[ Identification | Description | Input parameters | Links ]

# The `ESS_butterfly_tfocus_test` Instrument

Test instrument for the updated BF1 butterfly moderator design

## Identification

- Site: ESS
- Author: Peter Willendrup <pkwi@fysik.dtu.dk>
- Origin: ESS
- Date: 2016-08-24

## Description

    Test instrument for the updated BF1 butterfly moderator design.

    The below example gives a 50-50 (statistics-wise) cold/thermal beam at beamline N10.

## Input parameters

Parameters in boldface are required; the others are optional.

Name | Unit | Description | Default
sector | str | Defines the 'sector' of your instrument position. Valid values are "N","S","E" and "W" | "N"
beamline | 1 | Defines the 'beamline number' of your instrument position. Valid values are 1..10 or 1..11 depending on sector | 1
Lmin | AA | Minimum wavelength simulated | 0.2
Lmax | AA | Maximum wavelength simulated | 20
c_performance | 1 | Cold brilliance scalar performance multiplicator c_performance > 0 | 1
t_performance | 1 | Thermal brilliance scalar performance multiplicator t_performance > 0 | 1
index | 1 | Target index for source focusing. Defaults to illuminate the "cold collimated" brilliance monitor, thereby suppressing "dist" | 0
dist | m | Distance from origin to focusing rectangle; at (0,0,dist) - alternatively use target_index | 100
cold | 1 | Defines the statistical fraction of events emitted from the cold part of the moderator | 0.5
Yheight | m | Defines the moderator height. Valid values are 0.03 m and 0.06 m | 0.03
delta | m | Parameter that allows to scan "collimator" position | 0
tfocus_dist |  |  | 10
tfocus_time |  |  | 0.01
tfocus_width |  |  | 0.001

## Links

- Source code for `ESS_butterfly_tfocus_test.instr`.
- <reference/HTML link>
- Benchmarking website available at http://ess_butterfly.mcstas.org

[ Identification | Description | Input parameters | Links ]