11.9 ibsEmittance

• description: ibsEmittance computes growth rates and equilibrium emittances for electron rings due to intrabeam scattering (IBS). It will also integrate the growth rates to show the time evolution of the emittances. The IBS algorithm is based on the Bjorken and Mtingwa’s [15] formula, and with an extension of including vertical dispersion. The program can also estimate IBS growth rates for and transport line or linac beam, provided special attention paid to the beam’s energy change (splitting RF cavities as needed).
• examples: This example computes the IBS equilibrium parameters and the contributions to the growth rates (at equilibrium) vs position in the APS lattice.

  ibsEmittance aps.twi aps.ibs -charge=5 -coupling=0.02 -rf=voltage=9,harmonic=1296

• synopsis:

  ibsEmittance twissFile resultsFile -charge=nC|-particles=value -coupling=value|-emityInput=value [-emitInput=value] [-deltaInput=value] [-emit0=value] [-delta0=value] [-superperiods=value] [-isRing=1|0] -RF=Voltage=MV,harmonic=value|-length=mm [-energy=MeV] [-growthRatesOnly | -integrate=turns=number[,stepSize=number]] [-noWarning]

• files: twissFile is a twiss parameter file from the twiss_output command of elegant. You must use the radiation_integrals flag in twiss_output.
• switches:
  • -charge, -particles — Give the charge (in nanocoulombs) or the number of electrons.
  • -coupling — Give the emittance or “coupling” ratio, ϵ_y∕ϵ_x.
  • -emityInput — Give the initial vertical emittance in meters.
  • -emitInput — Give the initial total emittance in meters. If not specified, the value from the parameter ex0 in twissFile is used.
  • -deltaInput — Give the initial rms fractional momentum spread. If not specified, the value from the parameter Sdelta0 in twissFile is used.
  • -emit0, -delta0 — Redefine the equilibrium emittance and rms energy spread, if different from what is given in the twiss input file. Can be used, e.g., to include additional source of energy spread, such as microwave instability, from an external calculation.
  • -superperiods=value — If given, the number of superperiods in the lattice. twissFile is taken to pertain to a single sector.
  • -isRing — Specify the calculation is done for stored beam (isRing=1, default) or transport line/linac beam (isRing=0). When isRing is set to 0, the energy scaling and integration calculation will be disabled.
  • -RF=Voltage=MV,harmonic=value — Specify rf voltage and harmonic number.
  • -length=mm — Specify the rms bunch length.
  • -energy=MeV — Specify the beam energy. By default, this is taken from the pCentral parameter in twissFile.
  • -growthRatesOnly — If given, only the initial growth rates are computed. Equilibrium emittance values are not computed. resultsFile will contain columns of initial growth rate contributions from individual elements. Without this option, resultsFile would normally contain columns of growth rate contributions at equilibrium.
  • -integrate=turns=number[,stepSize=number] — If given, then resultsFile contains the result of integrating the differential equations for the emittances for the given number of turns and not the contributions of individual elements of growth rates. The step size is the number of turns for each integration step, and can be adjusted to get faster results. The options -growthRatesOnly and -integrate are not compatible.
  • -noWarning — Removes warning messages.
• author: A. Xiao, L. Emery, M. Borland, ANL/APS.