[ 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 |  |
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.

[ Identification | Description | Input parameters | Links ]