hera_minutes_020910.html

B.Holzer summarized the HERA operation of last week, see transparency

There were no major technical problems last week. Occasional background spikes due to changes in the positron tunes were observed. It is not clear what is causing these changes.
The proton optics and the positron injection optics were studied on Monday.
On Wednesday positron beam orbits without the vertical BI bump were prepared. It turned out that the horizontal beam position at S/NL 66 is very important. The decision was to keep the vertical bump, down instead of up, in order to protect H1 and ZEUS from direct synchrotron radiation.
Proton beam position and tilt scans were done at H1 and ZEUS.
NEG pumps SL27 to SL70 were activated on Friday.
Since Thursday HERA delivered several luminosity fills with increasing positron currents. The proton lifetime was slightly reduced in a fill with 60 bunches and high positron bunch currents, possibly dud to beam beam effects.
There are now automatic positron orbit steering programs for closing the ZEUS calorimeter and for going from injection to luminosity optics.
Yesterday the proton optics was improved, positron orbit response measurements were done and the positron injection efficiency was improved.

Data was successfully taken during the weekend. The collected integrated luminosity was 250nb-1. The chamber currents (at Ie=22mA, Ip=21mA) were better than extrapolated, which is due to a better vacuum.

The background was still high. The vacuum is still recovering from the venting of the IP. The off-momentum positron background was reduced by changing the horizontal tilt at the IP. It was only possible to turn on the chamber HV at the end of the fills. The integrated luminosity was only 1.7nb-1.

Had a good weekend. 36000 DIS were taken, the same number of events as in the whole month of August.

The weekend was very successful. The target was operated for 60 hours. J/Psi peaks are now seen with the electron and muon triggers.
The interaction rate has to be re-calibrated. It is slightly higher than expected. Presently, there is no reason to run at higher interaction rates.

Today: long positron fill starting at 30mA.
Tomorrow: Measure the positron beam emittance to determine the vertical coupling. Perform positron energy scan. Do horizontal position scan at ZEUS (positron beam).
Wednesday to Thursday night: Proton beam, activate Ti pumps SR.
Thursday to Monday: luminosity operation with special bunch pattern: 60 proton bunches (20mA), 120 positron bunches (24mA) (60 colliding, 60 non-colliding bunches) in order to study beam beam effects.
The GO/GG magnets at H1 and ZEUS will be warmed up and cooled down again next Tuesday for activation of the NEG pumps. The time estimate is 2 shifts.
H1 is the coordinating experiments.

Uwe Schneekloth