Minutes from target meeting held November 26 2010 in 892-1-B09

These minutes are available also from:

http://wwwcompass.cern.ch/compass/detector/target/Minutes/2010/

a) End of transversity data taking on Saturday 22:20. Measure polarizations
-79.8 %, +79.9 % and -78.0 % in longitudinal 2.5 T field. Test polarization
loss in zero field using dipole 0.63 T as holding field. The speer resistors
on the target cells used as thermometers (or bolometers). Sunday 0:40 in
zero field for alignment run. Start to repolarize central cell 11:00. 
Monday 7:30 +75.2 % reached. Due to microwave leakage the upstream cell 
polarized to +1.7 % and downstream to +5.1 %. On Monday ramp down the field
and measure the thermometer response.

b) Start removal of helium-3 on Monday afternoon. The rest of the gas (mostly
helium-4) removed on Tuesday. Total amount of gas smaller than in 2007.
Target loading platform installed on Wednesday after the detectors and
concrete blocks upstream of the polarized target had been removed. The target
holder removed at 15:30. Target material filled into the nylon socks for 
storage. After this the target holder was warmed up to room temperature to 
remove any water ice on it. Insert the empty target holder into the mixing 
chamber for empty target cell measurement of the background proton signal. 
Pump out air and fill helium gas. Leak in the indium joint detected. Fill 
the mixing chamber with liquid helium-4 on Thursday evening. The magnet 
refilled at the same time. Start empty cell calibration at 1.4 K on Friday 
afternoon. The gate valve in the helium-3 pumping line failed to open.

c) Yuri: after demagnetization of the ammonia proton spins some polarization
exchange between the protons and nitrogen-14 probably taking place. Also
polarization transfer to helium-3 possible. The final relaxation mechanism
unclear. Could be phonon mediated or dipolar interaction between the spins.

d) Kaori: replace coil #1 broken SMA-connector for the empty cell measurement.

e) The helium-4 pump control system was discussed.