[ Identification | Description | Input parameters | Links ]

# The `Guide_channeled` Component

Neutron guide with channels (bender section).

## Identification

- Site:
- Author: Christian Nielsen
- Origin: Risoe
- Date: 1999

## Description

    Models a rectangular guide tube centered on the Z axis. The entrance lies
    in the X-Y plane.
    The guide may be tapered, and may have vertical subdivisions (used for
    bender devices).

    There is a special rotating mode in order to approximate a Fermi Chopper
    behaviour, in the case the neutron trajectory is nearly linear inside the
    chopper slits, i.e. the neutrons are fast w/r/ to the chopper speed.
    Slits are straight, but may be super-mirror coated. In this case, the
    component is NOT centered, but located at its entry window. It should then
    be shifted by -l/2.

    Example: Guide_channeled(w1=0.1, h1=0.1, w2=0.1, h2=0.1, l=2.0,
    R0=0.99, Qcx=0.0219, Qcy=0.0219, alphax=6.07, alphay=6.07, W=0.003, nslit=1,
    d=0.0005, mx=1, my=1)

    %BUGS
    This component does not work with gravitation on. Use Guide_gravity.
    This component does not work in multichannel focusing geometry.

## Input parameters

Parameters in boldface are required; the others are optional.

Name | Unit | Description | Default |
w1 | m | Width at the guide entry |  |
h1 | m | Height at the guide entry |  |
w2 | m | Width at the guide exit | 0 |
h2 | m | Height at the guide exit | 0 |
l | m | Length of guide |  |
R0 | 1 | Low-angle reflectivity | 0.995 |
Qc | AA-1 | Critical scattering vector | 0 |
alpha | AA | Slope of reflectivity | 0 |
m | 1 | m-value of material. Zero means completely absorbing. | 0 |
nslit | 1 | Number of channels in the guide (>= 1) | 1 |
d | m | Thickness of subdividing absorbing walls | 0.0005 |
Qcx | AA-1 | Critical scattering vector for left and right vertical mirrors in each channel | 0.0218 |
Qcy | AA-1 | Critical scattering vector for top and bottom mirrors | 0.0218 |
alphax | AA | Slope of reflectivity for left and right vertical mirrors in each channel | 4.38 |
alphay | AA | Slope of reflectivity for top and bottom mirrors | 4.38 |
W | AA-1 | Width of supermirror cut-off for all mirrors | 0.003 |
mx | 1 | m-value of material for left and right vertical mirrors in each channel. Zero means completely absorbing. | 1 |
my | 1 | m-value of material for top and bottom mirrors. Zero means completely absorbing. | 1 |
nu | Hz | Rotation frequency (round/s) for Fermi Chopper approximation | 0 |
phase | deg | Phase shift for the Fermi Chopper approximation | 0 |

AT ( | , | , |  | ) RELATIVE |  |
ROTATED ( | , | , |  | ) RELATIVE |

## Links

- Source code for `Guide_channeled.comp`.

[ Identification | Description | Input parameters | Links ]