• Report from meetings
  • MEB -> MG
  • The magnet approval is continuing (to be approved 70 dipole, 15 SSS and 25 SpSSS, until mid-February).
  • On next MEB the 3rd spectrometer compensator and two missing D2 will be approved.
  • TCC -> JBJ
  • The engineering change request for the Y chambers in IR2 and 8 was briefly discussed. Although this may have impact on installation, Lyn was very firm, and positive for the change.
  • Last sector was finished and put under pressure at the end of October.
  • For sector 7-8 there was a pressure test. The arc performed well. On the other hand a Helium heat exchanger is damaged in a triplet magnet. The QRL performed satisfactorily, apart from three minor leaks.
  • Regarding installation progress, there is a problem in IR3, due to a delay on the superconducting link feeding all the correctors. The cable was too short by 5m (out of 400-500m), but the factory has discontinued the production.
    
  • LHCCWG -> MG, RWA (pdf file)
  • Three presentations regarding commissioning of the squeeze, one for optics from Massimo, one from Ralph for collimator settings and one from Mike for application software.
  • Regarding the squeeze there is a need to complete the studies on IR2 and IR8, ASAP. (Action: JJ, YP).
  • RA presents the possible collimator settings during the ramp.
  • Loss maps at the start and end of the ramp are computed: several magnets at top energy in IR8 (dispersion suppressor) go above the quench limit.
  • Answering a question by YP and FR, RA points out the the computations do not include neither snap-back effects nor momentum cleaning.
  • The n1 versus beta during the squeeze in IR1 and 5 diminishes. The final value seems to be too low. JBJ argues that the tolerances have to be verified to fit with the latest ones. TW will check this.
  • RA shows a draft squeeze procedure including the relevant collimator settings
    
  • SLM -> MG
  • The request for a fellow working on the on-line model was accepted. A Technical student for application software work was selected.
  • The ABP party will be on Tuesday 12th of December.
  • The DG will give his annual talk on the 18th of January. 
  • The PAC conference participation will be discussed on ABMB today.
  • LTC -> MG
  • A presentation was given by JBJ regarding the replacement of the Y vacuum chamber in IR2 and IR8.
  • Following a comment by SF, further investigations will be carried out concerning the available mechanical aperture for the D2 separation dipoles on the injection side in IR2 and 8. According to preliminary analysis of the geometrical data, IR2 aperture can be improved provided that the spare D2 magnet is installed in the place of the selected one. On the other hand not very much can be done for IR8, as the D2 magnet is already installed.
  • At the forthcoming LTC a presentation will be given by Luca Bottura regarding the MEB issue cards.
• New approach to IR8 crossing scheme -> WH, YP (pdf file)
• WH presents an alternative crossing scheme for IR8 in order to keep the choice of the external crossing angle the same independently of the spectrometer polarity. This is done by crossing in both horizontal (internal) and vertical plane (external) with the same crossing angle of 135μrad.
• The aperture is above 10σ for the two extreme cases of β* of 10 m and 2 m at top energy. On the other hand, at injection, the aperture is below 5σ around Q2.
• Therefore, the proposal consists in injecting using the old scheme, set up the vertical external crossing angle and remove the horizontal external crossing angle at top energy. This would allow squeezing with a crossing scheme independent on the spectrometer polarity. However, the injection process will differ depending on the sign of the spectrometer magnet.
• MG suggests to check wether the shift of the IP increases the aperture at injection and to find the minimum crossing angle which does not present aperture problems at injection.
• Integration of 90 m TOTEM optics in the V6.500 LHC optics -> HB, TR (pdf file)
• HB presents the early optics for TOTEM. He recalls that it is very difficult to achieve the nominal settings (high beta of amore than one thousand meters, different integer tune, etc), in the first machine runs.
• Aperture at 7 TeV is not an issue (above 12σ).
• While in the vertical plane the phase advance can be set to the correct value, in the horizontal one a tune change of δQ=0.083 has to be compensated for. Three solutions are at hand:
  • Using IR4: this generates dispersion in the cavities and it does nto seem the best approach.
  • Using MQTs: this gives a beta-beating of 3%.
  • Using MQs: this gives a beta-beating of 1%.
• The second solution is the preferred one. It is also highlighted that with the new optics version 6.501 the tune difference will be even smaller and a better solution is expected.
• Preliminary results are shown where the un-squeeze between 90 and 11 m is possible, but not not smooth for some knobs (MQTL11).
• MG asks if the tune compensation with IR4 is possible. HB replies that there is a solution and looks very normal even though this entails a non-zero dispersion at the cavities.
• There is no way of injecting with 90m optics in IR5, as aperture is reduced by a factor of 2.
• AOB
• Andres Gomez Alonso is a PhD student working with Rudiger Schmidt on machine protection issues and will join the LOC meetings. Currently he is working in the IR8 protection VELO.
• Riccardo is working on the new matching module. A presentation at the next meeting is scheduled.
  

Color code: