- type: setup/action command.
- function: set parameters for computation of SASE FEL gain and other properties.
- sequence: must follow run_setup and precede beam definition (bunched_beam or sdds_beam).
- Command syntax, including use of equations and subcommands, is discussed in 7.2.
STRING output = NULL;
STRING model = "Ming Xie";
double beta = 0;
double undulator_K = 3.1;
double undulator_period = 0.033;
double slice_fraction = 0.0;
long n_slices = 0;
- output — The (incomplete) filename of an SDDS file to which output will be written.
- model — The name of the FEL model used. At present, only one model is supported; the
“Ming-Xie” model is based on the simple parametrization M. Xie.
- beta — The value of the beta function, in meters.
- undulator_K — The K parameter of the undulator.
- undulator_period — The undulator period, in meters.
- slice_fraction, n_slices — The fraction of beam beam contained by each analysis slice and
the number of such slices. By default, no slice analysis is done. Instead, the beam is analyzed
only as a whole. If slice_fraction*n_slices is less than 1, then the slice analysis is centered
on the median of the time distribution. E.g., if n_slices=1 and slice_fraction=0.1, then
the central 10% of the beam would be analyzed. More typically, one gives values such that
slice_fraction*n_slices is equal to 1, so that every part of the beam is analyzed. There
are separate values in the output file for each slice, plus the whole-beam and slice-averaged