HERA
F.Willeke summarized HERA operation of last week,
see transparency
HERA delivered 3.6pb-1 last week. There were several technical problems.
Larger interruptions were due to: regeneration of NEG pumps,
problems with
the power system control system, GM magnet polarity switch,
208MHz tuners, LINAC cooling and quench protection system.
The specific luminosity was fine (about 1.5 10*30 cm-2 s-1 mA-2), but not
as high as with low bunch currents. One fill with larger proton
length had increased background.
The vacuum problem NR is still persistent. The configuration of the
scintillation counters NR6 was changed to see whether the back-scattering
occurs in the second GI vacuum chamber. The photon beam will be moved
down for a test.
Polarization was between 30 and 40%. It is still not understood why
it is lower with this rotator position. A new attempt will be tried
to tune the harmonic bumps.
ZEUS
The data taking efficiency increased significantly. It is now similar
to the 2000 data taking period. Some background increase was observed
for the fill with large proton bunch length. This did not cause CTD
HV trips. The background decreased again after the regeneration of
NEG pumps.
H1
The chamber currents are still improving. NEG pumps were regenerated
twice. The second time without warming up the GO/GG magnets.
Last night HV could be turned on at Ip x Ie = 100x33mA**2. 200nb-1
were lost at the beginning of the fill.
Saturday the proton beam position was changed to increase the acceptance
of the VFPS. The new orbit should be used as default if possible.
HERMES
The detector was switched on without problems, no HV trips.
Asymmetric background conditions were observed for some time, was
improved by beam steering. High background during proton injection
was reduced by HERA.
The quartz dissociator tube broke and was replaced last Tuesday.
In order to avoid damage the tube will now be exchanged every monthly
access.
A positron energy scan was requested in order to check the calibration
of the LPOL calorimeter.
Schedule
Luminosity operation will continue until Thursday 12.08.2004 07:00hrs.
Machine studies will be performed 12.08. to 15.08.2004,
see transparency
Study of longitudinal proton bunch instabilities (4 shifts). (No
positron operation.)
Positron beam based alignment in the arcs (1 shift) to make sure the
hardware
is working properly. The polarimeter information should be available.
Test proton operation with magnetic fields in electron configuration
(check effect of stray fields).
Luminosity studies were reduced to one shift, as they have to be
redone with electrons after the shutdown.
The positron energy scan (15, 20 and 25GeV) for HERMES will be
done in case there is a break in proton operation. It will be done
Thursday next week, if there no chance until then.