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

The Monochromator_curved Component

Identification

Description

Input parameters

Links

The `Monochromator_curved` Component