The Near and InterMediate Range Order Diffractometer (NIMROD) was built as a Day 1 instrument on the west side of the ISIS Second Target Station. It incorporates both small and wide angle arrays of high efficiency ZnS-based neutron scintillation detectors covering a wide solid angle from 2θ = 0.5 to 40°. This, combined with the longer wavelength neutrons available from the coupled hydrogen moderator on TS2, allows a routine simultaneous Q-range of 0.02 to 50 Å-1. NIMROD views both the hydrogen moderator and water pre-moderator, which gives rise to significantly enhanced fluxes at the shorter wavelengths. NIMROD bridges the traditional gap between SANS and wide-angle neutron scattering, by using a common calibration procedure for all Q-scales. The instrument makes full use of the longer wavelengths on the second target station, to increase the upper limit of the accessible correlation length, while also extracting high-resolution from the shorter wavelengths.
As with SANDALS both incident and scattered flight paths are under vacuum, but, unlike SANDALS, the incident collimator has a series of beam-defining adjustable apertures with associated monitors, which provide precise control of the beam footprint on the sample. The detectors are housed in a large temperature- and humidity-controlled blockhouse. In total there are 2,268 detectors with 756 of those being in the low angle bank, covering scattering angles of 0.5° to 2.2°. The remainder of the angular range, from 3.5° up to 40° is covered by seven banks of detectors arranged in Debye-Scherrer cones. For the wider angle detectors the design is similar to, but more efficient than, the detectors on SANDALS. In addition, due to the much higher neutron fluxes available, NIMROD is amenable to time dependent (kinetic) studies, with useful data acquired in as little as a few minutes of beam.
In 2009, NIMROD was inaugurated by Professor Maiani from the CNR Italian research council to celebrate the excellent working partnership between Italy, the UK and ISIS in neutron scattering. More information can be found in this archived news article.
NIMROD follows on from the success of SANDALS in allowing a comprehensive
structural understanding of many fundamental and applied hydrogen-containing liquid
systems. These include organic solvents, deep eutectic solvents, capacitor
electrolytes, aqueous solutions and ionic liquids. In addition, the array of
forward scattering detectors (minimising inelasticity effects for light
elements) also allows PDF analysis of hydrogen-containing crystalline materials. A fundamental design principle of NIMROD is to allow the simultaneous
measurement of atomistic and mesoscale correlations within a system. This has
opened up a number of new scientific areas for structural analysis using
neutrons, these include: Two-dimensional nanomaterials, studies of confined
fluids, micellar systems and polymer crystallisation. The ability to study
systems across multiple length-scales simultaneously combined with reasonable
time resolution have allowed an unprecedented in situ structural analysis of complex dynamic systems including
heterogeneous catalysis of aromatic hydrogenation, setting of dental cements, and the structural evolution of porous amorphous ice upon heating.
For more detailed examples, check the instrument's scientific highlights.
Further details of the technical aspects of the instrument and its performance characteristics can be found in:
NIMROD: The Near and InterMediate Range Order Diffractometer of the ISIS second target station D.T.Bowron, A.K.Soper, K.Jones, S.Ansell, S.Birch, J.Norris, L.Perrott, D.Riedel, N.J.Rhodes, A.Botti, M.-A.Ricci, F.Grazzi and M.Zoppi, Review of Scientific Instruments, 81, 033905 (2010).
The original scientific case for the instrument is available, as is a presentation containing some pictures following the construction of the beamline in 2008.