Minutes from target meeting held October 5 2007 in 892-1-D20

These minutes are available also from:

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

a) Takuma: Saturday September 29 to longitudinal field due to short alignment 
run. Tuesday October 2 NMR rack cooling water tube blocked. Disconnect air heat
exchanger on the rack. Temperature stability of the DCS pt100 thermometer
mounted at the cooling water outlet of the Q-meters becomes better and 
day/night variation disappears. Wednesday MD melt ice on top of LN2 trap with 
air blower. Measure polarizations +92.2 %, -80.3 % and +85.7 % at 2.5 T. 
The relaxation times in transverse 0.63 T after 131 h were 5980 h, 4340 h and 
3216 h. Thursday 22:00 stop microwaves with polarizations -84.7 %, +79.6 % and 
-91.5 %. Start transverse mode with 0.63 T. 

b) Thermometers and polarization relaxation were discussed. Target Wiki has
updated page on the thermometers. Jaakko gave talk in last analysis meeting 
on the polarization relaxation rates in 0.63 T transverse field.

c) Yuri: at low polarization values no clear asymmetry in the proton NMR line
of NH3 observed. This gives 6 - 10 kHz hysteresis to the lineshift during 
microwave reversals.

d) Fabrice: plan to sample the helium gas at the evaporator pump inlet to find
out impurities before and after the pumps. More than 100 ppm oxygen impurity
observed May 28 for 8 h, June 23 for 2 h, July 2 for 12 h and August 13 - 16. 
The detailed data until September 1 is available from 'cvs checkout Tdata' 
in na58pc057. Refurbishment of the helium-4 roots and rotary pumps was 
discussed.