Presents: RA, OB, HB, RdM, SF, MG, JBJ, JJ, AK, AL, SR, TR, GRD, FS, AV

• Follow-up of actions from previous meetings
  • Field errors for triplet magnets -> FS
    • In spite of a number of mails sent to CERN and US responsible, the data concerning field quality of single magnet is not available, yet. MEB will be informed of the situation to take the appropriate actions.
• Report from meetings
  • LTC -> OB
    • The status of the beam instrumentation for LHC was presented: the longitudinal density monitor will not be available since day 1. RF and ABP GRoups should think about specifications for such an instrument. The time scale is about one month.
    • There is serious concern for the BLM: they might not all be available since day 1.
    • Following a meeting of US-LARP it turned out that the contribution in the LHC commissioning could be marginal.
    • concerning the scrapers in the SPS: the analysis of resources required to move them will be made in BDI. ABP should analyse whether the collimators required for the LHC beam are compatible with other beams, e.g. CNGS -> HB.
  • SLM -> OB
    • Problem with the ion source.
  • MEB -> SF, MG
    • Slot allocation of SSS continues as well as discussion of missing cryodipoles for sectors 7-8 and 8-1. Strategy for dipoles selection for sector 4-5 defined: massive slot allocation should start in June 2005.
  • FQWG -> AL
    • Discussion of accuracy of transfer function measurement for SSS correctors. Some follow-up required -> AL
  • TCC -> JBJ
    • Second crane is installed and it will be soon commissioned in SMI2.
    • IR7 integration was discussed.
  • WGA -> JBJ
    • Sources of concern for SSS: external lines (new tolerances to be made available soon); inter-axis distance for lattice sextupoles: source is unknown and investigations are on-going leaded by AT/MAS Group.
  • InjWG -> HB
    • Analysis of trapped modes in TDI: this might induce heating (no cooling is foreseen). This issue should be followed-up by the RLC Section.
    • Interlock of transfer line is under discussion.
    • The position of the TCDI in TI2 is under discussion: the horizontal could be moved nearer to the septum, while the vertical should not move. Flexibility of the matching should be analysed.
    • All collimators will be available for installation well before beam commissioning in 2007: will they be installed in the standard installation campaign or afterwards (but before beam commissioning)? At the moment priority is given to minimise overall risk for LHC performance (do not delay production of most important collimators), while accepting a special installation of some collimators. All effort is taken in the collimation project to match standard installation slots without increasing the risk to LHC performance.
    • If risks and delays are encountered, the collimation project will propose that the priority will be determined based on the overall performance reach of the LHC, no matter whether this occurs first in the transfer line or the ring.
  • CWG -> RA
    • Preliminary discussion concerning Phase II collimators are on-going in collaboration with SLAC.
    • The studies concerning the energy deposition are positive, thus confirming the design choice. Values of quench limits are expected by K.-H. Mess.
    • Tungsten will also be used in IR3 for the active absorbers (while collimators will remain CC as planned): the impedance should be checked (RLC Section) as well as radionuclide produced.
  • LHCOP -> OB, FS
    • Main topics was the aperture kicker. It was agreed to have it since day 1 with a strength enough to kick the beam by 5 sigma at injection. In about 2 months the proposal should be finalised and presented to the LTC.
• IR4 tuneability with reduced aperture -> AV (pdf file)
  • Important issue: for achieving the quoted tuneability of IR4 MQTLs are powered to about 35% of their nominal strength (beam 1). This is an important point due to the weakness of the produced magnets. The required strength of MQTLs for beam 2 is not known, but the feeling is that it should not be too much different with respect to beam 1 settings.
  • The aperture bottleneck in IR4 is rather bad for beam 1, as the halo generated in IR3 will be lost in IR4.
  • The aperture bottleneck in IR4 is due to the beam separation in the dog-leg magnets.
• Loss maps with all LHC collimators, diluters and absorbers -> GRD (pdf file)
  • The new results show for the first time the ideal cleaning efficiency of the full collimation and protection system of the LHC (~50 collimators). This is a major achievement. The results demonstrate that many problems (shown in previous loss maps) have been successfully addressed by the addition of active absorbers and tertiary collimators. The design choices (materials, lengths, positions) are fully confirmed by the results."
  • It is planned to include various imperfections like orbit, beta beat, nonlinearities, etc.
  • It is planned to include a realistic beam energy distribution in upcoming studies
  • The final cleaning performance in IR3 and IR7 is limited by single-diffractive scattering and losses at the high-dispersion point in the downstream superconducting arc. This could only be overcome by adding a warm momentum cleaning section directly downstream of the betatron cleaning. This is excluded for the LHC due to missing space. Phase 2 will help somewhat by providing more absorption length.
  • The tools are available for usage in protection and beam loss studies for the first turns after injection in the LHC.
• LOC activities in 2005 -> OB (pdf file)
  • A general Group meeting will be held end of May to present the activities of each Section.
  • It is suggested to send agenda and minutes of LTC meeting to LOC Members for information.
• AOB
  • It seems that 600 A power converters have some performance problems: request for advice on impact on beam dynamics was requested by F. Bordy. Feddback reqceived by SF and AL. MG should comment for MQTL quadrupoles.

Colour code:

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