@article{wang_wang_peeples_yu_gardner_2012, title={Development of a simple detector response function generation program: The CEARDRFs code}, volume={70}, ISSN={["0969-8043"]}, DOI={10.1016/j.apradiso.2011.11.003}, abstractNote={A simple Monte Carlo program named CEARDRFs has been developed to generate very accurate detector response functions (DRFs) for scintillation detectors. It utilizes relatively rigorous gamma-ray transport with simple electron transport, and accounts for two phenomena that have rarely been treated: scintillator non-linearity and the variable flat continuum part of the DRF. It has been proven that these physics and treatments work well for 3×3″ and 6×6″ cylindrical NaI detector in CEAR's previous work. Now this approach has been expanded to cover more scintillation detectors with various common shapes and sizes. Benchmark experiments of 2×2″ cylindrical BGO detector and 2×4×16″ rectangular NaI detector have been carried out at CEAR with various radiactive sources. The simulation results of CEARDRFs have also been compared with MCNP5 calculations. The benchmark and comparison show that CEARDRFs can generate very accurate DRFs (more accurate than MCNP5) at a very fast speed (hundred times faster than MCNP5). The use of this program can significantly increase the accuracy of applications relying on detector spectroscopy like prompt gamma-ray neutron activation analysis, X-ray fluorescence analysis, oil well logging and homeland security.}, number={7}, journal={APPLIED RADIATION AND ISOTOPES}, author={Wang, Jiaxin and Wang, Zhijian and Peeples, Johanna and Yu, Huawei and Gardner, Robin P.}, year={2012}, month={Jul}, pages={1166–1174} }
 @article{meric_johansen_holstad_lee_calderon_wang_gardner_2011, title={A single scatter electron Monte Carlo approach for simulating gamma-ray stopping efficiencies of Geiger-Müller counters}, volume={654}, ISSN={0168-9002}, url={http://dx.doi.org/10.1016/J.NIMA.2011.06.065}, DOI={10.1016/j.nima.2011.06.065}, abstractNote={Abstract In spite of their relatively poor gamma-ray stopping efficiencies, the Geiger-Muller (GM) counter is still preferred in many radioisotope gauges for industrial measurements. This is because these detectors exhibit a high degree of robustness in harsh environments, are relatively insensitive to temperature changes in the environment, and are inexpensive compared to other types of radiation detectors. These properties could make the use of GM counters very feasible in a number of industrial applications, such as gamma-ray tomography and gamma-ray density gauges, provided that their gamma-ray stopping efficiencies can be improved. The Monte Carlo (MC) method is a powerful computational physics tool that is utilized very often in the design of radiation detectors and radioisotope gauges. In this work a MC model for GM counters that is benchmarked with experiments at the primary photon energy of 59.5 keV is proposed. This is a specific purpose MC simulation code that, as opposed to publicly available general purpose MC codes, employs single scatter (or microscopic) electron transport and is currently under development. In this paper, the MC code is described in detail and the results of the specific purpose MC code are benchmarked with experiments and two general purpose MC codes, MCNP5 and PENELOPE. It was observed that the specific purpose MC code improved the reduced chi-square value when compared to MCNP5 and PENELOPE.}, number={1}, journal={Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment}, publisher={Elsevier BV}, author={Meric, Ilker and Johansen, Geir A. and Holstad, Marie B. and Lee, Kyoung O. and Calderon, Adan F. and Wang, Jiaxin and Gardner, Robin P.}, year={2011}, month={Oct}, pages={279–287} }
 @article{yu_sun_wang_gardner_2011, title={Accuracy and borehole influences in pulsed neutron gamma density logging while drilling}, volume={69}, ISSN={["0969-8043"]}, DOI={10.1016/j.apradiso.2011.04.023}, abstractNote={A new pulsed neutron gamma density (NGD) logging has been developed to replace radioactive chemical sources in oil logging tools. The present paper describes studies of near and far density measurement accuracy of NGD logging at two spacings and the borehole influences using Monte-Carlo simulation. The results show that the accuracy of near density is not as good as far density. It is difficult to correct this for borehole effects by using conventional methods because both near and far density measurement is significantly sensitive to standoffs and mud properties.}, number={9}, journal={APPLIED RADIATION AND ISOTOPES}, author={Yu, Huawei and Sun, Jianmeng and Wang, Jiaxin and Gardner, Robin P.}, year={2011}, month={Sep}, pages={1313–1317} }
