Summary notes of the LCU meeting on 08/09/2009

Present:  RA, OB, HB, RDM, MG, WH, BH, JJ, EL, YL, JN, TR, AR, YS, RT, GV, SW, DW, FZ

Report from meetings

• SLM and general information -> MG
  HW commissioning needs volunteers for patrols who are asked to contact MG.
  There has been a follow up on apertures around the interaction regions with a presentation by MG of the current apertures in the meeting by R. Veness for beam pipe upgrades. The original specification of 15 mm mechanical tolerance allowed for initial large vertical movements of the experimental caverns. This is now settled and would allow decreasing the tolerance safely to 11 mm. With the 15 mm mechanical tolerance there is an aperture bottleneck at the level of the CT2 section of the CMS experimental vacuum pipe (injection and collision). RA comments that this is a serious issue and should be fixed by increasing beta* at injection from the current nominal value of 11 m to the old value of 17 m. MG comments that Ray and the CMS technical co-ordinator are informed of this situation and are expected to provide some feedback concerning whether the assumed value is compatible with the mechanical construction of the vacuum pipe (e.g., the CT2 section is not too far away from the TAS where a mechanical tolerance of 1 mm is assumed: this situation does not seem to be possible from a mechanical point of view). After the meeting MG discussed with SF: the change of beta* at injection will generate a negligible variation of beta at the level of the CT2 section of the CMS vacuum pipe, hence excluding this solution.
  Concerning alignment measurements, the vacuum chambers in LLS1 and 5 were re-aligned and they are all within ±3 mm. In case of LSS5 few vacuum chambers are displaced by up to 9 mm due to a collision with the collimators aside. The consequences of this will be checked for collimation. TAS positions in ATLAS were measured. On the right side, displacements up to 1.3 mm were observed. A re-alignment was requested provided this is compatible with the hardware constraints on transverse displacement of bellows. The longitudinal alignment is also not nominal and should be reflected in the as-built database.
  The staff reduction imposed to CERN some years ago was reached and CERN should now again be able to replace positions for staff leaving CERN. New job openings can be expected soon.
  A post on FIDEL implementation and settings generation is assigned to BE-ABP-LCU. the board is being organized.
• CWG -> RA (slides)
  Collimation working group meetings have been restarted. RA reported from the last meeting. Collimator settings and the commissioning procedures are being defined in detail in the CWG. The organization of the Phase II collimation was also presented.
• LBS -> HB
  The LHC background study group had its 6th meeting on Aug. 26. Slides and minutes are on indico. The last meeting was mostly on simulation with a discussion on the update of beam parameters relevant for simulations of the 3.5 TeV run.

Brainstorming discussion of beam parameters for 3.5 TeV run -> WH (slides)

Based on discussions in Chamonix 2009 and with the recent decision to have a run at intermediate energy of 3.5 TeV, a new set of beam parameters was collected by Mike Lamont and discussed in the commissioning meetings.
RA reminded that he requires for collimation an aperture of at least 11.3 sigma for intermediate collimator settings, and asked to determine and list the minimum n1 for any of the options discussed. This could be taken into account by specifying an interval of beta* corresponding to n1min=11.3 sigma (intermediate collimators settings) and n1min=7 sigma (nominal collimators settings). The two values will also correspond to "easy" and "challenging" targets for the beam commissioning.
According to WH, there should be no problem down to 2 m beta*. Experimental magnets should be taken into account, as turned fully on, even at injection. The spectrometer polarity is important for the options with crossing angle and only one polarity for LHCb will be used at 3.5 TeV.
There will be further follow up on parameters with a summary published as EDMS document and the outcome reflected in the optics database. MG says he will gather the relevant information concerning the longitudinal beam parameters as it was done for the 2008 parameters at 5 TeV.

AOB

A new fellow Maria Del Carmen Alabau Pons working on the LHC beam commissioning and online model under the supervision of FS started recently her activity in our section.

A new student Cesar Octavio Dominguez (Spanish trainee programme) working on the LHC performance model under the supervision of FZ also started recently his activity in the section.

FZ informed us that he was asked to be the secretary of a new CERN Machine Advisory Committee at CERN that will first meet on the 26 October.

Last update: 09-September-09

MG & HB

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