ANSTO :: Browsing by Author "Klapproth, A"

Browsing by Author "Klapproth, A"

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EMU - the high-resolution backscattering spectrometer at ANSTO
(Australian Institute of Nuclear Science and Engineering (AINSE), 2018-11-19) de Souza, NR; Klapproth, A
EMU, the high-resolution neutron spectrometer installed at the OPAL reactor, ANSTO [1] delivers 1 μeV FWHM energy transfer resolution for an accessible ± 31 μeV energy transfer range. The spectral resolution is achieved by neutron backscattering from Si (111) on the primary and second flight paths, which also determines the accessible 0.35 to 1.95 Å^-1 momentum transfer range. Two years of user operation document strong demand for QENS characterization of microscopic diffusion processes in energy materials such as solid-state electrolytes, and increasingly in bio-related soft materials [2,3]. Over the same time frame most experiments were carried out with standard cryo-furnaces (2 to 800 K temperature range). Spectrometer beam-time access is merit-based, thus welcoming experiments beyond the first two-year ‘sample’, and including experiments that may require other ancillary equipment such as (existing) controlled-gas delivery, pressure, applied fields, Page 29 ANBUG-AINSE Neutron Scattering Symposium, AANSS 2018 / Book of Abstracts etc. Examples of the spectrometer capabilities will be shown, with an emphasis on QENS line shape and mean-square displacements analyses. Scientific support is presently focused on enabling data analysis of the collected data, and on the instrumental side reaching the design 0.1 Å^-1 minimum momentum transfer range and growing signal-to-noise ratio beyond its current ~ 1650:1 value. © The Authors.
EMU, the backscattering spectrometer at the Australian Centre for Neutron Scattering
(International Conference on Neutron Scattering, 2017-07-12) Iles, GN; de Souza, NR; Klapproth, A
The cold-neutron backscattering spectrometer, EMU, one of the four spectrometers at ANSTO, received its operating licence in 2016. First spectra were obtained from measurements on laboratory standards such as polyethylene, m-Xylene and ammonia perchlorate [1]. The high energy resolution of EMU allows dynamics in the nanosecond timeframe to be observed. This high resolution is due to backscattering from the Si (111) crystal monochromator and analyser arrays, delivering a spectrometer FWHM energy resolution in the order of 1.2µeV. EMU also features a linear Doppler drive modulating incident neutron energies over ± 31 µeV. Scattered, analysed neutrons are counted in 3He LPSD arrays. By setting the Doppler-driven backscattering monochromator to zero motion, elastic fixed window scans (EFW) can be performed. Changes in intensity of the analysed neutrons,with changing temperature, for example, correspond to changing dynamics in the system. Alternatively, when the incident energy is modulated, quasi-elastic neutron scattering (QENS) can be used to observe changes in the profile shape of the elastic peak. Finally, EMU can be used to observe purely inelastic scattering, such as observed in samples exhibiting rotational tunnelling. Future work will involve developing MANTID software for data treatment and analysis, and continuing to improve the signal-to-noise ratio.
EMU, the cold-neutron backscattering spectrometer at the Bragg Institute, ANSTO
(Australian Institute of Physics, 2015-02-03) de Souza, NR; Klapproth, A; Iles, GN
The Bragg Institute is currently in the final installation stage of a cold-neutron backscattering spectrometer in the ANSTO OPAL research reactor neutron guide hall. This spectrometer, called EMU, is based on Si (111) crystal backscattering and extracts neutrons from a cold neutron guide via a double HOPG (002) crystal premonochromator setup. Backscattering occurs through implementation of spherical focusing between the Si (111) crystal monochromator and analyser arrays, aiming to deliver a spectrometer FWHM energy resolution in the order of 1.2 μeV. EMU also features a 7-metre long focusing guide located between the two premonochromators, a so-called graphite chopper alternating beam delivery to the backscattering crystal monochromator and then into the secondary spectrometer, and a linear Doppler drive modulating incident neutron energies over ± 31 μeV. Scattered, analysed neutrons are counted in 3He LPSD arrays. EMU is provisioned for future extensions of its dynamic range via higher-resolution, undeformed Si (111) crystal analyser arrays, and variable HOPG (002) crystal premonochromator reflection angles. Access to the EMU spectrometer will be via beam-time requests to the OPAL neutron-beam user facility. EMU is ideally suited for measuring relaxation times from a few 10 ps to over 1 ns, for momentum transfers up to 2 Å-1, and readily from cryogenic temperatures up to 700 K.
