[ Identification | Description | Input parameters | Links ]

# The `Monochromator_curved` Component

Double bent multiple crystal slabs with anisotropic gaussian mosaic.

## Identification

- Site:
- Author: Emmanuel Farhi, Kim, Lefmann, Peter Link
- Origin: ILL
- Date: Aug. 24th 2001

## Description

    Double bent infinitely thin mosaic crystal, useful as a monochromator or
    analyzer. which uses a small-mosaicity approximation and taking into account
    higher  order scattering. The mosaic is anisotropic gaussian, with different
    FWHMs in the Y and Z directions. The scattering vector is perpendicular to the
    surface. For an unrotated monochromator component, the crystal plane lies in
    the y-z plane (ie. parallel to the beam). The component works in reflection, but
    also transmits the non-diffracted beam. Reflectivity and transmission files may
    be used. The slabs are positioned in the vertical plane (not on a
    cylinder/sphere), and are rotated according to the curvature radius.
    When curvatures are set to 0, the monochromator is flat.
    The curvatures approximation for parallel beam focusing to distance L, with
    monochromator rotation angle A1 are:
    RV = 2*L*sin(DEG2RAD*A1);
    RH = 2*L/sin(DEG2RAD*A1);

    When you rotate the component by A1 = asin(Q/2/Ki)*RAD2DEG, do not forget to
    rotate the following components by A2=2*A1 (for 1st order) !

    Example: Monochromator_curved(zwidth=0.01, yheight=0.01, gap=0.0005, NH=11, NV=11, mosaich=30.0, mosaicv=30.0, r0=0.7, Q=1.8734)

    Monochromator lattice parameter
    PG       002 DM=3.355 AA (Highly Oriented Pyrolythic Graphite)
    PG       004 DM=1.677 AA
    Heusler  111 DM=3.362 AA (Cu2MnAl)
    CoFe         DM=1.771 AA (Co0.92Fe0.08)
    Ge       111 DM=3.266 AA
    Ge       311 DM=1.714 AA
    Ge       511 DM=1.089 AA
    Ge       533 DM=0.863 AA
    Si       111 DM=3.135 AA
    Cu       111 DM=2.087 AA
    Cu       002 DM=1.807 AA
    Cu       220 DM=1.278 AA
    Cu       111 DM=2.095 AA

## Input parameters

Parameters in boldface are required; the others are optional.

Name | Unit | Description | Default |
reflect | str | reflectivity file name of text file as 2 columns [k, R] | "NULL" |
transmit | str | transmission file name of text file as 2 columns [k, T] | "NULL" |
zwidth | m | horizontal width of an individual slab | 0.01 |
yheight | m | vertical height of an individual slab | 0.01 |
gap | m | typical gap between adjacent slabs | 0.0005 |
NH | int | number of slabs horizontal | 11 |
NV | int | number of slabs vertical | 11 |
mosaich | arc minutes | Horisontal mosaic FWHM | 30.0 |
mosaicv | arc minutes | Vertical mosaic FWHM | 30.0 |
r0 | 1 | Maximum reflectivity. O unactivates component | 0.7 |
t0 | 1 | transmission efficiency | 1.0 |
Q | AA-1 | Scattering vector | 1.8734 |
RV | m | radius of vertical focussing. flat for 0 | 0 |
RH | m | radius of horizontal focussing. flat for 0 | 0 |
DM | AA | monochromator d-spacing instead of Q=2*pi/DM | 0 |
mosaic | arc minutes | sets mosaich=mosaicv | 0 |
width | m | total width of monochromator, along Z | 0 |
height | m | total height of monochromator, along Y | 0 |
verbose | 0/1 | verbosity level | 0 |
order | 1 | specify the diffraction order, 1 is usually prefered. Use 0 for all | 0 |

AT ( | , | , |  | ) RELATIVE |  |
ROTATED ( | , | , |  | ) RELATIVE |

## Links

- Source code for `Monochromator_curved.comp`.
- Additional note from Peter Link.
- Obsolete Mosaic_anisotropic by Kristian Nielsen
- Contributed Monochromator_2foc by Peter Link

[ Identification | Description | Input parameters | Links ]