Minutes of HERA Meeting 26.04.2005

HERA

• HERA delivered 6.4pb-1 in 9 luminosity runs. Most fills had good conditions.
• There were only a few breaks: access for ZEUS and problems with the cryo system (failure of uninterruptable power supply). The was beam lost twice due ghost quenches and once when the proton dump kicker fired.
• Polarization was usually around 30%. It increased to 40% when the proton beam was lost.
  The major obstacle for higher polarization are the electron tunes. When the tune is reduced, as it was done before the BU repair, the proton background conditions get worse. Better tunes have to be found again.
  It was agreed to continue polarization tuning and not change the rotator positions or go to mirror tunes for the next few weeks.
• The expo hall sagged by about 2mm and has to be re-surveyed. This requires removing some of the PETRA shielding, which can only be done when there is no beam operation in PETRA. The plan is to do the survey during a HERA luminosity fill. In case one of the HERA beams is lost, the PETRA shielding can be re-installed within 1/2 hour.

ZEUS

• Background conditions were rather good. The proton background was typically a factor 2 below the (old) parameterization. The electron background improved when the collimator SL15 was moved out slightly. There were only few HV trips. The data taking efficiency was up to 90% (lumi tuning subtracted).
• The integrated e- p luminosity is now higher than the e+ p luminosity in 2004. The slope is significantly steeper. The electron current should be increased as much as possible.

H1

• Good operation last week. The HV efficiency was typically 70%, reaching 86% on Saturday (the best fill so far). The proton background was reduced by optimizing the collimator positions (WR33 and WL150).
• The normalized chamber currents are now 1.1 to 1.2, allowing stable operation. The fast track trigger rate is as expected.

HERMES

• The detector is taking data without problems. Tuesday the proton background improved when the proton collimator position was optimized for H1.

Schedule

• Luminosity operation. Increase electron current.

Shutdown Dates

• The shutdown dates of the pre-accelerators were fixed last week. The shutdown will start 14.11.2005.
• The machine group is still checking whether the HERA shutdown can start 1 or 2 weeks earlier.
• It should be checked whether the length of the shutdown can be reduced if HERMES is not moved out of the IR and all BU coils for ER and SL are brought in SL.

                Uwe Schneekloth