# The `Test_Lens` Instrument

*McStas: Demonstrate focusing effect of refractive lenses

%Example: lambda=10 position_PSD=8.2 Detector: Last_PSD_I=2.6829e-19*

## Identification

- **Site:** Tests_optics
- **Author:** E. Farhi/C. Monzat
- **Origin:** ILL
- **Date:** Dec 2009.

## Description

```text

```

## Input parameters

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

| Name | Unit | Description | Default |
|------|------|-------------|---------|
| lambda | Angs | Source wavelength | 10 |
| position_PSD | m | Distance from last lens to first monitor | 8.2 |

## Links

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

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