On Tuesday morning Bill Franklin noticed that the TDC distributions for
the right sector started to drop off for larger drift times (smaller
tdc values). This was a recurrence of the problem we had about 2 weeks
ago. I asked Bill to increase the gas flow to the WC and the problem
went away after a few hours.
Today during the access I checked with a helium sniffer and was unable
to find any noticeable leaks in the supply/return lines or on the
chamber. I did find a few pockets of accumulated helium gas trapped by
the copper covers but even these registered as small amounts on the
sniffer.
Conclusion is that we still do not understand the source of this
problem.
To counteract the problem I have increased the flow rate from 3 l/min
to 4 l/min and the TDC distributions should be monitored carefully by
each shift to spot any recurrence of the problem.
With the increased flow rate the 6-pack of helium will generally last
7.5 days which is fine as we change it every week anyway. However, if
we change the weekly access day, as we did this week, we have to be
careful that the helium supply is sufficient for the extra day.
Cheers,
Douglas
26-415 M.I.T.
Tel: +1 (617) 258-7199
77 Massachusetts Avenue Fax: +1 (617)
258-5440
Cambridge, MA 02139, USA E-mail:
hasell@mit.edu
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