Minutes of HERA/Experiment Coordination Meeting  30.11.2004

Agenda

• Brief summary reports
• Schedule and operation
  • machine studies
  • luminosity operation Dec04/2005
  • operation over Christmas and new year holidays
• Shutdown plans (What is the earliest date? When do we have to fix the date?)
  • Status of BU magnets
• Polarization Task Force

• Date of next meeting
• AoB

Minutes:

F.Willeke: HERA Status

• The re-commissioning schedule was kept until 11.11.2004 when a GN magnet coil was severely damaged. Six working days were needed to replace the defective magnet. Further problems were: ground fault of a QQ magnet east left, vacuum leak at a new proton beam position monitor, several water leaks and network problems. There is now a 5 to 7 day delay in the schedule.
• Staging the switch to electrons was very successful. Electron beam was stored within 2 hours. The beam optics was checked and empirically corrected. A concern is the electron injection efficiency, which will be more important if the luminosity lifetime is lower with electrons instead of positrons. There are indications for a large optical mismatch between the electron transfer beam line and HERA. This has to be improved.
• Beam-based alignment studies were performed. Everything looks fine in the south IP. An additional 2mrad orbit kick is needed in the north IP. This could be explained by a 7-10 mm misplacement of the GO magnet at the IP side. A 30% stronger dipole field (GG magnet) is needed to correct for this. Trying to move the GO magnet by 7mm on Friday failed. GO hit the H1 cryostat after 1mm movement. There will be a meeting this afternoon to discuss whether the H1 detector will be moved by 5mm. If yes, it will be done tomorrow or on Thursday.
• The sensitivity of the new temperature sensors at the GI vacuum chambers was checked with electron beam. The south IR looks fine. The space for vertical bumps is very limited in the north IR. More studies are needed.
• The present schedule is:
  • Complete beam-based alignment and temperature studies.
  • Set up luminosity running.
  • Start luminosity run end of this week.
  • Maintenance day 8.12.2004
  • Christmas break 23.-27.12.2004
• There have been quite a number of problems with normal conducting magnets in HERA.
  • All coils of the QS and QR magnets were already exchanged sometime ago.
  • Two BU magnet developed ground faults. Six BU coils were exchanged during the last shutdown. All had water leaks. It is possible that all other BU coils will fail sooner of later. During operation one ground fault can be tolerated by shifting the ground of the electrical circuit. Operation would not be possible in case of a second short. 24 further spare coils were therefore ordered. Delivery is scheduled to start in May 2005. 13 coils should be here by July, the rest until the end of 2005. Replacing one magnet would take about 10 days, without moving HERMES if necessary. Exchanging all magnets in one section would require about 4 weeks. So far there are no concrete plans which coils will be replaced first.
  • Two QC magnet have failed so far (1996 and 2001). 12 spares are available.
  • One GN magnet (vertically focusing proton septum quadruple with very high field) failed last month due to insufficient water cooling. It is not clear why the cooling was interrupted. No anomalies have been found so far. The failure occurred during tests at the maximum current of 1600A. The current of the power supply is now limited to 1400A. In case of another failure there is a spare set of coils, no complete magnet.
  • Ground faults have appeared at several QQ magnets (super-ferric proton correction quadrupoles). A possible cause for the shorts is radiation damage of the wiring boxes. Usually the shorts did not happen during luminosity operation, only when the magnets are run at higher current during the cycling procedure, Some of the defective quads are already connected to ground free power supplies. The remaining power supplies will be installed during the maintenance day 8.12.2004.
• From the machine point of view the preferred date of the 2005 shutdown is after the summer school vacation, i.e. starting middle of August. The annual interlock tests have to be done.

