Minutes of HERA Meeting 12.07.2005

HERA

• The GA problem, causing frequent background problems, was not really solved. The spikes did not reappear after the electric circuit was still into left and right of the IP.
• The integrated luminosity delivered since Thursday is 3.87pb-1. The initial specific luminosity was above 2 10^30 cm-2 s-1 mA-2, the peak luminosity up to 4.0 10^31 cm-2 s-1
• Polarization tuning started on the weekend, up to 45% has been achieved so far. The increase of polarization at the beginning of a fill is better than during the previous running with standard tunes. The main difference is that the rotator position was changed.
  There is a suspicion that the H1 solenoid is not compensated properly. The field calculations will be checked.
  The first round of energy and bumps scans is completed. Some fine scans will be continued.
• In general, background condition are fine, except some occasional spikes. It is unclear why the proton lifetime was low during the last fill.
• The risk and maximum number of NEG regenerations was discussed. The NEG material will be saturated at some point. More critical is a possible damage of the GO/GG cryostats after repeated warmups and cooldowns. It is very difficult to get any reliable estimates. The cryo group will be asked to write down their concerns.
• The proton current is sometimes limited by PETRA. Currents up to 95mA (in 150 bunches) are possible if everything is optimized. One problem is the cooling of the PETRA magnets. Temperature drifts lead to emittance blow-up during the ramp.
  More continuous support is needed.

ZEUS

• Running was fine. The first two fills (with reduced beam currents) had low background conditions. During the following fills the normalized proton background was a factor 2 higher, but still tolerable. There is a significant increase of the trigger rate when the proton lifetime drops below 100 hours.
• The electron background was slightly higher compared to conditions with mirror tunes. In general it is very low.
• The data taking efficiency was above 80%.

H1

• It was a good startup with standard tunes; high specific luminosity and good HV efficiency. The proton background decreased again after the NEG regeneration last week. The normalized fast track trigger rate is now as expected for good conditions. The pump readings indicated that the pressure at the IP is however still worse than at ZEUS. The NEG regeneration should be repeated during the August maintenence day.
• HV operation at Ip x Ie = 4500mA^2 is possible. In principle, the number of bunches could be increased to 180.

HERMES

• The recent increase of the polarization is appreciated. The electron current should be increased above 40mA.
• There was some confusion between the HERA and HERMES shift crews on the sign conventions in the LPOL display. The same display should be used in both control rooms.

Schedule

• Continue luminosity operation with increasing electron current.
• Continue polarization tuning (energy and bump fine scans).

                Uwe Schneekloth