Browsing by Author "Guenette, MC"
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- ItemApplication of the CORIS360 Gamma Ray Imager at a light source(JACoW Publishing, 2021-05-24) Tan, YRE; Boardman, DA; Chartier, L; Guenette, MC; Ilter, M; Watt, GCThe CORIS360 is a gamma-ray imager developed at Australian Nuclear Science and Technology (ANSTO) for identifying and localising sources of radiation typically from gamma emitting radionuclides. The low EMI and low noise power supply features of the imaging technology have enabled it to have a low energy detection threshold and to detect photons as low as 20 keV. This report shall present the initial measurements performed at the Australian Synchrotron, in the storage ring and beamlines, where the imager is able to detect radiation from all sources of synchrotron radiation (dipole, wiggler and undulator). The radiation imaging results from the injection system and scrapers (to dump the stored beam) will be discussed. Future developments for imaging in pulsed radiation environments and time varying environments will also be discussed. © 2021 JACoW
- ItemCathodic arc co-deposition of highly oriented hexagonal Ti and Ti2AlC MAX phase thin films(Elsevier, 2009-08-25) Guenette, MC; Tucker, MD; Ionescu, M; Bilek, MMM; McKenzie, DRTi2AlC belongs to a family of ternary nanolaminate alloys known as the MAX phases, which exhibit a unique combination of metallic and ceramic properties. Here we report pulsed cathodic arc deposition of c axis normal oriented Ti2AlC thin films on α-Al2O3 (001) single crystal substrates heated to 900°C, without an intentionally pre-deposited seed layer. Oriented hexagonal Ti is observed in some films and an in-plane epitaxial relationship between the α-Al2O3 (001) substrate, the hexagonal Ti and Ti2AlC MAX phase is observed. We observe formation of the Ti2AlC phase in all films despite variations in elemental composition. The electrical resistivity of our films was in the range 0.48–0.67 μΩ m, higher than other values found for Ti2AlC in the literature. © Elsevier B.V.
- ItemDeuterium retention and near-surface modification of ion-irradiated diamond exposed to fusion-relevant plasma(IOP Science, 2014-04-01) Deslandes, A; Guenette, MC; Corr, CS; Karatchevtseva, I; Thomsen, L; Lumpkin, GR; Riley, DPChemical vapour deposited diamond was irradiated with 5 MeV carbon ions to simulate the damage caused by collision cascades from neutron irradiation in a fusion environment. Ion-irradiated samples were then exposed to a deuterium plasma in MAGPIE with ion flux of ~1.3 × 1021 ions m−2 s−1. Raman and near edge x-ray absorption fine structure (NEXAFS) spectroscopy were used to characterize the degree of disorder and sp2-bonding induced by the ion irradiation. The signals of sp2-bonded and disordered carbon were observed to decrease after exposure to the deuterium plasma, although sharp Raman peaks indicative of vacancy and interstitial defects induced by the MeV ions were less affected. Recovery of a diamond-like surface after plasma exposure was evident in the NEXAFS spectra. Elastic recoil detection analysis showed that the ion-damaged diamond retained more deuterium than diamond exposed only to deuterium plasma. For the case of unirradiated samples, diamond retained more deuterium than graphite. However, for the case of the ion-irradiated samples, diamond exhibited less deuterium retention than graphite. © 2014, IAEA Vienna.
- ItemDiamond structure recovery during ion irradiation at elevated temperatures(Elsevier, 2015-12-15) Deslandes, A; Guenette, MC; Belay, K; Elliman, RG; Karatchevtseva, I; Thomsen, L; Riley, DP; Lumpkin, GRCVD diamond is irradiated by 5 MeV carbon ions, with each sample held at a different temperature (300–873 K) during irradiations. The defect structures resulting from the irradiations are evident as vacancy, interstitial and amorphous carbon signals in Raman spectra. The observed variation of the full width at half maximum (FWHM) and peak position of the diamond peak suggests that disorder in the diamond lattice is reduced for high temperature irradiations. The dumbbell interstitial signal is reduced for irradiations at 873 K, which suggests this defect is unstable at these temperatures and that interstitials have migrated to crystal surfaces. Near edge X-ray absorption fine structure (NEXAFS) spectroscopy results indicate that damage to the diamond structure at the surface has occurred for room temperature irradiations, however, this structure is at least partially recovered for irradiations performed at 473 K and above. The results suggest that, in a high temperature irradiation environment such as a nuclear fusion device, in situ annealing of radiation-created defects can maintain the diamond structure and prolong the lifetime of diamond components. © 2015 Elsevier B.V.
