Minutes of HERA Meeting      25.01.2004

HERA

• The recovery after the GN repair was quite fast. There was one luminosity fill per day. The delivered luminosity of last week was 4.1pb-1. Background spikes are correlated to proton collimator setting. Polarization reached 40% after continuing bump tuning.
• The peak luminosity was slightly above 3 10**31 cm-2 s-1 at H1, 10 - 15% lower at ZEUS. The specific luminosity continues to be larger than expected. Maximum beam currents are: protons 60mA (deliberately reduced) and electrons 30mA. The luminosity lifetime is very close to the electron beam lifetime.
• Operations: The accelerator is well under control. The time for luminosity tuning was reduced. There are no problems during injection. Last week there were 21 technical problems. 19h of operation time was lost.
• A correlation between the proton collimator settings and the background spikes was observed. The secondary collimator WL is not used anymore. A test will be performed to check whether the damaged collimator surface is causing bad background conditions. Last night the background became worse during the fill. It improved after the collimators were retraced.
  Spikes in the GN magnet circuit were observed on the transient recorder.
• Tuning with bumps increased polarization to 40% for colliding, 50% for non-colliding bunches. Polarization is growing during a fill. This is due to the beam-beam effect, which is reduced as the proton emittance grows during the fill.
  HERA would like to perform polarization studies instead of the high density end of fill run on short notice.
  The proposal is to change the rotator position during the maintenance day next week.
• The GN magnet, which was replaced a week ago, had a short between the main coil and the corrector coil. The correction coil was not connected. It looks like a fault during manufacturing. Copper was ordered for a complete set of spare coils for one IP (24 coils).
• The base pressure in the north IP is at the 10**-11 mbar level. H1 still needs a factor of 3 improvement to run at full currents. The GO/GG magnets should be warmed up and NEG pumps regenerated next Wednesday.
• The proposal is to try to reach electron currents of 34mA routinely and to stay with 120 bunches until this is achieved.
  Multipactoring was observed in the superconducting cavities, which requires continued conditioning before going to high electron currents.
• This morning the proton RF system in PETRA is down. In addition, a UPS is changed in the south.

ZEUS

• The detector is running fine. Background spikes are observed, but are usually not causing problems. The proton background became bad yesterday around 18:00hrs. The HV was off for about 1h.
• A new background display for synchrotron radiation is available in the lumi display to improve synchrotron radiation tuning. The rates in the display will be normalized.
• ZEUS proposes to combine the February and March maintenance days and to move the access to middle of February.
• The number of bunches should be increased to 180.

H1

• Background conditions are improving. The maximum beam currents for safe chamber operation increased from IpxIe = 1600mA**2 on 10.01. to 1600mA**2 24.01.2005 ( transparency). A factor 3 is still needed to operate the chamber at full currents as shown in the normalized chamber current transparency). The CJC1 HV is almost never on. With beam the vacuum pressure in the south is a factor of 10 better. NEG pumps should again be activated during the maintenance day.
• Another problem is proton spikes lasting several seconds and 2min background oscillations.
• The total delivered luminosity is almost 8pb-1 ( transparency), 2pb-1 with CJC2, 0.5pb-1 with CJC1.
• The background conditions are not yet sufficient to increase the number of bunches.

HERMES

• Smooth operation. Background conditions are fine. Could run with factor 2 higher current.
• The electron beam dump signal was issued once. The conditions for firing the beam dump were discussed. A new proposal will be made in the next meeting.
• The glass tube will be replaced during the maintenance day, the lambda wheel cooling will be repaired.

Schedule

• For the time being continue luminosity operation with 120 bunches. End of fill high density runs will start at 11mA.
• The maintenance day will be Wednesday next week as scheduled. GO/GG magnets will be warmed up in the north, NEG pumps regenerated. The spin rotators will be changed.

                Uwe Schneekloth