Minutes from target meeting held October 14 2011 in 892-2-009

These minutes are available also from:

http://wwwcompass.cern.ch/compass/detector/target/Minutes/2011/

a) Friday mistake in the field rotation. The "1T -> 2.5T" procedure was 
started on the SC expert panel instead of "2.5 T rotation". Polarization 
lost at around 14:00. Restart magnet power supplies. The polarization was 
started 17:00. Saturday 21:00 polarizations -85.3 %, +83.3 and -86.6 % 
reached. On Sunday morning 10:00 field rotation from positive solenoid 
current to negative. Restart polarizing on Monday 9:50. By 18:00 
polarizations -89.0 %, +87.2 % and -88.2 % reached with negative solenoid 
current. See
http://wwwcompass.cern.ch/elog/target_polar/140

b) During the polarization build up on the Friday/Saturday night alarm from
the LN2 buffer dewar pressure. The dewar was repressurized by opening two
heat exchanger valves on the top. No big air leaks found. 

Check the capacitive level gauge reading vs the measured weight of the 
buffer dewar. Seems to be linear down to 20-30 %. See 
http://wwwcompass.cern.ch/elog/target_polar/142

c) Check the Q-meter gains by taking baseline on Friday before the 
polarization build up with nominal gain of 206. See
http://wwwcompass.cern.ch/elog/target_polar/141

d) Magnet ramped from 2.5 T to 1 T on Wednesday 8:20 for the SPS machine
development. On Friday 14:00 field rotation in 1 T field from positive
solenoid current to negative. Ramp up the solenoid to 2.5 T with negative
solenoid current. Polarization loss in the 1 T field was in 2.28 days
-0.31 %/d, +0.20 %/d and -0.43 %/d. 

e) On Thursday melt ice block from the horizontal screen and cavity pumping
lines. The tape heater was off due to open circuit breaker. Due to the
problem with the cavity needle valve and thus high helium pressured ~0.1 bar 
this line is accumulating ice quite fast.

f) Fabrice: checking new o-rings for the magnet. Plan to close the magnet
with flanges after the removal of the dilution cryostat. The new isolation
vacuum diffusion pump system could then be tested directly on the magnet.

g) Yuri: possibility to detect nuclei with quadrupolar moment (e.g. 
nitrogen-14) from the lineshape of highly polarized protons in solid
materials. This should be tested by saturating the nitrogen-14 spins
by strong pumping at 6 - 7 MHz. After pumping the proton lineshape
should be measured in the frozen spin mode.