- ItemEffect of annealing upon retention of He and H in irradiated SiC(Trans Tech Publications, 2017) Ionescu, M; Deslandes, A; Holmes, R; Guenette, MC; Karatchevtseva, I; Lumpkin, GRSilicon carbide (3C-β SiC) samples were irradiated with He ions of energy up to 30 keV and a fluence up to 1016/cm2, to produce damage in the near-surface region. A duplicate set of He ion irradiated SiC samples, as well as undamaged SiC, were also irradiated with H2+ ions of energy up to 20 keV and a similar fluence, to study the interaction of H species with pristine SiC and with He radiation-damaged SiC. Samples were annealed in steps of 200 K, from 473 K to 1273 K, and the retention of H and He were measured using elastic recoil detection analysis with 7.8 MeV C3+ ions, after each anneal step. Modification to the surface following irradiation is observed via Raman spectroscopy, which exhibits development of damage states such as disordered carbon and Si-Si peaks. Only minor changes in the H and He profiles were observed up to 1073 K, however after the 1273 K anneal the H and He profiles changed considerably, with a marked difference between samples irradiated only with He and those irradiated with He and H. © 2025 Trans Tech Publications Ltd
- ItemEvaluation of novel gamma ray imaging technology(Australasian Radiation Protection Society, 2017-08-09) Guenette, MC; Boardman, DA; Sarbutt, A; Flynn, A; Prokopovich, DAWe present the imaging results from a novel single pixel gamma-ray imaging system, developed at ANSTO, which is capable of providing quantitative, spectroscopic gamma images using a fast and efficient imaging methodology. Gamma ray imaging can assist in surveying active areas by providing information of the radiation environment in areas which are hard to reach (e.g. in enclosed spaces or at height) and by gaining valuable information about the radiation environment whist limiting exposure to personnel in high dose rate environments. The system design provides a large field of view (360° × 70°) and covers a wide energy range of 40 keV to 1.5 MeV. The gamma ray image is overlaid on a 360° panoramic optical image of the scene, which allows for easy location of the gamma emitting radionuclides that are present. By selecting different regions of interest in the recorded gamma spectrum, separate radionuclide specific images, of the area being surveyed, can be visualised. Calibration of the detector allows for quantitative mapping of where each component of the dose rate at the detector originates. This can be converted into activity with a priori knowledge of the scene geometry. Gamma-ray images have been experimentally obtained for both point sources and extended sources in controlled testing environments and these results will be presented. The imaging results from a range of real world operational environments, around the ANSTO site, will be presented and demonstrate the systems capability for locating sources of radiation in nuclear industry applications.
- ItemHydrogen induced vacancy formation in tungsten(Elsevier, 2014-05) Middleburgh, SC; Voskoboinikov, RE; Guenette, MC; Riley, DPAtomic scale modelling methods have been used to study the change in vacancy population when H is introduced into the W bulk matrix. Vacancy defects are predicted to dominate in pure W, and the vacancy concentration is expected to be very small. A mechanism whereby H solutes facilitate vacancy formation has been outlined and a single H interstitial is predicted to reduce the vacancy formation energy from 2.95 eV to 2.23 eV. Clustering of H interstitials in W is predicted to be unfavourable without a W vacancy. H has also been shown to affect the vacancy binding characteristics in W, changing the behaviour from a repelling interaction in pure W, retarding the formation of small vacancy clusters, to an attractive interaction when vacancy-H clusters are considered. The changes in defect behaviour predicted, will have observable implications to operational properties and the application of W in fusion reactor components. © 2014, Elsevier B.V.
- ItemInfluence of plasma impurities on the effective performance of fusion relevant materials(Australian Institute of Physics, 2014-02-04) Riley, RP; Guenette, MC; Deslandes, A; Middleburgh, SC; Lumpkin, GR; Thomsen, L; Corr, CSThe development of a sustainable source of power derived from fusion energy is presently constrained by the limited number of materials capable of operating under such extreme conditions. Plasma facing components within magnetically confined fusion reactors must withstand extremes of temperature and loads, while maintaining a high tolerance to radiation damage from energetic particles or neutrons. More specifically, factors of sputtering yield, thermal conduction, electrical conduction and retention of fuel can all degrade the performance of the reactor and hence detrimentally lower the efficiency. In aiming to improve our understanding of materials capable of operating within the fusion environment, it is essential to establish how present generation materials become degraded. Use of ion beam accelerators and linear plasma devices simulate the respective impact of energetic neutron damage (14.1 MeV) and plasma erosion (H+, D+, He+) within a magnetically confined fusion environment. Methods of characterising changes in the local structure and chemistry of surface and near surface regions of fusion relevant materials quantify material degradation resulting from the uptake of plasma impurities. While complementary density functional theory (DFT) simulations have identified possible mechanisms for degradation of material performance. An overview of material evaluation methods will also be presented.
- ItemInitial damage processes for diamond film exposure to hydrogen plasma(Elsevier Science, 2013-12-01) Deslandes, A; Guenette, MC; Samuell, CM; Karatchevtseva, I; Ionescu, M; Cohen, DD; Blackwell, B; Corr, CS; Riley, DPDiamond is considered to be a possible alternative to other carbon based materials as a plasma facing material in nuclear fusion devices due to its high thermal conductivity and resistance to chemical erosion. In this work CVD diamond films were exposed to hydrogen plasma in the MAGnetized Plasma Interaction Experiment (MAGPIE): a linear plasma device at the Australian National University which simulates plasma conditions relevant to nuclear fusion. Various negative sample stage biases of magnitude less than 500 V were applied to control the energies of impinging ions. Characterisation results from SEM, Raman spectroscopy and ERDA are presented. No measureable quantity of hydrogen retention was observed, this is either due to no incorporation of hydrogen into the diamond structure or due to initial incorporation as a hydrocarbon followed by subsequent etching back into the plasma. A model is presented for the initial stages of diamond erosion in fusion relevant hydrogen plasma that involves chemical erosion of non-diamond material from the surface by hydrogen radicals and damage to the subsurface region from energetic hydrogen ions. These results show that the initial damage processes in this plasma regime are comparable to previous studies of the fundamental processes as reported for less extreme plasma such as in the development of diamond films. © 2013, Elsevier Ltd.
