Minutes of the weekly HERA Meeting
8.6.2004
- HERA last week (F. Willeke):
- Thu 3.6.04 was maintenance day.
- 3 shifts of machine studies: improve injection efficiency,
test p orbit monitoring.
- Up to 115 mA of protons could be filled, a new record.
- The proton coasting beam problem reappeared with full force
during the weekend, leading twice to completely unbunched beams.
- The 'phaseloop II' RF phase stabilization feedback system
is known to have problems, but cannot be responsible for all
instabilities. Work on this system continues.
- Proton HF hardware was checked thoroughly on Mon, and a bad
cable connection was found and fixed at 208 MHz station A.
- Since then, the RF signal from the p cavity is clean for the
first time in 3 months.
- The lumi fill on tue morning had small coasting beam (<1mA),
good background conditions, and high specific lumi (1.5).
- ZEUS (R. Carlin):
- The lumi fill Sat night 5./6.6. had abnormally high CTD
currents, above p and e background expectation, possibly due
to SynRad. Beam steering did not help. The problem did not
reappear.
- A 'spikiness' signal is now derived from 2-sec RMS of the
8m scintillator.
- Old coasting beam created spiky background, with a delay
of about 1 hour.
- The solenoid ramped down on Mon due to a failure in the
main power supply. Fixed, under investigation.
- IT switched off one subnet for ZEUS experiment control on Tue
morning - no data taking possible for 2 hours.
- H1 (C. Diaconu, D. Pitzl):
- Efficient data taking in the week before the maintenance day,
Lumi with HV on at 85%, similar to 2000, even above Ie = 40 mA.
- FPS 81m vertical station: blocked moving system cured on
maintenance day.
- VFPS 220m: one station operational, low light reception on a
clock signal at the other. Under investigation.
- MKK switched off the cooling water turbo pump for Hall North
at the maintenance day. The electronics trailer had to be
switched off, disrupting the test program.
- Forward Silicon Tracker: 60% of the 144 modules are not
operational anymore, since 17.5.04. The losses are continuing.
- Damage of the frontend CMOS chips cannot be excluded.
- Repair takes several months, requires 2 extended shutdowns
for removal and insertion. Schedule is being worked out.
- A separate meeting is required to agree on the shutdown plans.
- Hermes:
- Good running last week.
- ABS dissociator tube exchanged last week: quartz glass tube,
hopefully more robust.
- Lambda wheel electronics defect repaired.
- LPOL:
- The Hermes LPOL is not operational since the maintenance day.
- The signal output from the crystal calorimeter is low.
- Laser and beam steering have been checked with the scintillator
sandwich calorimeter: OK.
- Investigation continues.
- TPOL is operational.
- Run duration:
- F. Willeke reported on his calculation of the optimal
run length: dump at 18 mA.
This uses the average filling times and beam intensities from
the last 20 lumi runs and takes the increasing positron
lifetime and the proton emittance growth into accout.
One hour of lumi tuning and HV ramping was at not counted
at the beginniong of each fill.
- A decision on the dump current was postponed until we are
back at stable conditions. Higher beam currents and shorter
tuning times would lead to higher dump currents.
- Hermes is coordinating experiment.
Daniel Pitzl
Last modified: Tue Jun 8 14:45:06 MEST 2004