Models a stack of N refractive lenses, with a radius of curvature, r, at the apex.
The model is a thin-lens approximation where photons are refracted in a the XY plane
at Z=0. Absorption is generally disregarded may be handled through the use of the optional
transmission parameter T, where 0<=T<=1.
Thus, the lens has the focal length of f=R/(2*N*&delta) where the x-ray refractive
index is written: n = 1 - &delta + i &beta.
Parameters in boldface are required;
the others are optional.
Width of lens aperture.
Height of lens aperture.
Radius of lens aperture (overrides xwidth & yheight).
Transmission efficiency of the lens.
The radius of curvature of the lens.
The number of successive lenses in the stack.
Extra information for debugging.
Focal length - overrides the material_datafile - and diregards chromatic aberration.
File where the material parameters for the lens may be found. Format is similar to what may be found off the NISP website.