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Michigan B184 Update August 20, 2004 |
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1) Chambers passing CR test
a) Chambers passing CR test this week: EMS5A06
b) Total number of chambers passing CR test at CERN: 50
2) Chambers in progress
EMS4A06: CR test.
EMS4A08: CR test (already for one week now)
EMS5A04: Ready for CR test - Reapplied epoxy to the location between
Al and endplug for some tubes which have relatively larger leak
rate (a few 10^-5 ml/sec). The leak rate is now 1.9 and 5.6
mbar/day. This is all we can for this chamber in terms of the
leaks. This chamber is now ready for CR test.
EMS4A10: Doing dark current test.
EMS4C08: Doing dark current test.
3) Chambers in hospital. none.
4) Problems and other issues
a) Crane in bldg 184 has not been repaired. I contacted the
transportation support and I was told that there was a problem with
the bridge. They are searching for parts. After fixing it, the
crane needs to be security certified.
b) So far our big trouble is the CR test. Most of the chamber has to
have a few rounds of test, which of course is extremely time
consuming. Here are two examples:
- EMS4A06: During repeated HV on mezz cards scan, the warning to
the "low correlation eff." goes to different mezz cards,
indicating something is not stable, I guess. Sometimes mezz card
8 fails, sometimes, 6, and sometimes 3, or 4.
Also CR data shows two channels with strange width distributions
with two peaks overlapping each other so that the bkg cannot be
removed.
Additional comment on 8/23/04: Suspected that the HV cable, the
DAQ system was in a strong EMI enviroment. We moved the cables
and DAQ system from chamber short chamber side to long tube
side. Then we took CR data over the weekend. Now the two tubes
with funny width distributions are gone.
Also the Mezz scan with HV on is no longer a problem. Bingyun
worked this weekend to take the CR data and do the analysis for
this chamber.
- EMS4A08: Replaced three mezz cards to pass mezz scan HV off.
CR data is fine, except that one tube has a bad TDC spectrum
which typically indicates tubelet blockage. We found one half
blocked tubelet and replaced it. The second CR run shows that
this tube is fixed. However, another channel now has a funny
width distribution (same shape like the two of EMS4A06). Let me
remind you that this channel had no problem in the first run.
Additional comment on 8/23/04: We didn't do any change to the
chamber or DAQ system, except for flushing a little bit more
gas. We then restarted another round of data taking during the
weekend (Reza worked for it). Now this chamber looks good. The
funny width distribution with two peaks overlapping each other
is gone.
c) Needs
- The new DAQ system for CR test is not ready yet. Jeff has
ordered some parts and I wish this system could be ready soon.
- We do need new cables for MECCA test. so far all three don't
fully work.
- We have not yet received survey target.
I have to be away from next Tuesday to Sat. due to an unexpected
trip to Beijing that hardly I can avoid. Curtis will replace me
next week.
Zhengguo Zhao