Minutes of HERA Meeting 29.03.2005
HERA
F.Willeke summarized HERA operation of last week
- Operation was quite efficient over the weekend. HERA delivered 6pb-1,
the efficiency was almost 50%. The only unsolved problem is the
background conditions. It is not understood why the background
is poor for some fills.
On Thursday a power supply of the 208MHz proton RF system had to be
changed.
The electron current is still limited to about 35mA, since 1 of the
8 electron RF transmitters is defective and currently not in operation.
This morning injection was delayed due to a ground fault in PETRA,
which could not be repaired last night. PETRA can be operated with
floating ground.
- The horizontal vertex position at H1 was changed as discussed last
week. The improvements of the proton optics have not yet been
verified.
- Polarization studies confirmed that the main degradation of polarization
comes from beam beam effects. For some extreme tunes polarization
was higher, luminosity slightly lower. With "old" protons (emittance
28 mm mrad) and low electron current polarization of colliding
bunches was 47%.
- The steps, which are necessary to go to mirror tunes, will be discussed
next week. The change of the rotator positions was postponed.
H1
A. Bunyatyan summarized the H1 status
( transparencies)
- The delivered luminosity was 5.4pb-1, H1 active 4.65pb-1.
The HV efficiency was higher than before, up to 80%.
The main problem is background spikes.
For good fills the normalized CJC current is close to 1.
- The horizontal vertex is back to the previous position. The vertical
vertex is however off and still changing. The horizontal photon
position in the luminosity monitor is not centered.
F.Willeke remarked that the horizontal angle at the IP helps to
compensate distortions. The space between resonances is rather
limited. In principle the angle could be reduced during a fill.
- H1 would like to check whether the position of the central beam
pipe changes when the GO/GG magnets are turned on, which was
observed with cosmics. The idea is to take
proton only data with GO/GG on and off.
This should be done in case of a problem with the electron machine.
ZEUS
- In general, good data taking, although the efficiency was ranging
from 62 to 93% due to varying background conditions
( transparency).
- The detector recovered quickly from the power glitch.
HERMES
- HERMES had a good week. Good data taking, except 4hours which are
lost due to a HV failure. Last evening there was a problem with
the LPOL (alignment of mirrors for the laser).
The slope of collected DIS events is better than last year.
Schedule
- Changing the spin rotator positions was postponed.
- The steps, which are necessary to go to mirror tunes, will be discussed
next week.
H1 is the coordinating experiment.
Uwe Schneekloth