EMU, the high resolution backscattering spectrometer at ANSTO
(Australian Institute of Nuclear Science and Engineering, 2016-11-29) de Souza, NR; Klapproth, A; Iles, GN
The energy range and resolution of backscattering spectrometers are well suited to characterizing relaxations on an atomic and molecular scale, such as diffusion processes occurring in e.g. polymer chains, membranes, proteins, molecular crystals, between interstitial crystal lattice sites. The EMU spectrometer can be used to study the dynamics of water molecules in the confined space of a host structure or ionic diffusion in conductor materials. In addition, quantum rotational tunnelling of functional groups (e.g. -CH3, -NH4) and hyperfine splitting of nuclear energy levels can be investigated. Relaxation times from a few 10 ps to over 1 ns are accessible. We will present the first -CH3 tunneling and diffusional motion spectra, obtained during the instrument commission, as an example of EMU’s present capabilities. The experiments have been performed in a temperature range from 3 – 650K, using top- and bottom-loading cryo furnaces. Other sample environments such as pressure, magnetic fields, controlled gas delivery systems, sub-K cryostats etc. are also available or currently under testing. EMU entered user service in 2016 and we welcome proposals in a wide range of scientific disciplines. The EMU instrument has the highest energy resolution of the neutron spectrometers at ANSTO and provides a momentum transfer range from as low as 0.1 Å-1 up to 1.95 Å-1. The high energy resolution is obtained by neutron backscattering, which occurs twice, through spherical focusing onto the sample, located between the Si (111) crystal monochromator and the analyser arrays [1]. A linear Doppler drive modulates the incident neutron energies over an energy range of ± 31 µeV. The inelastic scattered neutrons are counted in two 3He linear-position sensitive detector arrays.
First spectrum measured on EMU, the cold-neutron backscattering spectrometer at the Bragg Institute, ANSTO
(Australian Institute of Physics, 2016-02-04) de Souza, NR; Klapproth, A; Iles, GN
The cold-neutron backscattering spectrometer, EMU, one of the four spectrometers at ANSTO received its commissioning licence in 2015. This allowed opening the neutron beam onto the instrument and after measuring nominal background radiation we made our first measurements with the instrument. EMU is based on Si(111) crystal backscattering and extracts neutrons from a cold neutron guide via a double HOPG (002) crystal premonochromator setup. Backscattering occurs through implementation of spherical focusing between the Si (111) crystal monochromators and analyser arrays, aiming to deliver a spectrometer FWHM energy resolution in the order of 1.2 μeV. EMU also features a 7-metre long focusing guide located between the two premonochromators, a so-called graphite chopper alternating beam delivery to the backscattering crystal monochromator and then into the secondary spectrometer [1] and a linear Doppler drive modulating incident neutron energies over ± 31 μeV. Scattered, analysed neutrons are counted in 3He LPSD arrays. We measured two samples, one a vanadium sample can and secondly a polyethylene sheet. Using event counting obtained from two temporarily placed 3He detector tubes, we were able to obtain a backscattered spectrum. It is critical to ensure that detected neutrons have been backscattered. Backscattered neutrons travel a further distance than those that scatter immediately at the sample and therefore the timing signal must be known accurately, to distinguish between spurious and actual data. Future work will involve developing MANTID software for data treatment and analysis.
