Abstract: A closed-cycle refrigerator provides cooling to extremely low temperatures, particularly in the range of 0.5 K to 2.0 K. A 4 K pulse-tube cryocooler cold head or G-M cryocooler cold head liquefies helium in a first cooling chamber at a pressure at approximately 1 atmosphere. Liquid helium flows from the first cooling chamber, through a Joule-Thomson valve, and into a second cooling chamber under a pressure differential created by a pump. Helium vapor extracted from the second cooling chamber by the pump is routed back to the first cooling chamber to be re-condensed. This closed-cycle design provides continuous cooling below 2 K. Cryocooler cold head cold sections have no physical contact with subsequent cooling elements, such as the first and second cooling chambers to reduce vibration transfer. In some embodiments the cryocooler cold head is connected to a vacuum chamber via a vibration damping coupler to further reduce vibration transfer.

Abstract: A cryocooler for liquefying gas in which the neck of the dewar or cryostat includes a cold end of a cryocooler with the first stage cooling station, the first stage regenerator, the second stage cooling station, the second stage regenerator, and a condenser thermally coupled to the second cooling station. Radiation baffles are also present within the neck portion of the dewar between the storage portion for the dewar and the condenser, such that when the cryocooler is turned off, the radiation baffles reduce heat radiation on the cryogen in the storage section of the dewar.

Abstract: A reliquifier using a cryocooler in which an insulated sleeve surrounds a portion of the cold head, a first stage cooling station, and a second stage cooling station, including a condenser. Gas is conveyed from a cryostat to the insulated sleeve, where it is liquefied as it passes over the cold head. An end of the insulated sleeve is connected to a liquid transfer tube for conveying condensed fluid back to the cryostat.

Abstract: An extra-low vibration cryostat, which incorporates a cryocooler and cryostat to cool and house a vibration-sensitive device, with the cryocooler and cryostat sealed gas-tight to each other, but mechanically isolated, so that vibration from the cryocooler does not affect the device.

Abstract: A cryocooler for liquefying gas in which the neck of the dewar or cryostat includes a cold end of a cryocooler with the first stage cooling station, the first stage regenerator, the second stage cooling station, the second stage regenerator, and a condenser thermally coupled to the second cooling station. Radiation baffles are also present within the neck portion of the dewar between the storage portion for the dewar and the condenser, such that when the cryocooler is turned off, the radiation baffles reduce heat radiation on the cryogen in the storage section of the dewar.

Abstract: A reliquifier using a cryocooler in which an insulated sleeve surrounds a portion of the cold head, a first stage cooling station, and a second stage cooling station, including a condenser. Gas is conveyed from a cryostat to the insulated sleeve, where it is liquefied as it passes over the cold head. An end of the insulated sleeve is connected to a liquid transfer tube for conveying condensed fluid back to the cryostat.

Abstract: A reliquifier using a cryocooler in which an insulated sleeve surrounds a portion of the cold head, a first stage cooling station, and a second stage cooling station, including a condenser. Gas is conveyed from a cryostat to the insulated sleeve, where it is liquefied as it passes over the cold head. An end of the insulated sleeve is connected to a liquid transfer tube for conveying condensed fluid back to the cryostat.

Abstract: A three-stage pulse-tube cryocooler, in which the third stage pulse tube is arranged below the second stage pulse tube, with a gas flow conduit between the second stage pulse tube heat exchanger and the cold end of the second stage regenerator. The design of the invention is much simpler than a conventional three-stage parallel pulse tube cooler, requiring only two pulse tubes at the warm (room temperature) end and two reservoirs, with a corresponding reduction in the number of associated orifices, passages, etc. In effect, this provides a three stage cryocooler with a two-stage warm end design by putting the second and third stage pulse tubes in series, with a gas flow passage providing gas flow between the second and third stages for gas expansion and refrigeration. The three-stage design allows an intermediate temperature connection between the temperatures of the first and third stages, for applications which require three cooling temperatures.

Abstract: A three-stage pulse-tube cryocooler, in which the third stage pulse tube is arranged below the second stage pulse tube, with a gas flow conduit between the second stage pulse tube heat exchanger and the cold end of the second stage regenerator. The design of the invention is much simpler than a conventional three-stage parallel pulse tube cooler, requiring only two pulse tubes at the warm (room temperature) end and two reservoirs, with a corresponding reduction in the number of associated orifices, passages, etc. In effect, this provides a three stage cryocooler with a two-stage warm end design by putting the second and third stage pulse tubes in series, with a gas flow passage providing gas flow between the second and third stages for gas expansion and refrigeration. The three-stage design allows an intermediate temperature connection between the temperatures of the first and third stages, for applications which require three cooling temperatures.

Abstract: A component for use in pulse tube cryorefrigerators which integrates the reservoirs (buffer volumes) as well as the housing for the rotary valve and valve plate and drive motor into a convenient, unified assembly. Other components required by the pulse-tube refrigerators, such as the heat sink, orifices, phase shifting valves, connecting tubing, etc., may also be integrated into the buffer volume/valve/motor housing within the teachings of the invention.

Abstract: A multi-stage cryogenic refrigerator utilizing the Gifford-McMahon cycle has an external regenerator in each stage. The external regenerators are vertically stacked and connected in series, so that expanding gas is allowed to flow through the regenerators without significant obstruction or turning motion. The lower regenerators operate at progressively lower temperatures. The packing material within each regenerator has a higher specific heat than that of the regenerator immediately above as determined at the operating temperature of the regenerator.

Abstract: A regenerator unit arranged for mounting in the flow circuit carrying a refrigerant (helium gas) between stages of a two-stage Gifford-McMahon cryorefrigerator. The unit is housed in a sleeve extending between the expansion chamber of the first stage and the low temperature heat exchanger. A locking mechanism both suspends and seals the regenerator within the sleeve so that the regenerator cannot move either axially or radially and refrigerant cannot bypass the unit. The locking mechanism makes assembling and disassembling the unit in the refrigerator readily simple.