- Status report
- Summary of background situation
- Shutdown activities
- Discussion: Operation until shutdown
Shutdown dates
- Date of next meeting
- AoB
Presentations:
HERA F.Willeke transparencies
The machine optics is good conditions. The lattice functions
are within 10% of the design values.
The maximum positron intensity is 41mA at injection, presently
limited by the vacuum. No major obstacles are expected to go
to the same currents as in 2000.
So far the proton current is limited to about 60mA. There are
still some technical problems with the proton RF system.
The vacuum, base and dynamic pressure, is about a factor of
2 larger than in 2000. The integrated positron current is 4hA,
30hA is needed for conditioning of the arcs.
The presence of methane in the IR vacuum system is a concern.
For low bunch currents the specific luminosity is close to the
design value. At medium bunch intensity (50% of proton design)
it is 30% low. Systematic studies for achieving design specific
luminosity at design bunch currents have started.
The operational procedures are well established. The reliability
and availability of the pre-accelerators and HERA has been improved.
About 10 weeks of accelerator studies are still required.
ZEUS M.Kuze transparencies
The positron and proton background is still too high. The synchrotron
radiation background has to be reduced by about a factor of 10.
Modifications of the collimators near the IP will improve the
synchrotron radiation by a factor of 6. Another factor of 1.8
is expected from the coating the absorber at 11m.
The off-momentum positron background can be reduced by a factor
of 2 by modifying the C5a collimator. A factor 5 improvement of
the vacuum is needed.
The proton beam gas background, as of middle of August, has to be
improved by more than a factor a 20. Last week it improved by a
factor of 3 after warming up the GO and GG magnets and activating
NEG and TSP pumps.
Two shut-down plans were presented. The minimum work, modification
of the interaction region and repair of under-carriage of the iron
yoke, would take 16 weeks. If the STT is repaired in addition, the
time estimate is 20 weeks. Shortening the schedule to 16 weeks might
be feasible.
The preferred schedule is: running until Christmas, switch over
to electrons over Christmas/New Year, run with electrons January
to March, start long shutdown in April.
The second choice is a common proposal with H1: polarization studies
and high current running (to demonstrate design specific luminosity)
until end of November and ep collisions in December and January.
The shut-down should start no later than February 2003.
H1 D. Pitzl transparencies
The positron and proton background conditions are too high. Safe
operation of the jet chamber is presently only possible for
Ie * Ip less than 1000mA**2. The synchrotron radiation background
will be improved by adding a 1mm thick lead shield around the backward
beam pipe between C5A and C5B and by coating the absorber at 11m.
Reducing the thickness of C5B will only decrease the proton background
by 11%. The main reduction of the background has to come from an
improvement of the vacuum.
Over the last 3 weekends H1 has collected an integrated luminosity
of 1.2pb-1, 0.66pb-1 with chamber HV on. The detector is working well.
Collecting 2 x 5pb-1 with polarization, would give a first measurement
of the polarization dependence of charged current interactions.
The main shutdown activities are: improvement of synchrotron
radiation shielding, exchange of front-end electronics of the Central
Inner Proportional Chamber and installation of the Very Forward Proton
Spectrometer. The time estimate is 16 weeks.
A common H1 and ZEUS proposal for HERA operation was presented,
see transparency
HERMES M.Bouwhuis transparencies 1, transparencies 2,
The beam loss monitor is now connected to the positron beam dump
kicker. There was about one alarm per week.
Data taking started in August. So far HERMES has collected a total of
180800 polarized and 209700 unpolarized DIS events. 1.4 10**6 DIS
events are needed for a meaningful physics program, corresponding
to an integrated positron current of 20Ah.
HERMES requested 20Ah of beam on polarized target before the beginning
of the shutdown.
If HERA will run with colliding beams, priority should be given to
HERA B and HERMES. Both experiments should then rotate as the
coordinating experiments.
Beam polarization is not required for this year, although it would be
beneficial.
The main shutdown activities are: survey and alignment, re-mapping of
the transverse target magnet and modification of the lambda wheels.
The time estimate is 6 weeks.
A 3 month shutdown at the end of 2004 is required in order to install
the recoil detector. A change from electrons to positrons should
occur after 2005.
HERA B M.Medinnis transparencies
The detector performance has been improved significantly, in particular
the calorimeter, muon pad chambers and inner tracker. There are no new
dead channels in the pad chambers since January 2002. The training
program of the inner tracker will be completed in October. K0 and
Lambda peak are observed. The average FLT tracking efficiency is 50%.
It is 75% for J/Psi in the planned 1 track trigger mode. The J/Psi
rates are 110 events/hour for both electron and muon triggers, a factor
of 5 higher than in 2000. The running conditions have been good to
excellent. For 180 bunches the Projected total rate is 1400 J/Psi per
hour.
The physics program for 2002 is: measurement of b bbar total cross
section, J/Psi, Psi' suppression and a first measurement of chi_c
suppression. Given the reduced running time, see draft schedule, the
planned measurement can still be done with 2 times larger errors,
except for the Psi' measurement which would become marginal.
Data taking is urgently needed. HERA B is suffering from a lack of
man-power. Four key groups announced that they will be unable to
maintain their systems after the shutdown.
The request is to get as much target time as possible. HERA B should
take part as coordinating experiment.
Polarimeter S.Schmitt transparencies
Both polarimeters are ready to measure polarization. About 2 shifts of
stable positron beam are needed for turning on and cross-calibration.
The Fabry-Perot cavity (longitudinal polarimeter) will be installed
during the shutdown. The time estimate is 6 weeks. Installation of
a silicon detector is planned for the transverse polarimeter.
Special requests are to run with a completely flat machine and high
polarization and a few days with the HERMES spin rotators on for
simultaneous calibration of both polarimeters.
Discussion of Schedule and Conclusions
Written by R. Klanner
R. Klanner presented the draft schedule which had been distributed on 24.9.02. For the Work List the priorities have been defined; their meaning is:
The option to run HERA with protons only for HERAb between Christmas and New Year is presently looked at.
In an open discussion, which took place in a constructive atmosphere the following agreements have been reached:
The date of the next coordination meeting is Thursday, 24.10.2002 08:00hrs
Uwe Schneekloth