Minutes of HERA Meeting
14.05.2002
HERA
- It took some time to get the proton machine operational again after
the access last Tuesday. The sextupole measurement of the reference magnet
was not working properly. Significant lengthening of the proton bunches
was caused by a mistake in the new RF frequency table. The beam was lost
several times due to temperature alarms of the GO/GG current leads in the
north IR.
Proton injection was somewhat difficult and had to be optimized. The
increase of the bunch length was improved by optimizing the 208MHz RF
system.
- No vacuum leak (NR) was found during the access. During beam "bake-out"
the vacuum pressure went up to 10**-7mbar.
- Stable proton beam was delivered to the experiments on Thursday.
- There were three luminosity fills on the weekend. Two proton fills lasting
over about 24 hours each. Proton bunch lengthening was observed twice
during positron injection.
- Machine studies have been performed Monday and today. It was not possible
to get a vertically flat positron beam through H1. One of the vertical
correction coils was at the maximum current. Beam based alignment
measurements indicate that the GO magnet at H1 is too low by 2.7mm.
The influence of the solenoids on the optics was studied.
H1
- The background was relatively high on Sunday (CJC chamber current of
90muA, only about 10% improvement during optimization). A positron current
of 0.8mA was still causing a significant contribution to the chamber
current. Plot of chamber currents
- Last night the positron beam was dumped by a radiation monitor alarm.
ZEUS
- During the proton beam only run the chamber current was about a factor
of 2 lower than previously. The maximum proton current (without positron
beam) would be 40 - 60mA. Plot of chamber currents
- The solenoid was from Saturday to Monday. The tracking detectors were
therefore not turned on during collisions on the weekend.
HERMES
- Complaint about the changes of the schedule (no bake-out as foreseen,
not allowed to turn on the transverse target magnet). The standard
procedure is: target magnet off during injection, turned on after
stable collision are achieved. Communication should be improved.
HERA B
- Operation on Sunday was very successful. All 4 target wires and the
vertex detector were moved in. Data for commissioning and alignment
were taken. The beam was dumped by HERA without information although
the injection veto was still set.
- Would like to take two runs per week.
Schedule
- Continue with machine shifts until tomorrow morning (positron beam
studies in the afternoon, protons at night).
- Starting tomorrow morning, positron background studies during the day.
(10 bunches with large bunch spacing tomorrow morning.)
- Stable single beam during night shifts. Switch between positron and
proton beam, starting with positrons Wednesday/Thursday night.
- There will be a 3 hour break of beam operation tomorrow at 13:30hrs
(Maintenance of ZEUS MVD cooling and improvement of GO/GG current leads
at H1).
- Machine studies on Monday and Tuesday.
- The schedule will be re-discussed Friday at15:00hrs, HERA control room.
- The next scheduled maintenance day is
Tuesday 4.06. to Wednesday 5.06.2002 16:00hrs.
- ZEUS is the coordinating experiments.
Uwe Schneekloth