Summary notes of the LCU meeting on 19/10/2010

Present: CA, OB, HB, HC, RdM, OD, MF, MG, BH, JJ, YL, TM, TR, MS, RT, 

Report from meetings

• SLM and general information -> MG
  MG informed us about some general (re-)organization at CERN. There will be three main machine projects:
  Consolidation (Simon Baird),
  HL-LHC (Lucio Rossi deputy Oliver Brüning)
  LHC Injector Upgrade (Roland Garoby) with several sub-projects.
  The project leaders are form the three machine departments and will also act as deputy department heads.
  The injector upgrade includes studies for a high power SPL. This is not strictly required for the LHC but has other interesting applications.
  One of the main goals, to reach 1.e32 luminosity in the LHC commissioning was reached in the last days, as communicated by a message from the DG.
  Part of the technical stop between the proton and ion run was advanced to this week to fix an aperture restriction injection septum for Beam 1.
  Significant dynamic pressure rises have been observed at the cold-warm transitions next to the triplet at higher intensities for many bunches, mostly around IP1 an appear to be caused by electron cloud effects.
  MG also reported from an LEB meeting. The experiments are interested in smaller beam pipes for their vertex detectors, mostly considered after 2016 after high beta* operation. More recently, ATLAS already asked if some reduction in beam pipe diameter could already be possible in the 2012 shutdown, based on a reduction and improved control of tolerances.
  An "LHC beam operation workshop" is organized on the 7-9 December 2010 in Evian.
  The 2012 shutdown could be postponed if there are signs for a major discovery in 2011. Schedules, consequences and the possible increase of the beam energy to 4-4.5 TeV will also be discussed in the January 2011 Chamonix.
• LBS -> HB
  The LBS#19 meeting was held on the 18. October. Presentations and minutes are available on the web. The presentation from LHCb on beam gas backgrounds also covered the determination of crossing angles in LHCb based on the reconstruction of vertices from beam-gas interactions. This showed that there is an asymmetry between the two beams in terms of crossing angle (already without the external one): this might be due to the way the closed orbit is corrected in the IRs. This does not seem to be an issue for LHCb.
  The report from the vacuum group also covered the recent observations of dynamic pressure rise in the presence of more bunches, high intensities and two beams. Small coils were installed around IP1 which allow to produce small solenoid fields. Powering these allowed to nearly cancel the dynamic pressure and can be interpreted as strong evidence for electron could effects as the principle cause of the dynamic pressure rise.

MADX vs LSA magnet polarisites -> MS (slides)

Marek recalled the conventions used for the signs of the magnetic fields and the magnet powering.

In LSA, power converters are considered as the hardware and magnets as logical elements.
For the checks he assigns non-zero strength to all multiples, imports from MADX to LSA, dumps all currents as generated by LSA and compares them with the MADX output, and confirmed that the signs are as expected.
However, for Beam 2 the information concerning the cabling of some circuits should be taken into account in order to establish the agreement between MAD-X and LSA.
A point to be followed-up is the polarity of MSS: from the beam measurements (see here) there is a polarity issue, while from the comparison carried out by Marek the situation should be ok.

The new optics solution for IR3 with cryo-collimators -> JJ (slides)

JJ presented a new geometry and optics design for IR3 with up to 4.5m displacements in the dispersion suppressor to allow for the installation of cryo-collimators for the upgrade of the collimation system. This also implies transverse position changes by up to 3mm and a very small (-0.026 mm) radial displacement. The LHC circumference would shrink by 2.8 mm and IP position would move by a fraction of this.  Other changes are small and rather going in the good direction:  improved aperture and more margin for quadrupole powering.
TR also helped here, producing alternative optics and layouts.
The final solution with be described in a note and hardware changes described as ECR. The earliest date for the implementation would be the 2012 shutdown.

AOB

None

Last update: 22-October-2010

MG & HB

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