Nima Ghal-Eh

Associate Professor of Nuclear Physics

  • TEL: +98-23-522 00 90
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  • Selected Publications

    Balaghi, S., Ghal-Eh, N., Mohammadi, A., Vega-Carrillo, H.R. A neutron scattering soil moisture measurement system with a linear response (2018) 142, pp. 167-172.

    DOI: 10.1016/j.apradiso.2018.10.002

    A prototype moisture measurement system was designed and constructed, based on neutron scattering, for preforming measurements in the laboratory. The system consisted of a rectangular soil container, an 241Am/Be neutron source and two parallel 10BF3 detectors (one near the source and the other far from it). Neutrons from the source are moderated and backscattered within the soil sample before being detected by two parallel counters, whose count ratios are shown to be linearly related to the soil moisture even within short measurement times. The system's performance was demonstrated using the Monte Carlo simulations, and a series of measurements on soil samples made of clay (40 wt%) and sand (60 wt%), mixed with different percentages of water. The results showed that the detectors response ratio is linear, up to about 25% of water content. © 2018 Elsevier Ltd

    AUTHOR KEYWORDS: Neutron; Scattering; Soil moisture
    INDEX KEYWORDS: Intelligent systems; Moisture determination; Moisture meters; Monte Carlo methods; Neutron scattering; Neutron sources; Neutrons; Scattering; Soil moisture, Back-scattered; Linear response; Measurement time; Moisture Measurement; Parallel counters; Soil moisture measurement; Soil sample; System's performance, Soil surveys, americium 241; beryllium; calcium; chloride; cobalt; iron; magnesium; manganese; phosphorus; potassium; rubidium; silicon; sodium; strontium; sulfur; titanium; water; zinc, Article; controlled study; equipment design; Monte Carlo method; neutron scattering; priority journal; sand; soil container; soil moisture; water content; X ray fluorescence spectrometry
    PUBLISHER: Elsevier Ltd

    Ghal-Eh, N., Aliannezhadi, M., Bedenko, S.V. Optical photon transport and geometry contributions to time response of scintillation detectors (2018) 29 (9), art. no. 1850091, .

    DOI: 10.1142/S0129183118500912

    The sensitivities of both time and energy resolutions of a typical scintillation detector to major optical parameters (i.e. paint reflectivity, quantum efficiency of photomultiplier tube and attenuation coefficient) have been estimated using a dedicated Monte Carlo (MC) optical photon transport (OPT) simulation code, PHOTRACK, and the OPT capabilities of general-purpose code, FLUKA. Both cylindrical and parallelepiped geometries have been considered for the scintillator cell and lightguide. The results determine the scintillation light wavelength regions that the energy and time resolution represent enhanced sensitivities to small change/uncertainty in optical parameters. © 2018 World Scientific Publishing Company.

    AUTHOR KEYWORDS: FLUKA; PHOTRACK; Scintillator; sensitivity; time resolution
    PUBLISHER: World Scientific Publishing Co. Pte Ltd

    Bayat, E., Afarideh, H., Davani, F.A., Ghal-Eh, N. Noise reduction of PGNAA spectrum using empirical mode decomposition technique (2018) 149, pp. 49-53.

    DOI: 10.1016/j.radphyschem.2018.01.015

    Prompt gamma neutron activation analysis (PGNAA) is frequently used in on–line analysis of raw materials in cement and coal industries which normally incorporates bismuth germanate (BGO) or sodium iodide (NaI(Tl)) scintillators. The quantitative results are basically undertaken through full–spectrum analysis method which requires an efficient noise reduction procedure to optimize PGNAA data. Here in this study, the empirical mode decomposition (EMD) technique has been used to reduce the noise level of PGNAA spectra of a neutron–irradiated NaCl·H2O solution and then the results have been compared with those of wavelet technique. The mean square errors (MSEs) comparisons confirm that both EMD and wavelet techniques can be efficiently used for noise reduction purposes, however, this study recommends the EMD technique for its independency of basic functions, simplicity and spectrum data-based operation. © 2018 Elsevier Ltd

    AUTHOR KEYWORDS: EMD technique; Material analysis; Noise reduction; PGNAA; Wavelet method
    INDEX KEYWORDS: Bismuth compounds; Cement industry; Coal industry; Iodine compounds; Mean square error; Noise abatement; Signal processing; Sodium chloride; Sodium Iodide; Spectrum analysis; Wavelet decomposition, EMD technique; Empirical Mode Decomposition; Material analysis; PGNAA; Prompt gamma neutron activation analysis; Quantitative result; Wavelet methods; Wavelet techniques, Neutron activation analysis, article; decomposition; error; neutron activation analysis; noise reduction
    PUBLISHER: Elsevier Ltd

    Salimi, M., Ghal-Eh, N., Amirabadi, E.A. Characterization of a new shielding rubber for use in neutron–gamma mixed fields (2018) 29 (3), art. no. 36, .

    DOI: 10.1007/s41365-018-0371-7

    A variety of formulations was investigated for the fabrication of an appropriate shielding rubber to be used in neutron–gamma mixed fields. Having considered the required mechanical properties together with tungsten as the gamma-ray absorbing element, calculations with MCNPX 2.6 code confirmed that the incorporation of 5 weight percentage (wt%) of boron carbide exhibited the best performance as a thermal neutron absorber. A series of both experimental and simulation results are provided for comparison. © 2018, Shanghai Institute of Applied Physics, Chinese Academy of Sciences, Chinese Nuclear Society, Science Press China and Springer Nature Singapore Pte Ltd.

