Minutes of the weekly HERA Meeting   21.12.2004

1. F. Willeke: HERA
   • Luminosity production resumed Fri 17.12.04.
     There were 5 lumi fills until Tue morning.
     HERA produced about 0.85 pb^-1 in 60 bunch mode with starting currents of Ip=19-27 mA and Ie=13-17 mA.
     Starting specific luminosties were always around 2.0, reaching 2.3 after tuning
     and dropping to 1.7 at the end of long fills, in units of 10^30/cm^2/s/mA^2.

   • A few 'nitty-gritty' problems had to be cured, like fake A1 alarms causing beam dumps
     and e RF transmitter failures.

   • On Sat evening the e beam was dump by a 70 degree Temperature alarm from the exchanged
     beam pipe at GI7 NR7m. Careful beam steering is needed here.

   • Experiments suffered from proton spikes.
     Small spikes occured every 30 to 60 seconds, usually tolerable.
     Large spikes tripped chambers. Some of these could be correlated with
     transients in the GA08 N power supply, see HERA logbook week 52, 21.12_n.
     MKK worked on it on Tue.

   • Polarization reached 20% after an energy scan.
     Harmonic bump scans have not been done so far.
     The influence of the H1 solenoid may require dedicated studies.
     The spin rotators are set positive helicity = right-handed electrons.

2. D. Pitzl: Backgrounds at H1
   • The proton background improved by a factor 4.5 compared to Dec 6, after
     the leaks NR6m and NL14 m were sealed, and NEGs were activated.
     Conditions are now similar to July 2004, after the June 19 leak.
     A further improvement by a factor of 4 is needed for safe operation at design beam currents.

   • The CJC was operated at moderate beam currents of 12*24 mA^2, suffering from
     frequent trips due to proton and occasional electron spikes.

   • Under present conditions the chamber could be operated at 20*40 mA^2.
     Extrapolating the background rates, beam currents of 25*65 mA^2 from 120 bunch
     operation could be tolerated.

   • The vertex position was reconstructed from the first ep data.
     It is found 2 mm ring inwards and 8 mm upwards from the center of the CJC.
     With e+p it was 2 to 3 mm inwards and 6 to 7 mm upwards.
     The shift of the e- beam by 7.5 mm ring outwards was compensated by the
     7 mm shift of H1.
     Collimators C5A and C5B inside of H1 are in the same position relative to the beam as with e+.

   • H1 shifts continue until Thu 23.12. and resume on Mon 3.1.2005.

   • Radiation and background monitoring will be provided to HERA, and the
     luminosity system will be available.

3. ZEUS
   • Chamber operation suffered from the large p background spikes.
   • The background base level is low.

   • ZEUS shifts continue until Thu 23.12. and resume on Mon 27.12.04.

4. Hermes:
   • Synchrotron radiation beam steering had to be done at the beginning of each fill.

   • Hermes shift operation stopped Mon 20.12. and resumes Wed 29.12.04.

   • The radiation monitor beam dump system is active.

   • Proton background indicators will be provided to HERA.

   • The LPOL calorimeter will be installed on the Jan 5 maintenance day.

5. Schedule:
   • Luminosity running continues until Wed 22.12. morning.

   • 3 shifts of machine studies for beam based alignment of the H1 and ZEUS
     IP regions, for p orbit improvements and e- injection efficiency optimization will follow.

   • Beam operation stops Thu 23.12. at 7:00.

   • Beam operation will restart on Mon 27.12.

   • One trial run with 10 on 10 bunches.

   • Then go to 120 bunch operation.

   • Maintenance day Wed 5.1.2005, with warm-up of the N and S interaction regions
     and NEG pump regeneration.

6. ZEUS is the coordinating experiment.

7. There will be a HERA meeting on Tue 28.12.04 at 10:00, 30b, 427.