crystal.get_amplidute function

[brttmnl]

Hello,

I would like to calculate the reflectivity of a crystal for small deviations from the Bragg angle for incoming or outgoing rays. For incoming rays I manage to get the expected reflectivity curve with Darwin width. However, when I keep beamInDotNormal and beamInDotHNormal constant (fixed incidence angle, fixed sample) and vary only beamOutDotNormal, I do not get a reasonable reflectivity curve.

get_amplitude(E, beamInDotNormal, beamOutDotNormal=None, beamInDotHNormal=None, xd=None, yd=None)

Could you please give me a hint, what I do not understand correctly?!

Many thanks!

[kklmn]

Hi,

What was your expectation and what did you get?

[brttmnl]

Hi,
I expected to also get a curve with the Darwin width for the symmetric Bragg case for the exiting intensity for small deviation from the Bragg angle, or, in the asymmetric Bragg case, the width should be scaled with the asymmetry factor sqrt(b), b=sin(theta-alpha)/sin(theta+alpha). However, the exit intensity was basically constant for small deviations from the Bragg angle (several Darwin widths).

[kklmn]

The outgoing direction is not selectable at will. It is defined by crystal orientation, d and crystal asymmetry, see the docs of reflect method in the Crystal rubric.
If you want to scan the outgoing direction, you should also reconstruct the incoming one rather than just keeping it constant.
Calculating the Borrmann triangle is another story, but this is not your case.