Michigan B184 Update April 2, 2004


1) Chamber CR tested this week: EML3C03, EMS5C12 
   total chamber CR tested: 6

2) Chambers in progress: 

   EML4A11: CR data taking

   EML4A09: Epoxy mark up done. cabling done. T sensor and inplane
            system tested. installed HV/SHH cards, MECCA test and dark
            current measurement done.

   EML3C09: Epoxy mark up done. cabling done. T sensor and inplane
            system tested. HV/SHH cards installed.

3) Chambers in hospital

   EMS5A08: (This is the chamber having endplug cracks). mass
            spectrometer (vecco) was used to scan leaks. certified to
            4.9 and 5.4 mbar/day with helium at 3 bar for each ML1 and
            ML2 respectively. will pressurize with AR+CO2, and move
            ahead.

   EMS5A02: Leak rates were about 16-20 mbar/day for helium at 3
            bar. Q196 and VECCO were used to scan leaks. high
            background from overall endplugs (10^-6-10^-5
            ml/sec). yesterday we pressurized it with AR+CO2, and leak
            rate are now around 30 mbar/day. Q196 is used to scan
            connectors and daq system, no leaks found at this level
            (sensitivity 10^-4 ml/sec for AR and CO2). This is a thing
            we have not yet understand.

4) Problems

a) Crane operation safety 

   We have a better way to use the sling to lifting the chamber, as I
   have sent some of you the pics. this is really a thing we all need
   to help watch, reminding.
 
a) Gas mixture in bldg 184

   AR(93%)+CO2(7%) from bottle gas was used to take CR data for
   EML3C03 chamber. TDC spectrum clearly improved. drift time is about
   700 ns.  incorrect fraction of co2 or the contaimination of the gas
   (water?) are the only reason to blame. Joerg Wotshok was informed the
   problem and he is working on analyzing the gas mixture in bldg 184.

b) Hot channels

   We now understand hot channels are mainly coming from larger mezz
   card threshold offsets, or lower threshold settings. hot channels
   disappeared after increasing the thresholds for the hot chnnels.

Zhenngguo Zhao
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