Presents:  HB, MG, WH, JBJ, JJ, AK, RdM, SR, TR, FS

• Follow-up of actions from previous meetings
  • Status of aperture model -> JJ (pdf file)
    • Tools to analyse MAD-like aperture model generated by S. Chemly are ready.
    • The aperture model provided by S. Chemly has 197 overlapping beam pipes.
    • The generation of the aperture model on LOC side is put in stand-by until the database is corrected (Action: TR, MG).
• Report from meetings
  • LTC -> MG
    • Discussion of the issue of ATLAS alignment: the proposal will be presented at LEMIC
  • MARIC -> MG
    • The performance of the MQT and MQS correctors is within specs.
    • The weak MQTLs will be located according to the list provided by MG to K.-H. Mess and R. Wolf via an official Memo. Co-ordination between AT-MEL and AT-MAS is being set-up.
  • MEB -> MG
    • Presentation of first triplet magnets for assignment to IR8 (imposed by installation schedule).
    • Slot allocation of cryodipoles for sector 4-5 in progress.
• Status of V6.500 model -> TR
  • The optics was correct since data extraction from the database.
  • Hardware  changes were found in the
    • positioning of the D1 separation dipoles
    • positioning of the correctors to generate the crossing scheme. This requires trimming of the crossing bumps as at present they are not perfectly closed.
    • hardware type of the correctors in Q5 R2 and A5 L8: they were MCBY type in V6.5 and they are now MCBC type. Consequences have to be evaluated (Action: MG, WH, TR).
  • Due to the growing number of optical configurations, it is agreed to generate for the V6.500 (and higher) separate strength files for each insertion (stored in separate directories): in the case of experimental insertions the files will be labeled with the value of beta*. Each file will contain both the quadrupoles' strength and the one of the crossing scheme elements. The flags "on_x*", "on_sep*", "on_lhcb", "on_alice" will be used to switch between nominal configurations. It will be left to the user to build the required LHC optical configuration. Sample files for the more common configurations will be provided for guidance (Action: TR).
  • A wrong value for the crossing angle of IP8 was detected by SF. WH checked and found the correct value. Verification of the aperture will be performed (Action: WH, JBJ). In case aperture is acceptable the corresponding file for V6.5 will be changed.
• Crossing angle issues -> WH (pdf file)
  • A complete review of the crossing schemes is on-going. One of  the objectives is to define the beam parameters required for fancy configurations (e.g. for CMS variants of the TOTEM optics) and to assess the hardware requirements to implements those optical configurations.
  • Such a study will also assess whether the spectrometers for ALICE and LHCb can be really operated with both polarities or whether there is one preferred polarity due to aperture issues.
  • The results will be reported in a paper in preparation.
  • The results will be used to create the appropriate files for MADX (e.g. the squeeze sequence) with the correct crossing scheme.
• Status of scrapers in the SPS -> HB (pdf file)
  • Installation of H/V scrapers in the SPS is now taken for granted.
  • Skew scraper could be installed in a second phase: it is confirmed that it will not be mandatory for typical beam conditions during commissioning phase.
  • Refined simulations should be performed to assess the performance of the system. More realistic beam distributions should be considered (non-Gaussian, superposition of Gaussian distributions to simulate the bunch-to-bunch fluctuations) as well as models, e.g. including also coupling.
  • A detailed study of the secondary collimators should also be performed considering also the issue of compatibility between the LHC and the high-intensity CNGS beam.
• Specification of field quality for MQY quadrupoles -> MG (pdf file)
  • Impact of FQ of MQY quadrupoles on DA is dominated by:
    • b10 -> allowed multipole
    • a9 -> non-allowed multipole. Induced by feed-down effects (vertical crossing angle)
  • DA is dominated by the MQYs in IR6.
  • The findings of the tracking studies have been communicated to relevant people (FQWG, SSSS Co-ordinator, MEB) as target field quality.
• Tracking MQX at injection -> MG (pdf file)
  • FQ of triplet quadrupoles has a clear impact on DA (now below 11 sigma).
  • DA is weakly affected by feed-down effects due to IR2 vertical crossing (b10 into a9).
  • DA does not differ significantly for the two optical configurations considered, i.e. nominal injection (beta*(IR1/IR5)=18 m) and pre-squeezed optics (beta*(IR1/IR5)=11 m).
  • Once more MQYs in IR6 dominate the scene.
• Slot assignment of triplet quadrupoles -> FS (pdf file)
  • The boundary conditions of this exercise are
    • The assemblies LQXA01, LQXA04, LQXB04 and LQXB05 have been selected for installation in IP8, which is top priority according to the installation schedule. Such a choice is made on the basis of the geometry.
    • The assembly LQXC03 is pre-selected for IP8 left, which is top priority according to the installation schedule.
    • The exact slot for the Q1 and Q2 is determined by evaluating the nonlinear correctors’ strength needed for the specific configuration.
    • As the field quality of the whole set of Q3 magnets is already available, the evaluation of the configuration take into account also the choice of the second Q3 for the right side of the insertion.
  • According to the results, no big difference in terms of correctors’ strength is found for the various configurations analysed. A slightly better configuration is the one featuring:
    • LQXA01 -> left side of IP8
    • LQXB04 -> left side of IP8
    • LQXC03 -> left side of IP8
    • LQXA04 -> right side of IP8
    • LQXB05 -> right side of IP8
• AOB
  • Effect of crossing and separation schemes on the design of the TCT and TCLIA collimators-> SR (pdf file)
    • The design of the TCT, tertiary collimators (all IPs), and TCLI, injection protection (IP2/IP8), should be finalised. The jaw movement should foresee an overshoot appropriate to the crossing scheme conditions.
    • A worst case analysis is presented.
  • Fiducialisation procedure for triplet quadrupoles-> JBJ (pdf file)
    • Discussions are in progress to define the details of the fiducialisation procedure for triplet quadrupoles.
  • Transfer line matching activities -> AK
    • The matching between TI2 and the LHC ring is being analysed. Dispersion matching is one of the topics. beta* knobs developed by W. Wittmer could be adapted to this aim.