Minutes of HERA Meeting      08.02.2005

HERA

• HERA operation was quite successful last week, except some problems with the quench protection system. The maintenance day started already on Tuesday to work on the electronics of the quench protection. Another repair was necessary on Friday. The source of the failures is now understood. Failing transistors in the electronics had been replaced by new transistors, which were not compatible. One set of spare board exists. New boards will be built.
• HERA has reached stable operation. 7 luminosity fills were delivered, typical currents Ip=65mA, Ie=34mA. The maximum luminosity was 3.4 10**31 cm-2 s-1.
• Proton spikes are still present. The situation has improved after work on magnet power supplies and better adjustment of the proton collimator positions. The "jaws to beam" procedure is now used instead of using the file values.
  The opposite collimator jaws are now moved to the beam. Small background and vertical orbit oscillations are still visible. It is not clear why. Power supplies are still being checked.
• Yesterday the proton beam was lost when collimators were adjusted. One jaw moved too close to the beam. Experts are checking what happened. For the time being the jaw WL150up is disabled. The electronics was exchanged some time ago.
• Beam parameters were studied during the machine studies Wednesday and Thursday. The horizontal emittance of the electron beam (35nm) is much larger than the design value (20nm).
  The beta beat of the proton optics was improved.
• After the rotator flip last Wednesday polarization was around 7%. 20% was achieved last night by harmonic bump steering. Polarization tuning will continue.
• A sudden brake-down of the electron lifetime occurred this morning caused by of a pressure increase in the north IR. It is not clear why (dust?).

ZEUS

• ZEUS is very happy with the running conditions. The data taking efficiency is typically between 80 and 90%. The delivered integrated luminosity is 16pb-1 ( figure). 13pb-1 have been written to tape with all HV on ( figure), which is more than the e+p luminosity at the time last year. Background conditions are fine, see plot of chamber currents for last week. The CTD current is far below the limit for safe operation (line at 360 in the figure).
• The electron current has not increased anymore ( figure). HERA should go to the full number of bunches.

H1

• The background improved by a factor of 2 after regeneration of NEG pumps last week ( figure). Before the regeneration the vacuum was an order on magnitude worse than in the south (vacuum before and after regeneration).
  The HV can now be turned on immediately. The last 2 fills were excellent. The background is still a factor 2 worse than best conditions in the last running period.
  The HV efficiency has improved significantly ( figure). The low point a few days was due to spikes. Adjustment of collimator positions was vetoed by HERMES.
• The integrated luminosity with all HV on is 3pb-1 out of 17pb-1 delivered ( figure).
• A running strategy was presented ( transparencies), trying to estimate the integrated H1 and ZEUS luminosities for 120 and 180 bunches. This started a lively discussion.

HERMES

• HERMES is very happy with the running conditions, good background conditions, no HV trips.
• There was some miscommunication concerning polarization tuning on the weekend. The TPOL display had a software problem. The LPOL was running without problems.
• HERMES is waiting for higher polarization and electron current.

Discussion

• There was no agreement between the experiments on the number of bunches after a very exciting discussion. B.Holzer proposed to continue with 120 bunches, increase bunch currents and go to 150 bunches when current limits are reached (Ip=70mA, Ie=37mA).

Schedule

• Continue luminosity operation with 120 bunches, increase bunch currents and go to 150 bunches when current limits are reached (Ip=70mA, Ie=37mA).

                Uwe Schneekloth