[ Identification | Description | Input parameters | Output parameters | Links ]

# The `ESS_moderator_short` Component

A parametrised pulsed source for modelling ESS short pulses.

## Identification

- Author: KL, February 2001
- Origin: Risoe
- Date:(Unknown)
- Version: 1.19
- Modification history:
  - KL, 18 November 2001

## Description

    Produces a time-of-flight spectrum, from the ESS parameters
    Chooses evenly in lambda, exponentially decaying in time .
    Adapted from Moderator by: KN, M.Hagen, August 1998

    Units of flux: n/cm^2/s/AA/ster
    (McStas units are in general neutrons/second)

## Input parameters

Parameters in boldface are required; the others are optional.

Name | Unit | Description | Default
--- | --- | --- | ---
size | m | Edge of cube shaped source |
l_low | AA | Lower edge of lambda distribution |
l_high | AA | Upper edge of energy distribution |
dist | m | Distance from source to focusing rectangle; at (0,0,dist) |
xw | m | Width of focusing rectangle |
yh | m | Height of focusing rectangle |
freq | Hz | Frequency of pulses |
T | K | Temperature of source |
tau | s | long time decay constant for pulse, 1a |
tau1 | s | long time decay constant for pulse, 1b (only for coupled water, else 0) |
tau2 | s/AA | long time decay constant for pulse, 2 |
n | 1 | pulse shape parameter 1 |
n2 | 1 | pulse shape parameter 2 |
chi2 | 1/AA | lambda-distribution parameter in pulse 2 |
I0 | flux | integrated flux 1 (in flux units, see above) (default 9e10) |
I2 | flux*AA | integrated flux 2 (default 4.6e10) |
branch1 | 1 | limit for switching between distribution 1 and 2. (has effect only for coupled water, tau1>0) |
branch2 | 1 | limit for switching between distribution 1 and 2. (default value 0.5) |
branchframe | 1 | limit for switching between 1st and 2nd pulse (if only one pulse wanted: 1) |

## Output parameters

Name | Unit | Description | Default
--- | --- | --- | ---
M |  |  |
F |  |  |
l_range |  |  |
w_mult |  |  |

## Links

- Source code for `ESS_moderator_short.comp`.

[ Identification | Description | Input parameters | Output parameters | Links ]