Minutes from target meeting held June 3 2011 in 892-2-009

These minutes are available also from:

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

a) Target holder warmed to 87 K during the weekend. Remove the target holder
from the mixing chamber on Monday afternoon and close the access tube
with the metallic plug. Load new ammonia on Tuesday afternoon. Leak test 
access tube volume and target holder isolation vacuum. NMR coils, heaters 
and thermometers working after loading. Pump out air and helium mixture from
the mixing chamber for an hour. Fill in helium gas and start to cool down
the target material. See http://wwwcompass.cern.ch/elog/target_polar/112

b) Magnet filled with LHe by Wednesday morning. Start helium-4 evaporator 
pumps in the morning and fill the mixing chamber with helium-4 the same day. 
Prepare the helium-3 vapor pressure thermometer on Thursday. Magnet started
on the afternoon for thermal equilibrium calibration at 1.5 K. Over filling
of the helium-4 evaporator made a small changed to the mixing chamber 
temperature during the night.

c) Fabrice: new control board received from Danfysik to the power supply
854S. Board installed into the power supply. The new control board has
the standard firmware and might not be compatible with the magnet safety 
system. Thus the old control board was installed back on Thursday. In the 
start up week before one interlock from the magnet safety system was forgotten.
This inhibited the normal operation of the power supply.

d) Polarization test at 1 K was discussed.

e) Norihiro showed slides from Hiroki on the tests of the Millitech DET-12
diode microwave power detector and the new attenuator. Cooling down of the
attenuator was discussed. Yuri: test microwave attenuator with Hiroki. 
The attenuator warmed up to +55 C (+78 C internal blade) with 5 W of power.

f) Norihiro: new PLC modules were accepted by the Step 7 after giving
the old reference number. New PT100 sensors need to be produced for 
monitoring the water cooled heat exchangers in the helium-3 roots blowers.
The LN2 dewar weighing scale will be read with an analog current input
module. Also analog input modules to read the needle valve positions are
available. The PLC status is also read by the COMPASS DCS system.

g) Alexander: from the 11 new ammonia samples 9 were successfully irradiated
in the Bonn linac. One sample melted and an other exploded. The total dose
was controlled from a charge detector behind the sample. The irradiation 
time was 9 - 15 hours. The production took about three months. A sample
was polarized at 1 K and 2.5 T. The relaxation curve was fit to a function
with two time constants. The first measurements end of January gave
constants 40 s and 120 s. Two months later these were 60 s and 60 s. 
The EPR measurement might indicate a new radical in addition to NH2.
The ammonia gas was cooled down slowly thus the beads are expected to have
a crystal structure.