    AUTHOR KEYWORDS: Gamma; MCNPX; Neutron; Rubber; Shielding
    PUBLISHER: Springer Singapore

    Ghal-Eh, N., Goudarzi, H., Rahmani, F. FLUKA simulation studies on in–phantom dosimetric parameters of a LINAC–based BNCT (2017) 141, pp. 36-40.

    DOI: 10.1016/j.radphyschem.2017.06.004

    The Monte Carlo simulation code, FLUKA version 2011.2c.5, has been used to estimate the in–phantom dosimetric parameters for use in BNCT studies. The in–phantom parameters of a typical Snyder head, which are necessary information prior to any clinical treatment, have been calculated with both FLUKA and MCNPX codes, which exhibit a promising agreement. The results confirm that FLUKA can be regarded as a good alternative for the MCNPX in BNCT dosimetry simulations. © 2017 Elsevier Ltd

    AUTHOR KEYWORDS: BNCT; Dosimetry; FLUKA; In–phantom parameters; MCNPX; Snyder head phantom
    INDEX KEYWORDS: Dosimetry; Intelligent systems, BNCT; FLUKA; MCNPX; Phantom parameters; Snyder head phantom, Monte Carlo methods, boron, Article; boron neutron capture therapy; brain; dose calculation; dosimetry; fast neutron radiation; gamma radiation; linear accelerator; Monte Carlo method; neutron dosimetry; neutron radiation; radiation depth dose; radiation dose; radiology phantom; skin; skull
    PUBLISHER: Elsevier Ltd

    Ghal-Eh, N., Kalaei, M., Mohammadi, A., Vega-Carrillo, H.R. Replacement of Bonner spheres with polyethylene cylinders for the unfolding of an 241Am–Be neutron energy spectrum (2017) 128, pp. 292-296.

    DOI: 10.1016/j.apradiso.2017.07.043

    In this study, a conventional Bonner sphere spectrometer, together with 6LiI(Eu) inorganic scintillator used as the central detector, was used to obtain the neutron energy spectrum of an 241Am–Be source. To achieve this, we calculated the response matrices corresponding to eight different sizes of polyethylene spheres for the neutron energies ranging from about 10-7 to 15 MeV in 54 energy groups by using the MCNPX2.6 code, and the 241Am–Be neutron spectrum was obtained using a modified version of the neutron spectrum unfolding code, AFITBUNKI. In a feasibility study, similar calculations were performed with different sizes of polyethylene cylinders. A comparison between the unfolded spectra of a typical 241Am–Be neutron source with those of Bonner spheres, cylinders of similar sizes, and standard 241Am–Be neutron energy spectra shows that the spectrometer with polyethylene cylinders can be used as a potential alternative for conventional Bonner spheres. © 2017 Elsevier Ltd

    AUTHOR KEYWORDS: 6LiI(Eu) scintillator; AFITBUNKI unfolding code; Bonner sphere spectrometer; Neutron
    INDEX KEYWORDS: Codes (symbols); Cylinders (shapes); Neutron sources; Neutron spectrometers; Polyethylenes; Scintillation counters; Spectrometers; Spectroscopy; Spheres, AFITBUNKI unfolding code; Bonner sphere spectrometer; Different sizes; Feasibility studies; Inorganic scintillator; Neutron energy spectrum; Polyethylene cylinders; Response matrices, Neutrons, americium 241; beryllium; polyethylene, algorithm; Article; Bonner sphere spectrometer; controlled study; elasticity; feasibility study; neutron radiation; priority journal; process optimization; radiation measurement; scintillation; spectrometer
    PUBLISHER: Elsevier Ltd

    Ghal-Eh, N., Green, S. A plastic scintillator-based 2D thermal neutron mapping system for use in BNCT studies (2016) 112, pp. 31-37.

    DOI: 10.1016/j.apradiso.2016.03.002

    In this study, a scintillator-based measurement instrument is proposed which is capable of measuring a two-dimensional map of thermal neutrons within a phantom based on the detection of 2.22 MeV gamma rays generated via nth+H→D+γ reaction. The proposed instrument locates around a small rectangular water phantom (14 cm×15 cm×20 cm) used in Birmingham BNCT facility. The whole system has been simulated using MCNPX 2.6. The results confirm that the thermal flux peaks somewhere between 2 cm and 4 cm distance from the system entrance which is in agreement with previous studies. © 2016 Elsevier Ltd.

    AUTHOR KEYWORDS: BNCT; MCNP; Scintillator; Thermal neutrons
    INDEX KEYWORDS: Neutrons; Phosphors; Scintillation counters, BNCT; Mapping systems; MCNP; Measurement instruments; Plastic scintillator; Thermal fluxes; Thermal neutrons; Two-dimensional map, Gamma rays, Article; equipment design; gamma radiation; heat transfer; image quality; neutron capture therapy; neutron therapy; priority journal; process development; radiation detection; radiation equipment; radiation response; sensitivity analysis; thermal neutron mapping system
    PUBLISHER: Elsevier Ltd

    Bayat, E., Afarideh, H., Davani, F.A., Ghal-Eh, N. A quality survey on different shielding configurations of gamma ray detector used with a portable PGNAA system (2016) 120, pp. 7-11.

