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McStas: ISIS_MERLIN Instrument at ISIS

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

The ISIS_MERLIN Instrument

MERLIN: High count rate, medium energy resolution, direct geometry chopper spectrometer.


  • Site: ISIS
  • Author: Rob Bewley
  • Origin: ISIS (UK)
  • Date: May 2017.
  • Version:(Unknown)


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


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

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Last Modified: Wednesday, 12-Jan-2022 16:13:21 CET
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