Minutes from target meeting held August 5 2011 in 892-2-009 These minutes are available also from: http://wwwcompass.cern.ch/compass/detector/target/Minutes/2011/ a) On Saturday 15:00 - 21:00 use microwaves to increase polarization from +89.9 %, -90.3 % and +90.2 % to +90.5 %, -91.5 % and +90.9 %. Continue to polarize on Monday 15:30 - 23:00 from +90.1 %, -89.9 % and +90.6 % to +90.6 %, -91.5 % and +91.8 %. Increase polarization on Wednesday 9:45 - 17:30 from +90.3 %, -90.6 % and +91.3 % to +90.8 %, -91.4 % and +92.2 %. b) Jaakko: the polarization values are based on the preliminary Curie- constants and the empty cell calibration from 2010. See http://wwwcompass.cern.ch/elog/target_polar/113 c) Alexander: on Sunday beam killed manually during the field rotation due to detector noise studies. The same exercises done on Monday and Tuesday. During the polarization of Monday the microwaves were retuned +-10 MHz. On Tuesday afternoon the pump room temperature reached +21 C and the helium-3 roots #1 motor temperature showed +48 C (+38 C from pt100 at different position). d) During the polarization of Wednesday the PLC interlock stopped the microwaves twice. The temperature recorded by DCS shows stable +28 C temperature well below the alarm limit set to +32 C. The rotating flow indicators were restarted and finally replaced on Thursday. The EIO water cooling tubes were cleaned and a cut from a plastic connection pipe was discovered and repaired. The internal water circuit of the EIO tubes can not cleaned due to risk of damage. Yuri: one of the water cooler unit pumps was replaced. Alexander: the microwave generator manual does not specify the lifetime of the EIO tubes. Oxygen filter in the water circuit was discussed. e) The repolarization schedule was discussed. Typical polarization losses in present +|--|+ configuration are 0.3 %/d for up- and downstream and 0.6 %/d for central cell in 2.5 T solenoid field. Thus if the repolarization is done on every positive solenoid current this gives about 0.5 % loss for up- and downstream and 1 % for central cell. In case of repolarization on every second positive solenoid current the loss is 1.5 % and 2.2 %. The loss of beam time is about Dt/t ~ 2 Dp/p = 0.0222, which gives 1.2 d for the more frequent repolarization schedule and 2.3 d for the less frequent case for about 100 d of beam. f) Jaakko: Calculate the helium-3/4 mixture condensed into the dilution cryostat on June 14 2011. This is the same mixture that was used in run 2010. g) Calculate the target material for run 2010. See http://wwwcompass.cern.ch/elog/target_polar/127 h) Fabrice: from the helium-4 pump group now the roots pumping speed, cavity valve opening and pumping line pressure are recorded by the COMPASS DCS system. In addition there are status signals from the roots and rotary pumps and from the security chain. Monitoring of the cooling water pressure and flow switches in the pumps was discussed. i) Fabrice: the delta-p of the cooling water in diffusion pump is already less than 1 bar. The filter needs to be replaced in coming weeks. j) Reading of the microwave frequency from the counters was discussed. k) Yuri: the Q-curves in positive and negative solenoid current should be compared to understand better the shift in the measured NMR-signal areas during the field rotation. The field rotation itself is an adiabatic process and does not change the target polarization.