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Michigan B184 Update August 6, 2004 |
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1) Chambers passing CR test
a) Chambers passing CR test this week: EMS4A16, EMS5C14
b) Total number of chamber passed CR test at CERN: 46
2) Chambers in progress
EMS4A04: Applied epoxy, cabling done, survey target and B sensor
platforms glued. Now measuring leak rate.
EMS5A06: the same as EMS4A04
EMS4A08: just opened crate
3) Chambers in hospital.
EMS4C08: has been doing CR test for one week. Failed all the time
the mezz scan test with HV off. We replaced failed mezz cards,
mother board, and the CSM and DAQ system. Still failed mezz card
scan (only for bottom multilayer). A noise scan was done and no
problem found. Now we are continuing mezz scan. If still fail mezz
scan, we plan to remove all electronics part on or side of the
bottom multilayer and reinstall them, as suggested by Tiesheng.
EMS5A04 (the fifth Michigan chamber): Leaks were found in the
location between Al ring and endplug for almost all tubes of both RO
and HV sides (previously we had 4 such a chambers). This chamber
failed long term gas leak tightness. We decide to apply epoxy to
the leak location for ALL tubes. We did careful clean before
applying epoxy. We will let the epoxy cure over weekend. then
measure leak rate.
EMS5C10: Bottom multilayer has high dark current (40-90 nA/tube for
all tubes), and the dark current is very sensitive to
humidity. Applying -HV does not help, as expected. We then very
carefully cleaned ALL tubes with alcohol of the multilayer on both
RO and HV sides. The dark current was reduced, but still much more
sensitive to humidity as compared with the top multilayer.
e.g. after first cleaning
at 3.1 kV
RH(%) 55 58 63 66
TOP (nA) 170 220 290 347
Bottom (nA) 570 1300 2330 4000
for 3.4 kV and RH=52% dark current for top is 470 nA and for bottom
is 580 nA. This of course already well satisfies ATLAS
specification.
To be safe, we decided to do once more further careful cleaning. It
didn't improve obviously.
We of course checked HV, SHH cards, and they have no high dark
current. We also flushed the gas and found no effect to the dark
current.
I myself don't think this problem is due to snoop. Usually snoop
spread on tube give much high dark current, at the level of micro A
/tube, and cleaning can cure the problem.
Since the dark current at RH=52% HV=3.4 kV are well satisfy ATLAS
specification, and all possible means we can think about have been
used. I think we can move ahead.
We will keep watch dark current of this multilayer during the CR
test period.
4) Problems and other issues
a) Everyday we are struggling for counting parts. shared parts with
UW makes life even more complicated. As expected, even we have a
logbook to register what UW used, once we ask for returning, our
numbers don't match. e.g. we preassembled all FC for both HV and SHH
cards. We did double double (Alan twice, Li twice)) independent
cross check and we know we have our parts for all our chambers
(except the a few Bing has asked from Hermann) now if I use Paul's
number, we are short of one full set for HV side and two full sets
for SHH sides.
We will have to continue keeping track all parts we needed so that
we can keep running.
We have run out of survey targets. So far we borrow from UW. Since
UW is sharing UM mezz cards, and they seems don't plan to return any
borrowed ones. UM definitely have not enough mezz cards. We have
total 14 chambers that need mezz cards (5 EMS5, 6 EMS4 and 3 EML5).
My counting tells that UM needs 64 more mezz cards.
UW told me they need 400 mezz cards.
b) Space
bldg184 is VERY crowded. I wish we all could pay more attention to
the safety issue.
c) We have not yet installed the DAQ system for gas leak. I have no
time to deal with it yet. This may be done next week.
d) I asked Matt for DCS box many times. I have not yet got any. I
will keep asking.
Zhengguo Zhao