MAPS technical information

MAPS instrument parameters

Technical Summary




300K water moderator poisoned at 1.5 cm

Incident energy

15-2000 meV

Energy resolution 

Depends on the choice of Fermi chopper

D hw /Ei = 2 – 5% FWHH at elastic line (hw  = 0)

» 1.5% FWHH at full energy transfer (hw  = Ei)

Primary flight path


Secondary flight path


Fermi Chopper

10m from moderator

50-600 Hz phased to ISIS pulse ±  0.1m s

Several chopper packages are available optimised for different incident energy and resolution requirements:


S chopper - flexible standard package suitable for 10<Ei<3000 meV, 1.5% - 5% Ei typical resolution, higher flux than the A chopper.


A chopper - high resolution package, suitable for Ei>100 meV; 1.5% - 5% Ei resolution

Background chopper

8.5m at 50 Hz or 100 Hz

Sample position

12.0m from moderator

Beam size at sample

55mm x 55mm, motorised jaws can define smaller beam sizes


6 m from sample position

approx 16m2 array of 147,456 pixel elements

Position sensitive 3He tubes (10 bar partial pressure) 2.5 cm diameter, resolution 15mm along their lengths

Low angle bank 3-20º, 30º in the corners (438 x 1m & 1.3m PSDs)

High angle bank 20-60º 1m (136 x 1m PSDs)

Intensity at sample 

5000 n cm-2 s-1  Dhw/E= 2% at elastic line

Ei = 500 meV

20000 n cm-2 s-1 Dhw/E= 5% at elastic line

Sample environment 

Accepts all standard sample environment equipment

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