hera_minutes_060307.html

HERA delivered a few nice luminosity fills Monday and Tuesday last week. The number of bunches was increased from 120 to 150.
The restart after the maintenance day was delayed due to technical problems, mainly RF problems.
The parameters of the 208 MHz system D were changed to get higher voltage in order to reduce intra-beam scattering. The longitudinal feedback system was studied.
The electron injection efficiency was investigated. The main reason for the low efficiency was a wrong kicker timing. Efficiencies of 60% can be achieved.
Operation over the weekend was not very efficient, mainly due to electron and proton RF problems. A klystron SL was replaced. The electron timing was slightly off.
The access this morning is for work on the electron RF system, repair of a small leakage current in PETRA and check of the temperature sensors and alarms NR.
Polarization of the non-colliding bunches is already quite good (50% level). The colliding bunches still have low polarization. Polarization tuning (harmonic bump scans) has started.

The delivered luminosity was 1.9pb-1 (Monday - Sunday). 1.3pb-1 was written to tape. Background conditions were varying. The fill on Friday and first part on Sunday was quite good. There were many HV trips during the last 2 h of the fill on Sunday. Changing the collimator position SL15a from 25.4 to 26.6mm improved the electron background.

The 40m and 6m taggers were installed during the maintenance day.
The normalized fast track trigger rate decreased to 1 for good fills after the NEG regeneration. Background conditions were mixed.

Shielding was installed during the access to reduce the fringe fields of the solenoid.
There were no background problems.
The solenoid quenched once without affecting the beam. The quench was due to problems with a gas flow controller for the gas output or a pump.

HERMES is the coordinating experiment.

Uwe Schneekloth