Minutes of HERA Meeting
04.06.2002
HERA
The schedule of last week was machine studies Monday/Tuesday, background
optimization for ZEUS Wednesday - Friday, stable beams and positron beam
bake-out over the weekend.
- Scraper measurements done on Tuesday showed that the positron beam tail
is somewhat larger than in 2000. The vertical distribution shows
non-Gaussian tail above 5 sigma. The tails are probably caused by
pressure bumps at the IPs, in particular in the south IP, and at the
superconducting cavities in the west straight section.
- There were two positron fill starting at 2mA and 7mA on Wednesday and
Thursday for background studies at ZEUS. The background (chamber currents)
was completely dominated by beam gas interactions. The vacuum is still
recovering from the replacement of a vacuum chamber 2 weeks ago. It was
therefore not possible to optimize the synchrotron radiation background.
- The electron machine was baked out with positron beam Thursday evening
to Friday afternoon.
- Stable beams (one 26h proton fill, 3 positron fills) were delivered to
HERMES and HERA B Friday to Saturday.
- Positron beam bake out was continued on Sunday. A leak between the GJ
magnet and main absorber NR11 developed during the bake-out. The leak was
fixed yesterday by tightening the screws of the flange.
- The wire scanner in the electron machine was tested yesterday. The
beam loss distribution looks fine at 12GeV. At full energy the statistics
is very small. Presently it is not possible to measure single bunch
emittances at 27GeV.
HERMES
- Got three positron fills on the weekend with good beam conditions.
The scheduled program, mainly tracking calibration, was completed.
The collimator positions in the file are not set correctly.
- The beam dump signal will be connected and tested. So far, HERMES
would have sent a beam abort signal twice.
HERA B
- Had a very productive weekend, about 26hrs of stable proton beam with
almost ideal beam conditions. The DAQ system was commissioned and
debugged.
Took 5*10**6 events. Did first multi-wire operation with tungsten and
first pre-trigger studies.
ZEUS
- The detector background was dominated by beam gas background. The vacuum
pressure at the IP was about 1*10-7mbar. Studying the synchrotron
radiation background was not possible. Background studies should be
repeated when the pressure is around 1*10-8mbar.
H1
- The detector was turned on during the positron fills Wednesday and
Thursday. During the second fill the background was relatively high,
without dedicated optimization.
- With both beams in the machine (about 15mA each) the rate of the
radiation monitor was 30kHz. The present limit is 50kHz.
- During the bake-out (30mA at 12GeV), the beam pipe temperature (bellows
section) went up to 60deg C. The alarm level is at 80deg C.
Schedule
- Access until tomorrow afternoon.
- Continue optimization ZEUS background conditions if the vacuum pressure
is sufficiently low (about 1*10**8 mbar), other wise improve vacuum by
beam bake-out.
- H1 is the coordinating experiments.
Uwe Schneekloth