Minutes of HERA Meeting
22.07.2002
HERA
- A vacuum leak at the main absorber SR11 was found on Wednesday. The
interaction region was vented. The seal at the electron vacuum chamber
was replaced. The inner diameter of the old seal was not correct.
The pressure without beam is now back to the 10-9mbar level.
- The GO/GG magnets at H1 were warmed up. The proton background in the H1
jet chamber decreased when the magnets were cooled down again on Sunday.
- Pumps of the proton vacuum system (NR 28, 61 and 75m) were heated during
a proton only fill in order to study the sensitivity to proton beam gas
interactions.
- Luminosity operation resumed Sunday morning. The specific luminosity
was around 1.2*10**30 cm-2 s-1 mA-2.
ZEUS
- During the access some lead shielding was installed near the main absorber
and in the veto wall area.
- On the weekend the HV of the forward drift chambers could be turned. Due
to the poor vacuum the background was too high to turn on the CTD.
- Requested a one to two day access in order to install some thin
lead shielding between the C5a collimator and the micro vertex detector.
H1
- During the cooling down of the GG magnet the CJC2 current decreased from
55 to 30muA.
The jet chamber current did not change when the upstream (28 to 75m)
proton vacuum pumps were heated.
Indicating that the detector is more sensitive to beam gas interactions
close to the interaction point.
HERMES
- No beam time. No report.
- Requested a one hour access before Wednesday.
HERA B
- Saturday and Sunday the target was on for 47%. A big increase of
chamber currents was observed Sunday morning when the proton orbit
was changed. Last night the proton collimators were too close. The
interaction rate was 1MHz.
- Would like to do a 4-5 hour run with magnet turned off. This should not
affect the other experiments.
Schedule
- One hour access this afternoon.
- Proton only fill, heat upstream vacuum pumps. If there is a big effect
do high intensity positron beam bake-out until Monday. Otherwise
luminosity operation including changes of optics to reduce the beta
beat and increase the specific luminosity.
- The August maintenance day was moved to next week Tuesday. The access
will extend until Wednesday if necessary for the installation of the
ZEUS lead shielding.
- ZEUS is the coordinating experiments.
Note added after the meeting. There was a vacuum leak in the north straight
section. Beam operation will resume on Saturday. The break was used to install
the lead shielding at ZEUS.
Uwe Schneekloth