Component Manual for the Neutron Ray-Tracing Package McStas, version 3.8.6

13.89  The SasView_surface_fractal McStas Component

SasView surface_fractal model component as sample description.

Identification

Description

SasView_surface_fractal component, generated from surface_fractal.c in sasmodels.

Example: SasView_surface_fractal(radius, fractal_dim_surf, cutoff_length, model_scale=1.0, model_abs=0.0, xwidth=0.01, yheight=0.01, zdepth=0.005, R=0, int target_index=1, target_x=0, target_y=0, target_z=1, focus_xw=0.5, focus_yh=0.5, focus_aw=0, focus_ah=0, focus_r=0, pd_radius=0.0, pd_cutoff_length=0.0)

Input parameters

Parameters in boldface are required; the others are optional.

Name

Unit

Description

Default

radius

Å

([0, inf]) Particle radius.

10.0

fractal_dim_surf

([1, 3]) Surface fractal dimension.

2.0

cutoff_length

Å

([0.0, inf]) Cut-off Length.

500.0

model_scale

Global scale factor for scattering kernel. For systems without inter-particle interference, the form factors can be related to the scattering intensity by the particle volume fraction.

1.0

model_abs

Absorption cross section density at 2200 m/s.

0.0

xwidth

m

([-inf, inf]) Horiz. dimension of sample, as a width.

0.01

yheight

m

([-inf, inf]) vert . dimension of sample, as a height for cylinder/box

0.01

zdepth

m

([-inf, inf]) depth of sample

0.005

R

m

Outer radius of sample in (x,z) plane for cylinder/sphere.

0

target_x

m

relative focus target position.

0

target_y

m

relative focus target position.

0

target_z

m

relative focus target position.

1

target_index

Relative index of component to focus at, e.g. next is +1.

1

focus_xw

m

horiz. dimension of a rectangular area.

0.5

focus_yh

m

, vert. dimension of a rectangular area.

0.5

focus_aw

deg

, horiz. angular dimension of a rectangular area.

0

focus_ah

deg

, vert. angular dimension of a rectangular area.

0

focus_r

m

case of circular focusing, focusing radius.

0

pd_radius

(0,inf) defined as (dx/x), where x is de mean value and dx the standard devition of the variable.

0.0

pd_cutoff_length

(0,inf) defined as (dx/x), where x is de mean value and dx the standard devition of the variable

0.0

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