Summary notes of the LCU meeting on 13/12/2010

Present: CA, RB, HB, RC, RdM, OD, MG, YL, TM, MS, RT, FZ, Zhao Yang (EPFL),  Jose Abelleira (Madrid)

Report from meetings

• SLM and general information -> MG
  Following the discussions in the Evian workshop last week, it can be considered likely that the beta* for the 2011 physics running will be lowered to 2 m or 1.5m in IP1&5. The optics are ready for IP&5. More work would be required in case ALICE would also ask for 2 m for ion operation. For IP8 it is unlikely that any beta* below 3.5m would be needed.
  The time spent at injection and in the squeeze should be reduced in 2011.
  Reducing the separation earlier at top energy from 2mm to 0.7mm will be considered.
  Sick leave up to 3 consecutive days and 7 days total per year can be left without certificate. However, it is mandatory to inform Delphine and the supervisor of the absence asap.
• LMC->FZ
  FZ reported from the last LMC. Details are available from the LMC minutes.

Simulations of macroparticles in the LHC -> Zhao Yang (slides)

ZY reported about studies of the dynamics of dust particles in the LHC, based on the model discussed in an earlier meeting.

The model simulates the dynamics under the combined effect of forces from gravitation electromagnetic phenomena (charge from the beam, charge of the macro-particle, image currents). Magnetic fields are currently not included and this would be the next step in the analysis.
ZY varied several parameters like the initial position and showed the predicted motion. The dust particles tend to be repelled by the beam and then they fall back aside of the beam. Time between the two approaches of the macro-particle to the beam is in nice agreement with the BLM measurements. However, the losses predicted are smaller for the second macro-particle-beam encounter than for the first one. This is in contradiction with observations. The addition of the external magnetic field might provide additional insight.
The observation that UFOs never occur at injection energy cannot be verified in numerical simulations. 

Comparing IBS with Data -> TM and JJ (slides)

TM analyzed recent LHC intensity and emittance evolutions and compared them to the prediction from intra beam scattering (IBS).

For the proton data, the longitudinal emittance growth is quite well reproduced. The observed transverse emittance growth is generally larger then predicted from IBS alone. FZ said he would expect to see large differences between the horizontal and vertical plane due to the differences in dispersion. This point is clarified after the meeting: an average between the horizontal and vertical growth rate is performed, which explains the results shown at the meeting.
Extra blow-up from the hump is expected to be more significant in the vertical plane.
TM also looked at data from the recent ion run in the LHC. IBS effects are larger for ions and the observed growth rates are closer to the predictions.

AOB

None

Last update: 16-December-2010

MG & HB

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