    DOI: 10.1016/j.radphyschem.2015.11.012

    The appropriate gamma-ray detector shielding configuration is critical for a precise prompt gamma neutron activation analysis (PGNAA) measurement. The shielding material has to prevent the radiation damage to the detector crystal and it must produce less activation gamma rays, whether prompt or delayed, which may interfere the gamma ray spectrum of the sample. In this research, using common shielding materials, a number of combinations have been studies to form a 50 cm long shield for portable PGNAA system against both fast and slow neutrons as well as gamma rays emitted by 20Ci Am-Be source. The measurement results show that in contrast with conventional shadow cone in which the shielding material starts with 20 cm heavy metals such as iron and ends with 30. cm polymer materials, in portable PGNAA systems, the shielding material gives better results if it starts with about 40 cm borated polymer material and ends with an appropriate thickness (7 cm to 10 cm) of heavy metal such as tungsten. © 2015 Elsevier Ltd.

    AUTHOR KEYWORDS: Activation analysis; Am-Be; PGNAA; Shielding
    INDEX KEYWORDS: Activation analysis; Chemical activation; Heavy metals; Neutron activation analysis; Polymers; Radiation damage; Radiation shielding; Shielding; Ultraviolet spectroscopy, Gamma ray detector; Gamma ray spectra; PGNAA; Polymer materials; Prompt gamma neutron activation analysis; Shielding materials; Slow neutrons, Gamma rays, americium; beryllium, Article; compton effect; gamma radiation; neutron activation analysis; prompt gamma neutron activation analysis; radiation absorption; radiation detector; radiation injury; radiation shield; sensitivity analysis; signal noise ratio; spectroscopy
    PUBLISHER: Elsevier Ltd

    Ghal-Eh, N., Ahmadi, P., Doost-Mohammadi, V. A quantitative PGNAA study for use in aqueous solution measurements using Am-Be neutron source and BGO scintillation detector (2016) 808, pp. 123-

    DOI: 10.1016/j.nima.2015.11.070

    A prompt gamma neutron activation analysis (PGNAA) system including an Am-Be neutron source and BGO scintillation detector are used for quantitative analysis of bulk samples. Both Monte Carlo-simulated and experimental data are considered as input data libraries for two different procedures based on neural network and least squares methods. The results confirm the feasibility and precision of the proposed methods. © 2015 Elsevier B.V.

    AUTHOR KEYWORDS: Least squares; MCNPX; Neural networks; PGNAA
    INDEX KEYWORDS: Activation analysis; Least squares approximations; Libraries; Monte Carlo methods; Neural networks; Neutron sources; Neutrons; Scintillation; Solutions, Am-Be neutron source; Bulk samples; Least Square; Least squares methods; MCNPX; PGNAA; PGNAA study; Prompt gamma neutron activation analysis, Neutron activation analysis
    PUBLISHER: Elsevier

    Ghal-Eh, N., Doostizadeh, H., Hazami, Z., Doust-Mohammadi, V. A Compton-suppression detection system for use in manganese bath measurements (2015) 112, pp. 34-39.

    DOI: 10.1016/j.radphyschem.2015.03.003

    The manganese sulfate bath technique is a standard tool for neutron source strength measurement (Park et al., 2005). However, the dominate Compton continuum of most sodium iodide scintillators used in manganese bath systems (MBSs) does not allow the precise identification of induced gamma rays required for such measurements. In this research, to resolve this problem, a Compton-suppression system has been proposed which consists of a 2in. by 2in. NaI(Tl) right cylindrical scintillator as the main and a set of eight rectangular NE102 plastic scintillators of 12×12×15cm3 dimensions as suppression detectors. Both detectors operate in anti-coincidence circuit to suppress the Compton continuum. The proposed system has been simulated with the MCNPX code with two different approaches and the corresponding measurements with 137Cs gamma-ray source and neutron-activated MnSO4 solution have been undertaken that give rise to a promising agreement. © 2015 Elsevier Ltd.

    AUTHOR KEYWORDS: Compton-suppression; Manganese Bath System (MBS); MCNPX; Neutron; Scintillator
    INDEX KEYWORDS: Ionization; Manganese; Neutron sources; Neutrons; Phosphors; Scintillation counters, Compton continuum; Compton suppression; Detection system; Gamma ray sources; Manganese sulfate; MCNPX; Neutron source strength; Plastic scintillator, Gamma rays, cesium 137; manganese sulfate, analytical equipment; Article; compton suppression detection system; concentration (parameters); manganese bath system; neutron; neutron radiation; process optimization; radiation detection; radiation physics; radioactivity; scintillation camera; simulation
    PUBLISHER: Elsevier Ltd

    Tajik, M., Ghal-Eh, N. Comparison of light transport-incorporated MCNPX and FLUKA codes in generating organic scintillators responses to neutrons and gamma rays (2015) 791, pp. 65-68.

    DOI: 10.1016/j.nima.2015.04.043

    The NE102 plastic scintillator response to 137Cs gamma rays and NE213 liquid scintillator response to both mono-energetic and 241Am-Be neutrons have been modeled using FLUKA's EVENTBIN and MCNPX's PTRAC cards. The comparison made in different energy regions confirms that the overall difference is less than 6%. © 2015 Elsevier B.V.

    AUTHOR KEYWORDS: MCNPX FLUKA PHOTRACK Scintillator Response Efficiency
    INDEX KEYWORDS: Scintillation counters, Comparison of lights; Energy regions; FLUKA codes; Liquid scintillator; Organic scintillator; Plastic scintillator; Response efficiencies, Gamma rays
    PUBLISHER: Elsevier

    Jamili, S., Bayat, E., Afarideh, H., Abbasi Davani, F., Ghal-Eh, N. Digital neutron-gamma discrimination in a wide energy range using pulse reconstruction method (2015) 109, pp. 13-16.

