Summary notes of the LCU meeting on 16/11/2010

Present: CA, HB, RC, RdM, OD, SF, MF, BH, YK, TM, FS, MS, RT, GV, SW

Report from meetings

• SLM and general information -> MG
  We will have an ABP Christmas party on the 10 December without formal presentations. There are also plans for a departmental BE Christmas party and a separate presentation of the highlights in the work in the department during 2010 next year.
  The next LCU meeting will be on Monday 29 November.
  The use of grid-computing in our group was discussed. The grid can be very powerful. It is however mainly built for experimental physics. We have no guaranteed CPU fraction. The overhead in terms of administration, getting started, and keeping things running can be rather heavy. LHC@home appears to be better adapted to our needs and has the support from Eric Macintosh (only).
  The organization of HL-LHC activities was discussed in a meeting between LCU members with a very preliminary list of tasks and names which can be expected to still change. One aim is to be ready with proposals for bids for extra resources from EU.
  Electron cloud effects in the LHC were recently found to be already very significant with 50ns spacing. This appears to be caused by a rather high secondary emission yield of 2.5. Scrubbing appears to help to some extent. The next 2-3 days ion operation will be stopped to change the lead source. The time without ions will be used to further study electron cloud effects in the LHC and in particular to compare electron cloud with 50ns and 75ns spacing.
• LBS -> HB
  The LBS#20 meeting yesterday had a presentation of Fluka simulations for IP1&5 by RB and presentations of observations of the experimental conditions with heavy ion operation in the LHC. Relative backgrounds  (background / collisions ratio) are of the order of 10% or significantly higher than for pp operation in the absence of strong ecloud effects. Details can be found on INDICO.

Beta-beating studies and thick model for the LHC -> CA (slides)

Beta beating can be modeled with the MAD-X thin model and accounts to about half of the observed effects. This model can include only quadrupolar errors in the main dipoles. To go beyond this it is necessary to use PTC. CA has shown the results of the analysis based on the use of a thick model using MAD-X and PTC. In this case all magnetic errors based on FiDeL estimates (stored in the official repository) have been used. Misalignments and data from magnetic centre position have been used as well. SF comments that the b2 errors for quadrupoles reported in the error tables are overestimated, in particular due to the large uncertainty on the warm-to-cold offset. It is then suggested to either use all seeds and then average beta-beating before comparing with measured values, or ask Per Hagen to generate a special error table (called seed 0) without the statistical uncertainty added to the warm-to-cold offset. It is also clear the the good agreement between the model and the measured data has to be expected only after having corrected the local errors.

Some ideas for improving software tools for HL-LHC -> RdM (slides)

RdM presented a list of relevant items for software tools developed so far and used for the design and studies for the nominal LHC. With the organisation of the HL-LHC project, it is considered important to review the situation in terms of software tools and to prepare a with-list new tools and/or improvements for the existing ones. For the time being no consideration in terms of resources needed to implement these tools has been made and this represents the next step.

RdM discussed existing and desirable tools for optics, aperture, correction of field imperfections, dynamic aperture, dynamic effects and working point optimization. The standard tools are mostly MAD-X and SIXTRACK and many enhancements were suggested, as well as request for documentation of existing tools.
RdM updated the list with the feedback given during the meeting. The updated list is linked to these minutes. Any additional feedback is more than welcome!
Feedback  concerning the needs for ions studies is awaited (JJ).

AOB

None

Last update: 16-November-2010

MG & HB

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