[ Identification | Description | Input parameters | Links ]

# The `Selector` Component

velocity selector (helical lamella type) such as V_selector component

## Identification

- Site:
- Author: Peter Link, Andreas Ostermann
- Origin: Uni. Gottingen (Germany)
- Date: MARCH 1999

## Description

    Velocity selector consisting of rotating Soller-like blades
    defining a helically twisted passage.
    Geometry is defined by two identical apertures at 12 o'clock position,
    The origin is at the ENTRANCE of the selector.

    Example: Selector(xmin=-0.015,  xmax=0.015,  ymin=-0.025, ymax=0.025, length=0.25,
    nslit=72,d=0.0004, radius=0.12, alpha=48.298, nu=500)
    These are values for the D11@ILL Dornier 'Dolores' Velocity Selector (NVS 023)

    %VALIDATION
    Jun 2005: extensive external test, one minor problem
    Jan 2006: problem solved (for McStas-1.9.1)
    Validated by: K. Lieutenant

    %BUGS
    for transmission calculation, each neutron is supposed to be in the guide centre

## Input parameters

Parameters in boldface are required; the others are optional.

Name | Unit | Description | Default |
xmin | m | Lower x bound of entry aperture | -0.015 |
xmax | m | Upper x bound of entry aperture | 0.015 |
ymin | m | Lower y bound of entry aperture | -0.025 |
ymax | m | Upper y bound of entry aperture | 0.025 |
length | m | rotor length | 0.25 |
xwidth | m | Width of entry. Overrides xmin,xmax. | 0 |
yheight | m | Height of entry. Overrides ymin,ymax. | 0 |
nslit | 1 | number of absorbing subdivinding spokes/lamella | 72 |
d | m | width of spokes at beam-center | 0.0004 |
radius | m | radius of beam-center | 0.12 |
alpha | deg | angle of torsion | 48.298 |
nu | Hz | frequency of rotation, which is ideally 3956*alpha*DEG2RAD/2/PI/lambda/length | 500 |

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

## Links

- Source code for `Selector.comp`.
- See also Additional notes March 1999 and Jan 2000.

[ Identification | Description | Input parameters | Links ]