    DOI: 10.1016/j.radphyschem.2014.12.004

    In this research, based on pulse reconstruction method, digital storage oscilloscopes with an 8-bit digital-to-analog convertor was used to successfully perform the neutron-gamma discrimination with NE213 (or its equivalent BC501A) scintillator anode pulses at minimum discrimination bias value of 95keVee (or keV electron equivalent). Also, a 100mCi 241Am-Be source and micro-Curie gamma ray sources (137Cs and 22Na) were used for the system calibration and discrimination studies. The results confirm the feasibility and simplicity of the proposed method. © 2014 Elsevier Ltd.

    AUTHOR KEYWORDS: Gamma; Neutron; NGD; Pulse reconstruction
    INDEX KEYWORDS: americium 241; cesium 137; sodium 22, analytical parameters; Article; calibration; feasibility study; gamma radiation; information processing; oscilloscope; pulse radiolysis; pulse reconstruction method; radiation energy; scintillation
    PUBLISHER: Elsevier Ltd

    Lotfi, Y., Etaati, G.R., Doust-Mohammadi, V., Ghal-Eh, N. Design and Fabrication of a Data Acquisition System for Pulsed Neutron Flux Measurement of Plasma Focus Devices (2015) 34 (2), pp. 411-421.

    DOI: 10.1007/s10894-014-9812-4

    Silver-activated Geiger counters together with a polyethylene layer as neutron moderator are frequently used in pulsed neutron flux measurements in research studies with plasma focus (PF) devices. In this study, an array of seven counters was used at seven different angles (0°, ±30°, ±60° and ±90°) to the PF-axis for which a software and a 10-channel data acquisition hardware (PCT2660) compatible with NIM standards have been designed and fabricated. In the proposed PCT2660, the preset timing algorithms are considered as general and they can be programmed for required detector calibrations and neutron flux measurements. The calibration constant measurement has been undertaken with a 16.5 Ci Am–Be source of 35 mm diameter by 70 mm cylindrical active volume located at anode top whilst the neutron flux at zero degree of PF device axis at 13.5 kV operating voltage and 13.54 × 10−2 PSI pressure is measured as (2.88 ± 0.29) × 108 neutrons per shot. Accordingly, the studies on the angular distribution of the PF neutron emission within the pressure range of 7.73 × 10−2–15.47 × 10−2 PSI confirm an anisotropy ranging from 1.53 ± 0.09 to 2.95 ± 0.24 and a symmetry of angular distribution around the anode axis. © 2014, Springer Science+Business Media New York.

    AUTHOR KEYWORDS: Data acquisition device; Neutron activation counter; Neutron flux; Plasma focus device; Pulsed neutron
    INDEX KEYWORDS: Angular distribution; Anodes; Fabrication; Neutron flux; Plasma devices, Calibration constants; Data acquisition hardware; Data acquisition system; Data-acquisition devices; Detector calibration; Neutron activation; Plasma focus devices; Pulsed neutron, Data acquisition
    PUBLISHER: Springer New York LLC

    Tajik, M., Ghal-Eh, N., Etaati, G.R., Afarideh, H. NE213/BC501A scintillator-lightguide assembly response to 241Am-Be neutrons: An MCNPX-PHOTRACK hybrid code simulation (2014) 97, pp. 319-324.

    DOI: 10.1016/j.radphyschem.2013.12.011

    The response of an NE213 (or its BICRON equivalent, BC501A) scintillator attached to different sizes of polished/painted lightguides when exposed to 241Am-Be neutrons has been simulated. This kind of simulation basically needs both particle and light transports: the transport of neutrons and neutron-induced charged particles such as alphas, protons, carbon nuclei and so on has been undertaken using MCNPX whilst the scintillation light transport has been performed with PHOTRACK codes. The comparison between simulated and experimental response functions of NE213 attached to different sizes of polished/painted lightguides and also the influence of length/covering of lightguide on the detection efficiency and uniformity of the scintillator-lightguide assembly response have been studied. © 2013 Elsevier Ltd.

    AUTHOR KEYWORDS: 241Am-Be; MCNPX; Neutron; PHOTRACK; Response; Scintillator
    INDEX KEYWORDS: 241Am-Be; Detection efficiency; Light transport; MCNPX; PHOTRACK; Response; Response functions; Scintillation light, Neutrons; Phosphors, Scintillation counters, americium 241; beryllium, article; intermethod comparison; light collection efficiency; light collection uniformity; light related phenomena; light transport; MCNPX PHOTRACK hybrid code; Monte Carlo method; NE213 scintillator; neutron radiation; process model; proton transport; radiation detection; radiation equipment; radiological parameters; response variable; scintillator lightguide assembly; simulation

    Safari, M.J., Afarideh, H., Ghal-Eh, N., Davani, F.A. Optix: A Monte Carlo scintillation light transport code (2014) 737, pp. 101-106.

    DOI: 10.1016/j.nima.2013.11.051

    The paper reports on the capabilities of Monte Carlo scintillation light transport code Optix, which is an extended version of previously introduced code Optics. Optix provides the user a variety of both numerical and graphical outputs with a very simple and user-friendly input structure. A benchmarking strategy has been adopted based on the comparison with experimental results, semi-analytical solutions, and other Monte Carlo simulation codes to verify various aspects of the developed code. Besides, some extensive comparisons have been made against the tracking abilities of general-purpose MCNPX and FLUKA codes. The presented benchmark results for the Optix code exhibit promising agreements. © 2013 Elsevier B.V.

