Minutes of HERA/Experiments Coordination Meeting Thursday, 24.10.2002
Agenda
- HERA status report
- Summary: Recommendations of background review
- Discussion: Operation until shutdown
- Update of shutdown activities
- Date of next meeting
- AoB
Minutes:
The program of the last weeks was luminosity and polarization studies.
- The specific luminosity at low beam currents determined using beam scans
is 2.4 10**30 cm-2 s-1 mA-2. The design value is 1.8 10**30 cm-2s-1mA-2 (at
full beam currents). The measured specific luminosity slightly decreases
as a function of the proton bunch intensity. The H1 and ZEUS online
luminosities are somewhat lower than expected. Acceptance corrections are not
included. There are no principle problems. At full currents the
expected luminosity is 4 10**31 cm-2 s-1.
- A polarization of about 40% was achieved (east rotator on, north and south
rotators off, H1/ZEUS solenoids off). It was difficult to go to the
polarization tunes. The resonances are stronger, beam lifetime and background
conditions are critical. Polarization studies were stopped because of
background and luminosity studies. The temperature of the GO/GG beam pipes
was increased in order to see whether there this has any effect on the
background conditions. Completing the polarization studies, turning on
spin rotator and solenoids, would take several weeks (see transparencies).
Commissioning is finished. The J/Psi data sample obtain so far is bigger than in 2000.
The achieved rate is 1000/live hour, with a dead-time of about 30%. Worki is on going
to improve the dead-time.
Best operation is achieved with 180 proton bunches.
Summary of External Review, R.Klanner transparencies
The preliminary "Observations and Recommendations" by the External Review
Committee were presented and discussed. The final
recommendations will be written by the Committee until Friday evening and
then generally available.
Discussion of Schedule
The discussion was mainly whether HERA should continue with polarization studies
or whether we should go to stable beam luminosity operation. Taking
polarized ep data would be very desirable for H1 and ZEUS. In addition, it would
be important to show that HERA can provide longitudinal polarization with
solenoids turned on and there were is no addition background when the north and
south rotators are not flat. On the other hand, going to luminosity operation
is very important for further understanding and improvement of the background
conditions, as recommended by the Background Review Committee.
Decisions
Written by R.Klanner
-
The HERA-Coordination Meeting will from now on take place once a month
at the time of the Tuesday HERA Scheduling Meeting - (exact date to be
arranged by U.Schneekloth)
-
HERA operating mode starting next week (approximately from Wednesday
on):
Reliable and stable running in luminosity mode with 180 bunches. The
currents will be slowly increased as long as they are compatible with the
stable running and the radiation tolerance of the collider experiments.
Two days/week (average) are reserved for those dedicated studies on HERA
improvements and background, which cannot be be performed in the shadow
of the stable running. The detailed schedule will be discussed and agreed
in the weekly HERA Scheduling Meetings.
This mode of operation should provide data for all four HERA experiments,
allow to gain experience in luminosity operation, progress in the
understanding of the background problems and improve the vacuum by
scrubbing with synchrotron radiation. The continuation of the polarization
programme is postponed.
Date of next meeting
The date of the next coordination meeting is Thursday, 19.11.2002 10:00hrs
Uwe Schneekloth