Module Chopper

# 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.