Minutes of HERA Meeting      13.01.2004

HERA

• HERA continued luminosity operation after the cooling failure on Tuesday until the maintenance day on Thursday.
• Two shifts were spent on machine studies after the access.
• Over the weekend HERA delivered only a few luminosity runs due to technical problems. There were several beam losses caused by failures of the electron RF system.
• The most serious problem is a superconducting cavity WR. Several attempts to condition the transmitter and cavity did not give any significant improvement. Break-down occurs when the RF power is increased. Today the SC cavity is being warmed up to 150K. A leak search will be performed. In case there is a leak at the diagnostics window it will be sealed. In case of a leak at the input coupler, the RF input will be disconnected. HERA will then be operated without this cavity.
• The transmitter SL will be in operation today after the radiation safety checks.
• The fast ACC proton current monitor was tested for about one week. Thresholds were adjusted. The system is working well. There have been no false alarms. It is now active. The DCCT proton current monitor was connected last week. There were 2 fake beam dumps. Presently, the system is not active. Thresholds are being adjusted. The plan is to implement the power supply monitoring during the April maintenance day. The BPM alarm is not active. The beam orbit is not stable enough to prevent fake beam aborts. The proton orbit stabilization procedure is still in progress. There was some discussion whether the present proton beam loss alarms are sufficient. They will be reviewed in the HERA coordination meeting next week.
• The temperature at the absorber 4 proton beam pipe (SR11) is significantly lower after the installation of cooling during the access last Thursday.

• Transverse beam scans were not performed due to technical problems and lack of time.
• A longitudinal ep scan was performed. The data can be fitted assuming the vertical proton beta function at IP of 0.28m instead of 0.18m or vertical positron beta function of 0.36 instead of 0.26m. There is no obvious explanation why any of the vertical beta functions is larger than expected. A transverse scan has to be done.
• The RF sum voltage can be reduced slightly. Reduction of the RF power would allow operation at higher positron current or increased stability at the same current.
• At tune step 1 (without polarization) the luminosity was the same as at tune step 4 (required for polarization).

H1

• The luminosity monitor was unstable Friday to Saturday night.
• Another cooling failure occurred on Saturday. The electronics was turned off during the luminosity run. Beam dumps were requested as there was no radiation monitoring anymore.
• The VFPS noise problem is understood (caused by step motors) and is being improved today. The FPS is in operation.
• A dose a 40kGy was observed at the 40m tagger in December.

ZEUS

• Took data. The DAQ efficiency is not yet sufficient.
• Some BCAL electronics is repaired today. Work is in progress to make the CAL position information in the HERA control room more reliable.

HERMES

• Took data. The polarized target was defective (broken glass tube). It is being repaired today.
• The synchrotron radiation background was large at the beginning of fills. The beam orbit is not very reproducible. The background can be improved by orbit steering.
• One fill is required in about one week to adjust the positron beam position for the LPOL cavity. This can be done during a regular luminosity run.

Schedule

• Repair of superconducting cavity and cool-down, ready tomorrow at 12hrs. Some RF conditioning may be required.
• Continue luminosity operation. Beam currents: Ip=60mA, Ie as much as possible without RF failures.

                Uwe Schneekloth