hera_minutes_011016.html

Beam scans were performed Monday last week. The results are 108um x 36um (south IP) and 116um x 46um (north IP) horizontal and vertical spot sizes assuming matched beams.
Measurements of the proton beta functions in the individually powered quadrupole magnets close to the IPs were performed, analysis in progress.
A ground fault of the proton dipole magnet circuit occurred several times on Tuesday and Wednesday. It was traced to a water leak in the south hall at the entrance to the tunnel, water dripping onto the conductor.
Stable positron beam was provided for experiments.
HERA is still recovering from the power outage on Saturday (short of the 10kV power station A). The present situation is: still problems with proton dipole power supply and quench protection, 2 correction magnet power supplies still defective (some 50 had broken fuses) and some fine grain granules from an ion exchanger blocking filters of the water cooling system. The hope is to restart beam operation tonight.

Part of the forward detector was turned on during the stable positron beam. Background conditions were acceptable.
The C5 timing information indicates that the interaction point is shifted to the left side (forward) by 15cm.
There were two failures of lumi monitor power supplies, requiring access to the tunnel.
Very preliminary analysis of runs taken 31.10. and 01.11.2001 gives specific luminosities of 0.7 and 1.0 10**30 cm-2 s-1 mA-2.
Still not able to turn on solenoid after the power failure.
The effect of closing F/RCAL on the positron beam has to be studied again.

Some detector components were turned on during the stable positron beam. Background rates of up to 1 MHz (luminosity optics) were observed in the SPACAL inner cells surrounding the GG magnet. Beam steering and closing collimators did not reduce the background significantly. At 27.5 GeV/injection optics the rate was 10**4 Hz. It was not possible to ramp the jet chamber high voltage to the nominal value, maximum was 800 V.
The power outage on Saturday triggered the lack of oxygen and evacuation alarm. There was no damage to detector components.

All 4 collimators were closed during the positron beam run. The whole detector was turned on. Background conditions were acceptable.
The beam position monitors seem to have large offsets.
Timing of the HERA clock is off by 20ns.
After the power failure the pressure in the IP went up, pumping down is in progress.
The lambda wheels will not be installed next week.

Recover from power failure. Turn on both machines.
Concentrate on positron beam studies (beam based alignment, background optimization). Find out whether magnets (including bridges at IPs) have to be moved during the access next week.
ZEUS is the coordinating experiment.

Uwe Schneekloth