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    LIU Beam Parameter WG meeting #13

    → Europe/Zurich
    874/R-018 - MEETING ROOM PRIORITY BE OP (CERN)

    874/R-018 - MEETING ROOM PRIORITY BE OP

    CERN

    20
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    Follow up from last meeting

    • An intense activity of MDs in the PSB-PS is continuing to address the questions raised at the last meeting
    • In particular, emittance growth from the dispersion mismatch at PS injection and then in the PS due to space charge are under close scrutiny in view of the achievement of the LIU/HL-LHC beam parameters
    • The official LIU beam parameters will be released officially shortly, but the values for bunch lengths and longitudinal emittances at SPS and LHC injection need to be clarified with Elena. In particular, we should perhaps have both first turn values (important as they are the extraction parameters from the previous machine) and those after filamentation (as they determine space charge)

    Chamonix talks on beam parameters: protons (Giovanni Rumolo, Rogelio Tomás)

    • In the common LIU/HL-LHC session there will be four talks devoted to beam parameters, which is the main common subject through which the LIU and HL-LHC projects are interfaced and need to work towards a common goal. Two talks will be on the protons and two on the ions (for both, one talk on the HL-LHC request and parameter response matrix and one on the LIU achievable parameter space).
    • The LIU beam parameters will be as usual shown with the global limitation diagram at SPS extraction, highlighting what improvement the LIU items provide for every limitation and how the LIU baseline has evolved over the years with the goal of meeting the HL-LHC requirement. 
    • The assumptions will be summarised (beam loss and emittance growth budgets, intensity limitations, brightness limitations) and the current situation reviewed - highlighting wherein lie the main risks in reaching the desired performance.
    • The highest risk will be identified to be the losses at the PS-SPS transfer and at the SPS flat bottom, which will be studied intensively in 2017 with the goal to define a path to solve it by end 2017 (and possibly make staged implementation plans even after LS2) 
    • Beam parameter reach for BCMS and 8b+4e will also have to be shown.
    • In the HL-LHC talk, Rogelio will focus on the HL-LHC baseline and show which underlying assumptions have been used to produce the beam parameters at LHC injection, which are now considered as the HL-LHC target.
    • The concept of ultimate luminosity will be considered, although it has no impact on the specification of the beam parameters at injection.
    • The BCMS will be considered as an alternative for larger-than-expected emittance growth in LHC, the 8b+4e will be the alternative in case of too strong electron cloud. For some given filling schemes, however, the BCMS might even become interesting as baseline.
    • The impact of LIU not reaching the requested parameters will be shown in terms of luminosity loss (or need of increased availability). The scenarios of 2e11 p/b at LHC injection with desired brightness or 2.3e11 p/b at LHC injection with lower brightness (10% - 20%?) will be considered.
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