First users on EMU, the cold-neutron backscattering spectrometer at the Australian Centre for Neutron Scattering
(Australian Institute of Physics, 2017-01-31) Iles, GN; de Souza, NR; Klapproth, A
The cold-neutron backscattering spectrometer, EMU, one of the four spectrometers at ANSTO, received its operating licence in 2016. First spectra were obtained from measurements on laboratory standards such as polyethylene, m-Xylene and ammonia perchlorate [1]. The high energy resolution of EMU, allows dynamics in the nanosecond timeframe to be observed. This high resolution is due to backscattering from the Si (111) crystal monochromator and analyser arrays, delivering a spectrometer FWHM energy resolution in the order of 1.2 geV. EMU also features a linear Doppler drive modulating incident neutron energies over ± 31 geV. Scattered, analysed neutrons are counted in 3He LPSD arrays. By setting the Doppler driven backscattering monochromator to zero motion, elastic fixed window scans (EFW) can be performed. Changes in intensity of the analysed neutrons, with changing temperature, for example, correspond to changing dynamics in the system. Alternatively, when the incident energy is modulated, quasi-elastic neutron scattering (QENS) can be used to observe changes in the profile shape of the elastic peak. Finally, EMU can be used to observe purely inelastic scattering, such as observed in samples exhibiting rotational tunnelling. The first users have now conducted experiments on EMU in a range of disciplines. We have measured the high temperature dynamics in lead-free ferroelectrics using (QENS) [2], and investigated the long-range oxygen diffusion in an ionic conductor [3]. We have also measured water diffusion in clays using (EFW) [4]. Future work will involve developing MANTID software for data treatment and analysis, and continuing to improve the signal-to noise ratio.
Hydrohalite formation in frozen clay brines
(Australian Institute of Nuclear Science and Engineering (AINSE), 2020-11-11) Gates, W; Bordallo, HN; Ferhervari, A; Klapproth, A; Acikel, A; Bouazza, A; Aldridge, LP; Iles, GN; Mole, RA
Hydrated forms of cryosalts in frozen brines play important roles in the polar landscape and troposphere of Earth [1], and their melting [2] is implicated in recurring slope lineae (RSL) in Antarctica’s McMurdo Dry Valley [3] and equator-facing, mid-latitude (42ºN-52ºS) slopes of Mars [4]. Observation of the widespread occurrence of clay minerals and salts on the Martian surface [5] indicates that saline groundwater [6] may still be present on Mars. The surface of Mars ranges in temperature from 293 K on the equator at noon to 120 K at the poles and mobility of sub-surface water ice will depend on the local temperature and the mobility of confined water in the crustal clays. We applied quasielastic neutron scattering using the backscattering spectrometer EMU (Australian Nuclear Science and Technology Organisation) at 1 μeE resolution, to the system: sodium montmorillonite – 5M NaCl (Na-Mt-NaCl and calcium montmorillonite – 5M CaCl2 (Ca-Mt-CaCl2); to establish boundary conditions influencing the dynamics of confined water. Results from elastic fixed window (EFW) data indicate a substantial increase in the mean square displacement of hydrogen (H) in the brine conditions at all temperatures above 100K, indicating enhanced mobility of water in the presence of brines. A phase transition was observed in Na-Mt-NaCl at 255K (on heating) indicating the presence of the cryosalt hydrohalite (NaCl·2H2O), but no phase transition was observed in Ca-Mt-CaCl2. In addition, quasielastic neutron scattering (QENS) spectra highlighted that water in the Ca-Mt-CaCl2 system was strongly confined at room temperature. Recently [6] hydrohalite was observed to form in frozen gels of Na-Mt brines, but not in Ca-Mt brines. They considered that textural differences in the two forms allowed the gel pores of the Na-Mt to retain liquid saline pore water to well below the freezing point of pure water. Based on our analysis, water is restricted to rotational mobility in the Na-Mt-NaCl below 255K, but presents more translational mobility above 255K. These findings largely support those of Yesilbas [7] in the importance of pore structure in controlling cryosalt formation, and further implicate their role in associated phenomena such as RSL.
