Minutes of HERA Meeting 10.05.2005

HERA

• HERA delivered an integrated luminosity of 6.2pb-1, measured by H1. (The ZEUS value was slightly higher.) A new peak luminosity of 4.9 10**31 cm-2 s-1 was achieved, which is close to the design for proton currents of 100mA.
  The efficiency was 57.5%, polarization up to 40%.
• There were a few technical problems: BU SR70 cooling water (blocked orifice), cavity vacuum SR transmitter and a vacuum leak in the rotator section SR. The leak occurred at a beam pipe flange, which did not have support welds. The electron lifetime is still slightly reduced after venting the section. It should be fine again after a few fills.
• Several runs had reduced electron lifetime. There were indications for dust trapping NR240.
• 30% polarization was achieved for Ie=30mA in one fill. Since yesterday the synchrotron frequency is reduced during the run to improve polarization.

• HERA will wait with the collimator scraping procedure until the injection vetos of the experiments are removed, in order to avoid high backgrounds in the chambers when the HV is still on.

H1

• H1 had a very good week. The HV efficiency was around 70%. Two fills were very good.
  The fill on Thursday had poor conditions at the beginning of the run.
  Background was low when HERA re-started after the vacuum leak repair Sunday to Monday night.
• On Sunday collimator scraping started while the HV was still ramping down. Scraping should start when all HV is off.
• The delivered luminosity is close to 75pb-1. 35pb-1 are on tape with HV on.

ZEUS

• In general, the data taking efficiency was good, most of the time above 80%. There was only a limited number of HV trips. For the second time 1pb-1 was written to tape on one day.
• The delivered luminosity was 6.38pb-1, excluding luminosity tuning. 5.3pb-1 were taken.

HERMES

• One fill was lost due to a VME crate being off. Otherwise data taking was fine. In the middle of the last week proton background was relatively high, data taking could however continued.
• After the repair of the HERA vacuum leak it took 3 hours until to background was sufficiently low to turn on HV.
• This morning unpolarized data was taken because of problems with target. The problem was fixed.

Schedule

• Luminosity operation. Increase electron current. Continue optimizing polarization.
• Maintenance day as scheduled, 1.06.2005.
• The position of the spin rotators will be changed during the maintenance day.

                Uwe Schneekloth