Summary notes of the LCU meeting on 18/05/2010

Present: CA, HB, RC, RDM, OD, SF, MF, MG, BH, JJ, YL, JN, RT, FZ

Report from meetings

• General information -> MG
  The IPAC'10 deadline for submission to the conference is tomorrow.
  A mail was circulated proposing the 16 June as date for a general ABP meeting.
  Manpower planning including fellow request for the next years will be discussed in a AB retreat on the 24 June.
  There have been further iterations on beta measurements in the LHC. The beta-beating of the uncorrected LHC could be de-creased by improved calibration curves for some magnets.
  The LHC is still mostly in set-up. It is planned to change this to a mode in which 70% of the time would be operation for physics and 30% for MD.
  The nominal bunch intensity was slightly exceeded (1.2e11).
  Collimators can now move in dynamically during the ramp.
  First clear signatures of collective instabilities were seen under these conditions and could be cured as expected by Landau damping using octupoles.
  Marek implemented the b2 for the dipoles in LSA so that this could be used in operation. He also implemented a2 and a3 corrections.
• LBS -> HB
  Yesterday's LBS meeting was mostly dedicated to the analysis of the absolute luminosity calibration using extended calibration scans. The data looks very clean and potentially allows to determine the effective beam-overlap size with an uncertainty well below our initial goal of 10%, which is very interesting for the physics studies of the experiments. It also allows to cross calibrate the experimental luminosities and to exclude significant luminosity differences between the experiments. According to J-J.Gras, the beam intensities are known with 1-2 % precision. The transverse length scales were measured by displacing both beams together and measuring the vertex position with the experiments and found to be very close (within 2%) of the nominal displacement. The excellent quality of the data also revealed several small sometimes puzzling effects which will require further studies and measurements to be better understood.
• LMC -> FZ
  FZ reported from the last LMC meetings. Among the subjects discussed was the future running strategy.
  The collimation team requested to increase beta* to at least 2.5 m or a very safe 5 m for operation with crossing angle. Details can be found in the minutes.
• CERN-MAC -> FZ
  The Machine Advisory committee met at CERN on 26 - 28 April 2010. One main subject was how to go up from 3.5 TeV towards 7 TeV and another the upgrade plans of the injector chain. FZ wrote minutes which, however, are not generally distributed. The MAC also recommended machine studies on the injector and the LHC to determine better intensity limitations and to review the choice of the longitudinal emittance in the lower energy injectors, which appears to be smaller than in comparable other machines with consequences on space charge.

Update on background studies -> YL (slides)

YL presented an update on machine background studies for the LHC. Details can be found on a web page.
Originally, simulations were mostly done for the nominal LHC parameters. As requested by the experiments, the simulations were now also done for the actual running parameters, and in particular for the beam energy of 3.5 TeV.
YL simulated in particular machine backgrounds from beam-gas scattering and losses originating in actual proton-proton collisions around the ring and potentially visible in other IPs as IR-cross talk. The vacuum conditions are excellent at the present LHC beam intensities and energies and current beam-gas rates visible but very low and no problem for the experiments. A rise in vacuum pressure by several orders of magnitude is expected for high intensity beams above 5 TeV.
YL searched for first signs of correlations of loss rates around the ring during separation scans as signs for distant backgrounds due to pp collisions.

FZ suggested to determine to which level beam-gas backgrounds could be used as a first indicator of potential He leaks.

AOB

None

Last update: 18-May-10

MG & HB

Back to LCU Minutes