# The `Bispectral` Instrument

*McStas: Example of bispectral extraction on ESS Butterfly moderator using Union components*

## Identification

- **Site:** ESS
- **Author:** Mads Bertelsen (mads.bertelsen@ess.eu)
- **Origin:** ESS
- **Date:** October 2025

## Description

```text
Bispectral switch conisting of Si blades with supermirror coating and Cu walls,
with different coatings. Materials are simulated using NCrystal.

Example: mcrun Bispectral.instr l_min=0.5 l_max=6.0
```

## Input parameters

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

| Name | Unit | Description | Default |
|------|------|-------------|---------|
| l_min | AA | Shortest simulated wavelength | 0.5 |
| l_max | AA | Longest simulated wavelength | 6.0 |

## Links

- [Source code](Bispectral.instr) for `Bispectral.instr`.
- A reference/HTML link for more information

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