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##

sasefel

- 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`

).

&sasefel
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;
&end

`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[13].
`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 results.

** Next:** save_lattice
** Up:** Namelist Command Dictionary
** Previous:** run_setup
Robert Soliday
2014-06-26