[ Identification | Description | Input parameters | Links ]

The V_sample Component

Vanadium sample.

Identification

• Site:
• Author: Kim Lefmann and Kristian Nielsen
• Origin: Risoe
• Date: 15.4.98

Description

A Double-cylinder shaped incoherent scatterer (a V-sample)
with both elastic and quasielastic (Lorentzian) components.
No multiple scattering. Absorbtion included.
The shape of the sample may be a box with dimensions xwidth, yheight, zthick.
The area to scatter to is a disk of radius 'focus_r' situated at the target.
This target area may also be rectangular if specified focus_xw and focus_yh
or focus_aw and focus_ah, respectively in meters and degrees.
The target itself is either situated according to given coordinates (x,y,z),
or defined with the relative target_index of the component to focus
to (next is +1).
This target position will be set to its AT position. When targeting to
centered components, such as spheres or cylinders, define an Arm component
where to focus to.

Example: V_sample(radius_i=0.001,radius_o=0.01,h=0.02,focus_r=0.035,pack=1,
target_index=1)

Input parameters

Parameters in boldface are required; the others are optional.

Name	Unit	Description	Default
radius	m	Outer radius of sample in (x,z) plane	0
thickness	m	Thickness of outer wall	0
zdepth	m	depth of box sample	0
Vc		Unit cell volume [AA^3]	13.827
sigma_abs	barns	Absorbtion cross section pr. unit cell	5.08
sigma_inc	barns	Incoherent scattering cross section pr. unit cell	5.08
radius_i	m	radius-thickness	0
radius_o	m	Same as radius	0
h	m	Same as yheight	0
focus_r	m	Radius of disk containing target. Use 0 for full space	0
pack	1	Packing factor	1
frac	1	MC Probability for scattering the ray; otherwise penetrate	1
f_QE	1	Fraction of quasielastic scattering (rest is elastic)	0
gamma	1	Lorentzian width of quasielastic broadening (HWHM)	0
target_x			0
target_y	m	position of target to focus at	0
target_z			0
focus_xw	m	horiz. dimension of a rectangular area	0
focus_yh	m	vert. dimension of a rectangular area	0
focus_aw	deg	angular width dimension of a rectangular area	0
focus_ah	deg	angular height dimension of a rectangular area	0
xwidth	m	horiz. dimension of sample	0
yheight	m	vert. dimension of sample	0
zthick	m	Same as zdepth	0
rad_sphere	m	Radius for a spherical sample	0
sig_a	barns	Same as sigma_abs	0
sig_i	barns	Same as sigma_inc	0
V0		Same as Vc [AA^3]	0
target_index	1	relative index of component to focus at, e.g. next is +1	0
multiples	1	Apply crude estimate for multiple scattering	1

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

Links

• Source code for V_sample.comp.
• Test
• results (not up-to-date).
• The test/example instrument vanadium_example.instr.
• The test/example instrument QENS_test.instr.

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[ Identification | Description | Input parameters | Links ]

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Last Modified: Monday, 30-Jun-2025 11:05:09 CEST