Minutes of HERA Meeting 16.08.2005

HERA

• HERA provided many luminosity runs last week. The integrated luminosity was 6.5pb-1. Unfortunately, only half of this was useful for ZEUS because of poor background conditions.
• There were technical problems with the proton RF system (one system is locking out occasionally). Locating the problem requires access and would be time consuming. HERA can continue operation for the time being.
• Conditioning the electron RF was not successful using the standard procedure. The procedure was changed.
• The main problem was the poor proton lifetime (sometimes 20 hours) and background conditions.
  The collimator positions were readjusted. Individual jaws were retracted.
  The H1 VFPS stations were retracted. The proton orbit change, which was introduced about a week ago, was removed as a test.
  Knowledge of the proton beam position in the straight sections is limited due to defective beam position monitors. Changing the orbit did not indicate any aperture limitation. The BPM situation (repair and spare parts) will be reviewed.
• The repair of the superconducting cavity is finished. The cavity has however not been cold tested. There will be a meeting this afternoon to discuss whether it make sense to reinstall the cavity.
• The electron transfer efficiency (PETRA to HERA) is fluctuating. The reason is not yet clear. The luminosity run Sunday afternoon started with only 17mA.
• Yesterday evening there was a break due to a cryo system failure.
• This morning beams were lost due to a trip of a UPS. Operation will continue within 1 h.
• Polarization was typically 35 - 45%, approaching 50% at the end of a fill.

ZEUS

• Background conditions were quite poor since Thursday. For several fills more than half was lost due to CTD trips. The conditions were always bad at the beginning of the fill for 11.-14.08. Sometimes conditions could be improved. The situation was much better for the last fill.
• HERA should investigate and improve the background conditions. The situation of the BPMs should be reviewed.

H1

• Last week the HV efficiency was between 60 and 85%, 90% for the most recent fill.
• The normalized fast track trigger rate is stable at 1. TSPs have to be activated once per week.
• The residual mass spectrum looks excellent. It is dominated by hydrogen.
  D.Trines remarked that it looks like there is a small leak.
• The specific luminosity has dropped below 2 10^30 cm-2 s-1 mA-2. The slope of delivered luminosity versus time is increasing again.
• The position of the GO magnet changed again by 2mm ring inwards. A small leak in the hydraulics was found. The magnet will be moved back to the proper position with electrons in the machine.

HERMES

• Nothing to complain. Smooth data taking, except for high dead-time during proton spikes.
• The LPOL/TPOL ratio is still off. The reason is not yet understood.
• The figure of merit for polarization with positive helicity is now larger than with negative helicity. HERMES would like to change the helicity soon and switch back again in this running period.

Schedule

• Continue luminosity operation.
• The change of helicity will be discussed again in the meeting next week.

                Uwe Schneekloth