Summary notes of the LCU meeting on 23/08/2011

Present: JA, CA, RB, LD, OD, SF, MF, MG, BH, JJ, YL, TM, TR, GV

Report from meetings

• SLM and general information -> MG
  Not much to report.
  CMAC: JJ reports that according to the latest discussions at the last CMSC meeting the knock-on resonances should not be an issue for LHC. There will be a seminar by W. Fischer on RHIC performance with p-A runs.

IBS and luminosity evolution with higher harmonic RF -> TM (slides)
This study was triggered by the recent observations of heating in beam screens and kickers in the LHC. A different longitudinal bunch shape might mitigate the issue or a bunch lengthening. The first can be achieved by adding a second harmonic RF system. TM has performed simulations to assess the impact on IBS growth rates and luminosity for protons and ions. Quadrupolar oscillations have been observed for mismatched bunches. However, for the main simulations a matched longitudinal distribution was always considered. It is also worth stressing that the luminosity computation takes into account the modified longitudinal profile.
The gain (debunching losses and luminosity increase) is larger for ions than for protons and it reduces from 3.5 TeV to 7 TeV (radiation damping has an impact here).
Shorter proton bunches provide a better performance both in terms of debunching losses and luminosity life time with a single harmonic RF system.

AOB

None

Last update: 03-August-2011

MG & HB

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