Michigan B184 Update April 8, 2004


1) Chambers passing CR test

Chamber passed CR test this week: EML4A09, EML3C09
Total number of chamber passed CR test:     9

2) Chambers in progress 

EML4A03: T sensors tested. cabling done. Installed HV and SHH cards. 
EML3C13: Opened crate, T sensors on the cross beam reglued. started cabling.

3) Chambers in hospital 

EMS5A08: (This is the one with 11 endplug cracks).  The leak rate is
   around 4-5 mbar/day, measured by mechanical P gauge. this rate has
   been so for about one week. MECCA test finished.

EMS5A02: Certified to about 11 mbar/day with AR+CO2. This is
   consistent with about 17 mbar/day for helium. We applied epoxy to
   the tube ends where endplugs is crimped for 24 tubes with the same
   length. We will measure the "background" leak after the epoxy is
   cured for three days.

4) Problems and issues to discuss 

a) Gas system in bldg 184

I scaled down the CO2 flow rate of the gas system in bldg 184 for
EML3C09. The CR test data clearly show that the TDC spectrum is much
improved.  The drift time shortened to about 770 ns (see plots below).

My conclusion is that the mass flow meters were not correctly
calibrated, or the control system has problems. in any case the
mixtured gas has too high CO2 component, roughly 2% higher than 7%.

I have informed Joerg about this issue. 

b) Hot channels 

We are once more convinced that the hot channels appearing in our
hitmaps are coming from larger Mezz card threshold offset, or lower
settings.  In the picture below, one can see about 8 hot channels
(some are not really hot). I checked their offset, their are around -8
to -13 mV.

In such a case, I think we should list all hot channels (mezz ID,
channel, off set) in our check list so that one can deal with this
problem with convenience in the future. I have add this item to our
checklist.

c) Grounding
 
Jeff is doing a test to investgate the grounding of SHV and splitter
box.  Still taking data.

About mezz card grounding, I would like to ask our experts to think
about whether what we are doing is what you expected. I received a few
messages about this issue in the last a couple of days. I myself feel
what we are doing is the way they requested. please check the chambers
at UM and confirm we are doing the right thing.

Easter is the second biggest holiday in europ, one sees much less
people at CERN this afternoon. we will let a few chamber running leak
rate measurement during the holiday.

d) Housing
It's now VERY difficult to reserve room at CERN hostel. 


Zhenngguo Zhao
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