 @article{wang_calderon_peeples_ai_gardner_2011, title={Monte Carlo investigation and optimization of coincidence prompt gamma-ray neutron activation analysis}, volume={652}, ISSN={["1872-9576"]}, DOI={10.1016/j.nima.2010.08.011}, abstractNote={Normal Prompt Gamma-Ray Neutron Activation Analysis (PGNAA) suffers from a large inherent noise or background. The coincidence PGNAA approach is being investigated for eliminating almost all of the interfering backgrounds and thereby significantly improving the signal-to-noise ratio (SNR). This can be done since almost all of the prompt gamma rays from elements of interest are emitted in coincidence except hydrogen. However, it has been found previously that while the use of two normal NaI detectors greatly reduces the background, the signal is also greatly reduced so that very little improvement in standard deviation is obtained. With the help of MCNP5, the general-purpose Monte Carlo N-Particle code, and CEARCPG, the specific purpose Monte Carlo code for Coincidence PGNAA, further optimization of the proposed coincidence system is being accomplished. The idea pursued here is the use of a large area plastic scintillation detector as the trigger for coincidence events together with a normal large NaI detector. In this approach the detection solid angle is increased greatly, which directly increases the probability of coincidence detection. The 2D-coincidence spectrum obtained can then be projected to the axis representing the NaI detector to overcome the drawback of low energy resolution and photopeak intensity of the plastic scintillation detector and utilize the overall higher coincidence counting rate. To reach the best coincidence detection, the placement of detectors, sample, and the moderator of the neutron source have been optimized through Monte Carlo simulation.}, number={1}, journal={NUCLEAR INSTRUMENTS & METHODS IN PHYSICS RESEARCH SECTION A-ACCELERATORS SPECTROMETERS DETECTORS AND ASSOCIATED EQUIPMENT}, author={Wang, Jiaxin and Calderon, Adan and Peeples, Cody R. and Ai, Xianyun and Gardner, Robin P.}, year={2011}, month={Oct}, pages={572–577} }
 @article{meric_johansen_holstad_wang_gardner_2011, title={Produced water characterization by prompt gamma-ray neutron activation analysis}, volume={22}, DOI={10.1088/0957-0233/22/12/125701}, abstractNote={Multiphase gas/oil/water measurement has been and still is a challenging task within the petroleum industry. The requirements of measurement efficiency and accuracy have been continuously increasing at the same time as the trend is to use subsea installations. As a response, the design of the SOFA (Subsea Online Fluid Analyser) concept was initiated by Christian Michelsen Research in cooperation with the University of Bergen. The final design of the analyser is yet to be completed. The ultimate goal of this design is the development of a permanently installed subsea metering station which is capable of characterizing all of the components that can be found in multiphase flow. One of the key challenges in this design is the detailed characterization of produced water samples which includes the identification of salt ions in the sample and their weight percentages. In this work, use of prompt gamma-ray neutron activation analysis (PGNAA) in conjunction with the so-called Monte Carlo library least-squares (MCLLS) approach is considered for characterization of the produced water component. A relatively simple produced water sample was prepared and the prompt gamma-ray spectrum of the sample was recorded using a large 6" × 6" NaI(Tl) scintillation detector. A specific purpose Monte Carlo code named CEARCPG was used to generate the pertinent elemental libraries that are required in the MCLLS approach. The results of this feasibility study have shown that the PGNAA in conjunction with the MCLLS approach would be feasible for determining the amounts of salt ions that can be found in produced water samples.}, number={12}, journal={Measurement Science & Technology}, author={Meric, I. and Johansen, G. A. and Holstad, M. B. and Wang, J. X. and Gardner, R. P.}, year={2011} }
