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

`Bragg_crystal_bent_BC`

Component-
**Author:**Marcus H Mendenhall, NIST -
**Origin:**Marcus H. Mendenhall, NIST, Gaithersburg, MD, USA -
**Date:**December 1, 2016 -
**Version:**2.0-a

Bragg_crystal_bent_BC.comp is intended to supercede Bragg_crystal_bent.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 NOTE: elliptical coordinate code and documentation taken from Mirror_elliptic.comp distributed in McXtrace v1.2 However, the coordinates are rotated to be consistent with Bragg_crystal_flat.comp and Perfect_Crystal.comp. Idealized elliptic mirror with surface ellipse and lattice ellipses independent, to allow construction of Johansson optics, for example.WARNING:

Name | Unit | Description | Default |
---|---|---|---|

x_a | m | 1st short half axis (along x). Commonly set to zero, which really implies infinite value, so crystal is an elliptic cylinder. | 0 |

y_b | m | 2nd short half axis (along y), which is also the presumed near-normal direction, reflection near the y-z plane. | 1.0 |

z_c | m | long half axis (along z). Commonly a=0. b=c, which creates a circular cylindrical surface. | 1.0 |

lattice_x_a | m | curvature matrix for underlying lattice, for bent/ground/rebent crystals THERE HAS BEEN NO TESTING for the case in which lattice_x_a != x_a. | 0 |

lattice_y_b | m | curvature matrix for underlying lattice, for bent/ground/rebent crystals | 1.0 |

lattice_z_c | m | curvature matrix for underlying lattice, for bent/ground/rebent crystals | 1.0 |

length | m | z depth (length) of the crystal. | 0.05 |

width | m | x width of the crystal. | 0.02 |

V | AA^3 | unit cell volume | 160.1826 |

form_factors | "FormFactors.txt" | ||

material | maybe also GaAs? | [ ] Si, Ge | "Si.txt" |

alpha | rad | asymmetry angle (alpha=0 for symmetric reflection, ie the Bragg planes are parallel to the crystal surface) alpha is defined so that positive alpha reduces the Bragg angle to the plane i.e. alpha=Thetain grazes the planes. if alpha!=0, one should restrict to rays which have small kx values, since otherwise the alpha rotation is not around the diffraction axis. | 0.0 |

R0 | Reflectivity. Overrides the computed Darwin reflectivity. Probably only useful for debugging. | 0 | |

debye_waller_B | AA^2 | Debye-Waller temperature factor, M=B*(sin(theta)/lambda)^2*(2/3), default=silicon at room temp. | 0.4632 |

crystal_type | 1 => Mx_crystal_explicit: provide explicit real and imaginary form factor multipliers structure_factor_scale_r, structure_factor_scale_i, 2 => Mx_crystal_diamond: diamond 3 => Mx_crystal_fcc: fcc 4 => Mx_crystal_fcc: bcc | 1 | |

h | Miller index of reflection | 1 | |

k | Miller index of reflection | 1 | |

l | Miller index of reflection | 1 | |

structure_factor_scale_r | 0.0 | ||

structure_factor_scale_i | 0.0 |

Name | Unit | Description | Default |
---|---|---|---|

prms |
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a2inv |
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b2inv |
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c2inv |
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l_a2inv |
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l_b2inv |
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l_c2inv |
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cos_alpha0 |
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sin_alpha0 |

- Source code for
`Bragg_crystal_bent_BC.comp`

.

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

Generated automatically by McDoc, Peter Willendrup <peter.willendrup@risoe.dk> / Tue Apr 28 09:59:35 2020