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Kovaltchouk V.,Bubble Technology Industries Inc. | MacHrafi R.,University of Ontario Institute of Technology
Annals of Nuclear Energy

Monte Carlo simulation of a detector response function presents a very challenging problem. The detector response functions have been calculated for different neutron and gamma detectors: 3He gas filled proportional counter, NE213 organic scintillator, BrillanCe 350 or LaCl3(Tl), and an ionization chamber with mixed gas composition. MCNPX code was used for simulations. The simulations were done with different neutron and gamma energies. The effects of neutron scattering, wall effects, recoil continua and contribution from charged particles have been included. The detector response function for the NE213 organic scintillator was obtained with consideration of light output curves of different products of neutron reactions with materials of the scintillator. The simulated data has been compared with experiments. © 2010 Elsevier Ltd. All rights reserved. Source

As part of the international Matroshka-R and Radi-N experiments, bubble detectors have been used on board the ISS in order to characterise the neutron dose and the energy spectrum of neutrons. Experiments using bubble dosemeters inside a tissue-equivalent phantom were performed during the ISS-16, ISS-18 and ISS-19 expeditions. During the ISS-20 and ISS-21 missions, the bubble dosemeters were supplemented by a bubble-detector spectrometer, a set of six detectors that was used to determine the neutron energy spectrum at various locations inside the ISS. The temperature-compensated spectrometer set used is the first to be developed specifically for space applications and its development is described in this paper. Results of the dose measurements indicate that the dose received at two different depths inside the phantom is not significantly different, suggesting that bubble detectors worn by a person provide an accurate reading of the dose received inside the body. The energy spectra measured using the spectrometer are in good agreement with previous measurements and do not show a strong dependence on the precise location inside the station. To aid the understanding of the bubble-detector response to charged particles in the space environment, calculations have been performed using a Monte-Carlo code, together with data collected on the ISS. These calculations indicate that charged particles contribute <2% to the bubble count on the ISS, and can therefore be considered as negligible for bubble-detector measurements in space. Source

Dick M.J.,University of New Brunswick | Dick M.J.,Bubble Technology Industries Inc. | Linton C.,University of New Brunswick | Adam A.G.,University of New Brunswick
Journal of Molecular Spectroscopy

High resolution spectra of holmium monofluoride, HoF and holmium monochloride, HoCl, prepared in a laser ablation source, have been obtained using laser induced fluorescence. Spectra of the A[19.1]9-X8 0-0 and 1-0 and B[21.68]8-X8 0-0 bands of HoF and the A[15.6]9-X8 0-0 band of HoCl all show resolved hyperfine structure. Analysis of the spectra yielded magnetic hyperfine parameters, h = 0.2240(5), 0.2210(6), 0.2177(6) and 0.2488(5) cm-1 for the X (v = 0), A (v = 0 and 1) and B (v = 0) states of HoF and 0.2355(32) and 0.2448(29) cm-1 for the X (v = 0) and A (v = 0) states of HoCl, respectively. The following quadrupole coupling constants were obtained for the above six states; eQq0(HoF) = -0.0874(67), -0.0586(44), -0.0579(56), -0.0840(64) cm-1 and eQq0(HoCl) = -0.082(11), -0.060(11) cm-1. Comparison with previously determined values for HoO and HoS show that the ground state magnetic hyperfine structure in HoF and HoCl is entirely due to the Ho 4f electron and is consistent with the ground state, X8, configuration of Ho+{4f10(5I8)6s2}X- (X = F, Cl). Calculations of the ground state magnetic, h(X8), and quadrupole, eQq0(X8) hyperfine parameters from atomic hyperfine parameters are found to be consistent with the observed values for both molecules. © 2015 Elsevier Inc. All rights reserved. Source

Drouin B.J.,Jet Propulsion Laboratory | Pearson J.C.,Jet Propulsion Laboratory | Dick M.J.,Bubble Technology Industries Inc.
Physical Review A - Atomic, Molecular, and Optical Physics

This response describes the authors' reaction to a critique of recent work on the ultracold physics of water. The possibility of spin-selective adsorption occurring in the context of the collisional cooling experiment is discussed. © 2010 The American Physical Society. Source

McFee J.E.,Defence R and D Canada Suffield | Faust A.A.,Defence R and D Canada Suffield | Andrews H.R.,Bubble Technology Industries Inc. | Clifford E.T.H.,Bubble Technology Industries Inc. | Mosquera C.M.,Defence R and D Canada Suffield
Nuclear Instruments and Methods in Physics Research, Section A: Accelerators, Spectrometers, Detectors and Associated Equipment

First generation thermal neutron activation (TNA) sensors, employing an isotopic source and NaI(Tl) gamma ray detectors, were deployed by Canadian Forces in 2002 as confirmation sensors on multi-sensor landmine detection systems. The second generation TNA detector is being developed with a number of improvements aimed at increasing sensitivity and facilitating ease of operation. Among these are an electronic neutron generator to increase sensitivity for deeper and horizontally displaced explosives; LaBr3(Ce) scintillators, to improve time response and energy resolution; improved thermal and electronic stability; improved sensor head geometry to minimize spatial response nonuniformity; and more robust data processing. The sensor is described, with emphasis on the improvements. Experiments to characterize the performance of the second generation TNA in detecting buried landmines and improvised explosive devices (IEDs) hidden in culverts are described. Performance results, including comparisons between the performance of the first and second generation systems are presented. © 2013 Elsevier B.V. All rights reserved. Source

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