Minutes of HERA/Experiment Coordination Meeting  11.01.2005

Agenda

• Brief status reports HERA and experiments
  including
  • Polarization working group
  • LPOL cavity and calorimeter
• Shutdown plans
  Status and milestones of shutdown preparation
  • Spare magnet situation
  • H1 FST/BST repair
  • ZEUS STT repair
  • HERMES Recoil detector
• Schedule and operation

• Date of next meeting
• AoB

Minutes:

F.Willeke: HERA Status

• In December HERA started luminosity operation with 60 bunches. By the end of December the vacuum conditions were sufficiently good to increase the number of bunches to 120.
• The startup after the Christmas break was a bit slow due to several technical problems. Operational statistics for 2005 so far: 45% faults, 26% luminosity operation.
• Operations improved last week. It is now possible to inject 80mA protons and about 34mA electrons. 82mA, record proton current per bunch, was accelerated to 920GeV. This would correspond to 123mA with 180 bunches. The beam currents were reduced somewhat due to the background conditions at H1 (last fill 65mA proton, 26mA electron current). The integrated luminosity of last week was 3.7pb-1. This is better than the average in 2004, in spite of the maintenance day on Wednesday.
• Last week the vacuum in the north IR was not improving anymore. The NEG pumps were therefore regenerated on Wednesday.
• Background spikes appeared again on the weekend. Two magnet power supplies are under suspicion: GA08 N30 causing large spikes and QQ24 OR229 rather frequent spikes. The QQ24 chopper will now be exchanged. The current leads of the magnet will be checked. In general, fine tuning of the machine is necessary to improving the background conditions. The present backgrounds might be related to the very high specific luminosity and small proton emittance.
• Progress on polarization tuning has been slow, maximum polarization around 30%. The usual procedures have been used, energy scan and harmonic bumps. Polarization was drifting during recent fills. It is not clear what is changing. The plan is to repeat tune and energy scans in the second half of a fill.
• So far there no difference in the lifetime between electrons and positrons.
• The proposal is to continue luminosity operation with 120 bunches, increasing the electron current as possible, until the background conditions have improved. Increase to 180 bunches in February.
• There was no news on the production status of the spare BU coils. This should be checked.

W.Zeuner: ZEUS Status

• In general, ZEUS is running fine. The detector has been operational since 27.12. During the holidays the delivered integrated luminosity was 700nb-1, 500nb-1 were taken. Recently, there were very nice luminosity fills. The proton background tuning is still slow.
• The general level of proton background is fine, although higher and more fluctuating that in Aug. 2004. The electron background is fine. Sometimes there is some direct synchrotron radiation which needs to be tuned away.
• ZEUS proposes to increase the electron current to the maximum H1 can tolerate. If necessary HERA should go to 180 bunches.
• Recently there were two major power cuts in the hall. The first one was due to unannounced maintenance of the smoke detection system. The second was caused by a fake gas and evacuation alarm. It always takes several hours to recover from power cuts. In addition several electronics components break. The situation was discussed with the technical emergency group. Tests of the safety system are only allowed if the technical coordinator of the experiment and HERA is informed in advance.
• The design of the FDET removal fixture is well advanced. The plan is to remove the FDET, in order to tighten the seal of the solenoid insulation vacuum and to improve the cooling, without removing the GO and GG magnets. Two engineers from Oxford University will act as external reviewers. The HERA coordinator will also be involved in the review. The final decision, whether the FDET will be removed during the shutdown, will be taken in mid June. The length of the shutdown would be 7 weeks.

D.Pitzl: H1 Status

• The detector is ready for data taking with all components operational. The background is improving. The proton gas background decreased by a factor 4.5 after repairing the leaks NR6 and NL14 and activation of the NEG pumps in December. Another factor 1.5 was gained after NEG regeneration last week. During the last fill the BToF rate was below 50 kHz, which is safe for HV operation. A rate of 100 kHz is the limit for long term operation without radiation damage of the CIP electronics.
• The background is dominated by proton gas interactions. Safe operation is possible at IexIp = 20x60mA**2 under quiet beam conditions. A factor 4 improvement is needed for safe operation at design currents. The present data is unusable for many physics analysis. NEG pumps should be regenerated again at the next occasion. H1 would like to stay with 120 bunches.
• Regular proton spikes make chamber operation even more difficult. Spikes seem to be correlated with the GA08 magnet in the north and QQ24 magnet in the east. The large proton spikes must be cured. Otherwise H1 cannot take physics data.
• The horizontal and vertical vertex positions were shown. After moving the detector by 7mm in early December the distance of C5a and C5b to the electron beam is now the same as to the positron beam in the previous running period. The interaction point is 7mm too high in H1. During the last shutdown an asymmetric keyhole C5b was installed to compensate for this.
• The FST repair and BST modifications are proceeding as planned. The goal is to be ready by June (FST) and August (BST). A milestone will be the test of the radiation hard APC chips end of February. The preferred date (end of August) and length (6 weeks) of the shutdown is unchanged.

P.Di Nezza: HERMES Status

• Data taking restarted 29.12.04. The spectrometer is fully operative. Maintenance work was performed during the access last week. The LPol calorimeter was reinstalled.
• The target had several problems: leak in the oxygen pipe, possible leak in the cooling water system and broken RF generator for the ABS. Everything was repaired. The quartz glass tube is more reliable than the pitex tube. It will be replaced at every monthly access. End of fill running, presently starting at 10mA, is very successful.
• The electron background conditions are excellent. High background, up to 2MHz spikes, occurs during proton injection.
• HERMES requests high electron currents, increasing the number of bunches to 180. More efforts, i.e. dedicated studies, should be spent on polarization.
• The preparations for installation of the recoil detector are in progress. Milestones for the next 2 months were presented. The detector should be ready for installation 1.04.05. The preferred start of the shutdown remains middle of August. The date should be fixed not later then June.
• Matthias Hartig is the new Run Coordinator.

T.Behnke: Polarization working group

• The TPOL and LPOL are running stably. The measurements are in agreement. A new TPOL display is available, showing the trend of the polarization.
• There was a communication problem between TPOL and HERA. The netmex server was fixed. The ORACLE data base can be updated.
• The LPOL calorimeter was installed last week. It was re-commissioned without problems.
• The temperature stabilization of the LPOL cavity was installed and commissioned. The system is working properly, some further tuning is needed.
• The design of the new LPOL calorimeter is making progress. The geometry was optimized. A potential problem of the design is the low light yield. The goal is to finish the design as soon as possible and start with the production.
  Presently, there is no schedule for the fabrication of the new calorimeter and the commissioning of the cavity.
• A discussion on optimizing polarization will take place end of January. The requirements and constraints from the experiments should be presented.

Schedule

• For the time being continue luminosity operation with 120 bunches. Steady increase of electron current.
• Increasing to 180 bunches will be decided in the weekly HERA meeting.

• The tentative date for the start of the shutdown is second half of August, length about 7 weeks.

• HERMES is the coordinating experiment.

Date of next meeting

Uwe Schneekloth