HERA meeting 8.10.2002

HERA:

• Lumi studies:
  • 14 lumi fills with varying bunch intensities
  • Spec. lumi is above design for low bunch currents, slightly below design at high bunch currents (250 uA e+, 500 uA p).
  • At low intensities the calculated lumi using the measured emittance and the optics is higher than the measured lumi, while the lumi determined from a lumi scan is close to the measured.
• Tunes: reached 'step 4' with lumi optics for H1 with good lifetime.
  Resonances are strong and wide, working space is tight.
• Next: collisions in N and S with polarization tunes.

ZEUS:

• Frequently high backgrounds at e+ injection
• Highest dose on MVD diodes is now 77 krad, above the yearly budget of 60 krad.

H1:

• Also suffers from losses at e+ injection.
• Pile-up corrections in the lumi measurement have been discussed, but were never active.
  Two effects occur at high counting rates:
  1. Loss, if two high energy photons occur in one bunch crossing. A correction for this was active last week.
  2. Gain, if two low energy photons add up and pass the threshold.
  The details depend on the exact energy spectrum and detector response. For the old lumi detector the effects cancelled for a threshold at 7 GeV. The current threshold is 5 GeV, but the resolution and low energy cutoff are different. Studies are ongoing.

Polarimeters:

• TPOL commissioned last Sat: OK and ready. Observed several jumps in e+ timing system.
• LPOL saw no signal last Sat, probably due to a timing problem following the power cut in East on Fri. Now solved, studies with beam and laser ongoing.
• Need stable and reproducible beam position at LPOL IP.

Hermes:

• Requested 1 hour access for repair after last Friday's emergency power off following cooling water supply interuption.

HERA-B:

• Had 2 efficient long proton fills.
• Requested 2 15-hour fills for this week.
• Requested 1 hour access for power supply replacement.

MKS, MVA:

• Last Tuesday (1.10.): tested heat load in GO,GG superconducting magnets with shield temperature at 110 K instead 55 K.
• Plan: increase shield temp in H1 and ZEUS GO,GG to 110 K, run like this for at least 1 week, for vacuum improvement.
• Fire TSPs around N and S IP.

Plans:

• Polarization studies, H1 and ZEUS solenoids off
  1. Establish polarization for Hermes.
  2. Set up North spin rotators (decided by fair coin toss), needs a few hours access.
  3. Set up injection and ramp files with North rotators.
  4. Get polarization with North rotators but solenoids still off.
  
  e+ current 15 to 25 mA in 180 bunches.
• Luminosity studies at high bunch currents: next week.

Schedule:

Fore reference, the current version is this:

------------------------------------------------------------------------
Tue October 8            
S    HERA-B proton beam
N    HERA-B proton beam
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Wed October  9            
F    Warm Up GG pipe to 110K (1h), Polarization Studies
S    Polarization Studies
N    Polarization Studies
------------------------------------------------------------------------
Thu October 10
F    Polarization Studies
S    Polarization Studies
N    Polarization Studies
------------------------------------------------------------------------
Fri October 11
F    turn-on Rotator North,  HERA-B proton run
S    HERA-B proton beam
N    HERA-B proton beam, Machine set up e with rotator hera North
------------------------------------------------------------------------
Sat October 12
F    Machine set up e with rotator hera North& East
S    Machine set up e with rotator hera North& East
N    Machine set up e with rotator hera North& East
------------------------------------------------------------------------
Sun October 13
F    Machine set up e with rotator hera North& East
S    Machine set up e with rotator hera North& East
N    Machine set up e with rotator hera North& East
------------------------------------------------------------------------
Mon October 14
F    polarization studies  with rotators  North +East
S    polarization studies  with rotators  North +East
N    polarization studies  with rotators  North +East
------------------------------------------------------------------------
Tue October 15
F    polarization studies  with rotators  North +East
S    polarization studies  with rotators  North +East
N    polarization studies  with rotators  North +East
------------------------------------------------------------------------