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Cryopump Repair Kits
Oxford Instruments supplies cryopump rebuild kits for the vacuum side of the cryopump. There are three main components to the vacuum side of a cryopump inlet array, radiation shield and charcoal arrays (15K array)
The two-stage cryocooler using the GM (Gifford-McMahon)-cycle refrigerator was initially used in radio telescope applications and eventually, it became a cryopump when condensing arrays were added to the cold stages, activated charcoal was added to the 15 kelvin condensing array (to pump light gases) and the whole mechanism was enclosed in a vacuum vessel.
The cryopump therefore has two different and separate ‘sides’ to it – the helium side, that is the mechanism with motor that drives the displacers and valving within the two-stage cylinder – and – the vacuum side, the condensing and adsorbing arrays attached to the cold stations.
Rebuild of the helium side of the pump requires specialized knowledge and tooling but the vacuum side can be easily disassembled, cleaned and rebuilt by any customer. Austin Scientific offer various array rebuild kits.
The inlet array, radiation shield and charcoal arrays are attached to the cold stations using standard bolt, lock washer hardware. Because the pump operates under high vacuum, any spaces between mating surfaces would be an insulation layer that would reduce the conduction of heat (and cold) from the cold stations to the arrays. All mating surfaces use an indium gasket to ‘fill’ the spaces and conduct the heat away effectively. The array kits contain die-cut indium gaskets for all surfaces.
Any high vacuum mechanism has to be void of contaminants such as finger prints, oils etc. Wearing powder-free latex gloves (provided in the rebuild kits with instructions), it is quite a straight forward operation to remove the old arrays and replace with new.