Minutes of HERA/Experiment Coordination Meeting  3.05.2005

Agenda

• Brief status reports, HERA and experiments
• Shutdown
  • Status and milestones of shutdown preparation
  • Shutdown dates
• Schedule and operation
  • Change of spin rotator position
  • Discussion of mirror tunes mid May (17. or 18.05.)

• Date of next meeting
• AoB

Minutes:

F.Willeke: HERA Status

• The main proton background problem is solved for the time being. There are no major operational or technical problems.
• There was not much progress in increasing the beam currents in April. The electron intensity was reduced after the BU break. Proton currents above 100mA have been achieved with 150 bunches. Presently, there are no technical limitations for the electron current.
• The efficiency has slightly increased (April 54% without BU repair). In spite of the one week break, the integrated luminosity in April (23pb-1) was close to the March value. The overall efficiency for this running period is 43%.
  A new record luminosity of 4.77 10**31 cm-2 s-1 was achieved. The total integrated luminosity is 79pb-1. The slope is significantly steeper than last year.

• The emphasis is on increasing the electron current and consolidating performance. The number of bunches should be increased once Ie > 40mA is achieved regularly.
• Some machine shifts are planned after the maintenance day in June.
• The rotators can be switched any time, although switching during a maintenance day is preferred.
• Mirror tunes can be tried out any time. It would take about one week to get back to good running conditions.
• Mirror tunes will be discussed in the HERA meeting 17.05.2005.

• The machine prefers to start the HERA shutdown 14.11.2005, at the time as the pre-accelerators. Beam operation would start again last week of January, luminosity operation 2nd week of February.
• Delaying the shutdown to November allows to refurbish all remaining BU magnets with new coils. In case another BU coil fails before the shutdown, it can be repaired within one week, even in case of SL/OR.
  There is no news from the BU monitoring. BU magnets SL are presently monitored.
• After this shutdown no further interlock tests have to be performed until the end of HERA operation.

• The refurbishing of GN magnets is parked for the time being.
• Cables for the temperature monitors at the IRs are suffering from radiation damage and need to be replaced.
• The monitoring of magnet currents, part of the protection against uncontrolled proton beam losses, is tested and will be activated.
• The redundancy of the cryo system is being improved.
• The longitudinal proton feedback cavity is built. Work is going on on the control system. The cavity will be installed during the shutdown.
• The electron orbit jumps by about 200mum. Orbit stabilization is ready to be implemented.
• Beam based alignment (electron beam) in the arcs is prepared.

M.Vogt: Polarization

• Polarization has not fully recovered after the BU-repair break. This is mainly due to substantial orbit changes, which require new harmonic bump settings. All first harmonic bumps were scanned again. 2nd order scans are partly done.
• Before the BU repair, periodic proton spikes partially masked other background problems. Background tuning is still necessary, leaving little time for polarization tuning.
• Polarization favors low vertical electron tunes. There was a suspicion that low e-tunes increase the proton background. No correlation between the horizontal or vertical e-tunes and the H1 or ZEUS chamber currents was found.
• The next step is to continue running with low e-tunes. For large proton currents the expected polarization is 40-43% (without mirror tunes).
• Mirror tunes will be discussed in the HERA meeting 17.06.2005. The spin rotators will be flipped during the next maintenance day.

W.Zeuner: ZEUS Status

• Congratulations to the HERA crew. Very good beam conditions can be provided since the BU coils were replaced. The delivered luminosity is 71pb-1 (66pb-1) without (with) subtracting luminosity tuning. The luminosity on tape (with all HV on) is 48pb-1. HERA delivered 1pb-1/day a few times. On Friday 1pb-1 was written to tape.
• The detector is in good shape. All components are running. The data taking efficiency is above 80%.
• For good fills the background conditions are far below the predictions, a factor of 2 for the proton background. Conditions are still acceptable if the background is similar to the predictions from the beam currents. Background conditions were bad for some fills causing high dead-time, although the CTD HV was not tripping.
  The background predictions will be updated.
  Updating (reducing) the background predictions in the background display caused some criticism. The dependence of the dead-time on the background conditions and the new parameterization should be presented in the next HERA meeting.
• The next step should be to increase luminosity by increasing the beam currents and continue polarization tuning.

