Minutes of HERA Meeting      04.01.2004

HERA

F.Willeke summarized HERA operation of last week.

• Starting up the accelerator after the Christmas break went as planned. First luminosity was achieved last Tuesday. The first long fill happened Jan 1.
• The specific luminosity is still quite high, up to 2 10**30 cm-2 s-1 mA-2 in one interaction region. It is typically around 1.7 at the other IP.
• A manual procedure is used to bring the beams into collisions. This takes about 15 minutes instead of a few minutes with the automatic procedure. The automatic procedure will be used again once operations is more stable.
• In general background conditions are fine, except some periods with increased proton background. Running conditions have to stabilize. The background oscillations which occurred before Christmas have not reappeared. A quadrupole magnet power supply in the north was repaired. It is not clear whether this was the source of the background oscillations.
• The efficiency has been relatively poor due to several technical problems: quench protection system, PETRA proton machine, proton power supply and proton RF system trips last weekend. Fixing the quench protection system took several days. Some electronics was changed.
• The improvement of the vacuum pressure in the north IR has slowed down. NEG pumps will therefore be regenerated tomorrow.
• The aperture limitation SL which was noticed before Christmas has not been checked again. So far there is no serious problem. A leak check was performed in December. Temperature sensors were installed.
• Polarization tuning has started. Presently, polarization is around 25%.

ZEUS

• In general conditions are fine. The proton background was still high for some extended periods ( transparency). There was also some synchrotron radiation background, which requires orbit tuning.
• There was a significant radiation dose 31.12.2004 4 and 1krad. The reason was power supply trips of the electron machine.

HERMES

• Background conditions were really bad at the beginning of fills. High background appeared during proton injection, significantly worse than before Christmas. HERA will optimize the proton orbit. It is planned to re-survey the upstream proton vacuum chamber during the maintenance day tomorrow. In addition, it will be checked for radiation. (Nothing was found before the Christmas break.)

H1

• Some activation occurred during proton injection on 29.12., see transparency. The background stayed at a high level after the beam loss.
• During luminosity operation the BTOF background rate is around 100 kHz transparency. Safe chamber operation is possible at about 50 kHz.
• The base pressure is at the 10**-10 mbar level. With beam it is several 10**-9 mbar, above 10**-8 mbar during electron injection ( transparency). The NEG pumps should be regenerated tomorrow.
• The chamber gas was started yesterday. HV can be turned on from tomorrow.

Schedule

• Maintenance day tomorrow
  • Start warming up GO/GG at midnight
    Some proton studies will be performed during the night shift.
  • Interlocks WR and NL will be opened.
  • Close tunnel 14:00, close experiments 22:00hrs
• After maintenance day continue luminosity operation with 120 bunches (no machine studies).
• Priority is stable luminosity operation. There is still room to increase the the electron bunch current. A factor of 1.5 increase in luminosity should be possible without increasing the number of bunches.
• HERMES high density runs will start at Ie=10mA and will last for 1h.

                Uwe Schneekloth