Refrigerator Cryopump With A Simple Oil-Free Roughing Pump

For the operation of a refrigerator cryopump a roughing pump is necessary to pro vide a sufficient low starting pressure prior to cool-down. Usually oil lubricated rotary vane pumps are used for that purpose. However, the demand for a fully hydrocarbon-free high vacuum system does not allow that type of roughing pump. Therefore we performed investigations with a dry oil-free diaphragm pump as a roughing pump for a refrigerator cryopump. We were able to show that in spite of the high ultimate pressure a diaphragm pump can be used. The combination of a cryopump with a diaphragm pump meets the requirement of a hydrocarbon-free high vacuum system.