Minutes of HERA Meeting 14.06.2005
HERA
M.Bieler and F.Willeke summarized HERA operation of last week
(transparencies 1,
2)
- Last week operation was interrupted by the maintenance day on Wednesday.
NEG pumps were regenerated. Some machine studies were performed
after the maintenance day.
- HERA delivered 3.2pb-1, with typical currents of
80-90mA protons and 25-35mA electrons in 150 bunches.
- The initial specific luminosity was up to 2 10^30 cm-2 s-1 mA-2,
decaying to less than 1.5 10^30 towards the end of the fill.
There have been some attempts to optimize the working point
in order to reduce the blowup of the proton beam. The tune was shifted
away from the low order satellite.
- A few fills had short electron lifetime immediately after bringing
beams into collision.
- The main technical problem was a ground fault of a BU magnet ER, which
occurred on Friday. The virtual ground point was moved to
ER. The coil has to be exchanged in case another BU ground fault
appears.
- Other technical problems were a failure of the HERA timing system and
defective
ion getter pumps (SR3.6, SR6), probably due to shorted cables.
The pumps will be checked in case there is a break. In the meantime
TSPs should be fired regularly.
M.Vogt summarized the polarization studies
- The 1st order and most of the 2nd harmonic bump scans were
completed. The machine is not yet fully optimized.
- A tune scan was performed yesterday afternoon
(transparency).
The vertical electron tune was lowered. (The horizontal tune could
not be decreased without increasing the H1 background rate.)
The specific luminosity decreased due to an increase of the vertical
electron emittance.
Polarization of the colliding bunches went up to 43%.
When the tune was changed back to the previous value, the
specific luminosity increased from 0.95 10^30 cm-2 s-1 mA-2
to 1.1 (1.2) 10^30 at ZEUS (H1).
This tune is clearly not a proper working point for luminosity operation.
ZEUS
R.Carlin summarized the ZEUS status
(transparencies)
- The proton background improved significantly after the regeneration
of NEG pumps on Wednesday. It now a factor of 2 lower than the
prediction. Last week the data taking efficiency was quite
high, 90 to 95%. Losses due to HV trips and DAQ problems were
a few percent.
- It is not clear whether the defective getter pumps SR3.6 and SR6 have
any significant affect on the background conditions.
H1
Th.Kluge summarized the H1 status
(transparencies )
- The background improved after the NEG pump regeneration. The normalized
fast track trigger rate decreased from 2 to 1.2.
The HV efficiency was 80 to 90%. Background conditions should be
acceptable for Ie=40mA.
- The horizontal position of the photons in the luminosity monitor
is at 2cm, which is somewhat out of the acceptance. The IP position
should be moved horizontally in order to change the photon position.
HERMES
- Low background conditions, good data taking.
Schedule
- Continue luminosity operation with mirror tunes. Increase electron
beam current.
- Mirror tunes will be discussed Thursday, 16.06. 11:00hrs, room 459
(to be confirmed).
ZEUS is the coordinating experiment.
Uwe Schneekloth