Minutes of HERA Meeting
18.12.2001
HERA
- The machine studies program was completed as presented last week, mainly
beam based alignment (e beam) and measurements of proton beta functions.
A few measurements of proton beta functions at the interaction region
still have to be done. In general, the optics of both machines are well
understood. The 20% beta beat in the electron ring is acceptable,
no need for urgent improvement.
- Closing of the ZEUS F/RCAL was again tested on Friday with a new orbit
correction procedure using orbit displacements measured by the BPMs.
The previous procedure was only working reliably if the initial GO and GG
currents were unchanged. The beam was still lost a few times when the
calorimeter was opened. (The opening speed has to be reduced or the BPM
readout frequency increased.)
- Collisions were reestablished on the weekend: protons 15mA in 60 bunches,
positrons 1.5mA in 12 bunches (9 colliding).
H1
- Sunday and yesterday the SPACAL background rate was again reduced to a
few kHz. The tracking detectors were at full HV. Data were taken for a
few hours. The data was mainly upstream beam gas events.
- Today the beam orbit was changed at the BI magnet (possible source
of direct synchrotron radiation). There was no effect.
- This morning the position of the proton collimators was optimized (small
effect).
- This afternoon the jet chambers will be purged with non-flammable gas.
ZEUS
- The detector was turned on during the stable proton run. Chamber currents
were fine.
- After closing the calorimeter the positron background rate (Ie=0.2mA) was
optimized using the SRTD background rate. It was possible to ramp up the
RTD to full HV. The CTD could only be turned on to 80% of its nominal HV.
- The dark currents of some upper part Si detectors of the MVD has increased
since November, an indication of possible radiation damage.
HERMES
- In general, good background conditions. Needed only small orbit adjustments.
- Took data, re-commissioning of the detector is completed.
HERA B
- Targets and vertex detector pots were inserted several times.
- Took data, timed in detector subsystems.
- A bug in the reconstruction code was found. Would like one more
shift of data taking.
- The up to date background conditions of the other experiments (netmex data)
are not available.
Schedule
- Continue optimizing ZEUS background conditions.
- Finish measurement of proton beta functions at IPs.
- Determine specific luminosity using beam scans after recent optics
improvements.
- ZEUS is continuing as coordinating experiment.
- End of beam operation Friday, 21.12.01 6:00hrs. Ramp down magnets.
- Break experimental interlocks around 6:30hrs.
- Temporary access is only possible until Friday 15:00hrs.
- HERA interlock will remain set until 2.01.2002.
- Beam operation will start 16.01.2002
- Turning on both machines will take about 12 days.
- Polarization studies (flat rotators north and south, detector solenoids
off) 5 days.
- The detailed schedule will be discussed in the next meeting Tuesday,
15.01.2002 11:00hrs.
Uwe Schneekloth