@article{metwally_gardner_sood_2007, title={Using gamma-gamma coincidence measurements to validate Monte Carlo generated detector response functions}, volume={263}, ISSN={["0168-583X"]}, DOI={10.1016/j.nimb.2007.04.137}, abstractNote={Monte Carlo simulation of gamma-ray transport for the purpose of performing elemental analysis of bulk samples requires the tracking of gamma rays in the sample and also in the detector(s) used. Detector response functions (DRF’s) are an efficient and accurate variance reduction technique that greatly decreases the simulation time by substituting the tracking of gamma rays inside the detector by predefined single energy gamma-ray spectra. These spectra correspond to the average response of the detector for incident gamma rays. DRF’s are generated by Monte Carlo methods and are benchmarked with experimental data. In this work, prompt gamma–gamma coincidence measurements are presented as a way to validate DRF’s for high-energy gamma rays.}, number={1}, journal={NUCLEAR INSTRUMENTS & METHODS IN PHYSICS RESEARCH SECTION B-BEAM INTERACTIONS WITH MATERIALS AND ATOMS}, author={Metwally, W. A. and Gardner, R. P. and Sood, A.}, year={2007}, month={Oct}, pages={50–53} }
 @article{han_gardner_metwally_2006, title={CEARCPG: A Monte Carlo simulation code for normal and coincidence prompt-gamma-ray neutron activation analysis}, volume={155}, DOI={10.13182/nse07-a2652}, abstractNote={Abstract A new Monte Carlo code named CEARCPG has been developed to generate both the normal and coincidence library spectra for the prompt-gamma-ray neutron activation analysis (PGNAA) inverse analysis problem. A new algorithm for sampling the neutron-induced prompt gamma rays has been developed and implemented within the CEARCPG code, making it possible to calculate the coincidence spectrum by the Monte Carlo method. Compared to the previous code CEARPGA II, which was for normal PGNAA, several improvements have been made, including implementation of the coincidence spectrum simulation and elimination of the “big weight” problem by implementing a new algorithm to generate prompt gamma rays. Several experiments have been carried out to benchmark the new CEARCPG code, and simulation results are also compared with MCNP5 calculations.}, number={1}, journal={Nuclear Science and Engineering}, author={Han, X. G. and Gardner, R. P. and Metwally, W. A.}, year={2006}, pages={143–153} }
 @article{gardner_metwally_han_2005, title={A new NaI detector arrangement for efficient detection of high energy gamma-rays}, volume={264}, ISSN={["1588-2780"]}, DOI={10.1007/s10967-005-0685-x}, number={1}, journal={JOURNAL OF RADIOANALYTICAL AND NUCLEAR CHEMISTRY}, author={Gardner, RP and Metwally, WA and Han, XG}, year={2005}, month={Apr}, pages={133–137} }
 @article{metwally_mayo_han_gardner_2005, title={Coincidence counting for PGNAA applications: Is it the optimum method?}, volume={265}, ISSN={["1588-2780"]}, DOI={10.1007/s10967-005-0826-2}, number={2}, journal={JOURNAL OF RADIOANALYTICAL AND NUCLEAR CHEMISTRY}, author={Metwally, WA and Mayo, CW and Han, X and Gardner, RP}, year={2005}, month={Aug}, pages={309–314} }
 @article{gardner_zhang_metwally_2005, title={Status of software for PGNAA bulk analysis by the Monte Carlo - Library Least-Squares (MCLLS) approach}, volume={264}, ISSN={["0236-5731"]}, DOI={10.1007/s10967-005-0697-6}, number={1}, journal={JOURNAL OF RADIOANALYTICAL AND NUCLEAR CHEMISTRY}, author={Gardner, RP and Zhang, W and Metwally, WA}, year={2005}, month={Apr}, pages={221–228} }
 @article{gardner_metwally_shehata_2004, title={A semi-empirical model for a Sr-90 beta-particle transmission thickness gauge for aluminum alloys}, volume={213}, ISSN={["0168-583X"]}, DOI={10.1016/S0168-583X(03)01582-9}, abstractNote={A semi-empirical model is derived and tested for a 90Sr beta-particle transmission thickness gauge for aluminum alloys. Monte Carlo simulation is also used to verify the forward scatter part of the model. The model accurately accounts for thickness as well as forward scatter, gamma-ray background, and the measurement interference of sample density and composition. The model parameters are obtained and the model is benchmarked with industrial experimental data from a 90Sr(90Y) gauge.}, journal={NUCLEAR INSTRUMENTS & METHODS IN PHYSICS RESEARCH SECTION B-BEAM INTERACTIONS WITH MATERIALS AND ATOMS}, author={Gardner, RP and Metwally, WA and Shehata, A}, year={2004}, month={Jan}, pages={357–363} }
 @article{metwally_gardner_mayo_2004, title={Elemental PGNAA analysis using gamma-gamma coincidence counting with the library least-squares approach}, volume={213}, ISSN={["1872-9584"]}, DOI={10.1016/S0168-583X(03)01660-4}, abstractNote={Abstract An accurate method for determining elemental analysis using gamma–gamma coincidence counting is presented. To demonstrate the feasibility of this method for PGNAA, a system of three radioisotopes (Na-24, Co-60 and Cs-134) that emit coincident gamma rays was used. Two HPGe detectors were connected to a system that allowed both singles and coincidences to be collected simultaneously. A known mixture of the three radioisotopes was used and data was deliberately collected at relatively high counting rates to determine the effect of pulse pile-up distortion. The results obtained, with the library least-squares analysis, of both the normal and coincidence counting are presented and compared to the known amounts. The coincidence results are shown to give much better accuracy. It appears that in addition to the expected advantage of reduced background, the coincidence approach is considerably more resistant to pulse pile-up distortion.}, journal={NUCLEAR INSTRUMENTS & METHODS IN PHYSICS RESEARCH SECTION B-BEAM INTERACTIONS WITH MATERIALS AND ATOMS}, author={Metwally, WA and Gardner, RP and Mayo, CW}, year={2004}, month={Jan}, pages={394–399} }