    AUTHOR KEYWORDS: Light transport; Monte Carlo; Optics; Optix; Scintillator
    INDEX KEYWORDS: Extended versions; FLUKA codes; Light transport; Monte- carlo simulations; Optix; Scintillation light; Semi-analytical solution; Tracking ability, Light transmission; Optics; Phosphors; Scintillation, Monte Carlo methods

    Bayat, E., Doust-Mohammadi, V., Ghorbani, P., Ghal-Eh, N., Mohammadi, R. Scintillation of XP2020 PMT glass window (2014) 102, pp. 1-4.

    DOI: 10.1016/j.radphyschem.2014.04.009

    Scintillation of the photomultiplier glass window and its effects on the detector response were studied. It was proved that effects could have a considerable contribution to the pulse-height spectrum, especially when low-efficiency scintillators were used. © 2014.

    AUTHOR KEYWORDS: Glass window; Photomultiplier tube; Scintillator
    INDEX KEYWORDS: Phosphors; Photomultipliers; Scintillation; Scintillation counters, Detector response; Glass windows; Photo multiplier tube; Pulse height spectrum, Glass, accuracy; article; gamma radiation; ionizing radiation; neutron radiation; photomultiplier tube glass window; radiation energy; radiation equipment; radiation exposure; radiation measurement; scintillation; spectrometry
    PUBLISHER: Elsevier Ltd

    Zare, S., Ghal-Eh, N., Bayat, E. On timing response improvement of an NE213 scintillator attached to two PMTs (2013) 90, pp. 6-10.

    DOI: 10.1016/j.radphyschem.2013.04.036

    A 5cm diameter by 6cm height NE213 scintillator attached to two XP2282 PHOTONIS photomultiplier tubes (PMTs) exposed to 241Americium-Berylium (Am-Be) neutron-gamma source has been used for timing response studies. The neutron-gamma discrimination (NGD) measurements based on a modified zero-crossing (ZC) method show that the discrimination quality, usually expressed in figure-of-merit (FoM) and peak-to-valley (P/V) values, has been improved. The timing response evaluated with Monte Carlo light transport code, PHOTRACK, also verifies this improvement. © 2013 Elsevier Ltd.

    AUTHOR KEYWORDS: Neutron-gamma discrimination; PHOTRACK; PMT; Scintillator; Timing response
    INDEX KEYWORDS: Figure of merits; Light transport; NE213 scintillator; Neutron-gamma discrimination; Photo multiplier tube (PMTs); PHOTRACK; PMT; Timing response, Neutrons; Phosphors, Scintillation counters, americium 241; beryllium, analytical equipment; article; equipment design; gamma radiation; Monte Carlo method; photomultiplier tube; process optimization; scintillation; scintillator; simulation

    Shahri, A., Ghal-Eh, N., Etaati, G.R. Modelling Boron-Lined proportional counter response to neutrons (2013) 156 (3), art. no. nct066, pp. 349-355.

    DOI: 10.1093/rpd/nct066

    The detailed Monte Carlo simulation of a boron-lined proportional counter response to a neutron source has been presented. The MCNP4C and experimental data on different source-moderator geometries have been given for comparison. The influence of different irradiation geometries and boron-lining thicknesses on the detector response has been studied. © The Author 2013. Published by Oxford University Press. All rights reserved.

    INDEX KEYWORDS: americium; beryllium; boron, article; chemistry; computer simulation; equipment; magnetic and electromagnetic equipment; Monte Carlo method; neutron; radiation dose, Americium; Beryllium; Boron; Computer Simulation; Monte Carlo Method; Neutrons; Particle Accelerators; Radiotherapy Dosage

    Ghorbani, P., Bayat, E., Ghal-Eh, N. A comparison study on three different radiation detectors used for liquid levelmetry (2013) 156 (1), pp. 103-108.

    DOI: 10.1093/rpd/nct046

    In this paper, three different radiation detectors (BF3 counter, NE213 and BGO scintillators) and an 241Am-Be isotopic neutron-gamma source have been used for a typical liquid levelmetry. The study shows that the use of the Am-Be source together with an NE213 scintillator has the best performance. © The Author 2013. Published by Oxford University Press. All rights reserved.

    INDEX KEYWORDS: americium; beryllium; hydrogen; water, article; chemistry; comparative study; equipment design; gamma radiation; gamma spectrometry; methodology; neutron; radiation dose; radiometry; scintillation counting, Americium; Beryllium; Equipment Design; Gamma Rays; Hydrogen; Neutrons; Radiation Dosage; Radiometry; Scintillation Counting; Spectrometry, Gamma; Water

    Tajik, M., Ghal-Eh, N., Etaati, G.R., Afarideh, H. Modeling NE213 scintillator response to neutrons using an MCNPX-PHOTRACK hybrid code (2013) 704, pp. 104-110.

    DOI: 10.1016/j.nima.2012.12.001

    This paper reports on how to generate the response function of an NE213 scintillator when exposed to mono-energetic neutrons using the PTRAC card of the MCNPX code. The light transport part of the simulation has been undertaken with the Monte Carlo PHOTRACK code. The comparison confirms that the simulated response function represents a promising agreement with the previously published simulations and experiments. © 2012 Elsevier B.V.

    AUTHOR KEYWORDS: MCNPX; Neutron; PHOTRACK; Response function; Scintillator
    INDEX KEYWORDS: Light transport; MCNPX; MCNPX code; Mono-energetic neutrons; MONTE CARLO; NE213 scintillator; PHOTRACK; Response functions; Simulated response, Neutrons; Phosphors, Monte Carlo methods

    Divani-Vais, N., Bayat, E., Firoozabadi, M.M., Ghal-Eh, N. Neutron-gamma discrimination with ugab scintillator using zero-crossing method (2013) 154 (3), pp. 381-384.

