Minutes of HERA Meeting 12.04.2005

HERA

• HERA delivered 8 luminosity fills. The integrated luminosity was 5.0pb-1 (4.8pb-1) for H1 (ZEUS). The efficiency was 38%. A new record luminosity was achieved 4.8 10**31 cm-2 s-1. Background conditions were difficult when spikes were present and very good for periods without spikes.
• There were several breaks due to repair of ZEUS luminosity monitor (Tuesday), 52MHz RF phase problems (Wednesday), again 52MHz phase and ZEUS lumi monitor and electron RF system NR (Thursday), false ZEUS gas alarm (Saturday) and PETRA ramp tables (Saturday and Sunday).
• The exchange of the BU coils SR started yesterday. Supports were welded, the tram was moved into the tunnel. The coils will be removed this afternoon. The work is slightly ahead of schedule. Beam operation will restart on the weekend.
• Small voltage changes were observed on a BU magnet SL. The amplitude is only 10% of the fluctuations seen SR. The time structure is different.

H1

• Last week HERA delivered 5.0pb-1, 4.3pb-1 was written to tape. For the last 17 fills the HV was lower than before due to proton spikes (BU magnet). On the weekend the HV efficiency was 54%.
• The luminosity correction for satellite bunches is about 2%. This is now included in the calculation of the integrated luminosity.
• For good fills the normalized fast track trigger rate and chamber current are now close to the goal.
• The vertex position has been stable for the last 15 days. The change of the vertical beam position is correlated with a movement of the GO magnet.
• The distribution system of the dry air for the GO lead tower was broken. It was replaced.
  The detector was opened for maintenance. It will be closed tomorrow.

ZEUS

• The electronics of the luminosity monitor was repaired last week. It is not clear what caused the damage.
• The fake gas alarm occurred due to an electrical discharge when a member of the shift crew touched the front panel of the gas alarm system. The power was turned off. It took some time until the solenoid was back in operation.

HERMES

• Two fills were good on the weekend. Background conditions were poor for the last fill.
• The target cell is presently being replaced by a spare cell (same dimensions). The work will be finished on Thursday. Leak checks will be performed on Friday.

Schedule

• Finish BU repair as soon as possible. The plan is to restart beam operation on Saturday. It might be faster if everything goes well.
• HERA will probably start with 1 shift of electron beam only machine studies (preparation of mirror tunes) until the proton vacuum is sufficient to open the valves of the vented section.
• Continue luminosity operation.

                Uwe Schneekloth