bmad_4160_111005.lat

October 3, 2005 Lattice: /nfs/cesr/user/dlr/lat/bmad_4160_111005.lat

• Design strategy
  • Turn sextupoles off
    • I. Set horizontal separators to 20% nominal.Example first_stage constraint file.
      • Constrain IR for four-pair compensation, using sc_sk_q01, sc_sk_q02, sk_q02/3, sk_q04
      • Turn off b_param, and I_bunch constraints. Include pretzel efficiency.
      • Maximum arc eta for both positrons and electrons < 3.0. (BMADZ has been repaired 11/10/05 so that arc eta_electrons and arc eta (positrons) are computed the same way.
      • Maximum eta positrons and electrons at IP ~1e-3.
      • No constraint on etap. Constrain alpha at IP, IP_L3
      • Optimize with all quads
    • At this point the optics, including dispersion will be very nearly east west symmetric

    • II. Set horizontal separators to nominal. The dispersion will no longer be symmetric. Example second_stage constraint file.
      • Restore constraint on b_param and I_bunch
      • Constrain arc eta_electrons and eta (positrons) constraint to 3.3m
      • Optimize with all quads
    • Now electron dispersion will be the mirror image of positron dispersion

  • Restore 2 family sextupoles overlayed E/W. Dispersion will be east west symmetric and electron and positron equal.
    • III. Optimize sextupoles. Example sextupole constraint file.

• linear lattice constraints
• non linear lattice constraints

• lattice file
• Optical parameters and orbits
  • table
  • Lattice gif

  • Parasitic crossing parameters
    • Luminosity pretzel - pc parameters , b_param

  • Dynamic aperture
    111105 and initialization energies 0.0 0.003 0.006, Qx=0.518,Qy=0.584, Qz=-0.089

  • Parameters for beam-beam simulation including radiation integrals, damping decrement, etc.
  • Closed orbit output
  • c12_c22 in IR
  • Dispersion with vertical separators off
  • Dispersion with vertical separators on

  Single particle scans

  • 111105 and initialization , fs=-0.089, positrons, nolrbbi, no beambeam_ip, lat_and_layout (including apertures)

  bmad_4160_2ma_113005.lat
  Including parasitic beambeam and re-optimize quadrupoles

  Add 9 5-bunch trains with 2ma/bunch as a counterrotating beam. The positron parameters (beta, phase, b_param, emittance, etc.) are computed including the effects of a strong beam of 45 bunches of electrons. The electron parameters are computed including the effects of a strong beam of 45 bunches of positrons. The lattice is reoptimized according to all of the usual constraints using all quadrupoles. Sextupoles are not changed. The data summarized below as constraint files, tabulated and plotted beta and orbit, are all computed assuming the counterrotating strong beam for the lattice file lattice file The optimization proceeds according to constraint file cons_quad_2ma.in

  • linear lattice constraints

  • Optical parameters and orbits
    • table
    • Lattice gif
    • Beta difference 9X5 2mA - 0mA
    • Parasitic crossing parameters
      • Luminosity pretzel - pc parameters , b_param

      Luminosity vs current

  • Beam beam simulation of luminosity vs bunch current with 9X4 for both bmad_4160_111005.lat(compensated) and bmad_4160_2ma_113005.lat (uncompensated) is lum_v_current (and bb_120205.in , bb_113005.in shows no significant difference from 0.5 to 2.5 mA/bunch. Beyond 2.5 mA in the uncompensated lattice particles are lost. Inverse lifetime shows that the compensated optics have a higher bunch current limit.

    Finally include in the comparison, luminosity and lifetime vs current computed in the uncompensated optics (bmad_4160_111005.lat) assuming a single bunch in each beam. The luminosity plot shows no significant difference in specific luminosity to . The lifetime plot show no degradation of lifetime in the single bunch case up to 3.5mA, and no degradation of lifetime with 9X4X2mA in the compensated optics to 3mA/bunch, whereas the lifetime begins to be degraded at 2.25mA/bunch with 9X4X2mA in the uncompensated optics.

    Best luminosity to date is with 8X3 and two bunches missing (22 bunches/beam), day 362. Electron current is about 2/3 positron current. Luminosity per bunch vs average bunch current and simulation 120205 is day 326 luminosity . Specific luminosity is still well below prediction.