Minutes from target meeting held September 7 2007 in 892-1-B09

These minutes are available also from:

http://wwwcompass.cern.ch/compass/detector/target/Minutes/2007/

a) Jacques: on Friday August 31 polarizations +93.1 %, -82 % and +86.5 %. 
Start 1 T field at 12:30 noon. On Tuesday September 4 back to 2.5 T with 
polarizations +92.3 %, -80.7 % and +85.0 %. Field rotation every morning
between 08:00 and 09:00 at 1 T. The relaxations times were 11000 h,
6000 h and 5300 h - similar to those calculated by Stefan Goertz. On Tuesday
at 2.5 T field from 08:00 to 20:00 due to SPS MD. Thursday evening 19:30
PLC CPU failure again. The vacuum diffusion pumps restarted. Friday September
7 maintenance intervention to the pump room air conditioning unit. 
Ambient temperature outside cold enough to stop the unit for a few hours.
Jaakko: delay in new PLC CPU micro memory card due to CERN purchase procedure
(the person responsible left CERN in August).

b) Fabrice: more memory was added to the dilution cryostat PC. The broken 
cavity mass flow meter display unit needs to be replaced. The LN2 filling
to the target material storage dewars was discussed. Presently there is
a check list that is filled after adding LN2 to the dewars. Norihiro
proposed using pt100 thermometers to check the correct filling of the dewars.
Jaakko: one possibility is to measure the total weight of the dewars
with a scale (for example http://www.kern-sohn.com ).

c) Takahiro: new EIO tube and power supply ordered from CPI 
http://www.cpii.com/ . 

d) Jaakko updated target thermometer Wiki page and analyzed the helium
temperatures during transverse data taking periods for TTH4, TTH5 and TTH6.
TTH7 on the upstream target cell is not recorded correctly by the dilution 
cryostat slow control PC. Speer resistors TTH1 and TTH2 are ok. TTH4 is well
shielded from the muon beam and showed stable value around 62 mK. The TTH5
and TTH6 are warmed up by the beam spill and their value is fluctuating
between 47 and 75 mK.

e) The helium gas purity was discussed. For example Linde Kryotechnik is
selling analyser for N2, H2O, CxHy and oil mist (but no O2) in helium gas 
http://www.linde-kryotechnik.ch/public/datenblaetter/impuritydetector.pdf