Typical measurement times are between 6 and 8 hours for a hydrogen-containing sample and shorter for a deuterium or non-hydrogen containing sample. Instrument backgrounds have been minimised to very low levels, which, together with the detector stability, mean SANDALS can reliably perform isotopic difference measurements at the few % difference level. SANDALS can achieve a resolution of 2% Δ Q/ Q across most of its operating Q-range. Owing to the forward scattering arrangement of detectors with a maximum 2 θ of 38°, resolution of Bragg features in the measured diffraction patterns is limited in comparison to a traditional crystallography instrument. This delivers sub-Angstrom distance resolution (~0.1 Å) for pair distribution studies of liquids and disordered materials out to a maximum length scale of ~30 Å. The delivered wavelength bandpass combined with the detector angle coverage result in a practical operating Q-range for SANDALS of 0.1 Å -1 ≤ Q ≤ 50 Å -1. As with GEM, to help minimise backgrounds, the beam collimation and sample space are under vacuum during data collection to prevent air scattering. This arrangement of detectors means SANDALS is optimised for looking at samples containing light elements such as hydrogen or lithium as the contribution to the data by inelastic neutron scattering is minimised.
![n eutron n eutron](https://supernova.eso.org/static/archives/exhibitionimages/screen/1217_B_colliding-neutron-stars-orig-CCfinal.jpg)
This angular range comprises of 18 banks of 20 × 1 × 2 cm (height × width × depth) ZnS scintillator detectors providing a 0.7 sr solid angle coverage with a 50% efficiency for 1 Å neutrons and 0.1% stability over the timescales of a typical experiment. The 'small angle' part of the SANDALS name reflects the forward scattering arrangement of its 660 detectors, which cover 2 θ = 3 – 38°. One set of B 4C jaws and a B 4C final beam scraper aperture are used to define the beam geometry, which most commonly has a 30 mm diameter circular cross-section. The Small Angle Neutron Diffractometer for Amorphous and Liquid Samples (SANDALS) is located on the north side of ISIS Target Station 1 and views the liquid methane moderator, making use of neutrons with wavelengths ranging from 0.05 – 4.95 Å.