Minutes of HERA Meeting      20.01.2004

HERA

• The superconducting cavity, which had a leak, was disconnected from the RF during the access Tuesday and Wednesday. It is one out of 16 superconducting cavities. The radiation safety check of the transmitter SL was done. The transmitter is again in operation. Higher positron currents are now possible. The goal is to increase the positron current to 35mA before going to the full number of bunches.
• HERA delivered 10 luminosity fills since Thursday with maximum proton currents of 64mA. There were no major technical problems.
• Proton background conditions were poor for some fills, in particular for ZEUS. The source of the background is not known. It was improved by changing the proton tunes.
• The preliminary results of the longitudinal beam scan presented last week were revised. The data are well described assuming the design beta functions (p vertical beta function of 0.198m instead of 0.18m) and a scaling factor of 0.79. It is not understood why the scaling factor is needed. There are no indications for dynamic effects. The transverse scan has not yet been done. There will be a special meeting on Monday 16:00hrs to discuss the specific luminosity and required studies.

• The work is progressing as planned with a few exceptions. Regular meetings are being held.
  • Increased preventive maintenance of the low-beta proton magnet power supplies is being done since November.
  • Connecting power supply alarms to the alarm loop: A test was successfully done in December. A prototype of the final electronics is being assembled and will be tested next week. 16 of the 40 power supplies will be equipped during the February maintenance, the remaining power supplies in March.
  • Monitoring of fast current changes of power supplies: The design of the electronics is ready. A prototype will be tested end of January. Critical power supplies will be equipped in March (slight delay).
  • Beam dump signal without delay: Was implemented in December. Is in operation without problems.
  • Faster processing of alarm loop signals: Electronics was changed during January maintenance day.
  • Fast AC beam current monitor: In operation. Issued a beam abort signal when a GA failed on 21.12.2003.
  • Fast DC beam current monitor: Electronics installed in December. Being tested. Created two false alarms. Waiting for final approval.
  • BPM alarms: Working in principle, not active. Reference orbits and thresholds have to be improved. Goal: active in March.
  • Proton collimators are moved closer to the beam during e-injection and acceleration since December.
  • Additional beam loss monitors (scintillators) at north IP: Work in progress.

H1

• HERA delivered 1.5pb-1 last week, H1 took 1.2pb-1 (0.84pb-1 with all HV on). In general, background conditions were acceptable.
• The scaled chamber current is not improving as a function of time. The maximum beam currents are still Ie x Ip= 30mAx60mA. Warm-up of GO/GG and regeneration of NEG pumps has to be done during the February maintenance day. The central beam pipe got hot and the vacuum quite poor when the positron injection took a long time.
• Proton collimators and p orbit should not be moved without agreement from all experiments.

ZEUS

• Background conditions were acceptable for some fills. For other fills the proton background was very unstable (visible in C5 and proton collimator rates), causing frequent HV trips.
• A calibration run for the luminosity spectrometer was taken yesterday. This did not affect the calibration of the photon detector.

HERMES

• HERMES had only 3 good fills after the access. At the beginning of the fills the background was quite high. HV could only be turned on after about 2 hours. Yesterday the proton background was high.
• The target was repaired during a temporary access.

Polarimeter

• The DAQ system of the cavity LPOL has been improved. Compton photon have been observed. A 2 hours access is required to replace a defective camera.

Schedule

• Continue luminosity operation with increasing beam currents.
• Access for LPOL cavity in case of a break or in coincidence with calibration of ZEUS calorimeter.
• Meeting on specific luminosity and required studies on Monday 16:00hrs.

                Uwe Schneekloth