The `IncoherentPhonon_process` Component

A component to simulate inelastic scattering in the incoherent approximation Takes into account one, two, and three phonon scattering explicitly, and multi-phonon scattering (with n>4) via the saddle point method

Identification

Site:
Author: Victor Laliena
Origin: University of Zaragoza
Date: 06.11.2018

Description

Part of the Union components, a set of components that work together and thus
expects geometry and physics within McStas.
The use of this component requires other components to be used.

1) One specifies a number of processes using process components like this one
2) These are gathered into material definitions using Union_make_material
3) Geometries are placed using Union_box / Union_cylinder, assigned a material
4) A Union_master component placed after all of the above


Algorithm:
Described elsewhere, see e.g. https://doi.org/10.3233/JNR-190117

Input parameters

Parameters in boldface are required; the others are optional.

Name	Unit	Description	Default
T	K	Temperature	394
density	g/cm3	Material density	6.0
M	amu	ion mass	50.94
sigmaCoh	barns	Coherent scattering cross section	0.0184
sigmaInc	barns	Incoherent scattering cross section	5.08
DOSfn	string	Path to the file that contains the DoS	NULL
nphe_exact	1	Number of terms in the phonon expansion taken exact. Has to be between 1 and 3.	1
nphe_approx	1	Number of terms in the phonon expansion taken approximate.	0
approx	1	Approximation type: 0 gaussian, 1 saddle point	0
mph_resum	0/1	Resumate the remaining terms of the phonon expansion via a saddle point: 0 No, 1 Yes	0
nxs	1	Number of energy points at which the total cross sections are precomputed	1000
kabsmin	A^-1	Lower cut-off for the neutron wave-vector k	0.1
kabsmax	A^-1	Higher cut-off for the neutron wave-vector k	25
interact_fraction	1	How large a part of the scattering events should use this process 0-1 (sum of all processes in material = 1)	-1
init			"init"

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

The IncoherentPhonon_process Component

Identification

Description

Input parameters

Links

The `IncoherentPhonon_process` Component