I brief summary of the weekly spin group meeting Friday 5-6.30 i) Machine (Mei) is making good progress in understanding ramp and store, albeit uptime is still low. Understand some of the significant losses during ramp; beam-beam interactions. reintroduced vertical bumps during this phase, and in particulr during beta squeeze. Discussion on emittance blow up from 10pimrad to 30pimrad during ear;ly ramp. Machine people see tune/orbit corrections around Phenix that varies with 24 hour cycle (temperature!?). This is one of the issue that have caused problems in reproducibility of ramps. Are still investigating. ii)polarimeter good progress. si-det changed. Vacuum no issue. Both blue and yellow have pol around 45-50%. Notice that a 'new' asymmetry from the Carbon CN at 100 Gev is used to polo have gone up by ~20% without improving machine, just understanding th reference measurements better. issue on lifetime of detectors, sees too much rate during wire insertion and retraction. Estimate that det. may only last ~4 weeks not the estimated 8 until end of run. iii)Star has issues with background. A few stores are good, but most not and gicve rise to backgrouind paralelle to beamline triggering streaks in barrel calorimeters. It may partly be a orbit issue, but could also be a lack of shielding in STAR. Thus may request dump of stores if too bad. iv)Store length so far will stick with 8 hours. Phenix thinks this is a bit on the long side, but will agree to keep this until more experience is gained with good stores. v)Lum. improvement. during enxt week mainly improved luminosity by reducing losses, and injecting more ions per bunch. Possible in aboput a week try to increase #bunches gradually. Gerry wants to have other bunch patterns too.Wants to ensure that the actual patterns from source are in fact stored/archieved. For now stick to +-+-+-... and ++--++-- (~1 week) Flemming ---------------------------------------------------------------- Flemming Videbaek Physics Department Brookhaven National Laboratory e-mail: videbaek@bnl.gov phone: 631-344-4106 _______________________________________________ Brahms-l mailing list Brahms-l@lists.bnl.gov http://lists.bnl.gov/mailman/listinfo/brahms-lReceived on Sat Apr 23 17:59:17 2005
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