Minutes of HERA Meeting 22.03.2005
HERA
F.Willeke summarized HERA operation of last week
- Last week the delivered luminosity was 4.9pb-1. The operational
efficiency was 55%. The specific luminosity was not as high as before.
The electron lifetime was only reduced for one fill. This was probably
not related to dust.
- The maintenance day went as scheduled. NEG pumps were regenerated in the
north and south IRs.
- Thursday and Friday there were problems with temperature alarms NR.
Some sensors were giving false temperatures, probably due to radiation
damage of the cable.
The affected sensors are not critical and were disabled.
On Sunday the electron beam was repeatedly lost due to RF problems.
Yesterday operations was interrupted because of the broken water pipe
on the DESY site.
- Another tune scan was done to optimize polarization.
- In general, conditions are not as good as previously, the background
is somewhat higher, luminosity slightly less. Several things are
under suspicion. The proton optics was improved a few weeks ago.
There was however no time so far to verify the updated optics.
The electron tune is not at the optimum.
The plan for next week is to improve running conditions, and not
to concentrate on polarization.
Some tests should be done, which will mainly be parasitically.
Checking the proton optics will take about 4 hours (non-parasitic).
The machine group will not be ready to go to mirror tunes next week.
ZEUS
- In general, running conditions were fine, except some periods with
increased background. The ZEUS background display should be used
for background optimization.
- The vacuum pressure decreased after the NEG pump regeneration last week.
H1
S.Levonian summarized the H1 status
( transparencies)
- The corrected total delivered luminosity is 39pb-1.The H1 gated
luminosity with all HV on is only about 14pb-1.
- Last week H1 took 1.7pb-1 with all HV on out of 3.5pb-1 delivered by
HERA. The overall efficiency was only 50% (30-75%) due to frequent
HV trips of tracking chambers.
After the maintenance the vacuum improved. The base line is 25-30% lower.
The general background was however worse than before.
The typical background behavior was: first 2 hours acceptable
proton background, but increased synchrotron radiation, electron
background improved, but proton background developed 2min spike
structure. In addition, the photon spot at the luminosity
monitor was shifted horizontally. The electron orbit seems to be
distorted in the north IR. The horizontal vertex position
changed by 0.4mm.
Background conditions were excellent for the last fill. The HV efficiency
was 85%.
- F.Willeke remarked that the horizontal angle was changed intentionally
in order to change the dispersion. Otherwise the tune window is
too small. The electron tune is not where it should be. It is
not know why the satellite resonances are stronger than in February.
The beam position monitors close to the IP do not work properly
anymore, making it difficult the orbit fit difficult.
HERMES
- The ABS was repaired during the maintenance day, the dissociator
tube was replaced. A water leak was found after the detector
was closed. The leak was repaired during a temporary access
Friday morning.
- The detector is in routine operation. Background conditions are
acceptable.
As always higher electron current is appreciated.
Schedule
- The plan for next week is to improve the running conditions, and not
to concentrate on polarization.
Some tests will be done, which will mainly be parasitically.
Checking the proton optics will take about 4 hours (non-parasitic).
HERMES is the coordinating experiment.
Uwe Schneekloth