Incoherent sample (such as Vanadium) sample, with quasielastic component.
Author: Kim Lefmann and Kristian Nielsen
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! As above multiple scattering is ignored .
Reynald Arnerin, ILL, 2008: Added option to handle a complex geometry (OFF files)
A Double-cylinder shaped incoherent scatterer (like Vanadium)
with both elastic and quasielastic (Lorentzian) components.
No multiple scattering (but approximation available). Absorption included.
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.
Sample shape may be a cylinder, a sphere, a box or any other shape
box/plate: xwidth x yheight x zdepth (thickness=0)
hollow box/plate:xwidth x yheight x zdepth and thickness>0
cylinder: radius x yheight (thickness=0)
hollow cylinder: radius x yheight and thickness>0
sphere: radius (yheight=0 thickness=0)
hollow sphere: radius and thickness>0 (yheight=0)
any shape: geometry=OFF file
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 PLY, OFF and NOFF file format but not COFF (colored faces).
Such files may be generated from XYZ data using:
qhull < coordinates.xyz Qx Qv Tv o > geomview.off
and viewed with geomview or java -jar jroff.jar (see below).
The default size of the object depends of the OFF file data, but its
bounding box may be resized using xwidth,yheight and zdepth.
Example: Incoherent(radius=0.05,focus_r=0.035, pack=1, target_index=1)
Incoherent(geometry="socket.off",focus_r=0.035, pack=1, target_index=1)
Parameters in boldface are required;
the others are optional.
Name of an Object File Format (OFF) or PLY file for complex geometry. The OFF/PLY file may be generated from XYZ coordinates using qhull/powercrust
Outer radius of sample in (x,z) plane
Horiz. dimension of sample (bounding box if off file), as a width
Vert. dimension of sample (bounding box if off file), as a height. A sphere shape is used when 0 and radius is set
bounding box if off file
[m] Depth of sample
Thickness of hollow sample
position of target to focus at
Radius of disk containing target. Use 0 for full space
horiz. dimension of a rectangular area
vert. dimension of a rectangular area
horiz. angular dimension of a rectangular area
vert. angular dimension of a rectangular area
Relative index of component to focus at, e.g. next is +1
MC Probability for scattering the ray; otherwise transmit
rest is elastic
 Fraction of quasielastic scattering
 Lorentzian width of quasielastic broadening
Absorption cross section pr. unit cell at 2200 m/s
Incoherent scattering cross section pr. unit cell
Unit cell volume
only for box, cylinder, sphere
 Indicate that this component has a hollow geometry and may contain other components. It should then be duplicated after the inside part
Limit multiple scattering up to given order 0:all (default), 1:single, 2:double, ...