Minutes from target meeting held July 19 2010 in 892-2-009

These minutes are available also from:

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

a) Kaori: transverse data taking until Tuesday morning. The four largest 
helium-3 roots stopped due to opening of motor thermal protection relay in pump
#10. No indication of abnormal motor temperature observed however. The mixing
chamber warmed up to 1 K and the polarization was lost from at about 77 %. 
Restart the roots blowers and polarize the target with microwaves from 11:00.
On Thursday morning 3:10 -79.4 %, 80.1 % and -78.0 % reached. Go to 1 T field
and start to take transverse data from 6:00 after the alignment run.

b) Jan: install USB data logger on the roots #10 motor and monitor 
the temperature for 20 hours. Normal day/night variation of about 2 C observed,
but no other anomalies seen. Temperature stayed below 42 C.

c) Kaori: Friday morning roots #10 thermal relay opened and the four largest 
pumps stopped. There is no alarm if only some the pumps stop but the others
keep on running and the gas flow continues. Polarization lost. 

d) Jaakko: replace the Ziehl MSR 220 Z motor protection relay with a new one. 
Check the PTC resistors inside the motor coils with a multimeter. The values
between 100 - 300 ohms. 

e) Restart polarization on Friday morning. Saturday 8:00 -69.2 %, +73.7 % 
and -72.4 % reached. Go to transverse 0.63 T field.

f) Jaakko: back to longitudinal 2.5 T field on Sunday evening 20:30 due to
long MD. The polarizations -68.6 %, +73.0 % and -71.5 %. Test loss of 
polarization in 2.5 T after 1 minute and 5 minutes pump stop. No polarization
lost in this test. Store the helium-3 back to the tanks and measure 
the polarization at 1 K. The polarization went to zero in about two hours. 

g) The possibility to replace a complete motor was discussed. This has been 
done in the past by the Cryolab (Rieubland) to the already commissioned and 
operational polarized target system. Three small and one big motor (coils) 
in the storage. These are used ones, but probably still working. 
Laura: Pfeiffer could be contacted for the refurbishment of the spare motors.

h) Proposal to move the target platform 2.5 m upstream for the Drell-Yan 
physics was discussed. Some remarks: the platform rotation lost, probably
different fixing on the floor needed, cabling and piping on both Saleve and
Jura sides need to be redone, longer LN2 precooling line may be necessary, 
access inside the radiation protection shield may be difficult and may need
some cool down time of the activated materials, target loading platform needs
to be modified to the fit the smaller space.