Summary notes of the LCU meeting on 18/01/2011

Present: CA, RA, OB, RB, HB, RC, RdM, OD, SF, MF, MG, BH, JJ, YL, MS, SW, DW, FZ

Report from meetings

• SLM and general information -> MG
  This was scheduled as first, shorter meeting in the new year just before the Chamonix week. The normal bi-weekly meetings will restart after Chamonix. There has been a first follow up of items which came up in Evian: the squeeze sequence for IR2 has been extended well-below 2 m beta* and intermediate matched points have been added (Thys for optics, Emanuele for crossing angle, Olav for database). Thys is also going to see what can be done to minimise the beta-beating bump that is observed for the squeeze sequence for IR1/5, Beam 2, in the vertical plane. There was a discussion on the dynamic beta-beating tolerable in between matched optics: a quantitative answer is expected from Machine Protection. After this it will be possible to determine which matched optics could be removed and the subsequent gain in squeeze time. SF asks what could be the gain/removed optics. MS replies that it is of the order of 20 s.
  The more likely beta* value for the 2011 run are 1.5/10/1.5/3-5 for IR1/2/5/8. Collision in IR2 will be with separated beams.
  There was a TETM meeting yesterday to discuss hardware changes related to cryomagnets in the next long shutdown. The meeting was attend by SF and MG from our team. The changes discussed are: replacement of dipoles (and one IR quadrupole) to reduce the maximum resistance of the splices of installed magnets. It is worth stressing that there is no clear evidence of correlation between resistance and mechanical stability. Then, wrongly-oriented beam screen could be replaced as well as SSS with wrong correctors in sector 3-4 and Q5L8 (with failing orbit corrector). Our preference is given to restoring the missing skew quadrupoles in sector 3-4. The issue of wrongly-oriented beam screens will be co-ordinated by M. Jimenez with contributions from VSC, CRG, ABP (FZ). Concerning the Q5.L8, it was checked with J. Wenninger that the warm corrector could be used at much higher energies (currently it is power up to 22 A against 550 A). Hence, there is no particular priority - from beam dynamics considerations - to replace the Q5L8 because of the failing orbit corrector.
• LBS : LUMI-DAYS -> HB
  HB reported from the lumi days last week which were organized as combined theory/experiments/machine workshop to discuss the subject of absolute luminosity calibration in the LHC. Encouraged by the excellent results from the machine calibration using luminosity scans which reached 11% in the very first scans and probably around 5% precision for the later scans in 2010, there is a strong interest from the physics side that these efforts will be continued and further improved. Another precise calibration can also be expected from high-beta operation.
  It remains to be seen how the requests for precision measurements can be realized with the limited manpower on our side and the pressure to maximize the high-luminosity running.
  SW will present some conclusions in his Chamonix talk on luminosity calibration next week.
  RA asked what are the plans for studies about beam-gas interaction: MG proposed to review the outcome of the lumi days in terms of studies to be done and required resources outside the meeting and to have a presentation at a future LCU meeting, 
• Trip to SLAC -> FZ (slides)
  FZ reported from his recent trip to SLAC as CERN member from a newly created committee to prioritize accelerator R&D proposals for the SLAC facilities including FACET.
  Proposals for studies include ultrafast processes, plasma wakefield acceleration, studies for CLIC and some more exotic proposals including a PASER.
  FZ also attended at SLAC a meeting on ATF2 and ATF3 to further develop emittance minimization and final focus principles with importance for CLIC. For the time being the target emittance value has not been achieved. Possible cause could be the non-linear field errors, even if numerical simulations showed that convergence of the settings towards the nominal value of the emittance should be possible. 

AOB

None

Last update: 18-January-2011

MG & HB

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