Minutes of HERA/Experiments Coordination Meeting  17.12.2002

Agenda

• Short status reports
• Review of schedule
• Preparation of shutdown

• Date of next meeting
• AoB

Minutes:

HERA, F.Willeke transparency

• HERA delivered only 3 luminosity fills last week. Increasing the proton current to 40mA did not cause any problems.
• Machine and background studies were performed on Tuesday and Wednesday. The proton files had to be optimized on the weekend. 
• Yesterday the positron beam was dumped three times because of radiation alarms. The high background was due to problems with the automatic orbit steering program. The data transfer was not working properly.
• The positron injection efficiency is still poor.
  

• In December the running efficiency (27% luminosity operation) was slightly worse than in November (32% luminosity operation).
  

• The proposed schedule was presented, see transparencies: luminosity operation until 18.12.2002, machine studies until 22.12.2002, break from 23.12. to 3.01.2003.  It was proposed not to open the vacuum system in the north IP during the break. 

• Continuous running without interruption for machine or background studies was proposed for January.  

• Modification of the GA positron vacuum chamber SL(NL)27-32m is being studied. Holes would have to be cut into the magnet yoke. Preliminary calculations show that the magnetic field would still be acceptable. Modification of the GA magnet SL would require moving HERMES out of the beam position. 
• The fixed synchrotron radiation collimators at  NL/SL66 will be replaced by a movable collimator.
  

H1, D.Pitzl transparencies 1, 2 , 3 , 4 , 5

• The total delivered integrated luminosity since 30.10.2002 is 3.6 pb-1. The collected luminosity is 3.2pb-1 (H1 active), 1.4pb-1 (HV on).  The detector is performing well. 
• The highest current with detector turned on were Ip * Ie = 910mA**2 with good background conditions. 
• Over the last 210 days the vacuum pressure at the IP has decreased by a factor of 10. A significant improvement was observed the last few weeks. The pressure is presently a factor of 2 higher than in 2000. 
• The proposed beam currents are Ip > 40mA, Ie > 28mA.,. 
• The VFPS bypass passed the 22bar pressure test. It will be delivered to DESY today. 
• Components for the repair of the inner tracking detector will be ready for the shutdown
• Small items, e.g. modified  collimator and integrated ion getter pump will be ready the shutdown. Other items (modified bellows) won't be ready.
  

ZEUS, W.Zeuner transparencies

• Since Oct. 30 the delivered luminosity is 2.3pb-1. 1.4pb-1 has been collected on tape. 
• The radiation monitor of the MVD has now accumulated a dose of 100kRad.  Radiation damage of the detector will occur at 300kRad.  Some high currents in the MVD diodes have been seen during normal operation. 
• The ratio of the measured to expected CTD chamber current is now similar to the value in September. Last month the pressure at the IP and the background conditions was relatively high. Recently it improved by a factor of 2. The pressure at the IP, measure using the lumi e gas rate, is now a factor of 4 higher than in 2000. The highest beam currents with CTD HV on were Ip * Ie = 1000 mA**2. Chamber currents were well below the trip threshold. 
• There is progress on the design of the modified collimators. 
• It is planned to repair the forward tracker (STT) during the shutdown. The final recommendations of the review are not yet available. 
• Improving the upstream vacuum, in particular SL27-32 (GA magnet), is very desirable for reducing the off-momentum positron background.  
  

HERMES, E.Aschenauer transparencies

• HERMES has taken 534000 DIS events. Assuming the present rate, the expected number of DIS events at the end of the running period is 0.9 10**6 events, before data quality cuts. 1.4 10**6 events are needed for the physics program. Recently the average positron current decreased to 20 - 25mA. The current should be increase to 30 - 35 mA. HERMES would ask for non-colliding beam operation if the higher positron currents cannot be achieved. 

• One high  positron current (> 30mA) is needed before the Christmas break to study depolarization resonances. 
• The detector interlock will  remain set during the Christmas break.
• The shutdown activities have not changed.
  

HERA B,  J.Spengler transparencies

• Recently, the target has only been in operation for 30% of the time, mainly due to technical problems of HERA and  inefficient positron injection. With a HERA B efficiency of 71%,  only 21% of the time has been physics running. The hope was 37%. The present data sample of 150000 J/Psi events is 43% of the expected data sample was collected in 67% of the allocated beam time. The goal is to collect 300000 J/Psis. 
• The HERA B efficiency is slightly lower than expected. A tungsten wire broke on 25.11.2002. It was replaced during the last access. Last week there was a power outage due to a false alarm of the smoke detection system. Some beam time was lost due to improper setting of the proton collimators. Yesterday there was a period of 10 hours with protons only and several positron injections. The detector could not be turned on.  
• Two requests were made: 
• Dump the positron beam at 4 mA instead of 8 mA. This would increase the increase target operation from 30 to 36%.
• Extend the luminosity period beyond 26.01.2003  (by about 4 week).

Schedule

• Continue luminosity operation until Wednesday
• Machine studies Thursday to Sunday afternoon.
• Sunday evening, start warming up GO/GG magnets in north and south IPs. The vacuum system of the north IP will not be vented to install a residual mass spectrometer.  
• 2./3.01.2003: Startup accelerators, continue luminosity operation without weekly machine and background studies. A few days of background studies are planned starting 20.01.2003

• The regular monthly maintenance was moved from Tuesday to the first Thursday of the month. The January access, 09.01.2003, is likely to be canceled There is no need from the experiments for the access. It still has to be checked whether is it necessary for the machine..

• H1 is the coordinating experiment.

Date of next meeting

Uwe Schneekloth