Shutdown metalica SNF 2011-04-10 15:28:06: Unable to pump down

carterlin at snf.stanford.edu carterlin at snf.stanford.edu
Sun Apr 10 15:28:06 PDT 2011


At the start of my session, I realize the Hoist Ready light is on and the pressure gauge shows atm pressure. it seems that previous user did not pump down the chamber.
After loading, unable to pump down the chamber with roughing pump for 15min. Pressure gauge sits at atm. Usually the chamber can be pumped down to 30 micron after 5 min. After closing roughing valve, the valve does NOT keep turning but comes to a stop, at which position giving off a hissing sound and roughing pump noise.
Mistakenly open gate valve at this stage, hearing noise and observing cryopump temp going up. Turn off gate valve immediately and cryotemp shoots up to 59K max and gradually comes down




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