HERA meeting 16.7.2002

HERA:

• 5 day shutdown Wed-Sun 10.-14.7. for vacuum at North IP
  Turbopumps and mass spectrometers installed at NR26 and NL26m.
• North GO and GG warmed up completely on Wed evening. Mass spectrum shows CH4 and CH3 as main peaks, and the full Methane chain of CH2 down to CH1. Also the Ethane chain from C2H6 down to C2 is seen. Propane chain (C3Hx) with a boiling point of 231K was seen after 2-3h of warmning up. Also a small Ar and Ar++ peak at mass 40 and 20 was seen.
• Leak search with He for all flanges within +-26m, including the H1 central beam pipe.
  Leak at flange NL 11m between GM and BO found. Closed by tightening flange screws.
  Getter pump NL10.8m now active.
• Fri evening: heating of getter pumps
• Sat: base pressure still unsatisfactory: several 10^-8 mbar.
  TSPs fired, NEGs regenerated.
  Decide to heat pumps at higher temperature over night.
• Sun 14.7.:
  Pump down, fire TSPs, start GO/GG cool down at 19:30, pressure steadily falling.
• Sun night proton beam:
  52 MHz RF system failed, managed to ramp 13 mA p, badly de-bunched.
• Mon 15.7.:
  Repair of the 52 MHz system, and at preaccelerators.
  Machine studies postponed: possible source of e optic error found in rotator magnets.
• Tue 16.7.:
  ep collisions.

H1:

• Vacuum: base pressure is few to several 10^-9 mbar for 7 pumps NL10 to NR10, at least 4 pumps show improvement.
• Proton run Sun night:
  C5 collimators not seen in vertex distribution from tracks.
  Possible reason: electron machine is off.
• GO movement:
  excursions of up to 7 mm during cool down, measured between end-can and GI magnet bridge.
  Movement completely reversed (within 0.2mm) after closing H1, cooldown, and ramping up the solenoid field.

ZEUS:

• Reapir work on calorimeter during shutdown.
• Partial lead shield around beam pipe in C5a region under preperation.
  May need more than 1 day to install.
• Observe large pressure peaks (several 10^-7 mbar) during e+ injection.
  Dedicated bake out required. Postponed.
• Radiation monitor triggered two e+ beam dumps on Monday.

Hermes:

• Calibration done in shutdown.

HERA-B:

• Suffered from broken 52 MHz system on Sunday night. Data taking not possible.
• Had 20 shifts with beam since mid May.
  Min. bias data taking established.
  Ecal pretrigger commissioning underway.
  Work on online FLT started.
• Need 30 more shifts until 1.9. to commission trigger and establish performance: 5 shifts with beam per week.

Plans:

• Regular ep operation for all 4 experiments, not pushing beam currents.
• Postpone bake out until vacuum in North has settled.
• The HERA-B request requires higher duty cycle and operational efficiency, which is in conflict with dedicated study shifts.
• Compromise: do studies 'parasitically' in ep fills:
  Protons-only with e machine off at the end of the next fill.
  Add a single isolated e+ bunch in the kicker gap for timing studies.
  Do e+ beam steering around ZEUS at the end of a fill.
  Do single-beam studies during machine shifts on Monday: long e+ fill.
• H1 is coordinating experiment for the week.
• Next meeting: Monday 22.7. at 11:00 in the usual Bldg. 30b Sem. room.