Minutes of HERA Meeting
10.12.2002
HERA
F.Willeke summarized HERA operation of last week, see transparencies . The operational efficiency was relatively poor.
- During the maintenance day last Tuesday the HERA vacuum system was opened
in the west straight section in order to replace the broken HERA B wire.
Beam operation started again on Wednesday.
- Machine studies were performed on Wednesday. The positron beta beat was reduced.
The positron injection efficiency could not be improved.
- Stable proton beam was delivered to HERA B, target magnet off, for alignment
studies.
- High proton current, 106 mA, were injected once as a test and for conditioning
of the proton vacuum system.
- Luminosity operation was delayed due to several problems. A new transmitter
tube was installed in LINAC III, which had insufficient water cooling and
had to be replaced again. In addition, there were failures of the proton
208MHz RF system, the electron dipole power supply and the cryo system.
- There was an emergency access for HERMES on Friday.
- Three luminosity fills were delivered on the weekend.
- Last night there was a severe power failure. A safety switch at the 10kV
power station in the north hall was at the maximum current. HERA is still
recovering from the power outage.
H1
- The background conditions have improved considerably since end of
November, see plots of: chamber currents , coefficients and projected chamber currents .
The ratio of the pressures at the IP 2002/2000 improved from 8 - 10 to
2.5, see plot , after 12GeV bake-out (21./22.11.2002), cooling GO/GG beam pipes
down from 120 to 55K (26.11.) and regeneration of NEG pumps last week.
Heating of the central beam pipe during injection is reduced due to
faster positron injection.
- H1 would like to increase the proton current to 40mA.
ZEUS
- In general, background conditions were very good on the weekend. The
maximum beam currents are now Ie*Ip = 1000mA**2.
Saturday morning the background rate was high. It decreased when the
HERA B target rate was reduced.
- Electronics had to be turned off after the power failure last night.
The emergency cooling could not be turned on as the main pumps were still
on.
HERA B
- The broken tungsten wire was replaced last Tuesday. The target was
re-calibrated. The carbon wire showed some strange behavior, probably
due to the venting of the vacuum system.
- The alignment runs with target magnet off were done until the
beam was lost. The statistics is barely sufficient.
- The uptime of the target was only 24%.
HERMES
- Work was done on the target polarimeter during the maintenance day
and the special access on Friday (repair of a pump and replacement
of detector).
- Good quality data were taken on the weekend.
- The electronics had to be turned off after the power failure.
- Would like higher positron beam current.
Schedule
- Today: machine studies (positron injection)
- Tomorrow: background studies ("operating HERA as molecular mass
spectrometer", bunch lengthening at 12 GeV).
- Tomorrow evening/night: continue luminosity operation.
- Perform positron tilt scans for acceptance of luminosity monitors
at the end of a lumi fill.
- No machine studies next Tuesday.
- Starting next Thursday: machine studies.
- Sunday, 22.12.2002, afternoon: start warmup of GO/GG magnets.
- ZEUS is the coordinating experiments.
Uwe Schneekloth