from the second cooled stage to the target assembly during the gas gap cooling mode via the one or more gas gap heat switches.

The apparatus is for use with an electron microscope, a sample, a source of high pressure gas and a vacuum pump system. The apparatus includes a holder part a body part and a Joule-Thomson refrigerator. The holder part is adapted to receive the sample and adapted to present the sample to the microscope for inspection in use. The body part defines a cavity, the cavity being evacuated by the vacuum pump system for use. The refrigerator is disposed within the cavity and thermally-coupled to the holder part, the refrigerator being coupled in use to the source of high pressure gas to maintain the sample at about a predetermined temperature.