REFRIGERATOR CRYOPUMP WITH A SIMPLE OIL-FREE ROUGHING PUMP

For the operation of a refrigerator cryopump a roughing pump is necess ary to pro vide a sufficient low starting pressure prior to cool-down. Usually oil lubricated rotary vane pumps are used for that purpose. H owever, the demand for a fully hydrocarbon-free high vacuum system doe s not allow that type of roughing pump. Therefore we performed investi gations with a dry oil-free diaphragm pump as a roughing pump for a re frigerator cryopump. We were able to show that in spite of the high ul timate pressure a diaphragm pump can be used. The combination of a cry opump with a diaphragm pump meets the requirement of a hydrocarbon-fre e high vacuum system.