    DOI: 10.1093/rpd/ncs252

    The new-type scintillator, Ultima Gold Alpha-Beta (UGAB), was studied for its neutron-gamma discrimination capability. The figure-of-merit and peak-to-valley values for the neutron-gamma discrimination spectra of UGAB scintillator when exposed to 241Am-Be neutron source were presented. The results show that this new-type scintillator can efficiently be used in neutron-gamma discrimination experiments. ©The Author 2012. Published by Oxford University Press.

    PUBLISHER: Oxford University Press

    Binaei Bash, Z., Ghal-Eh, N., Bayat, E., Etaati, G.R. Lightguide influence on timing response of scintillation detectors (2013) 82 (1), pp. 1-6.

    DOI: 10.1016/j.radphyschem.2012.09.013

    In this paper, using zero-crossing method, the neutron-gamma discrimination has been discussed to estimate the contribution of light transport on the timing characteristics of scintillation detectors. Both experimental and simulation verifications for the influence of lightguide length on the neutron-gamma discrimination quality of a 2×2 in. NE213 scintillator have been presented. © 2012 Elsevier Ltd.

    AUTHOR KEYWORDS: Light transport; Monte Carlo; Neutron-gamma discrimination; Scintillator
    INDEX KEYWORDS: Light transport; MONTE CARLO; NE213 scintillator; Neutron-gamma discrimination; Simulation verification; Timing characteristics; Zero crossing methods, Light transmission; Neutrons; Phosphors, Neutron detectors, article; comparative study; compton effect; correlational study; experimental study; gamma radiation; light intensity; magnetic field; Monte Carlo method; process model; radiation detector; scintillation; spectroscopy

    Rasoulinejad, M., Izadi Najafabadi, R., Ghal-Eh, N. A simple well-logging tool using boron-lined sodium iodide scintillators and an 241Am-Be neutron source (2012) 151 (3), art. no. ncs030, pp. 580-585.

    DOI: 10.1093/rpd/ncs030

    A couple of 2-inch by 2-inch right cylinder sodium iodide scintillators and an Am-Be radioisotope neutron source have been used in a neutron porosity well-logging tool to explore the variation of hydrogen contents in a prototype formation. Both Monte Carlo N-particle transport code simulation and experimental results of the near- to far-detector responses confirm the reliable sensitivity of proposed tool to the formation porosity. © The Author 2012. Published by Oxford University Press. All rights reserved.

    INDEX KEYWORDS: americium; beryllium; boron; hydrogen; sodium iodide, article; chemistry; computer simulation; instrumentation; Monte Carlo method; neutron; porosity; scintillation counting, Americium; Beryllium; Boron; Computer Simulation; Hydrogen; Monte Carlo Method; Neutrons; Porosity; Scintillation Counting; Sodium Iodide

    Ranjbar Kohan, M., Etaati, G.R., Ghal-Eh, N., Safari, M.J., Afarideh, H., Asadi, E. Modelling plastic scintillator response to gamma rays using light transport incorporated FLUKA code (2012) 70 (5), pp. 864-867.

    DOI: 10.1016/j.apradiso.2012.01.014

    The response function of NE102 plastic scintillator to gamma rays has been simulated using a joint FLUKA+PHOTRACK Monte Carlo code. The multi-purpose particle transport code, FLUKA, has been responsible for gamma transport whilst the light transport code, PHOTRACK, has simulated the transport of scintillation photons through scintillator and lightguide. The simulation results of plastic scintillator with/without light guides of different surface coverings have been successfully verified with experiments. © 2012 Elsevier Ltd.

    AUTHOR KEYWORDS: Detection resolution; FLUKA; Monte carlo; PHOTRACK; Response function; Scintillator
    INDEX KEYWORDS: FLUKA; FLUKA codes; Gamma transport; Light guides; Light transport; MONTE CARLO; Monte Carlo codes; Multi-purpose; Particle transport; PHOTRACK; Plastic scintillator; Response functions; Scintillation photons; Surface covering, Gamma rays; Light transmission; Monte Carlo methods; Optical fibers; Phosphors, Scintillation, analytic method; article; controlled study; gamma radiation; gamma spectrometry; Monte Carlo method; priority journal; radiation detection; scintillation; simulation

    Bayat, E., Divani-Vais, N., Firoozabadi, M.M., Ghal-Eh, N. A comparative study on neutron-gamma discrimination with NE213 and UGLLT scintillators using zero-crossing method (2012) 81 (3), pp. 217-220.

    DOI: 10.1016/j.radphyschem.2011.10.016

    The neutron-gamma discrimination capability of the new-type UGLLT liquid scintillator has been compared with NE213 (or its Bicron equivalent, BC501A). An Am-Be combined neutron-gamma isotopic source and a zero-crossing circuitry were used to explore various biases resulting the optimum figure of merits (FOMs) of 1.52 and 1.18 for NE213 and UGLLT at 170. keVee bias, respectively. The study shows that the UGLLT scintillator can be a good alternative for NE213 in pulse-shape discrimination experiments. © 2011 Elsevier Ltd.

    AUTHOR KEYWORDS: Neutron-gamma discrimination; PSD; Scintillator; UGLLT
    INDEX KEYWORDS: Comparative studies; Liquid scintillator; Neutron-gamma discrimination; PSD; Pulse shape discrimination; Scintillator; UGLLT; Zero crossing methods; Zero-crossings, Scintillation; Scintillation counters, Neutrons, article; calibration; comparative study; controlled study; gamma radiation; geometry; instrument; kernel method; neutron radiation; quantitative analysis; scintillation; scintillator

    Fard, O.S., Ghal-Eh, N. Numerical solutions for linear system of first-order fuzzy differential equations with fuzzy constant coefficients (2011) 181 (20), pp. 4765-4779.

