Minutes of the HERA Meeting   6.11.2001

1. HERA:
   • Lumi scans were done for the optics with reduced horizontal-vertical coupling (compensating the effect of the H1 and ZEUS solenoids) resulting in specific luminosities of
     L_spec=1.7 10³⁰/cm² s mA² at the South IP
     L_spec=1.45 10³⁰/cm² s mA² at the North IP
   • Background studies with positrons for the ZEUS MVD diodes revealed the BHL64 dipole at 64m left as a source of backscattered synchrotron radiation. A vertical beam tilt larger than 0.15 mrad leads to synrad hitting the beam pipe at 4.5m instead of entering the photon beam tube.
   • Observed reduces proton beam lifetime in collision mode. Under study.
   • Standard machine operation is now done by operators.
   • A ground fault in the HERA proton ring was searched for on Sunday, but disappeared before it could be localized.
2. HERA-B
   • Requested target activity to do HV training before the Nov 19-21 shutdown. Rate around 1.5 MHz with 60 bunches.
   • First step: find the beam with the wire target.
   • The spectrometer magnet should be powered for test before the shutdown. It will be in regular operation afterwards.
3. Hermes:
   • Access on Friday for repair on the target was successful.
   • Need stable positron beam to condition chambers
   • First signal seen from lumi monitor, although with low rate due to low e current.
   • Need 1 shift for alignment/adjustment of beam position monitors.
   • Backgrounds are still high. However, the collimators are not fully closed yet.
4. ZEUS:
   • The effect of closing the calorimeter on GG and GO fields and the positron beam must be studied again.
   • The solenoid tripped on Monday, related to a HERA Cryo problem.
   • The central drift chamber will be ready for HV and background tests next week.
   • Radiation monitoring: A beam dump signal can now be generated using the diode current and a 'leaky bucket principle'. It would have generated positron beam dumps on Friday and Sunday. The 'bad incidence' on Sunday could be cured after 24 min by HERA beam steering. A pre-dump warning or level indicator of the leaky bucket for the HERA shift crew was requested.
5. H1:
   • Central drift chamber successfully tested with proper gas but without beam. Ready for test with beam and background studies.
   • The position of the lumi photon detector and the solenoid current are now indicated for the HERA shift.
   • The current in the first proton bunch, which is used for timing and synchronization, was low in the last fills. At least 40 micro amps are needed. Losses occur at injection to HERA and further due to tune excitation from the positron beam. Wished to improve the injection also for the first bunch and to move the tune excitation to another bunch.
6. Program: A schedule by F. Willeke for the next 2 weeks is here.
7. Next meeting: next Tuesday, 13.11.2001, 11:00, Geb 30b, Rm 459

Last modified: Wed Nov 7 13:22:20 MET 2001