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McStas: Bragg_crystal_BC

[ Identification | Description | Input parameters | Output parameters | Links ]

The Bragg_crystal_BC Component

* * Perfect, reflecting crystal with common cubic structures (diamond, fcc, or bcc, and others if symmetry form factor multipliers provided explicitly) * *

Identification

  • Site:
  • Author: Marcus H Mendenhall, NIST
  • Origin: NIST
  • Date: May, 2017

Description

* Bragg_crystal_BC.comp is intended to supercede Bragg_Crystal.comp.
*
* For details see:
* The optics of focusing bent-crystal monochromators on X-ray powder diffractometers with application to lattice parameter determination and microstructure analysis,
* Marcus H. Mendenhall,* David Black and James P. Cline, J. Appl. Cryst. (2019). 52, https://doi.org/10.1107/S1600576719010951
*
* Reads atomic formfactors from a data input file.
* The Bragg_Crystal code reflects ray in an ideal geometry, does not include surface imperfections or mosaicity
*
* The crystal code reflects ray in an ideal geometry, i.e. does not include surface imperfections or mosaicity.
* The crystal planes from which the reflection is made lies in the X-Z plane on the unbent crystal rotated
* by an angle alpha about the Y axis with respect to the crystal surface.
*
* The crystal itself is set in the X-Z plane positioned such that the long axis of the crystal surface coincides with
* the Z-axis, withs normal pointing in the poisitivce Y-direction.
*
* N.B. The component does not work for rays hitting the back of the monochromator.
*
* Bragg_crystal_BC.comp is written by Marcus H. Mendenhall, NIST, Gaithersburg, MD, USA
* It is based on the full vector math and exact solution  of the dispersion relation in
* Batterman and Cole, Reviews of Modern Physics 36 number 3, page 681, July 1964
*
* This code has been validated against both experimental data
* (2 channel-cut 3-bounce Si 440 crystals together in non-dispersive mode, at Cu kalpha)
* and against theoretical rocking rocking curves from XOP for Si220 at Sc kalpha and Si440 at Cu kalpha.
*
* Non-copyright notice:
* Contributed by the National Institute of Standards and Technology; not subject to copyright in the United States.
* This is not an official contribution, in that the results are in no way certified by NIST.
*
*

Input parameters

Parameters in boldface are required; the others are optional.
NameUnitDescriptionDefault
length0.05
width0.02
V160.1826
form_factors"FormFactors.txt"
material"Si.txt"
alphax0.0
alphay1.0
alphaz0.0
R00
debye_waller_B0.4632
crystal_type1
h1
k1
l1
structure_factor_scale_r0.0
structure_factor_scale_i0.0
verbose0

Output parameters

Parameters in boldface are required; the others are optional.
NameUnitDescriptionDefault

Links


[ Identification | Description | Input parameters | Output parameters | Links ]

Generated on 2022-02-07 20:46:44


Last Modified: Wednesday, 11-May-2022 22:46:12 CEST
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