Neutron scattering studies on the formation and decomposition of gas hydrates near the ice point
(Curran Associates, 2011-07-17) Klapproth, A; Piltz, RO; Kennedy, SJ; Peterson, VK; Garvey, CJ; Kozielski, P; Hartley, PG
Gas hydrates pose a major risk of disruption to the marine pipelines of the oil and gas industry. At the temperatures and pressures in these pipelines gas hydrates can form large solid plugs. A clearer understanding of these processes would allow implementation of effective strategies to avoid production losses in gas pipelines. In-situ neutron powder diffraction was used to study hydrate growth and dissociation for 10% propane-methane gas and D2O ice and liquid water in the temperature and pressure range of 263 – 288 K and 3.0 – 4.8 MPa. Of our three samples one formed a mixed sI and sII hydrate while the other two formed single sII hydrate. Thermodynamic stability calculations could not accurately predict if a mixed hydrate would be formed. Our hydrate dissociation experiments question the relevance of anomalous hydrate preservation in our particular case. Furthermore these experiments elucidate the importance of the heat flow of the reaction processes and the role of a free liquid-gas interface. Copyright© (2011) by Hydrafact Ltd
Position-dependent segmental relaxation in Bottlebrush polymers
(American Chemical Society, 2024-05-11) Bichler, KJ; Jakobi, B; Klapproth, A; Mole, RA; Schneider, GJ
Segmental dynamics of specifically labeled poly(propylene oxide), PPO, based bottlebrush polymers, PNB-g-PPO, were studied using quasi-elastic neutron scattering. The focus was set to different parts of the side chains to investigate the hypothetical gradual relaxation behavior within the side chains of a bottlebrush polymer. Different sections of the side chains were highlighted for QENS via sequential polymerization of protonated and deuterated monomers to allow the study of the relaxation behavior of the inner and outer parts of the side chain separately. A comparison of these two parts reveals a slowdown due to the grafting process happening across the different regions. This is seen for the segmental relaxation time as well as on the time-dependent mean-square displacement. Additionally, the non-Gaussian parameter, α, shows a decreasing difference from Gaussian behavior with the distance to the backbone. Altogether, this leads to the conclusion that gradual relaxation behavior exists. © 2024 The Authors. Published by American Chemical Society. - Open Access CC BY licence.
TBAB semi-clathrates studied by Quasi Elastic Neutron Scattering (QENS) using Emu, the high resolution backscattering spectrometer at ANSTO
(Australian Institute of Nuclear Science and Engineering (AINSE), 2020-11-11) Klapproth, A; Piltz, RO; Pirim, C; Rodriguez, CT; Chazallon, B.
Potential applications for gas hydrates include gas purification, water desalination, and CO2 capture that is possibly combined with methane extraction. All of these rely on the high selectivity of the guest gas molecules in hydrates. It has been shown, that the addition of TBAB (i.e. Tetra-n-butyl ammonium bromide) softens the thermodynamic conditions of gas hydrate formation without compromising the CO2 selectivity, a substantial benefit in reducing the carbon output from existing fossil-fuel power plants. The hydrate structure formed using TBAB is known as a semiclathrate which differs from the more common clathrate structures that are formed from pure water and gas. For common clathrate structures (sI, sII, or sH) only the gas molecules are entrapped in the cavities of the water structure. Semi-clathrates generally crystallize into two structure types known as type A and B.The Br-anion of TBAB participates to the water molecule framework, while the tetra n-butyl cation is located at the center of 4 large cages. Additional smaller cavities are available for the enclathration of gas molecules. It has been shown recently that these cavities are distorted by the inclusion of guest molecules like CO2 (Muromachi et al., 2014). We present here our first quasi-elastic neutron scattering (QENS) results for TBAB semi-clathrates formed with type A and B using the EMU backscattering spectrometer at ANSTO. This technique is well suited to studying the libration of the butyl chains confined within the host cages, and how the slow dynamics changes with the enclathration of CO2 molecules. Neutron diffraction was applied on the same samples in order to confirm their crystallographic structure. QENS measurements are highly sensitive to hydrogen (H) atoms while being very insensitive to the deuterated (D) atoms. As well, the method is also insensitive to the dynamics of CO2 molecules. We use these characteristics to suppress scattering from the water framework by making it from D2O rather than H2O. As a result, only the dynamics of the n-butyl chains are observed. Early results suggest the interaction of the CO2 molecules with the mobile butyl chains is key to the improved selectivity of TBAB semi-clathrates. © The Authors

Browsing by Author "Klapproth, A"

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