Loadlock Gauge problem/observations possibly crash related
eap at gloworm.Stanford.EDU
Sun Feb 17 17:52:26 PST 2002
Just a few extra details on the several problems this weekend:
Crashes seem to be related to a loadlock pumpdown timeout error.
The pressure in the loadlock drops, and then seems to hit some
kind of "base" pressure which is above the required (~80mT) setpoint
pressure for venting, loading, etc. The "base" pressure is usually different
each time (from 120 mT to 700 mT).
I can think of three possible causes of this:
1). pump problem
or 3). gauge error.
Since it is intermittent, and sometimes pumps quite normally,
and the leakup rate seems normal, 1&2 seem less likely. Also,
I've seen it pump down to "good" base, then fail on a subsequent
pumpdown with no actions that would create a leak inbetween.
It seems as if the pirani CC gauge is giving a bad reading, but there
is no other readout to verify this reading (There is a baratron
on the loadlock, but I don't know where to read this).
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