    DOI: 10.1016/j.ins.2011.06.007

    In this paper, a novel iterative method is proposed to obtain approximate-analytical solutions for the linear systems of first-order fuzzy differential equations (FDEs) with fuzzy constant coefficients (FCCs) while avoiding the complexities of eigen-value computations. A theorem for the convergence and the validity of the approach is also presented in detail. Numerical experiments and comparisons with exact solutions reveal that the proposed method is capable of generating accurate results. © 2011 Elsevier Inc. All rights reserved.

    AUTHOR KEYWORDS: Approximate-analytical solution; System of first-order linear FDEs; Variational iteration method
    INDEX KEYWORDS: Approximate-analytical solution; Constant coefficients; Eigen-value; Exact solution; First-order; Fuzzy differential equations; Numerical experiments; Numerical solution; Variational iteration method, Differential equations; Iterative methods; Linear systems; Numerical methods, Differentiation (calculus)

    Ghal-Eh, N. Light transport contribution to the timing characteristics of scintillation detectors (2011) 80 (3), pp. 365-368.

    DOI: 10.1016/j.radphyschem.2010.11.005

    A Monte Carlo simulation of the light transit time in scintillation detectors is described, with the wavelength dependencies of different interaction processes being taken into account. The simulation results presented give an estimate of the contribution of light transport to the timing resolution of scintillation detectors. © 2010 Elsevier Ltd.

    AUTHOR KEYWORDS: Monte Carlo; PHOTRACK; Scintillator; Timing resolution; Timing response
    INDEX KEYWORDS: MONTE CARLO; PHOTRACK; Scintillator; Timing resolutions; Timing response, Computer simulation; Detectors; Monte Carlo methods; Neutron detectors, Scintillation, article; controlled study; light; Monte Carlo method; radiation detector; scintillation; spectral sensitivity

    Etaati, G.R., Amrollahi, R., Doust-Mohammadi, V., Ghal-Eh, N., Habibi, M. Calibration constant of a silver activated geiger counter used for neutron efficiency measurements in plasma focus devices: Theoretical vs. experimental studies (2010) 29 (4), pp. 381-386.

    DOI: 10.1007/s10894-010-9292-0

    The silver activated Geiger counters are frequently used for measuring pulsed neutron fluxes especially in plasma focus devices. These counters basically utilize a Geiger-Mueller (GM) counter surrounded by a silver layer as an activation medium and also a polyethylene layer as a neutron moderator. Neutrons are slowed down in polyethylene prior to activating the silver layer. The neutron flux can be estimated through measuring the silver activity by Geiger-Mueller counter. In this paper, the construction of an activation counter is explained and the Monte Carlo MCNP4C code is used to calculate the calibration constant. Finally, the calculated calibration constant is compared with the measurement undertaken with an Am-Be neutron source, based on the saturation count rate method. The comparison represents a good agreement between simulation and experimental values of calibration constant. The Amir Kabir Plasma Focus (APF) device is used as a fast neutron source. © Springer Science+Business Media, LLC 2010.

    AUTHOR KEYWORDS: Calibration constant; MCNP code; Neutron; Plasma focus; Silver activated geiger counters counter
    INDEX KEYWORDS: Am-Be neutron source; Calibration constants; Count rates; Efficiency measurement; Experimental studies; Experimental values; Fast neutron source; MCNP code; MCNP4C codes; MONTE CARLO; Mueller; Neutron moderators; Plasma focus; Plasma focus devices; Pulsed neutron; Silver layer, Calibration; Chemical activation; Geiger counters; Neutron beams; Neutron flux; Neutron sources; Plasma devices; Polyethylenes; Silver; Thermoplastics, Plasmas

    Mottaghian, M., Koohi-Fayegh, R., Ghal-Eh, N., Etaati, G.R. Photocathode non-uniformity contribution to the energy resolution of scintillators (2010) 140 (1), art. no. ncq041, pp. 16-24.

    DOI: 10.1093/rpd/ncq041

    This paper introduces the basics of the light transport simulation in scintillators and the wavelength-dependencies in the process. The non-uniformity measurement of the photocathode surface is undertaken, showing that for the photocathode used in this study the quantum efficiency falls to about 4 % of its maximum value, especially in areas far from the centre. The wavelength-and position-dependent quantum efficiency is implemented in the Monte Carlo light transport code, showing that, the contribution of the photocathode non-uniformity to the energy resolution is estimated to be around 18 %, when all position-and wavelength-dependencies are included. © The Author 2010. Published by Oxford University Press. All rights reserved. For Permissions, please email:

    INDEX KEYWORDS: article; instrumentation; Monte Carlo method; photometry; photon; radiography; radiometry; scintillation counting; devices; photometry; radiography; radiometry, Monte Carlo Method; Photometry; Photons; Radiography; Radiometry; Scintillation Counting, Monte Carlo Method; Photometry; Photons; Radiography; Radiometry; Scintillation Counting

    Ghal-Eh, N., Etaati, G.R. On the necessity of light transport simulation in scintillators (2009) 129 (1), pp. 95-99.

    DOI: 10.1016/j.jlumin.2008.09.001

    In this study, the light transport simulation in scintillators is introduced, the wavelength-dependencies in the process are taken into account, the effect of different shapes/lengths of lightguides on the response of the scintillation detectors are investigated and finally the need for such a simulation in addition to the particle transport simulation in a perfect response function predicting code is explained. © 2008 Elsevier B.V. All rights reserved.

