Summary notes of the LCU meeting on 10/03/2009

Present: MA, RA, CB, HB, SF, MG, AG, WH, JJ, EL, YL, JN, SP, TR, FR, AR, FS, RT, GV, SY, FZ

Report from meetings

• SLM -> MG (pdf)
  The radial and vertical alignment of the vacuum chambers in LSS4 was measured and the results shown. The data represent the of the centre of the flanges with respect to the nominal beam trajectory, therefore any voluntary misalignment of vacuum chambers is not taken into account in this analysis. This because the debugging of the information concerning the positioning of the vacuum chambers in the layout database is not complete.
  Some quite significant misalignments were seen, in particular in the vertical plane displacement up to 17 mm were measured. Furthermore, while in the horizontal plane the misalignments are randomly distributed around zero, in the vertical one, no negative displacement is observed.
  A meeting will be organized with SU, layout database, and vacuum experts to discuss the next steps (measurements, re-alignments).
  It is also planned to have a presentation by SU concerning the results of alignment measurements in the LHC tunnel (magnets, this time).

• LBS -> HB
  HB reported from the first LBS meeting. Talks are on indico. There is a strong request from the experiments to get a list of machine parameters for the 2009/2010 run as input for background simulations.
  MG suggests that for beam loss studies involving off-momentum particles we should know the precision of our tools as function of delta p. FS said that he compared SIXTRACK and PTC and found excellent agreement up to few percent of Dp/p. Further follow up by YL is planned.

• Upgrade activity -> SF
  A layout and optics were finalised recently. 
  The complete set of information is now in the official optics database. This includes both the setting and a series of tools to be used for the assessment of the proposed layout and optics. Next step will be the determination of dynamic aperture and then beam-beam effects.

Trip report to ESA -> FZ  (pdf)

FZ reported about his trip with FC to the technology centre ESTEC of ESA in Noordwijk close to Amsterdam. During their visit they talked about possible collaboration between CERN and ESA. There appear to be many subjects which are both interesting for CERN and ESA, including electron cloud, surface coating and microwave and x-ray technology. Both CLIC and LHC might profit from these collaborations. ESA is considering building a tests facility for high power rf research, but also to perform beam tests at CERN.
FZ has already contacted relevant people ad CERN to assess the possibility of setting up collaborations with ESA.

Recent progress with MAD-X -> FS  (pdf)

A lot of work has already been invested to prepare the new production version 4 of MAD-X. Among the many issues and improvements is the elimination of the bv flag, which makes this new version backward incompatible for input which still uses the individual bv flag. This change, which was required to correct some bugs, will also require changing the LHC sequence (Beam 2).
A lot of work was also invested in bug fixing, mostly related to memory handling resulting in MAD-X crashes. FS also showed a list of known issues and said that further new developments would depend on the availability of additional resources.

Status report on studies for new optics version -> MA  (pdf)

As reported previously in several meetings, there has been an effort to rematch the LHC optics so that the phase advance differences between IP1 & 5 are multiples of pi/2 in both planes. This main reason for this is to minimize the off-momentum beta-beating in the momentum collimation section. This study is now well advanced. MA showed tables for the phase advance contributions from the various insertions. There are changes in most insertions, but IP1&5 remain as before. RA expressed his concern about any further reduction of the aperture at Q6 in IR3 which already was tight (the proposed optics as an n1 reduction of 5×10^-3 with respect to the previous one). Pre-squeeze and squeeze files will still have to be made. SW will help with the matching of the separation bumps.
The plans are to make the injection optics as well as some other configurations with reduced beta* at collision energy available for preparing the thin lens version. Then, a tracking campaign will be launched to assess the actual performance of the new optics.

The Phase 2 collimation review -> RA  (pdf)

RA reported about work on the upgrade of the collimation system which is required to reach nominal and ultimate intensities.
This work involves studies on metallic low impedance collimators, cryogenic collimators in the dispersion suppressors and more recently in collaboration with FNAL / SLAC a study to use a hollow e-beam lens for scraping of halo in the LHC.
A conceptual review on phase II collimation will be organised at CERN beginning of April. RA showed the proposed planning for this review (see the slides) and asked for feedback. While most of this work is done to improve the collimation efficiency and reduce the risk of beam induced quenches, there will also be a talk from the experiments on experimental requirements.
HB said it will be important to understand backgrounds in the actual LHC as followed up in the LBS and to allow for feedback from first beam experience for collimation upgrades.

AOB

None

Last update: 11-March-09

MG & HB

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