Velocity selector consisting of rotating Soller-like blades
defining a helically twisted passage.
Geometry defined by two identical, centered apertures at 12 o'clock
position, Origo is at the centre of the selector (input is at -zdepth/2).
Transmission is analytical assuming a continuous source.
Example: V_selector(xwidth=0.03, yheight=0.05, zdepth=0.30, radius=0.12, alpha=48.298,
length=0.25, d=0.0004, nu=20000, nslit=72)
These are values for the D11@ILL Dornier 'Dolores' Velocity Selector (NVS 023)
Jun 2005: extensive external test, no problems found
Validated by: K. Lieutenant
Parameters in boldface are required;
the others are optional.
Width of entry aperture
Height of entry aperture
Distance between apertures, for housing containing the rotor
Height from aperture centre to rotation axis
Twist angle along the cylinder
Length of cylinder/rotor (less than zdepth)
Thickness of blades
Cylinder rotation speed, counter-clockwise,
which is ideally 3956*alpha*DEG2RAD/2/PI/lambda/length