W.Zeuner: ZEUS Status

• The detector is ready for data taking. All components are operational except the STT. Two hours without beam are still needed every week for calorimeter calibration.
• Large background spikes have been observed, mainly at injection. The dark current of the radiation monitor has increased. HERA should not continue injecting if the efficiency is very poor.
• ZEUS is prepared to take data over New Year. Shifts will stop 23.12. and will continue 27.12.2004.
• The cooling of the STT is insufficient. Temperature changes in the safety volume, switching the STT on or off, lead to temporary leaks in the insulation vacuum of the solenoid, and were causing magnet discharges during the last running period. Removal of the STT for improving the cooling and tightening of the insulation vacuum flange is planned for the next shutdown.
  Using the present installation fixtures removal and re-installation of the STT would take 4 months, requiring opening of the vacuum system and removal of the GO and GG magnets. A new installation jig is in preparation, which allows to slide the FDET over the GO magnet. The main challenge will be to guarantee that the central beam pipe will not be damaged. A repair should be possible within 7 weeks. The plan is to be ready in May 2005 in case of an early shutdown.

D.Pitzl: H1 Status

• The backward and forward silicon detectors were removed during the shutdown. The central silicon detector is fully operational. The most radiation sensitive electronics is now the CIP readout. A new radiation monitor (scintillation counter) was installed. It has to be calibrated. Shifts started 29.11.2004. Flammable gases for tracking detectors will be ready early next week.
• The position of the GO magnet towards the IP is only known to about 5mm. The whole detector is about 5mm too far ring inwards. The GO tip could only be moved by 1mm last Friday until it hit the cryostat. In principle the H1 detector can be moved horizontally by 5mm. This will take a full day.
• The base pressure at NR6m is presently 10**-8 mbar. An improvement of 2 orders in needed in order to operate the tracking detectors. Beam currents must be limited to prevent radiation damage of the CIP electronics. Dedicated electron beam bake-out might accelerate the vacuum conditioning. It is not requested now.
• H1 will be operated over New Year if some reasonable data taking can be expected.
• The FST and BST repair plan aims for installation in early September 2005. The shutdown should start 1 week earlier and should last 6 weeks if there is no further repair work.
  Milestones of the FST/BST repair should be presented and reviewed regularly.

P.Di Nezza: HERMES Status

• Maintenance work was performed during the shutdown. The spectrometer and DAQ are fully operative. Shifts started yesterday. No dramatic background spikes have been observed during injection. The LPOL calorimeter has not yet been installed to prevent radiation damage. Installation will take a few hours.
  Christmas break: shifts will stop 20.12. and restart 29.12.2004.
• The preferred beginning of the 2005 shutdown is middle on July to mid August, total length of 6 weeks. An earlier shutdown will cut into the physics program.
• The low polarization compromises the HERMES physics program. A polarization task force is strongly required.
• Several glass dissociator tubes broke last year. The dissociator tube will now be replaced during every monthly maintenance day.

T.Behnke: Polarimeter Status

• There were no major modifications of the polarimeters during the shutdown. A short access is required of reinstall the LPOL calorimeter.
• The serious problem with the LPOL cavity during the last running period are hopefully solved. Shielding was installed. The electronics was move to a radiation safe location. All damaged components were repaired. The cavity was locked successfully during the shutdown. Commissioning the cavity with beam will take a few weeks.
• The design of the new radiation hard calorimeter is almost finished. A brief note on the design should be distributed. Fabrication of the calorimeter will start early next year.

Polarization "Task Force"

• Several members of the experiments (HERMES, ZEUS and polarimeters) are interested to get involved in improving polarization. A list of items, including simulation of polarization tuning, beam based alignment and depolarization, will be prepared. Ties Behnke will organize a meeting. Ferdi Willeke asked about the priorities and whether dedicated machine time should be spent on polarization tuning.

Schedule

• Complete beam-based alignment and temperature studies.
• Set up luminosity running.
• Start luminosity run end of this week.
  Luminosity operation until 20.12.2004
• Maintenance day 8.12.2004
• Machine studies 20.-23.12.2004
• Christmas break 23.-27.12.2004
• Resume luminosity operation 27.12.2004

Date of next meeting

Uwe Schneekloth