Summary notes of the LCU meeting on 20/03/2012

Present: HB, LD, SF, MF, MG, BH, JJ, SR, MS, MSt, FZ

Report from meetings

• SLM and general information -> MG
  Massimo worked on the experimental beam-pipe model. He will soon release new or updated aperture files in the MAD-X input database (see further  information here).
  He was also contacted by ATLAS members on the on the AFP forward detector plans with possible installation of a "Hamburg" beam pipe between Q5 and Q6.
  Massimo was also contacted by TOTEM who asked to flip the horizontal crossing in IP5 to get a different dispersion in normal physics.
  Global aperture measurements have already started in the LHC with beam this year. They can now be done faster using controlled emittance blow-up by the damper.
  Massimo said there is a possible interference at injection such that part of the injected beams could be lost in case of mis-injection  on the TCTVs. Stefano said he is confident this can be avoid by using appropriate TCTV settings.
  John said he is now the BE representative on the CERN  Scientific Information Policy Board. Among points discussed in the last meeting were the systematic posting of CERN papers on http://arXiv.com at the same time as CDS.  This needs to be implemented in the Accelerator Sector. It greatly improves visibility of our work.
  The CERN library has now a significant fraction (>30%) of books as ebooks which can be borrowed. Wiedemann's, "Particle Accelerator Physics" is the 3rd most popular title. 
  Usage statistics show a lot of use of the Oxford English Dictionary which (perhaps surprisingly) is not appropriate in CERN. The Concise Oxford Dictionary, available from the CERN Library as part of Oxford Reference Online http://www.oxfordreference.com/views/GLOBAL.html  at http://library.web.cern.ch/library/Library/dictionaries_and_encyclopedias.html  is a much better guide to writing modern, international English.
• LHC Status -> BH
  LHC recommissioning with beams started last Wednesday and made excellent progress. The new 4 TeV top energy and beta* = 60 cm were already reached. Beta beat was measured and corrected on the bare machine. See the LHC-latest-news.
• LMC -> FZ
  The LMC las week had reports on the accidental CMS magnet turn off, vacuum status and a summary of the Lumi days given by Benedetto Gorini. For further subjects and details see the link to the LMC.
• LBS -> HB
  The last LBS meeting on Monday 19 March had presentations on background related simulations presented by Giovanni Iadarola and Roderik Bruce and and follow up of the lumi days. Electron cloud simulations were recently performed for the large 800 mm vacuum chamber at IP2. Even in this large chamber, electron cloud effects become significant in the presence of many bunches and two crossing beams. This will be followed up with the vacuum group. For more details see the talks and minutes on indico.
• MAD-X status -> LD
  There were several new releases with updates on IBS by Frank and Fanouria and on PTC.

Review of new crossing scheme for LHCb at 3 m beta* -> BH   (slides)
LHCb wants regular polarity changes of the order of once per few weeks to cancel systematic uncertainties. Furthermore, they would like to have the same absolute value of the net angle for both spectrometer polarities. This is not possible with the current crossing scheme featuring horizontal crossing.
The LHCb requirements can be fulfilled by using a vertical crossing angle, though. This was studied in the past by WH et al. The point is that at injection the aperture is rather tight and the MPP has stated against this exercise in normal operation. Therefore, it was decided to implement a special manipulation of the crossing bumps at top energy when beta* is 3 m. At this stage the standard crossing scheme (H crossing and V separation) will be switched to a new one (V crossing H separation) gradually in order to ensure the necessary beam-beam separation.
the additional bumps have been implemented and stored in the official afs repository. Tests in standard operation will be scheduled soon.

Last update: 23-March-2012

MG & HB

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