Minutes of the HERA Meeting 6.9.2005

F. Willeke: HERA week 35

   achieved > 90 mA protons due to improved PETRA acceptance.
   possibly at the cost of lower specific luminosity (rather 1.8 than 2.0).
   Hermes suffers from high p background at injection - will be studied.

   Progress with electron intensity is slow, reaching 38 mA, limited by
   e RF stability. There is a narrow margin between conditioning and
   damaging the cavities, and only small steps can be made.

   Peak lumi reached 4 10^31/cm^2/s
   Integrated lumi over the week close to 6 pb^-1

   Several fills suffered from low e- lifetime, dropping from 10 to 5h just
   after lumi is established, sometimes increasing in steps after a few hours.
   An attempt was made to release a possible trapped dust particle by
   firing the injection kicker magnet for 40 us. The first attempt was
   correlated with an increase in lifetime, but not further improvement was
   reached.
   
   Duty cycle for the week was only 44%. The largest interruption was 16h
   for investigation of GN06 p magnets, finally curing the problem at the
   power supply. An HV connector for e RF transmitter SL burned out and had
   to be replaced. Further problems include e RF SR, p 52 MHz A and a
   chopper power supply.

D. South: H1

   Appreciated the increased proton current but noted the reduced specific
   lumi.
   HV efficiency was only 65% on average, still suffering from periods of
   rough p backgrounds and occasional short (ms) e spikes. Collected 3 pb^-1
   with HV on.

Y. Yamazaki: ZEUS

   p background improved significantly since last Thursday 31.8. when a
   problem with a p collimator was cured by HERA.
   HV efficiency was up to 89% on the weekend, limited by isolated e spikes.
   Small complaint: the Charged Current trigger suffered from low p lifetime
   (below 100h) on Mon night.
   ZEUS also noted the reduced specific lumi and observes a faster reduction
   during the fill than at H1, dropping to 1.5.

A. Airapetian: Hermes

   Suffers from p background at injection, up to 3 MHz, and also during
   lumi running, leading to downscaling of some triggers.
   Suffered from 3 e beam losses on Tue and Wed night, leading to reduced
   polarisation in the target cell for some time.
   Higher e- current desired.

P. Schuler: Polarimeters

   Large discrepancy between TPOL and LPOL since one month. Want to use
   depolarizing kicker magnet at the end of the next fill for risetime
   calibration studies.

M. Bieler: maintenance day
   lots of activities all around the ring, see
   http://adweb.desy.de/~bieler/Zugang.Hera/temporary.html

   GO/GG warmup in the North starting Tue night, NEG pump regeneration Wed
   morning, then tunnel access in the North.
   Other sections can be entered from 6:00, West after D3 radiation check.

   Tunnel closing starts after lunch in the North, for power supply tests.

   In the North, the original, repaired GA08 power supply will be used
   again, for safety resons: it is equipped with fast trip detection and
   dump generation to prevent uncontrolled p beam losses.

   All 3 pairs of spin rotators will be moved for a helicity flip.

   GO/GG cooldown Wed eve and night.

   A wire at the p wire scanner will be exchanged, requiring access WL for
   leak check on Thu morning.

F. Willeke: machine studies

   3 shifts, starting Wed night: check p optics, study e ramp file problem,
   establish files with flipped rotators, test improved p tune control
   software.

   Lumi operation should resume on Thu night.
   Polarisation tuning will be done parasitically over several days:
   dispersion compensation, E scan, harmonic bump scans.


ZEUS is coordinating experiment.


D. Pitzl, 6.9.2005