 @article{guo_gardner_metwally_2004, title={Preliminary studies on K and L coincidence spectroscopy for optimizing the in vivo XRF measurement of lead in bone}, volume={213}, ISSN={["0168-583X"]}, DOI={10.1016/S0168-583X(03)01674-4}, abstractNote={Previous studies treated the optimal combined K and L XRF system which consists of a Cd-109 point source, a low energy Ge detector (LEGe) and a Si(Li) detector. The Monte-Carlo library least-squares (MCLLS) approach and differential operator approach were treated separately. In this work, an approach for combining the MCLLS approach with the differential operator approach (MCDOLLS) is presented and an optimal configuration for coincidence spectroscopy of K and L X-rays is proposed based on preliminary experimental data.}, journal={NUCLEAR INSTRUMENTS & METHODS IN PHYSICS RESEARCH SECTION B-BEAM INTERACTIONS WITH MATERIALS AND ATOMS}, author={Guo, WJ and Gardner, RP and Metwally, WA}, year={2004}, month={Jan}, pages={574–578} }
 @article{metwally_gardner_2004, title={Stabilization of prompt gamma-ray neutron activation analysis (PGNAA) spectra from NaI detectors}, volume={525}, ISSN={["1872-9576"]}, DOI={10.1016/j.nima.2004.02.011}, abstractNote={Abstract NaI detectors are still used frequently in industrial Prompt Gamma-Ray Neutron Activation Analysis applications such as in bulk material analysis. They have the advantages of being efficient for high-energy gamma rays, being relatively rugged, and being able to be used without cooling. When using NaI detectors, and consequently photomultiplier tubes, the quality of the data can drastically deteriorate through gain and zero shifts that result in spectral smearing due to temperature and/or counting rate changes. A new offline approach is presented to stabilize the NaI spectral drift. The approach is not sensitive to the cause of the drift and takes into account the NaI and ADC non-linearities. Peak resolution is improved substantially when this approach is used in the presence of spectral drift.}, number={3}, journal={NUCLEAR INSTRUMENTS & METHODS IN PHYSICS RESEARCH SECTION A-ACCELERATORS SPECTROMETERS DETECTORS AND ASSOCIATED EQUIPMENT}, author={Metwally, WA and Gardner, RP}, year={2004}, month={Jun}, pages={518–521} }
 @article{metwally_gardner_mayo_2004, title={Two-dimensional diagonal summing of coincidence spectra for bulk PGNAA applications}, volume={525}, ISSN={["1872-9576"]}, DOI={10.1016/j.nima.2004.02.012}, abstractNote={Abstract In the past 10 years, new electronic devices have been developed that allow fast coincidence measurements to be performed that are capable of simultaneously recording the individual spectra as well as the coincidence spectra of multiple detectors. Utilizing these devices with computer software allows multiparameter data acquisition which adds much more flexibility in data analysis. One of the capabilities that is enabled is that of obtaining two-dimensional spectra. In this work, the use of this equipment and the two-dimensional spectra obtained with it are used to allow two-dimensional diagonal summing. The main advantages of this approach are improved peak resolution and very low background (Compton continuum). Possible uses of the two-dimensional diagonal summing are identifying coincidence schemes, performing elemental analysis, and identifying trace elements in bulk samples. The spectra obtained are very promising for these applications.}, number={3}, journal={NUCLEAR INSTRUMENTS & METHODS IN PHYSICS RESEARCH SECTION A-ACCELERATORS SPECTROMETERS DETECTORS AND ASSOCIATED EQUIPMENT}, author={Metwally, WA and Gardner, RP and Mayo, CW}, year={2004}, month={Jun}, pages={511–517} }
 @article{gardner_mayo_el-sayyed_metwally_zheng_poezart_2000, title={A feasibility study of a coincidence counting approach for PGNAA applications}, volume={53}, ISSN={["0969-8043"]}, DOI={10.1016/S0969-8043(00)00206-2}, abstractNote={Prompt gamma-ray nutron activation analysis (PGNAA) has an inherently low signal-to-noise (S/N) ratio primarily because of the large background (noise) associated with it. Most elements emit a significant fraction of their prompt gamma rays in coincidence with one or more other prompt gamma rays. This paper reports on initial efforts to use coincidence counting in PGNAA to significantly reduce the several sources of background and thereby increase the S/N ratio. An added benefit is the elimination of the often dominant hydrogen prompt gamma-ray spectrum which emits only a single prompt gamma ray with an energy of 2.223 MeV. Preliminary results are given for both in situ bulk analysis applications with a 252Cf neutron source and for nuclear reactor thermal neutron beam applications for small laboratory samples.}, number={4-5}, journal={APPLIED RADIATION AND ISOTOPES}, author={Gardner, RP and Mayo, CW and El-Sayyed, ES and Metwally, WA and Zheng, Y and Poezart, M}, year={2000}, pages={515–526} }