load_particles

• description:

  Allows loading particles from an SDDS file. This is an alternative to using a cathode and can provide essentially arbitrary particle distributions. Since spiffe is a 2.5 dimensional code, the ``particles'' are really rings at a given radius and longitudinal position.

• example:

  &load_particles
      filename = "particles.sdds",
  &end
  

  This loads particles from the file particles.sdds.

• synopsis and defaults:

  #namelist load_particles
          STRING filename = NULL;
          long sample_interval = 1;
          double stiffness = 1;
  #end
  

• details:
  • filename: Name of the SDDS file from which to take particle data. The file must have the following columns with the following units:

    z

    : longitudinal position in meters.

    r

    : radial poition in meters. If the particle position is initially outside the problem region or inside a metal volume, it will move ballistically until it enters the problem region or emerges from the metal.

    pz

    : longitudinal momentum, $\beta_z \gamma$.

    pr

    : radial momentum, $\beta_r \gamma$.

    pphi

    : azimuthal momentum, $\beta_\phi \gamma$.

    q

    : charge, in Coulombs.

  • sample_interval: Causes spiffe to take only every sample_interval$^{th}$ particle from the file.

  • stiffness: Allows making the beam artificially stiff. Equivalent to increasing the particle mass by the given factor.