Minutes from target meeting held September 23 2011 in 888

These minutes are available also from:

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

a) Takahiro: while tuning magnet trim coils on Thursday a fast discharge
happened 10:22 at 320 A or 1.23 T. The new trim coil settings were programmed
and the magnet was ramped back to 2.5 T. Target repolarization was started
at 13:30. About 80 % was reached by Friday morning 10:00. In the beginning
high microwave power produced high outlet pressure (0.6 bar abs) of helium-3 
on the roots pumps and opened the over pressure valve to the storage tanks.

b) Install LN2 trap buffer dewar on the digital weighing scale plate in 
the pump room.

c) Takahiro: On Wednesday check the remote control motor of the microwave 
attenuator. The motor operates normally, but the magnetic shield bends
the motor axis. Better fixing might help or an ultrasonic motor could be used
instead.

d) Fabrice: On Wednesday shift the solenoid field by 0.5 A and observe
the position of the NMR peaks with Alain. From this data it looks like
the upstream trim coil G1 is shorted in similar way like the G2 at downstream.
It may then trap slowly decaying current, which could possibly be eliminated
with a ramping and heating procedure. From Thursday new trim settings
are used with H1 set now to 1 A. The field homogeneity is quite good now
and should allow equal polarization build up on all target cells.
See also the weekly report from September 23.

e) Kaori: open the varactor diode bias power supply on Wednesday. Replace 
the red power-on LED and series resistor with new ones. Bad soldering found 
from the linear regulator 7824 ground connection. After resoldering the 
power supply was reinstalled into the NMR-rack. Test the Q-meter #4 tuning
with a 9 V battery. The tuning works normally, so the reason for the observed
shifted Q-curve is wrong voltage setting. 

f) Fabrice: the diffusion pump cooling water filter could be replaced during
the next SPS MD. Norihiro: this is complicated now due to problem in the
butterfly valve.