Minutes of HERA Meeting
06.01.2004
HERA
F.Willeke summarized HERA operation of last week.
- HERA had a very successful startup after the Christmas
break (29.12.2003). Luminosity operation started on 30.12. The operating
efficiency was 47%. An integrated luminosity of about 380nb-1 was
delivered per day with typical currents of Ip=50mA, Ie=30mA. The
peak luminosity was 1.6 10**31 cm-2 s-1, Lsp 1.4 10**30 cm-1 s-1 mA-2,
which is somewhat less than the design value. There were no major
technical problems. Beam polarization was between 20 and 30%. It was
not optimized as the ZEUS calorimeter was not closed. After the
calorimeter was moved again, polarization was increased to 40%,
similar to December.
- Several technical problems happened yesterday. Both proton RF systems
had to be repaired. Last night there was a pilotherm problem.
During the repair cooling pumps were turned off accidentally this
morning. Cooling and power is being turned on again.
- A ground fault appeared on the first cold correction coil QQ17NL114
just before the Christmas break. The short is in the cold system. A
repair of the magnet would be very difficult. It is now connected to
another power supply and operated ground
free. Another option would be to modify the optics and to run without
the correction coil. This would in principle be possible but would
limit the aperture at injection energy.
- A fire occurred in the south hall power supply room, caused by a
failure of a switch. Another small fire happened in the LINAC. There
was no serious damage.
- The last brazing of the spare absorber 4 before Christmas was not leak
tight. It has to be repeated.
- At present beam conditions, the absorber 4 proton beam pipe (SR11)
heats up to 180deg C. The temperature limit is at 185 deg C.
Cooling will be improved during the access on Thursday. The goal
is to increase the positron current to 50mA.
- The 8th RF was ready again just before the Christmas break. It will
be in operation after some final checks on Thursday. Higher positron
currents will be possible.
- Polarization tuning will be continued during luminosity operation.
A faster polarization measurement (new LPOL) would be very useful for
optimization.
H1
- Congratulations to HERA for the fast restart. The delivered luminosity
since 30.12.2003 was 2.1pb-1, 1.77pb-1 on tape, 1.4pb-1 with full HV.
Turning on all chambers is still relatively slow. Background conditions
were good, although not as good as the best conditions in December.
The chamber current was 100muA for Ie=20mA, Ip=50mA.
The positron beam gas background is a factor of 2 lower than one year
ago. Optimizing the synchrotron radiation background is still critical.
Beam currents of
30 on 60mA should be possible. A factor of 2 is still needed for operation
at design currents.
- The electronics had to be turned off after the cooling failure this
morning. The solenoid warmed up to 30K, is being cooled down again.
It will take about 2 hours until it will be at full current.
ZEUS
- Components which are essential for HERA were turned on 29.12.2003. Shifts
started 2.01.2004. After some initial problems all components are now
ready for data taking.
- Background conditions are not as good as in December. The proton upstream
vacuum pressure is a factor of 10 worse than in December. TSPs have to
be activated again.
- The electronics and solenoid were turned off after the cooling water
failure this morning. The magnet is back on. Cooling and power cuts
have to be avoided because of damage to the electronics.
HERMES
- Good data taking since shifts started 02.01.2004. Higher polarization
would be desirable.
Schedule
- Continue luminosity operation. Beam currents: Ip=60mA, Ie=30mA.
- Maintenance day: Thursday 06:00 to 22:00hrs (interlocks set)
- The absorber 4 will be surveyed.
- GO/GG magnets will not be warmed up.
- About 2 shifts of machine studies after the access, mainly to increase
the specific luminosity (3-dimensional beam scans).
- Continue luminosity operation Friday afternoon.
ZEUS is the coordinating experiment.
Uwe Schneekloth