[ Identification | Description | Input parameters | Output parameters | Links ]

# The `V_sample` Component

Vanadium sample.

## Identification

- Author: Kim Lefmann and Kristian Nielsen
- Origin: Risoe
- Date: 15.4.98
- Version: 1.36
- Modification history:
  - Aziz Daoud-aladine, ISIS, 2007: Added option to handle a spherical sample shape
  - Peter Christiansen, Risoe: Added outgoing polarization: P' = 1/3*P-2/3P = -1/3P NB! Multiple scattering is ignored .
  - Reynald Arnerin, ILL, 2008: Added option to handle a complex geometry (OFF files)

## 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.
    The complex geometry option handles any closed non-convex polyhedra.
    It computes the intersection points of the neutron ray with the object transparently
    so that it can be used like a regular sample object.
    It supports the OFF and NOFF file format but not COFF (colored faces).
    The default size of the object depends of the file datas.

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

    Example: V_sample(offfile=pc.off,focus_r=0.035,pack=1,
              target_index=1)

## Input parameters

Parameters in boldface are required; the others are optional.

Name | Unit | Description | Default
--- | --- | --- | ---
*offfile |  |  | 0
radius_i | m | Inner radius of sample in (x,z) plane | 0
radius_o | m | Outer radius of sample in (x,z) plane | 0
h | m | Height of sample y direction | 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 | horiz. angular dimension of a rectangular area | 0
focus_ah | deg | vert. angular dimension of a rectangular area | 0
xwidth | m | horiz. dimension of sample (bounding box if off file), as a width | 0
yheight | m | vert. dimension of sample (bounding box if off file), as a height | 0
zthick | m | thickness of sample (bounding box if off file) | 0
rad_sphere | m | Radius for a spherical sample | 0
sig_a | barns | Absorbtion cross section pr. unit cell | 5.08
sig_i | barns | Incoherent scattering cross section pr. unit cell | 5.08
V0 | AA^3 | Unit cell volume | 13.827
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

## Output parameters

Name | Unit | Description | Default
--- | --- | --- | ---
VarsV |  |  |
offdata |  |  |

## 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.

[ Identification | Description | Input parameters | Output parameters | Links ]