VITESS Module Straight Fermi Chopper

This module simulates a Fermi chopper with straight channels i.e. the very fast neutrons are transmitted with only a time modulation and lower speed neutrons are modulated both in time of flight and wavelength.
The geometry of the chopper consists of a rectangular shape object with a wide channel system built in perpendicular direction to the beam (when transmitting) - this is inserted into a cylinder frame in order not to transmit neutrons which do not fly throught the channels (when the rectangular channel system is rotated by 90°). The rotation axix coincides with Z.

Module parameters

Parameter
Unit
Description Command option
position X, Y, Z 
[cm]
center position of the Fermi chopper in the input frame X, -Y, -V
height, width, depth
[cm] 
dimensions of the Fermi chopper, depth means the length of the channels  -a   -b   -c
number of channels number of straight channels -l
wall thickness
[cm] 
thickness of the wall between channels -m
diameter
[cm] 
diameter of the shadowing cylinder -r
rotations per second                  frequency of rotation -n
phase
[deg]
dephasing angle at zero time  -q 


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Last modified:Thu Jan 29 15:10:25 MET 2004, G.Zs.