Summary notes of the LCU meeting on 25/08/2009

Present:  RA, OB, CB, HB, MG, WH, JJ, EL, YL, FR, AR, FS, YS, RT, GV, SW, FZ, AX

Report from meetings

• SLM and general information -> MG 
  MG reported on follow up of alignment campaign for the LHC straight sections LSS (see slides). Most large offsets have been removed, see the slides. Some LSS require more work on re-alignment.
  Thanks to the help by AR (who analysed the official drawings to derive the aperture of the experimental pipes vs. s), MG has started setting up a new aperture model. A comparison between the old (built by SR in 2004) and the new one is also made (see slides).
• LMC -> FZ
  Following the LMC meeting on the 5. Aug, the target beam energy for the first LHC physics run was fixed to 3.5 TeV. Please see the news given by the DG. The following LMC had a presentation by Mike Lamont with estimates for the luminosity for the 2009/2010 run.
  RA said that collimation group meetings restarted, with one meeting every two weeks. There will be a regular report at the LCU meetings.

Comparison of codes for off momentum background tracking -> YL (slides)

YL compared tacking codes for off-momentum particles. For beam-gas simulation, he would like to be able to track particles from beam energy down to ideally zero energy with reasonable precision.
He finds excellent agreement between SIXTRACK and PTC up to at least 4% energy offset. This is very encouraging. Particles with larger momentum offsets are outside the LHC arc momentum acceptance and therefore only relevant for short distance tracking close in or close to the straight sections.
He also had a first look at loss locations predicted with SIXTRACK, PTC and MAD-X THINTRACK for particles with larger energy offsets. He finds some differences, which can mostly be explained by differences in the aperture models used. This will be further followed up to check if SIXTRACK is adequate for all energies relevant for off-momentum backgrounds to the LHC detectors.

Effect of dust particles on beam -> AX (slides)

AX reported about her work as summer student with FZ in our group. The topic is triggered by the sector 3-4 incident and the presence of MLI debris and soot in the beam screens and cold bore.
Dust particles in the LHC beam can potentially interact with the beam in the LHC resulting in losses of beam particles. She considers dust ionization, electrical forces from the beam and image charges which can accelerate the dust particles as well as gravity. Once conclusion is that it is unlikely that dust particles on the bottom of the beam-pipe will accelerated towards the beam.  Ionization of dust by stripping off electrons can only produce positive ions which would be repelled by the LHC beams. Dust particles, falling down through the beam instead could result in spikes in losses. The order-of-magnitude lifetime estimates need some re-checking.

AOB

FeRo leaves this group to join the BI group. Many thanks to him for the work in this group and best wishes for the future!

Last update: 26-August-09

MG & HB

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