Minutes of HERA Meeting 24.05.2005

HERA

• A vacuum leak (proton vacuum chamber NR14) occurred Tuesday to Wednesday night after the electron beam was dumped by a temperature alarm in the south. The temperature alarm was caused by changing the horizontal and vertical beam angles at the IP. The leak was repaired Wednesday morning using glue.
• The position of the spin rotators was changed on Wednesday. Beam operation started with machine studies.
• The leak re-occurred Thursday evening. The proton GM vacuum chamber was removed in order to re-weld the welding seam. The leak was probably caused by local heating of the proton chamber just after the flange due to synchrotron radiation. The chamber was manufactured slightly out of tolerance.
  Temperature sensors were installed at the welding seam, north and south IPs.
• HERA performed beam bake-out over the weekend. GO/GG magnets in the north were warmed up last night. NEG pumps were activated this morning.

• Mirror tune studies started Thursday evening. The injection efficiency was 77%. Setting up the tune controller took somewhat longer than expected. Acceleration was cumbersome, needs orbit tuning.
• One luminosity test run was done with 9 colliding bunches with mirror tunes. The specific luminosity was 1.6 (ZEUS) and 1.3 10^30 cm^-2 s^-1 mA^-2 (H1). It is not clear why the specific luminosity was low; not really optimized or indeed smaller due to the different resonance structure, which is similar for positrons. Studies have to be continued.
• Last night the electron beam was again ramped with the mirror tune setup. Orbit files were improved. The ZEUS background was below the parameterization.

• The GO/GG magnets will be cooled down this evening. Beam operation will resume tomorrow.

H1

• H1 should be able to tolerate beam currents of 60 x 30mA, but will not be able to turn on HV.
• NEG pumps should be regenerated in two weeks from now.

HERMES

• The cooling of the lambda wheels is not working reliably. Experts will come for repair.
  The schedule of the technician will be checked.

Schedule

• Resume luminosity operation with reduced currents, Ip x Ie = 60x30mA^2. The experiments proposed to continue with mirror tunes to minimize the loss of luminosity.
• The maintenance day 1.06., including regeneration of NEG pumps, will be shifted by about one week.

                Uwe Schneekloth