[ Identification | Description | Input parameters | Links ]

# The `ISIS_MERLIN` Instrument

## Identification

- Site: ISIS
- Author: Rob Bewley
- Origin: ISIS (UK)
- Date: May 2017.

## Description

    Merlin has been in user operation since 2008. It was designed to be a high intensity, medium energy
    resolution spectrometer that would complement the high-resolution MAPS spectrometer, and replace
    the HET spectrometer. Merlin's design exploited recent advances in technology with a supermirror
    guide to enhance flux, as well as 3 m long position-sensitive detectors in a vacuum, making it
    ideal for the study of single crystals. The detector bank covers a massive \pi steradians of solid
    angle with an angular range from -45 to 135 degrees in the horizontal plane, and \pm 30 degrees in
    the vertical plane. This allows large swathes of Q,\omega space to be accessed in a single run.

    Since 2014, Merlin has been running in event mode, and by using the new Gd chopper combined with a
    disk chopper, it is able to run in repetition-rate multiplication (RRM) mode, allowing users to
    simultaneously measure with several incident energies.

## Input parameters

Parameters in boldface are required; the others are optional.

Name | Unit | Description | Default
E_min | meV | lowest energy sampled [meV] | 1.0
E_max | meV | highest energy sampled [meV] | 2000.0
m | float | m value of guides | 3.0
E_foc | meV | energy selected by chopper [meV] | 80.0
nu_hz | Hz | frequency of chopper rotation [Hz] | 200.0
type | int | chopper package selected sloppy chopper = 1, B chopper = 2, Gd chopper = 3 | 3

## Links

- Source code for `ISIS_MERLIN.instr`.
- http://www.isis.stfc.ac.uk/instruments/merlin

[ Identification | Description | Input parameters | Links ]