The `Single_crystal_inelastic` Component

An extension of Single crystal with material dispersion

Identification

Site:
Author: Some Guy
Origin: DTU Physics
Date: August 2020

Description

The component handles a 4D S(q,w) material dispersion, and scatters neutrons
out of it. It is based on the Isotropic_Sqw methodology, extended to 4D.

A number of approximations are applied:

- geometry is restricted to box, cylinder and sphere
- ignore absorption, multiple scattering and incoherent scattering
- no temperature handling. The temperature must be taken into account when
generating the S(q,w) data sets, which should contain Bose/detailed balance.
- intensity is used as provided by the S(q,w) data set

We recommend that you first try the Test_Single_crystal_inelastic example to
learn how to use this complex component.

4D S(q,w) data files
--------------------

The input data file derives from other McStas formats. It may contain structural
information as in Lau/Laz files, and a list of S(q,w) [one per row] with 5 columns

[ H K L E S(q,w) ]

An example file example.sqw4 is provided in the McStas/Data directory.

You may generate such files using iFit  such as:

s = sqw_vaks('defaults');             % a 4D model
d = iData(s);                         % use default coarse grid for axes [-0.5:0.5]
saveas(d, 'sx_coh.sqw4', 'mcstas');   % export to 4D Sqw file

%VALIDATION:
This component is undergoing validation.

Input parameters

Parameters in boldface are required; the others are optional.

Name	Unit	Description	Default
mosaic_AB	arcmin,arcmin,1,1,1,1,1,1	In Plane mosaic rotation and plane vectors (anisotropic),	Mosaic_AB_Undefined
sqw			0
geometry	string	Name of an Object File Format (OFF) or PLY file for complex geometry. The OFF/PLY file may be generated from XYZ coordinates using qhull/powercrust.	0
qwidth			0.05
xwidth	m	Width of crystal.	0
yheight	m	Height of crystal.	0
zdepth	m	Depth of crystal (no extinction simulated)	0
radius	m	Outer radius of sample in (x,z) plane.	0
delta_d_d	1	Lattice spacing variance, gaussian RMS.	1e-4
mosaic	arcmin	Isotropic crystal mosaic, gaussian RMS. Puts the crystal in the isotropic mosaic model state, thus disregarding other mosaicity parameters.	-1
mosaic_a	arcmin	Horizontal (rotation around lattice vector a) mosaic (anisotropic), gaussian RMS. Put the crystal in the anisotropic crystal vector state. I.e. model mosaicity through rotation around the crystal lattice vectors. Has precedence over in-plane mosaic model.	-1
mosaic_b	arcmin	Vertical (rotation around lattice vector b) mosaic (anisotropic), gaussian RMS.	-1
mosaic_c	arcmin	Out-of-plane (Rotation around lattice vector c) mosaic (anisotropic), gaussian RMS.	-1
recip_cell	1	Choice of direct/reciprocal (0/1) unit cell definition.	0
barns	1	Flag to indicate if \|F\|^2 from 'reflections' is in barns or fm^2.	0
ax	AA / AA^-1	Coordinates of first (direct/recip) unit cell vector.	0
ay	AA / AA^-1	a on y axis	0
az	AA / AA^-1	a on z axis	0
bx	AA / AA^-1	Coordinates of second (direct/recip) unit cell vector.	0
by	AA / AA^-1	b on y axis	0
bz	AA / AA^-1	b on z axis	0
cx	AA / AA^-1	Coordinates of third (direct/recip) unit cell vector.	0
cy	AA / AA^-1	c on y axis	0
cz	AA / AA^-1	c on z axis	0
p_transmit	1	Monte Carlo probability for neutrons to be transmitted	-1
sigma_abs	barns	Absorption cross-section per unit cell at 2200 m/s.	0
sigma_inc	barns	Incoherent scattering cross-section per unit cell.	0
aa	deg	Unit cell angles alpha, beta and gamma. Then uses norms of	0
bb	deg	Beta angle.	0
cc	deg	Gamma angle.	0
order	1	Limit multiple scattering up to given order	0
RX	m	Radius of horizontal along X lattice curvature. flat for 0.	0
RY	m	Radius of vertical lattice curvature. flat for 0.	0
RZ	m	Radius of horizontal along Z lattice curvature. flat for 0.	0
max_stored_ki			1000
max_bad			10000

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

The Single_crystal_inelastic Component

Identification

Description

Input parameters

Links

The `Single_crystal_inelastic` Component