I would appreciate any direction with the following Prism II problem:

Our machine has been running great for sometime.  At initial opening of the
flight tube with both bellows open and ref gas in, we normally have a
initial major beam of about 1.1e-9.

Suddenly, the same scenario starts us out with an initial major beam of
over 1e-8.  To get the major beam down we have to have very little gas in,
which might not be that bad, but what is bad is that the major beam is very
jumpy...constantly jumping around .5-1e-9 mA, back and forth.

The obvious first guess if some new instability in the electronics or
focusing has caused the 10-fold sensitivity increase and the jumpiness.
Any suggestions?

Thanks!

Dave Mrofka
UC Riverside Earth Sciences