The Cryogenic Gas Pump (CryoPump) utilizes cold molecular sieve (MS) zeolite to adsorb gases. Rapid heating and cooling of the medium is obtained by intimately bonding the liquid nitrogen cooling circuit and the heater to the pumping medium circuit.
As the media is cooled it will adsorb all gases except for helium, thereby pumping down any attached volumes. The high capacity of the media at 77 K facilitates pumping large gas volumes and compressing low-pressure gases to high pressures.
The media can be heated to intermediate temperatures between 77K and 300K to release different gases. This selective release of gases means that hydrogen isotopes can be desorbed before any other gases, providing an excellent method for extracting impurities from hydrogen .
The brazed tubing is housed in an evacuated vessel to maintain thermal insulation and minimize tritium release to the environment. The media may be regenerate at 350 ˚C to release all adsorbed gasses.
The Cryopump is designed for robustness. The ability to operate at both low and high temperatures ensures that multiple absorption/desorption cycles will not damage the bed. Stainless-steel containment is used to separate the media from the liquid nitrogen to lower the risk of cross-contamination. A stainless-steel integrated heater and sheathed thermocouples ensure the device that can operate continuously over the temperature range -200 to 350oC.
The Cryopump comes standard with metal bellows isolation hand valves fitted with copper stem tips and VCR-8 female nuts. An integrated liquid nitrogen cooling circuit is optional. The unit is helium leak tight to 1×10-9 scc/sec at the operating temperature which is suitable for tritium service.