------------------------------------------------------------ Date: Mon Aug 28 00:02:29 2000, Shift: 16:00-24:00 Supervisor: FV, with: FV,AJ, Bergen Log book#5 pages 28 - 34 Shift Summary: ------------------------------------------------------------ Machine was off during day (8 to about 19) for the RHIC open house During this period some work was done in the IR (RAS,KO,RD,ZM) i) Re-install and checkout of L1458B with the repaired powersupply module (RAS, ZM) ii) Interchange of TPC trigger cable between T1 and T2. The sync error rate is now acceptable (85 in two hours with beam this evening). iii) Checkout of T3,T5 with Bertran Supplies. After closeup it was realized there is some problem with a T5 sub module drawing excessive current. iv) Checkout of fb1 readout i.e. for WM2. v) Installation of Hall probe in D2. vi) connection of tpc drift velocity monitor for TPM2. HV and signal cables connected to HV supplies and FEHut. Await inclusion in data readout (Camac?) vii) No apparent obstacles on MRS rails (around 63 deg.) viii) Two tiles were hung from D5 behind TPM1 and cable runs checked out. ix) Called CAS watch to ensure all magnets D1-D5 can be turned on. RD raised concern about polarities for D2. When D5 and D2 are both at B-setting Ramiro expected to see same sign field for Hal probes but saw opposite sign . Needs investigation. Area was closed up at 17.00. Beam accelerated and cogged at about 20.30 with intensities of B (16e09) Y (17e09) but 1. ZDC coinc rates were ~1200 a factor 4 bigger than expected andmost single rates (BB, H1 and Yellow ZDC) a factor of 20 higher than previous runs. The TPC anode wires were all drawing high leakage currents. 2. After must talking, as well as investigations by MCR, it was realized that work has gone on during the day on the yellow ring (warm sector 3) possible to improve vacuum but in effect the vacuum was up to e-6 and thus cause for the very bad background. It was estimated that it can take at least a day before this becomes good again. During this MCR had invesitgated bumps and other poosible causes. This background do not show up at other experiments, but causes a much faster decay of yellow beam. 3. I informed MCR that this beam is unusable for BRAHMS and will shut experiment down until vacuum has improved. It should be followed up at tomorrws 8.30 meeting (Dana) at what time we hopefully have better estimate of when vacuum is improved. MCR will make triplet studies around 2 o'clock. Quench link interlock at 23.05. 4. Magnet turned stby/off. Beam Beam HV mainframe turned off. 5. One data run 2457 was taken under the bad beam conditions. (240K events at about 70 sec). All triggers were downscaled. Thus in short an unhappy ending after the productive opening during the day. ------------------------------------------------------------
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