Minutes of HERA Meeting 07.06.2005

HERA

• HERA performed machine studies Tuesday to Thursday to prepare for and optimize operations with mirror tunes.
  • The coupling of the electron beam was compensated with solenoids turned off.
  • The dispersion in the new optics was measured (small at the IP).
  • Beam tilts at the IP were corrected.
  • Orbit response measurements were performed. The optics is in good shape.
• Luminosity operation resumed on Thursday with 120 bunches, currents up to 65mA (protons) and 36mA (electrons).
• The initial specific luminosity was 1.9 to 2.0 10^30 cm-3 s-1 mA-2, decaying to 1.3 to 1.5 10^30 towards the end of a fill. The decrease is correlated to an increase of the proton emittance. It is not yet clear whether this can be prevented by using better tunes.
• There were a few hick-ups due to the experiments:
  • The HERMES target magnet was turned on during injection, making injection very difficult.
  • The electron was dumped once at the end of fill when the ZEUS calorimeter was opened without the orbit feedback.
  • Early last week the electron beam was dumped four times due to temperature alarms caused by large beam tilts at the north IP. The shiftcrew had tried to center the photons in the H1 luminosity monitor which was not positioned properly.
• HERA will increase the beam currents. The plan is to go to 150 bunches after the maintenance day. A tune scan will be performed in order to see whether the decay of the specific luminosity can be reduced.
• The temperature thresholds were adjusted. At 14m from the IP typical values are 80% of the threshold. Additional cooling is being prepared and will be installed when it is ready.
  Note added after the meeting: The cooling will be improved tomorrow.

• An energy scan was performed. The curve is somewhat asymmetric. Scanning the first order bumps is almost completed. 30% polarization was achieved after a few days. The results of the bump scan will be included in the file. Polarization tuning will continue.

ZEUS

• In principle good conditions, taking data with high efficiency. The proton background got slightly worse during a fill. A calorimeter calibration will be performed before the access.

H1

• The background conditions has been slowly improving. The normalized track trigger rate is now at 2. The average HV efficiency increased from 56% to 66% since 31.05.
• The proton background was high during the present fill. It improved when the coupling was changed.
• Proton currents of 100mA should be possible. The number of bunches should be increased to 150.

HERMES

• Low background conditions, good data taking.

Schedule

• Maintenance day tomorrow:
  • Stop beam operation, start warming up GO/GG magnet N/S at midnight
  • Turn off experimental solenoids 5:00hrs
  • Regenerated NEG pumps 8:00hrs
  • Tunnel access 8:30 - 13:00hrs
  • Exp. interlocks set before 23:00hrs
  • Start cool-down GO/GG 24:00hrs
• Wednesday to Thursday night electron injection studies
• Thursday morning improve electron 23GeV file
• Thursday continue luminosity operation with 150 bunches, Ip=100mA slowly increasing Ie.

• Mirror tunes will be discussed Thursday, 16.06. 10:00hrs (room 459).

                Uwe Schneekloth