HERA meeting 9.7.2002

HERA:

• Machine studies Tue 2.7.:
  Measured influence of stray field from p-magnets on the e+ beam. To be analyzed.
  Measured proton beta function at several places around the ring, at 40 and 920 GeV. Deviations of 20-40% from theory seen in some places.
• Maintenance day Wed 3.7.:
  NEG pumps around the North IP activated/regenerated. No improvement in pressure seen.
  Leak search at flanges North right, negative.
  Quench protection for vertical correction coils in GO and GG are bypassed for currents below +-10A.
  Polarities of 10-poles and 12-poles checke: OK.
• Thu 3.7.:
  stable e+ beam with reduced mini-beta at IPs for SynRad studies in ZEUS with every 7th bunch filled.
  7.7 mA stable p-beam for beam-gas studies
  Later added some e+ at 12 GeV to increase vacuum pressure
  Finally ramped to 27.5 GeV
  Timing analysis in progress, aim for task force meeting Fri 12.7. 13:00.
• Fri 4.7.:
  2 bake-out fills with up to 24 mA at 12 GeV, integrated current about 0.07 Ah.
• Weekend:
  ep collisions with 25-30 mA p, 12-16 mA e+.
  Smooth operation on Sat and Sun.
• Mon 8.7. machine studies:
  Measurement of e+ chromaticity and x-y coupling.
  e+ orbit response matrix measured, beta function phase determined, some quads adjusted.
  Temperature strips glued to beam pipe in GI magnets North Right, to be evaluated Wednesday.
  Monday night: coupling studies with and without H1, ZEUS solenoid fields.
• Tue 9.7.:
  ep collisions.

ZEUS:

• CTD timing analysis underway.
• p-beam-gas events on C5 collimator mostly occur above the beam line. H1 sees a similar up-down asymmetry. Are both detectors low w.r.t. the beam line?
• The p-beam could be lowered by only 0.5 mm in the stable proton run, too little to see an effect on the collimator events.
• Outstanding request: long e+ fill to study chamber current and trigger rates vs beam current. Postponed until xy coupling is settled.

H1:

• Took data in 3 lumi fills over the weekend: 90 nb^-1 delivered.
  Chambers on for 21h total.
  CJCs on with highest e+ current so far: 11.7 mA on Sunday. Chamber currents 130 uA in CJC2, 160 uA in CJC1 just tolerable. Proton current was 30.7 mA.
  Some e+ beam steering and collimator closing is required in each fill to reduce the chamber currents, until all SynRad passes through the IP region.

Hermes:

• Nice data taking
  p-background much reduced compared to last week, scalable to 100 mA.
  More e+ current desired.

HERA-B:

• 28h of target operation in 3 lumi fills over the weekend.
  Backgrounds acceptable.
  Background from e+ injection and e+ dumps reduced compared to last week.
• Request: 1 shift without HERA-B magnet, for beam alignment and vertex detector alignment. Not scheduled yet.

Plans:

• Vacuum problem in the North:
  Activation of pumps last Wed showed no improvement.
  Argon peak was seen in a mass spectrum taken last Wed, and also after the flange leak on June 2. Getter pumps may be saturated with Ar.
  Another source might be the cold beam pipe in GO and GG.
• Shutdown:
  Start Wed 10.7. morning, MVA installs pump stands and mass spectrometers at 26m North left and right.
  Warm up full GO and GG magnets to room temperature, takes up to 24h.
  Thu: integral leak search for O2, specific leak checks with He for H1 central beam pipe.
  Decide upon results: locate leak, or exchange getter pumps, or cool down again.
  Earliest beam operation: Thu evening.
• Repair work on ZEUS calorimeter:
  Need 2 days with scaffolding in Hall South.
• Planing for the weekend: meet Fri 12.7. at 15:00 in BKR.