Merlin
Merlin is a high-intensity, medium energy resolution direct geometry chopper spectrometer ideal for single crystal studies. It features a supermirror guide, large-angle detector coverage and is able to run in repetition-rate multiplication mode, allowing users to simultaneously measure with several incident energies.
Instrument scientists
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Technical information
| Beamline | S4/5 |
| Moderator | 300K dedicated water moderator centrally poisoned with Gd |
| Neutron guides | Supermirror converging m3 guides |
| Incident energy | 7-2000 meV |
| Energy resolution | Depends on the choice and speed of Fermi chopper. Δhω/Ei=4-7% FWHM at the elastic line |
| Primary flight path | 11.8 m |
| Secondary flight path | 2.5 m |
| Fermi chopper | 10 m from the moderator. 50-600 Hz phased to ISIS pulse ±0.1 ms - Sloppy package is available optimised for high flux and medium resolution. - Alternatively Gd chopper package enables operation in RRM mode, but places upper limit of 200 meV on incident energy. |
| Background chopper | 8.5 m at 50 Hz |
| Sample position | 11.8 m from the moderator |
| Beam size at the sample | 50 x 50 mm, motorised jaws can define a smaller beam size |
| Detectors | 2.5 m from the sample position. Position sensitive 3He tubes (10 bar partial pressure) 2.5 cm diameter, 3 m long, resolution 21 mm along the tube. Angular range: -45° to 135° horizontal; ±30° vertical direction. Smallest scattering angle 3°. |
| Intensity at the sample (Ei= 45 mev, Δhω/Ei=5%) | 6x104 ncm-2 s-1 |
| Detector pixels | 69632 |
| Solid angle (Sr) | 3.1 |
| Sample enviroment | Accepts all standard sample environment. Instrument tank constrains maximum magnetic field available: - 4 T in 7.5 T standard magnet - 2 T in wide-angle 9 T magnet |
Related resources
Technical overview
Merlin has been in user operation since 2008. Its design exploits 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 idea for the study of single crystals.
The detector bank covers a massive π steradians of solid angle with an angular range from –45o to +135o in the horizontal plane, and ±30o in the vertical plane. This allows large swathes of Q, ω space to be accessed in a single run.
Since 2014, Merlin has been running in event mode, and by using a 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 between 7 meV and 2000 meV.
Sample environment
Merlin has top-loading CCR operating in the temperature range 6 – 575 K, an orange cryostat operating in the temperature range 2 – 300 K and a dilution fridge operating in the temperature range 0.1 – 4 K.
Recent publications
Instrument reference
All publications and datasets based on experiments using Merlin should cite that the data is collected by DOI: 10.5286/isis.instrument.9632. Experiment DOIs follow the format 10.5286/ISIS.E.RBXXXXXXX, where XXXXXXX is the 7-digit experiment (RB) number and these can be viewed via the Data Gateway.