Neutron source with Gaussian or uniform divergence
Date: November 20, 1998
KL, 8 October 2001
The routine is a rectangular neutron source, which has a gaussian or uniform
divergent output in the forward direction.
The neutron energy is distributed between lambda0-dlambda and
lambda0+dlambda or between E0-dE and E0+dE. The flux unit is specified
in n/cm2/s/st/energy unit (meV or Angs).
In the case of uniform distribution (gauss=0), angles are uniformly distributed
between -focus_aw and +focus_aw as well as -focus_ah and +focus_ah.
For Gaussian distribution (gauss=1), 'focus_aw' and 'focus_ah' define the
FWHM of a Gaussian distribution. Energy/wavelength distribution is also
Example: Source_div(xwidth=0.1, yheight=0.1, focus_aw=2, focus_ah=2, E0=14, dE=2, gauss=0)
Feb 2005: tested by Kim Lefmann (o.k.)
Apr 2005: energy distribution used in external tests of Fermi choppers (o.k.)
Jun 2005: wavelength distribution used in external tests of velocity selectors (o.k.)
Validated by: K. Lieutenant
distribution is uniform in (hor. and vert.) angle (relative to moderator normal),
therefore not suited for large angles
Parameters in boldface are required;
the others are optional.
Width of source
Height of source
FWHM (Gaussian) or maximal (uniform) horz. width divergence
FWHM (Gaussian) or maximal (uniform) vert. height divergence