• Follow up of actions
  • Comments on the phase advance between IPs and beam-beam effects -> WH
  • During the discussion about the chromatic behaviour of the recent LHC optics, the question about the relationship between phase advance between insertions and beam-beam effects was raised.
  • WH reminded that there is no reason to have a special phase advance between IPs: even a non-symmetric one can work.
  • With the alternating crossing plane the Pacman effect is minimized and there is no issue for the compensation of the orbit effect.
  • The symmetry breaking for resonance compensation is not a serious drawback for Hadron colliders.
  • SF asked about the dependence of DA on the phase advance. WH answered that Dobrin is running simulations and preliminary results suggest that the minimum is just moved among the different tunes.
  • Concerning the strategy to tackle the issue of chromatic behaviour of the V6.500 optics:
    • SF commented that for optimizing the arc phase advance, the effect of the b2 from dipoles should be included. The general sorting efficiency should not be a problem, as a local compensation was performed in both dipoles and quadrupoles.
    • In mail discussions it was agreed to test the impact of the correction of the second order chromaticity performed with four circuits of the off-momentum beta-beating. Then, correction of both the second order chromaticity and the off-momentum beta-beating should be studied (Action: TR).
• Report from meetings
  • ICC -> MG
  • The new committee came as a continuation of the TCC chaired by P. Proudlock, who is going to retire. The new committee is chaired by Lyn Evans with Roberto Saban as deputy and Roger Bailey as scientific secretary. The representative from ABP is MG with Simon Baird. The meeting rate was first proposed to be every two weeks. It was later decided to  have one official meeting every 4 weeks followed by an informal one without minutes, in two weeks.
  • There was a presentation on the problem with the heat exchanger of the triplets. Ranko Ostojic reported about possible solutions. A new type of tube will be built and installed ensuring the required robustness of the system against pressure.
  • The cool-down for sector 7-8 is continuing smoothly (80 K at the time of the meeting)
  • There was an AoB by TS/SU colleagues stressing the lack of documentation for the alignment of certain components  (mostly from AB).
  • SF asks about the status of LTC. MG explains that the mandate of ICC is on installation and beam commissioning and that the LTC and LHCWG have a mandate close to this one as well. Hence, good co-ordination between the three bodies is mandatory. 
  • LHCCWG -> FZ
  • There was a presentation by Roger Bailey concerning the objectives for 2007. The main tasks are the preparation of procedures and documentation from last years meetings and the finalization of the measurement program  (e.g., with the AC dipole).
  • FZ had a presentation on tolerances, measurement program (a long list for 2007 when not much time might be allocated to this), possible problems that may be encountered (aperture, lifetime) and action plan to be addressed.
  • During the next meeting WH and Elias Métral will report on the alternative filling schemes for the LHC (48 bunches from the PS).
  • It was suggested that the EICs and CICs should participate on systems' commissioning.
  • MEB -> SF
  • Within 10 (S)SSS and 10 dipoles all allocation work is finished (in one month roughly).
  • MG reported that SSS523 for slot Q11R2 features a non-nominal MQ. It did not reach the nominal current. However, worse than this, it might feature an inter-turn short circuit. Therefore, it was decided by magnet experts that:
    • The magnet should not be powered to higher current than 2 kA. This corresponds to about 1 TeV. This will have an impact on the procedure used to commission the sector 2-3.
    • The magnet should not be quenched! This means that it should not be exposed to beam.
    • A spare SSS is being prepared and it might be ready bt May, but it will be late for tunnel installation. Hence, SSS523 will be installed and used for the hardware commissioning, but it will need to be replaced before the 2007 run.
      
• Discussion of the operational procedure for squeezing the beams -> SR
• SR presented the relevant documentation for the LHC commissioning topics followed up by EICs and Verena Kain.
• A web page is set up describing the different phases of beam commissioning. SR encouraged everybody to look in detail at what was prepared and to give feedback to the EIC's team.
  
• For each phase, prerequisite conditions are defined, a list of procedures, a list of milestones (exit conditions) and possible problems and open questions.
• List of prerequisites for the squeeze are presented (machine conditions, optics, aperture measurements, collimation, etc.).
  
• The procedure includes the use of the TCT to protect the triplets, running the squeeze, preparation to bring the beam into collision, etc.
• Exit conditions are defined. RA comments that the squeeze should always be done in steps and this should be explicitly mentioned in the procedure.
• FeRo triggers a discussion on the orbit definition. SF comments that the measurement and set-up of the orbit should be done for each β* value.
• In order to complete the measurement program for each β* step, feed-back is needed from LCU section. SF remarks that coupling measurement should be added.
• It is recalled that the effect of the decay of the insertion quadrupoles during the stops needed to perform optics measurements will be presented by Walter Venturini at a forthcoming LHCCWG meeting. TP asked whether there is a special program for measurements on the magnetic field quality during the squeeze. SF replied that there is a special program decided by FQWG.
• RT asks whether time estimates for the squeeze procedure are available. SR answers that for the moment there are not yet detailed time estimates because we first want to find out what is necessary for each procedure. Whenever time estimates will be available (e.g. if provided by the experts that will define the measurement programs) they will be used to estimate the required time for commissioning.
• RA adds that milestones should be added, mentioning clearly which intensity and what conditions are acceptable within a predefined goal. MG agrees and adds that some quantitative statements should be given.
  
• Update on the collimators -> RA
• RA informs that the serious issues related with the collimators production is over. Another 6 collimators were received, with a total of 20 collimators available. Among them, 14 can be installed. There are on-going discussions with the company concerning the production rate. 28 collimators are needed and if this is not achieved  the machine will have to start commissioning with intensity reduced with respect to the one foreseen. 86 collimators are needed for the 2008 run.
• In parallel, after the successful control test in the SPS, a function driven movement will be implemented. SR is looking at the implementation for the real collimators in LHC and a test with a prototype will be done in spring.
• A crystal collimation workshop will be organized, VP will help with the organization. An FP7 proposal should be set up by May.
• MG  asks if there are any news with respect to installation schedule for 2008. RA answers that there is not a problem putting down the collimators but the bake out is very time consuming and it may be dropped.
  
• AOB
• The new section mandate was presented by MG to the new section members.
• New section members are presented:
  • Malika Meddahi coming from the ATB group
  • new fellow Ilia Agapov
  • doctoral student Roderik Bruce (previously in LII section)
  • doctoral student Ulrich Dorda and Tatiana Pieloni (previously in RLC section)
• Change of the LINUX operating system (from 32 to 64 bits) generated a lot of problems. There were missing links, compilers, and programs (Tex, LaTex). The routines of the CERN library did/do not work anymore and the NAG libraries are also missing. It was stated once more by the IT department that FORTRAN is not officially supported. FS comments that it took a week to fix things. RF and BT groups were also affected by this change. A Memo to IT is being prepared.
  

Colour code:

• Black: proposed agenda
• Red: outcome of discussion at the meeting

Last update: 20-Feb-07
MG & YP

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