Minutes of HERA Meeting 25.10.2005

HERA

• HERA delivered 9.2pb-1 in 12 runs, a new record for the weekly luminosity. The maximum luminosity was 5.1 10^31 cm-2 s-1. The efficiency was 68%.
• There were some periods with high backgrounds, which required careful tuning.
• Another leak occurred in the rotator section NR a few meters away from the leak of last week. A bellows section had to be replaced.
• The current of the rotator magnets was scanned in the north and south. The results are as expected. There are no hints which could explain the asymmetry.

• The shutdown activities are unchanged, except for addition work on the vacuum system and an orbit stabilization feedback.
• The (28) bellows in the rotator sections will be modified in order to prevent any further leaks.
• A cavity window will be exchanged SR. New ion getter pumps will be installed in this RF section.
• An orbit stabilization feedback for the electron beam is in preparation. Some simple correction coils have to be installed.

ZEUS

• Unfortunately, the week was not so good. There were many chamber trips. Beam tuning at the beginning of the fill took a long time. In addition, there were trips with unknown reasons, some possibly due to synchrotron radiation background.
• In general, the proton lifetime was good (>200hrs), not causing any trigger problems.
• F.Willeke remarked that the background conditions become more critical with higher electron currents. Large drifts are observed, which require re-tuning of the machine. Sometimes the proton collimators do not reach the file values if the collimator rates are high. Yesterday the proton emittance was already somewhat poor at the beginning. The synchrotron radiation background was checked.

• The schedule has not changed. The installation tool for the FDET is ready. The deformation of the GO temporary support is as expected, when a horizontal force is applied.

H1

• Data taking was very good last week. The average HV efficiency was 83%.
• The integrated luminosity with HV on has now reached 100pb-1. The recent slope luminosity vs. day is very nice.

• There are no changes in the shutdown schedule.
• Flammable gases will be stopped Friday (11.11.) morning.
• After re-installation of the vertex detector, pumping down will be started before the Christmas break.

HERMES

• The background conditions did not improve since last week. The electron background was usually high at the beginning of the fill, the proton background increased during the run. This did not prevent HERMES from data taking, but required pre-scaling of some triggers.

• There are no major changes of the schedule.
• The polarized target will be removed. The size of the new beam pipe and collimators will not be changed.

Polarimeters

• The group is trying to get the cavity polarimeter running before the end of the data taking period. An access is needed to exchange some electronics. This will be done during the next calibration of the ZEUS calorimeter.
• No major activities are planned for the shutdown.

Schedule

• Continue luminosity operation. Try to increase electron current.
• Luminosity operation will stop Friday (11.11.) morning. HERA will continue with 3 days of machine studies.
  • Tests of the orbit stabilization feedback.
  • Check whether the aperture is sufficient for new optics. The idea is to reduce the size of the proton beam at the IP for a better match of the beams. The electron beam is presently smaller due to the pinch effect.
  • The solenoids and luminosity monitors should be on for the machine machine studies.

                Uwe Schneekloth