Summary notes of the LCU meeting on 02/11/2010

Present: HB, RdM OD, MF, MG, BH, JJ, YL, TM, MS, RT, GV, SW

Report from meetings

• SLM and general information -> MG
  Last Friday, the luminosity production with 150ns bunch spacing in the LHC stopped. The last days of proton operation are now mainly devoted to study shorter bunch spacings and in particular 50ns operation with potential limitations from electron cloud relevant for  next year.
  First signs of electron cloud had already been seen in few locations at 150ns spacing in the presence of both Beam 1 and Beam 2. With shorter bunch spacing this is now rather generally observed also with single beams. Scrubbing at injection appears to help.
  The aperture limitation observed recently for Beam1 at injection was removed by temporarily changing a transition piece which was incorrectly installed. This will be permanently fixed in the winter stop. The injection region of Beam 2 was checked and found ok.
  There was some confusion in the sign of the ALICE spectrometer polarity which became apparent in combination with the external crossing angle and requires further clarification.
  As mentioned previously, there are currently discussion on the organization of  HL-LHC ( the LHC upgrade work ). In addition to our LCU section in which the "U" stands for upgrade, other sections, like ICE, are also involved. Proposals for a new name of our section without direct reference to upgrade are welcome.
  Mikko Karppinen is leading a project proposing a shorter Nb3Sb dipole in the DS to make room for the cryo-collimators. This is followed up in our group by Bernard Holzer. The new magnet technology promises higher fields and shorter magnets but also implies increased persistent current effects.
  We were informed about several workshops planned for the near future:
  The 3rd LHeC workshop, the indico page is here
  LHC Beam Operation Workshop - Evian 7-9 December 2010, link here
  Chamonix 2011 - LHC Performance Workshop, 24-28 January 2011
  LHC-CC10, 4th LHC Crab Cavity Workshop, link here
  Lumi 2011 workshop 13-14 January 2011, link here

• LEB -> MG
  There have been requests for new smaller beam pipes by several experiments on the time scale of 2016. More recently ALICE asked to look into the feasibility of a decrease from 29 mm down to 20 mm already for the 2012 shutdown. This has more generally brought up the question of aperture limitations from special optics and in particular the very high beta optics requested for IP1 and IP5 with operation before 2016.
  The next step consists in reviewing the mechanical tolerance budget (currently 11 mm), including the new observations and beam data.

Comparing IBS calculation with measurements -> TM (slides)

Tom Mertens showed a  first preliminary comparison of recent LHC data with growth rates expected from IBS. He used the measured bunch length from rf-data and transverse emittances calculated from luminosities observed with the BRAN. The general trend of the emittance increase is similar in simulations and data. Depending on the fill, the rates of increase differe by factors of two. SW proposed to use the luminosity data from the experiments as basis for the transverse emittance calculation instead of BRAN data. It is planned to do a similar analysis for the upcoming heavy ion run.

AOB

None

Last update: 04-November-2010

MG & HB

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