Browsing by Author "Wakeham, D"

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    Australian centre for neutron scattering: sample environment report
    (Australian Institute of Nuclear Science and Engineering (AINSE), 2018-11-19) Manning, AG; Wakeham, D; Davidson, G; Booth, N; Imperia, P; White, R; Lee, S; D'Adam, TM
    In the past 2 years since the 2016 AANSS symposium, the sample environment group of the Australian Centre for Neutron Scattering (ACNS) has continued to facilitate neutron experiments and expand sample environment capability. This report will present the current sample environment and laboratory facilities and recent developments. We have made progress in light irradiation and spectroscopy developments; on a new temperature controlled multi-sample changer with tumbling capability; on a rotational PE Cell; and on new sample probes made from composite materials. Other improvements include new high pressure couplings for helium compressors and modifications to a dilution insert to allow larger samples and use in other cryostats extending the capability. Ongoing major projects are a new superconducting split-coil magnet dedicated to SANS and TOFPAS, two new cryostats (1.5 K to 800 K temperature range) with the aim of halving the system and sample cooling time and a new dilution fridge that will allow top-loading of samples and the ability to take much larger samples than the existing dilution insert. There have also been staffing changes with previous Sample Environment Group Leader, Paolo Imperia moving into the Operations Manager position. The new group leader, Rachel White, was recently appointed. Our Laboratory Manager, Deborah Wakeham, joined us in July 2017. © The Authors.
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    Quokka, the pinhole small-angle neutron scattering instrument
    (Australian Institute of Nuclear Science and Engineering (AINSE), 2020-11-11) Wood, K; Garvey, CJ; Mata, JP; Wakeham, D; Wu, CM; Gilbert, EP
    Quokka was the first Small Angle Neutron Scattering instrument to be in operation at the Australian research reactor, OPAL [1]. It is a 40 m pinhole instrument operating with a neutron velocity selector, an adjustable collimation system providing source-sample distances of up to 20 m and a two dimensional 1 metre square position-sensitive detector, capable of measuring neutrons scattered from the sample over a secondary flight path of up to 20 m. Also offering incident beam polarization and analysis capability as well as lens focusing optics, Quokka has been designed as a general purpose SANS instrument with a large sample area, capable of accommodating a variety of sample environments. Calibrated absolute scattering intensity measurements in a standard setup may be made over a range of wavelengths between 4 x 10-3 Å-1 and 0.7 Å-1. Here we describe Quokka’s design characteristics, performance and operation, including a high count rate detector, installed in 2018. Outputs from Quokka have been published in diverse fields such as magnetism, metallurgy, mineralogy, structural biology, polymers, food science and soft matter. We present here a selection of recent scientific highlights. © 2020 The Authors.
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    Structure of the ethylammonium nitrate surface: an x-ray reflectivity and vibrational sum frequency spectroscopy study
    (American Chemical Society, 2010-06-01) Niga, P; Wakeham, D; Nelson, A; Warr, GG; Rutland, M; Atkin, R
    X-ray reflectivity and vibrational sum frequency spectroscopy are used to probe the structure of the ethylammonium nitrate (EAN)−air interface. X-ray reflectivity reveals that the EAN−air interface is structured and consists of alternating nonpolar and charged layers that extend 31 Å into the bulk. Vibrational sum frequency spectroscopy reveals interfacial cations have their ethyl moieties oriented toward air, with the CH3 C3 axis positioned 36.5° from interface normal. This structure is invariant between 15 and 51°C. On account of its molecular symmetry, the orientation of the nitrate anion cannot be determined with certainty. © 2010, American Chemical Society