Comment metalica 2003-11-22 15:12:35: main chamber vacuum gauge

[zia at snf.stanford.edu]

the main vacuum gauge seems to be misreading.  after a fifteen minute roughing period, the reading was only at ~200 microns.  After checking for open lines, I decided to try the cryopump.  Immediately the reading dropped, but did not go below 50 microns.   Using the ion gauge though, the chamber was at 1e-5 T.   I let the chamber pump down for two hours to reach a base pressure of 6e-7 T, so my guess is that there is just something wrong with the main gauge.....
thanks, 
rashid.