• Construction of the STT removal tool is almost finished. A test setup will start in a few days.
• There are no objections against start the shutdown in autumn. The shutdown should not start later than 14.11.2005. Starting one or two weeks earlier is preferable. A preliminary schedule for the ZEUS activities exists. It safely fits into the planning of HERA.

D.Pitzl: H1 Status

• HERA has delivered 78pb-1 so far. The H1 DAQ efficiency is 95%. 67.8pb-1 are on tape. The average delivered luminosity is 0.5pb-1/day, the maximum was 1.5pb-1/day.
  The 2005 luminosity production is well ahead of 2004. Congratulations to the HERA crew for successful e- p operation.
  The collected luminosity with full HV is slightly ahead of 2004.
• The HV efficiency improved significantly after the BU repair, exceeding 80% for long fills. Short (mostly electron) spikes cause chamber trips. The source is unknown.
  Background conditions usually improve if the horizontal angle at the IP is changed. This reduces the acceptance of the luminosity monitor.
• The chamber current still scales with Ie x Ip. The background is dominated by proton gas background. Safe operation at Ie x Ip = 3500mA**2 is possible. Operation at 5000mA**2 should be possible.
• There has been a steady reduction of the proton background over the last 3 months, in particular after NEG pump regenerations. Best values of June 2004 have been achieved.

• The FST repair and BST modification are making good progress. The goal is to be ready by end of August.
• System tests will possible since the shutdown is moved to November.

• The electron current should be increased towards 50mA. Switch to 180 bunches as soon as the bunch current limit is reached.
• Polarization tuning should be done parasitically as long as possible. The helicity should be changed in the near future.
• GO/GG warm-up and NEG regenerations are expected to continue improving the background conditions.
• Starting the shutdown in November is supported. Vacuum conditioning can start before Christmas if the shutdown starts 7.11.2005.

M.Hartig: HERMES Status

• This year HERMES has collected 1.7 10**6 polarized DIS events. The data taking efficiency is 98%. With the present polarization 20 10**6 DIS events would be required to achieved the HERA II goal (7 10**6 DIS events with 50% polarization).
• The target alternates between Xe and D for unpolarized running. Kr will be used.
• The detector is performing well. The target recovered quickly. The target polarization (>82%) and alpha value (90%) are higher than before, but not as good as expected.
• A cooling problem of the lambda wheels is being investigated. HERMES may request to advance the June maintenance day by 1 or 2 weeks.
• Polarization should be improved. Try to achieve >40% after 2 hours.
• HERA should switch to 180 bunches to reduce the beam-beam effect to increase polarization.
  F.Willeke pointed out that going to 180 bunches will not improve polarization. Increasing the number of bunches makes only sense if the electron current can be increased as well.

• The test installation of the recoil detector is completed. Components are being commissioned. The aim for the next weeks is cosmics data taking with all components.
• Moving HERMES into service and back into position will take 2 weeks.
• Installation of the recoil detector will take 8 weeks
• A detailed schedule will be ready in a few weeks.

T.Behnke: Polarimeters

• The TPOL and LPOL are running stably without major problems. The overall efficiency of both polarimeters is about 97%.
  There was a small accident with the Si detector of the TPOL. It was repaired during the last access.
  The LPOL/TPOL ratio is close to one.
• The LPOL cavity is operational. The energy spectrum is in reasonable agreement with the expectation. Problems with locking in the presence of beam were traced to 50Hz pickup noise. A different feedback diode is used.
  More data will be taken to improve the understanding of the spectra.
  The new calorimeter is in construction, materials have arrived, parts are being fabricated. The goal is to install the calorimeter this summer.
• The depolarization was tested a few weeks ago. The test has to be repeated. The scan was done too fast.

Schedule

• The HERA shutdown will start 14.11.2005
• Beam operation will start again last week of January 2006, luminosity operation 2nd week of February.

• The rotator positions will be changed during the next maintenance day.

• ZEUS is the coordinating experiment.

Uwe Schneekloth