- ItemIon irradiated graphite exposed to fusion-relevant deuterium plasma(Elsevier, 2014-12-01) Deslandes, A; Guenette, MC; Corr, CS; Karatchevtseva, I; Thomsen, L; Ionescu, M; Lumpkin, GR; Riley, DPGraphite samples were irradiated with 5 MeV carbon ions to simulate the damage caused by collision cascades from neutron irradiation in a fusion environment. The ion irradiated graphite samples were then exposed to a deuterium plasma in the linear plasma device, MAGPIE, for a total ion fluence of ∼1 × 1024 ions m−2. Raman and near edge X-ray absorption fine structure (NEXAFS) spectroscopy were used to characterize modifications to the graphitic structure. Ion irradiation was observed to decrease the graphitic content and induce disorder in the graphite. Subsequent plasma exposure decreased the graphitic content further. Structural and surface chemistry changes were observed to be greatest for the sample irradiated with the greatest fluence of MeV ions. D retention was measured using elastic recoil detection analysis and showed that ion irradiation increased the amount of retained deuterium in graphite by a factor of four. © 2014, Elsevier B.V.
- ItemNEXAFS spectroscopy of CVD diamond films exposed to fusion, relevant hydrogen plasma(Elsevier, 2013-04-01) Guenette, MC; Deslandes, A; Samuell, CM; Tadich, A; Thomsen, L; Cowie, BCC; Corr, CS; Riley, DPA series of CVD diamond films have been exposed to hydrogen plasma in the linear magnetized plasma device, MAGPIE, with various applied sample stage biases between 0 V (no applied bias) to − 500 V. The plasma-induced damage to the surface structure of the diamond films has been investigated by Near Edge X-ray Absorption Fine Structure (NEXAFS) spectroscopy in both the Auger electron yield (AEY) and total fluorescence yield (TFY) modes. The key diamond NEXAFS spectral features (diamond core exciton and second absolute band gap) are found to be diminished following plasma exposure as measured in the surface sensitive, AEY spectra, whilst these features remain unchanged relative to an unexposed diamond reference film as measured using the bulk sensitive, TFY spectra. These results, in conjunction with SRIM simulations, show definitively that the damage to the surface of the diamond films is restricted to the scale of the penetration depth of the H ions and no damage is induced at greater depths. The power and sensitivity of NEXAFS spectroscopy in assessing damage to the surface of diamond from fusion-relevant plasma-surface interactions are demonstrated. © 2013, Elsevier B.V.
- ItemRetention and damage in 3C-β SiC irradiated with He and H ions(Elsevier B.V., 2016-02-01) Deslandes, A; Guenette, MC; Thomsen, L; Ionescu, M; Karatchevtseva, I; Lumpkin, GR3C-β SiC was implanted with He and H ions using plasma immersion ion implantation (PIII). Regions of damage were created at various depths by applying a sample stage bias of 5 kV, 10 kV, 20 kV or 30 kV. Raman spectroscopy results indicate that He irradiation leads to more damage compared to H irradiation, as observed via increased disordered C and Si signals, as well as broadening of the SiC peaks. X-ray photoelectron spectroscopy (XPS) and near edge X-ray absorption fine structure spectroscopy (NEXAFS) results indicate significant change to the SiC structure and that surface oxidation has occurred following irradiation, with the degree of change varying dependent on impinging He fluence. The distributions of implanted species were measured using elastic recoil detection analysis. Despite the varying degree and depth of damage created in the SiC by the He ion irradiations, the retained H distribution was observed to not be affected by preceding He implantation. © 2015 Elsevier B.V.
- ItemSingle pixel compressive gamma-ray imaging with randomly encoded masks(IOP Publishing, 2020-04-15) Boardman, DA; Sarbutt, A; Flynn, A; Guenette, MCWe report on the development and demonstration of a single pixel spectroscopic gamma-ray imaging concept based on the principles of compressed sensing. Compressive gamma-ray images were obtained for both point sources and complex extended sources. The reconstruction of images at different photon energies allowed the spatial mapping of different radionuclides. When compared to traditional aperture based gamma-ray imaging techniques, the point source images were generated with ten times fewer measurements. More complex extended source images were generated with up to three times fewer measurements. Gamma-ray imaging techniques designed around the principles of compressed sensing have the potential to exploit the sparsity typically found in gamma-ray images, leading to a new class of fast and low cost imaging systems. © Copyright 2020 IOP Publishing