F.Willeke summarized HERA operation of last week,
see transparencies
HERA delivered an integrated luminosity of 5.1pb-1 last week, the
best week so far. The maximum luminosity was 3.3 10**31 cm-2 s-1.
Polarization was around 50% in the beginning, dropping to 40% after
luminosity re-tuning. Optimization is in progress.
Since Friday the coasting beam production was reduced by about a factor
of 2 by increasing the 52MHz and decreasing the 208MHz voltage. This
observation was confirmed by tracking calculations. The proton bunch
length is still a bit longer. Coupled bunch instabilities are
observed during acceleration, but not yet understood.
There were only few technical problems: last night a jump of the timing
system, causing longitudinal beam separation, and a defective RF
interlock cassette, which was repaired this morning.
F.Willeke was unhappy about the 3 hour access last night and would like
to be informed in case of future requests for access.
H1
Efficient data taking. The luminosity slope increased significantly.
Over the weekend and yesterday there were very few chamber HV trips due
to background spikes.
The forward Si vertex detector is essentially dead, efficiency of 50%,
due to radiation damage. The situation is similar to the radiation
damage of the backward Si system in 2002. It is not yet clear which
part of the electronics was damaged. The radiation monitor rates are
usually high during proton injection. Recently, the synchrotron radiation
collimators are already closed at 17GeV instead of 21GeV.
The background situation improved significantly since Friday. CTD HV
trips occurred much less frequently than before. The efficiency loss
due to trips is now similar to losses due to problems with the
detector and data acquisition system. For the last fills the efficiency
was 50 to 70%.
The baseline background conditions are very good now (best conditions
up to now). In principle, positron currents of 65mA could be tolerated
at Ip=100mA. One fill last weekend had high CTD background, possibly
due to synchrotron radiation.
Positron beam tilt scans were performed last week to check the acceptance
of the luminosity monitor. Lines which indicate the region of 95%
acceptance are now included in the luminosity display. The online
acceptance correction is now only applied if the acceptance is greater
than 90%.
RMS values of the scintillator background rates are now available which
should indicate the spikiness of the background.
HERMES
The proton background conditions were fine. The positron charged particle
background was a problem. The positron polarization is still low
and should be improved.
The glass tube disassociator of the target broke again on Saturday. Data
was taken with the unpolarized target. The target was repaired during the
access yesterday evening. A quartz tube will be installed, which should
be more robust.
Polarimeters
Depolarization
The hardware of the depolarization kicker was tested on Tuesday.
No effect on the beam was observed during the frequency scans a few
weeks ago. The kicker amplitude was too low. A stronger amplifier
should be used. (In 1997 it was not possible to completely
depolarize the beam using the present kicker.)
LPOL cavity
In case of a break, a short access was requested to remove dosimeters
from the shielding of the electronics. The plan is to install
the electronics next week.
There was some discussion whether it makes sense to get the LPOL
cavity polarimeter into operation. The LPOL calorimeter would
be radiation damaged during operation. No dedicated HERA time should
be spent unless there is a detailed plan.
A detailed schedule should be presented in the HERA meeting.
Schedule
Continue luminosity operation. Continue optimizing proton RF voltage
and production of coasting beam.
In case of a break, short access to remove dosimeters at the
LPOL cavity.
Warming up of the GO/GG magnets should be avoided during the access
Thursday next week. The decision whether the magnets are warmed up
for regeneration of NEG pumps will be made next Tuesday.
The orientation of the spin rotators will be changed during the
July maintenance day.