Minutes of HERA Meeting
03.09.2002
HERA
Summary of last week:
- Restarting of HERA after the access on Tuesday was delayed due to the
power outage. The positron injection efficiency was only 10%. An aperture
limitation, bellows at SL57, was found Thursday night after systematic beam
steering. The electron machine vacuum section including the interaction region
had to be vented. The aperture limitation had been caused by RF strings, see
picture, which were probably hit by synchrotron radiation generated in the
BI magnet.
The bellows was replaced. In addition, the valve SL27 was exchanged.
- Proton beam operation started again on Saturday.
- Over the weekend there were a few luminosity fills with positron currents of
up to 8mA, still limited by the poor vacuum SL.
- The new automatic positron beam steering program was tested successfully.
- A redesign of the bellows is being considered (protect of RF strings). It will
be studied whether the vertical BI bump is still necessary.
ZEUS
- The access last Tuesday was successful.
- The positron beam gas background is very high after venting the upstream vacuum
section.
- Most of the planned background studies cannot be done as long as the vacuum
pressure is high. Proton beam scans can be done.
H1
- During the proton only run (luminosity optics) the CJC2 chamber current was a
factor of 2 higher than in previous fills (proton beam separation optics). The
chamber current was reduced when the beam was moved down.
- The updated chamber currents vs beam current plot was shown, ps file
- A specific luminosity of up 2 10**30 cm-2 s-1 mA-2 was measured.
- The position reconstruction algorithm was improved on Sunday. The calculated
horizontal position changed by 2mm.
HERMES
- The access on Tuesday was successful. A second access was necessary to fix a
magnet problem.
- HERMES took only a very limited number of events in August: 72000 event without
data quality monitoring, 35600 events with data quality monitoring.
HERA B
- A second access was needed last week.
- Data was taken during the weekend. The electron trigger is stable. The rate is
still high. First muon trigger runs were taken. First level trigger studies
were done parasiticly.
- Last night the target position was calibrated with respect to the vertex detector
position.
- A proton current of > 15mA is sufficient for the present studies.
Schedule
- Today:
- Continue positron fill until evening shift.
- Evening shift: proton beam scans.
- Night shift: collisions, Ip=20mA, Ie=15mA, 60 bunches
- Tomorrow:
- Day shift: positron beam 1 to 2mA, study vertical BI bump
- Starting evening shift: Luminosity operation, Ip 20 to 30mA, Ie 18mA
- Until Monday continue luminosity operation with increasing positron
currents, 180 bunches.
- ZEUS is the coordinating experiments.
Next week the HERA meeting will be in the HERA control room.
Uwe Schneekloth