 @article{gardner_ai_peeples_wang_lee_peeples_calderon_2011, title={Use of an iterative convolution approach for qualitative and quantitative peak analysis in low resolution gamma-ray spectra}, volume={652}, ISSN={["0168-9002"]}, DOI={10.1016/j.nima.2010.12.224}, abstractNote={In many applications, low resolution gamma-ray spectrometers, such as sodium iodide scintillation detectors, are widely used primarily due to their relatively low cost and high detection efficiency. There is widespread interest in improved methods for analyzing spectral data acquired with such devices, using inverse analysis. Peak means and peak areas in gamma- and X-ray spectra are needed for both qualitative and quantitative analysis. This paper introduces the PEAKSI code package that was developed at the Center for Engineering Applications of Radioisotopes (CEAR). The basic approach described here is to use accurate forward models and iterative convolution instead of direct deconvolution. Rather than smoothing and differentiation a combination of linear regression and non-linear searching is used to minimize the reduced chi-square, since this approach retains the capability of establishing uncertainties in the estimated peak parameters. The PEAKSI package uses a Levenberg–Marquardt (LM) non-linear search method combined with multiple linear regression (MLR) to minimize the reduced chi-square value for fitting single or multiple overlapping peaks to determine peak parameters, including peak means, peak standard deviations or full width at half maximum (FWHM), net peak counts, and background counts of peaks in experimental gamma-ray spectra. This approach maintains the natural error structure so that parameter uncertainties can be estimated. The plan is to release this code to the public in the near future.}, number={1}, journal={NUCLEAR INSTRUMENTS & METHODS IN PHYSICS RESEARCH SECTION A-ACCELERATORS SPECTROMETERS DETECTORS AND ASSOCIATED EQUIPMENT}, author={Gardner, Robin P. and Ai, Xianyun and Peeples, Cody R. and Wang, Jiaxin and Lee, Kyoung and Peeples, Johanna L. and Calderon, Adan}, year={2011}, month={Oct}, pages={544–549} }
 @article{wang_li_gardner_2008, title={On the use of prompt gamma-ray neutron activation analysis for determining phase amounts in multiphase flow}, volume={19}, ISSN={["1361-6501"]}, DOI={10.1088/0957-0233/19/9/094005}, abstractNote={Prompt gamma-ray neutron activation analysis (PGNAA) is considered for the measurement of the in situ multiphase flow amounts of oil, gas, water and salt in a deep sea oil well. PGNAA has the advantages for this application that: (1) useful characteristic prompt gamma rays are produced by neutron interactions with almost all elements, (2) it is a rapid non-destructive measurement method, (3) a large sample volume is measured and (4) it can be used under the relatively extreme conditions present for undersea oil recovery. Feasibility calculations have been made with the previously developed Monte Carlo–library least-squares (MCLLS) measurement approach used with the specific purpose Monte Carlo code named CEARCPG that was previously developed at CEAR for PGNAA bulk material analysis. A slight modification of the MCLLS measurement approach previously developed for the nonlinear PGNAA and energy dispersive x-ray analysis (EDXRF) measurement applications is used for the present application. This modification allows the use of the very accurate forward Monte Carlo calculation of the PGNAA response and consists of using first the three components oil plus gas, water and salt as library spectra rather than the normal use of individual elemental libraries. Then the gamma-ray transmission density gauge response from the Cs-137 source is used to obtain the amount of gas. This approach allows one to determine the four parameters of primary interest directly. The arrangement considered is the use of a Cf-252 neutron source and a Cs-137 gamma-ray source with a large NaI detector placed on the opposite side of a right circular cylindrical sample holder for an assumed homogeneous mixture of oil, gas and seawater. A background that was previously obtained experimentally in bulk analysis applications was added in various amounts to the response here to make the calculations more reasonable. More experimental results for benchmarking will be taken in the future. Results indicate that this approach would be accurate and is feasible.}, number={9}, journal={MEASUREMENT SCIENCE AND TECHNOLOGY}, author={Wang, Jiaxin and Li, Fusheng and Gardner, Robin P.}, year={2008}, month={Sep} }