Summary notes of the LCU meeting on 17/11/2009

Present:  MA, OB, CB, HB, RC, OD, MF, MG, BH, JJ, DK, EL, JN, FS, MS, YS, RT, GV, SW, DW, FZ

Report from meetings

• SLM and general information -> MG
  MG introduced a US-LARP fellow Ryoichi Miyamoto who will be working with us on the AC dipole and with BI on luminosity monitor.
  Thanks for the many contributions sent to MG for the yearly report which filled eight pages, were two would have been sufficient.
  As requested by email: please send any proposals for abstracts to IPAC this week, remembering that at least one of the authors should actually be present at the conference.
  The ABP end of year party is scheduled for Thursday 17 December at 16:30.
  LHC sequences have been updated to reflect the LHC as presently installed. Due to the pressure imposed by the LHC beam commissioning, changes have been requested to the people responsible of the layout database, but the sequences were manually edited without waiting for the implementation o f the changes. Extra sequences like the thin sequence are available as well. Reviewing and if needed updating of all strength files for the insertions is in progress.
  A sign inconsistency for skew elements between MAD files and the actual machine was revealed by tests with the beam as discussed further in the presentation of RT today.
  MG showed results of a recent re-alignment campaign in LSS3,4,7, see the slides. A very small number of points remains outside the target tolerance. Most of these are in places with a good margin in aperture and should not cause any problem. The most critical point found is in the horizontal plane on the right of LSS4. We will also look with beam for local losses and realign later if required.
  A potential aperture reduction was observed with beams in the injection region in IR8. the test should be repeated to confirm the observation. SU provided recent data about the alignment of vacuum chambers in the region between MSI and Q5 (that was installed tilted longitudinally to improve the aperture for the injected beam).
  MG presented few plots from the recent aperture measurement campaign in the LHC.
  The 2009 HW re-commissioning is nearly complete and beams could be circulating again in the LHC by Friday night.
  The note on 3.5 TeV beam parameters is in preparation.
• CWG -> CB
  CB reported shortly from the last CWG. Simulations at 3.5 TeV are in process. Ideas for measurements with beams are collected and will be discussed in the next CWG.
• FZ -> LMC
  The LMC discussed upgrade plans based on a more realistic updated LHC schedule for the next years. It is in any case foreseen to have a number of sessions at the Chamonix Workshop devoted to the upgrade projects and studies.
  Details of the other topics dealt with can be found in the minutes.

FiDeL and settings generation: recent cross-checks -> MS (slides)

MS presented an overview of the FiDeL implemented in LSA. The gradients are taken from the optics files; the calibration curve is generated based on FiDeL model (a set of equations to represent the various components of the magnetic field); the current depends on K and momentum:  the calibration curve is used to convert B to I.
The LSA implementation of FiDeL is currently cross-checked against WISE (the code developed by P. Hagen): starting from optics settings (plus some artificial settings for correctors normally not powered) the currents are generated via FideL in LSA or WISe and the results compared. Very nice agreement is obtained for the static components, the dynamic ones will be checked later on. SF suggests to link the number of points in the calibration table to the accuracy required for a given beam observable, rather fixing a priori the number of points.

Latest polarity and coupling measurements during the last sector test -> RT (slides)

RT explained how polarities are checked using left/right offsets and trajectories in magnets. No new individual magnet polarity errors were observed.
The tests revealed a systematic difference in sign conventions for skew elements. This error is present both in the MAD-X sequence polarity flag and in the corresponding quantity implemented in LSA. MG will follow this up.
It was also possible to give a first look at coupling and spool elements and to verify to some level the b2, a2 and b3 correctors using the measured data.

AC dipole in MADX thintrack module -> YS (slides)

YS implemented the AC dipole in the MAD-X code and in the SixTrack convertor (AC dipole was already available inside SixTrack).The results of first tests are shown. Once finalised, an AC dipole element will be included in the official LHC sequence for further use.

AOB

None

Last update: 18-November-09

MG & HB

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