# The `Test_Selectors` Instrument

*McStas: Cross comparison of velocity selector components*

## Identification

- **Site:** Tests_optics
- **Author:** E. Farhi [farhi@ill.fr]
- **Origin:** ILL
- **Date:** Sept 28th, 2010

## Description

```text
Cross comparison of Selector components, using McStas and
contributed components. It shows that all implementations are equivalent.
```

## Input parameters

Parameters in **boldface** are required; the others are optional.

| Name | Unit | Description | Default |
|------|------|-------------|---------|
| selector | 1 | Choice of the velocity selector to test, with | 1 |
| lambda | Angs | neutron wavelength selected by the velocity selector | 4 |
| phi | deg | velocity selector twist angle | 48.3 |
| d_vs | m | velocity selector rotating drum length | 0.25 |

## Links

- [Source code](Test_Selectors.instr) for `Test_Selectors.instr`.

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