Minutes from target meeting held September 22 2006 in 888

These minutes are available also from:

http://wwwcompass.cern.ch/compass/detector/target/Minutes/2006/

a) Jacques: magnet fast discharge happened on Wednesday September 20 due to 
blocking of the user interface on the magnet controlling computer. The problem 
is under investigation. The magnet is ready for the transversity run with 
central dipole field of 0.6 T. In the COMPASS magnet lower current is needed 
than before with the SMC magnet to get the same dipole field 

b) The 3He/4He mixture was removed on Wednesday September 20 and the mixing
chamber was filled with 4He on Thursday. TE-calibration at 1.6 K was started 
on Friday evening after the magnet and microwave tests.

c) Temperature analysis of the July calibration period was discussed. Jaakko
showed calculated spin temperatures. The preliminary analysis was done similar 
way like in the COMPASS note 2004-14. First 15 hours of good thermal 
equilibrium data at 1.124 K, then 11 hours of data at 1.414 K and finally 
8 hours of data at 1.599 K. Problems in the calibration: magnetic field was 
ramped down after 1.1 K and later back to the nominal field. Thus the spin 
system starts to go back to the equilibrium only after the field is back 
to the nominal value. Second problem was error by the shift to switch on all 
the roots blowers in 1.6 K calibration period. The thermal equilibrium was 
lost. Third problem was the wrong input voltage scale used in recording 
the baratron pressure at 1.6 K. Cross calibration with the resistive 
thermometers can be used to correct the temperature in this period. An other 
possibility is to make magnetic field corrections to the ruthenium oxide 
thermometers. The statistical error in the spin temperatures is about 
3 mK and systematic about 2 - 3 mK.  


Comments from Norihiro:

Dear PT crews,

I would like to comment a few words on temperature analysis because my opinion
and my results what I showed in the meeting are not mentioned in the minutes.

I have analyzed temperature data since 2001 and never seen any problems of the
ruthenium oxide thermometer (TTH4) under 2.5T magnetic field because the
magnetic effect to the resistance value has been considered all the time.
The results of independent analysis of 3He vapor pressure (Baratron) and TTH4 
in this year show that temperature of TTH4 can be used for the TE calibration 
at 1.6K region instead of Baratron, please check the attachment file which is
almost the same as I showed in the meeting, because the value of TTH4 is in
agreement with values of Baratron within their errors at other temperature
regions.

Regards,
Nori