Minutes of HERA Meeting 18.10.2005

HERA

• HERA delivered 8.1pb-1 in 12 runs, in spite of a vacuum leak. The maximum luminosity was 4.5 10^31 cm-2 s-1. The efficiency was 60%. The total delivered luminosity is now 189pb-1.
• In general, background conditions were acceptable. The proton orbit was critical. The proton background was improved by changing the proton orbit upstream of the IPs. This is somewhat difficult due to problems with the beam position monitors in the straight sections. (Some of the BPM electronics will be replaced during the shutdown.)
• Last Wednesday a leak occurred in the rotator section NR. The support welding seam, which had been added during the last shutdown, was not strong enough. The vacuum recovered relatively quickly.
  All 28 similar bellows sections in the rotators will be fixed in the shutdown.
• The electron transmitter WL was repaired this morning.
• Polarization was significantly less than the previous week. The electron tunes could not be reduced as preferred for good polarization due to electron background conditions.
  A rotator scan (scanning BF magnet) was prepared and will be started during the next fill.
• The NEG pumps in the rotator section NR will be activated in case of a break.

ZEUS

• The detector performance was relatively good. The average data taking efficiency was above 80%. The baseline background is low. There were however some periods with background spikes causing HV trips.

H1

• 6.5pb-1 were written to tape. The HV efficiency was 82%, compared to 64% last week.
• The total integrated luminosity (H1 active) is now 180pb-1, 97pb-1 with HV turned on.
• The present fill started with somewhat high proton background. It was improved by changing the proton orbit upstream of the IP. This fill is suffering from satellite bunches.

HERMES

• The detector is performing fine. The main concern is high proton background. Calibration triggers had to be pre-scaled.
• Large electron background has been observed, in particular at the beginning of a fill, since the leak in the rotator section.
• There were only few high density runs this week due to unscheduled beam dumps.

Schedule

• Continue luminosity operation. Try to increase electron current.
• A rotator scan (BF magnet) will be started next fill.
• The NEG pumps (rotator section NR) will be activated in case of a longer break.

• The shutdown activities will be reviewed in the meeting next week.

                Uwe Schneekloth