Minutes from target meeting held July 19 2013 in 892-2-009

These minutes are available also from:

http://wwwcompass.cern.ch/compass/detector/target/Minutes/2013/

a) Compass note on 2011 polarization calculation available from
http://wwwcompass.cern.ch/compass/notes/2013-7/2013-7.pdf

b) Helium-3 roots water cooled heat exchanger disassembled at Pfeiffer. See 
the talks in
https://espace.cern.ch/na58-mgt-tb/Technical%20Board/default.aspx?InstanceID=38

c) Fabrice: solenoid and dipole assembly rolled into the magnet vacuum vessel. 
Suspension planned for next week with both stainless steel and glassfiber
cables. Four new current leads prepared with several hollow small diameter
tinned brass pipes connected in parallel. The protection diodes are outside
of the magnet at room temperature. The power converters can control the 
ramping up of the magnet current at 1.5 A/s, but ramping down needs to be 
done by dissipating the stored energy in the external diodes and resistors.
The simulated slope looks almost linear with ramping down speed of 0.7 A/s.
This would give a field rotation time of 40 - 45 minutes.

d) Fabrice: the direct current current transducer (DCCT) control rack can not
be placed on the target platform as was originally planned due to high 
radiation level. New position will be next to the platform on Jura side.
Two other racks for cable batch panels will be installed in the same place.
Totally about 80 control cables and 8 power cables. Place for the cryocooler
compressor to be found. 15 m pipe available between the cryocooler and the
compressor. Electrical services for the magnet racks and target platform 
are under discussion. Cooling water will still be needed for the NMR rack
and isolation vacuum pumps, but the new power converters are air cooled
and demineralized water will not be needed any more. Compressed air is
needed for the electropneumatic valves in the magnet and isolation vacuum
systems and for controlling of LHe transfer from the buffer dewar. In addition
computer network will be needed for the PVSS/WinCC-OA connected to the
magnet PLC system. Local control of the PLC is possible from a touch panel.
See http://j2eeps.cern.ch/wikis/display/EN/PVSS+Service
 
e) Yuri: microwave cavity was mounted on the dilution cryostat on Monday.
The cavity has a new internal cylindrical part with only one 20 cm long 
microwave stopper between the two target cells. The overall precision of
the mounting is about 1 mm. A week before the mounting an extensive testing 
of microwave components was done. The microwave leakage through the central 
stopper could explain up to 3 % "loss" of polarization in runs 2007, 2010 
and 2011.

The mixing chamber is supported internally by the target holder Kevlar tube.
An early warning of a small leak on the glassfiber mixing chamber could be
done by monitoring the isolation vacuum space with a helium-3 leak detector
(vapor pressure much more than for helium-4 and no contamination).

f) Updated instructions for CAD drawings:
http://wwwcompass.cern.ch/twiki/bin/view/PolarizedTarget/PolTargDrawings