Minutes from target meeting held October 19 2007 in 888

These minutes are available also from:

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

a) Fabrice: Tuesday October 16 09:00 at zero field for an hour. Polarization
-27 % upstream and +7 % middle cell after. Start microwave reversal 11:15.
On Thursday 15:30 polarizations +91.5 %, -81.5 % and +86.6 % reached. 
Relaxation times in frozen spin mode in transverse 0.63 T field October 
10 - 16 were 4268 h, 4234 h and 2400 h.

b) Fabrice: pump helium from 4He pumping line with a small non hermetic 
12 m^3/h rotary pump. The pump outlet is connected through oil mist eliminator 
to an oxygen analyzer. The oxygen level is practically 0 ppm, while in the 
recovery line after the magnet and dilution cryostat 10 - 12 ppm is normally 
observed.

c) Mixing chamber temperature and microwave leakage were discussed. Yuri: lower
polarization measured by coils 6,7 and 8 can be due to microwave leakage in 
the downstream stopper. Jaakko: an other explanation is better material packing
at the downstream end of the target cells. 

d) Yuri: the NMR frequencies are shifting about 10 kHz in the beginning of
the polarization. More careful analysis of this process is needed.