    AUTHOR KEYWORDS: Monte Carlo; PHOTRACK; SCINFUL; Scintillator
    INDEX KEYWORDS: Electromagnetic waves; Ionization; Light emission; Luminescence; Phosphors; Scintillation counters, Monte Carlo; PHOTRACK; SCINFUL; Scintillator, Scintillation

    Etaati, G.R., Ghal-Eh, N. Light transport feature for SCINFUL (2008) 66 (3), pp. 395-400.

    DOI: 10.1016/j.apradiso.2007.09.014

    An extended version of the scintillator response function prediction code SCINFUL has been developed by incorporating PHOTRACK, a Monte Carlo light transport code. Comparisons of calculated and experimental results for organic scintillators exposed to neutrons show that the extended code improves the predictive capability of SCINFUL. © 2007 Elsevier Ltd. All rights reserved.

    AUTHOR KEYWORDS: NE213 scintillator; PHOTRACK; Response function; SCINFUL
    INDEX KEYWORDS: Computer simulation; Light transmission; Monte Carlo methods; Phosphors, Light transport codes; NE213 scintillators; Organic scintillators; PHOTRACKs; Response functions, Codes (symbols), article; device; experimental study; light; Monte Carlo method; neutron; prediction; priority journal; radiation detector; scintillation

    Ghal-Eh, N., Koohi-Fayegh, R. A sensitivity analysis approach to optical parameters of scintillation detectors (2008) 128 (1), pp. 11-14.

    DOI: 10.1016/j.jlumin.2007.04.013

    In this study, an extended version of the Monte Carlo light transport code, PHOTRACK, has been used for a sensitivity analysis to estimate the importance of different wavelength-dependent parameters in the modelling of light collection process in scintillators. © 2007 Elsevier B.V. All rights reserved.

    AUTHOR KEYWORDS: Monte Carlo; Scintillation detectors; Sensitivity analysis; Wavelength
    INDEX KEYWORDS: Codes (standards); Monte Carlo methods; Sensitivity analysis; Wavelength, Light collection process; Light transport codes; Wavelength dependent parameters, Scintillation counters

    Ghal-Eh, N., Koohi-Fayegh, R., Hamidi, S. Low-energy neutron flux measurement using a resonance absorption filter surrounding a lithium glass scintillator (2007) 76 (6), pp. 917-920.

    DOI: 10.1016/j.radphyschem.2007.01.003

    The resonance absorption filter technique has been used to determine the thermal/epithermal neutron flux. The main idea in this technique is to use an element with a high and essentially singular resonance in the neutron absorption cross section as a filter surrounding a miniature-type lithium glass scintillator. The count with and without the filter surrounding the detector gives the number of resonance-energy neutrons. Some preliminary results and a comparison with the MCNP code are shown. © 2007 Elsevier Ltd. All rights reserved.

    AUTHOR KEYWORDS: Filter; Glass scintillators; MCNP code; Resonance absorption
    INDEX KEYWORDS: Electric filters; Glass; Lithium; Neutron absorption; Phosphors; Resonance, Lithium glass scintillator; Resonance absorption filter; Resonance-energy neutrons, Neutron flux, glass; lithium, absorption; article; filter; low energy radiation; Monte Carlo method; neutron radiation; radiation physics; resonance absorption filter; scintillation

    Rahimi, M.F., Ghal-Eh, N. Monte Carlo simulation of electron transport in metallic and biological materials (2006) 80 (7), pp. 727-736.

    A simple Monte Carlo procedure is described for simulating the multiple scattering and absorption of electrons with a definite incident energy in the range of keV up to 20 MeV, moving perpendicular or at a definite angle through one slab, or two adjacent slabs of uniformly-distributed material of given atomic number, density and thickness. The simulation is based on a Screened Rutherford cross section and Bethe continuous energy-loss equation. Programs were written in FORTRAN to determine: scattering, backscattering, transmission and absorption coefficients, providing the user with a graphical output of the electron trajectories. The results of several simulations are presented by using various numbers of electrons. The program is used to analyze the relation between the energy and the range of electron in the slab, the scattering, backscattering, absorption, transmission coefficients and the angular distribution. The technique has been applied to the transport properties of the electron through body tissue, bone and water slab by dividing media into several parts of different materials. Comparisons show that the results are in good agreement with the MCNP code within the range of energy considered and with the experimental data of Linear Electron Accelerator of Imam-Reza Hospital in Mashhad, Iran. © 2006 IACS.

    AUTHOR KEYWORDS: Biological materials; Electron linear accelerator; Electron transport; MCNP code; Monte Carlo simulation

    Ghal-Eh, N., Koohi-Fayegh, R. Light collection behaviour of scintillators with different surface coverings (2006) 41 (3), pp. 289-294.

    DOI: 10.1016/j.radmeas.2005.06.039

    The effect of different surface coverings of scintillation counters on the light collection efficiency and the detection resolution is investigated using an extended version of PHOTRACK, a Monte Carlo light transport code, which has been verified by reproducing other workers' experimental and theoretical results. The underlying wavelength dependencies in light collection process are also presented. © 2005 Elsevier Ltd. All rights reserved.

    AUTHOR KEYWORDS: Model; Monte Carlo; Painting methods; Scintillation detectors; Wavelength
    INDEX KEYWORDS: Monte Carlo methods; Scintillation counters, Light collection; Model; Painting methods, Phosphors