A novel method for calculating number buildup factor in gamma-ray transmission measurements using narrow beam geometry
Huynh Dinh CHUONG , Le Thi Ngoc TRANG, Nguyen Thi Truc LINH, Vo Hoang NGUYEN and Tran Thien THANH
Nuclear Technology and Radiation Protection 2024 Volume 39, Issue 3, Pages: 185-198
Abstract:
In this article, we present a novel method to calculate the number buildup factor for arbitrary materials in gamma-ray transmission measurements using a narrow beam geometry. The MCNP6 code was used to simulate photon transport within a collimated transmission configuration, which included a NaI(Tl) scintillation detector paired with a 137Cs or 60Co radioactive source. From these simulations, the number buildup factor values were computed forvarious materials at gamma-ray energies of 661.7 keV, 1173.2 keV, and 1332.5 keV, with sample thicknesses ranging from 0.1-7.0 cm. At each specific gamma-ray energy and material, the number buildup factor values exhibited a strong linear relationship with the sample thickness. Furthermore, the slope of these linear relationships can be expressed as a product of mass density and a cubic polynomial function of the atomic number. Based on these findings, we developed a fitting formula to calculate the number buildup factor using the input variables of sample thickness, mass density, and atomic number. The accuracy of the fitting formula was evaluated by comparing its results with number buildup factor values computed by MCNP6 code. The comparison showed relative deviations below 1% for all the investigated cases, demonstrating the high accuracy and reliability of the fitting formula.
More detail >>
Huynh Dinh Chuong, Le Thi Ngoc Trang, Hoang Duc Tam, Vo Hoang Nguyen, Tran Thien Thanh
NDT & E International Available online 4 May 2020, 102281
A Geant4 procedure for precise simulation of PGNAA prompt gamma‑ray spectrum in a wide energy range up to 8 MeV
Thanh Tai Chau, Ngoc Son Pham, Thien Thanh Tran, Cong Phat Vo, Van Tao Chau
Journal of Radioanalytical and Nuclear Chemistry
Abstract:
In reality, after subtracting the beam background from the prompt g-ray spectrum induced by the irradiated sample with the same time measurement, it still exists the remaining g-ray background induced by the nuclei capturing the thermal neutrons scattered by the sample. This makes it difficult to validate the accuracy of the PGNAA detector response between the simulation and the experiment in the wide energy range. In this study, a simple method to construct the remaining g-ray background in the simulation prompt g-ray spectrum of 35Cl(n,g)36Cl reaction is proposed. Then the simulation prompt g-ray spectrum with the remaining g-ray background is compared to the experimental spectrum to validate the simulation PGNAA detector response in the energy range from 0.1 MeV to about 9 MeV.
More detail>>
A dual-energy gamma-ray transmission method using 137Cs and 241Am sources for determining effective atomic number and mass attenuation coefficient of lightweight materials
Le Thi Ngoc Trang, Huynh Dinh Chuong, Vo Hoang Nguyen, Tran Thien Thanh
Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment 1086 (2026) 171390
Abstract
This paper presents a dual-energy gamma-ray transmission method for determining the effective atomic number (Zeff) and mass attenuation coefficient (MAC) of lightweight materials. The experimental setup consists of sealed 137Cs and 241Am sources and a NaI(Tl) detector arranged in a narrow-beam transmission geometry to measure gamma rays transmitted through the sample. A corresponding MCNP6 model was developed to closely reproduce the experimental configuration. Using this model, pulse-height spectra were simulated for a set of materials with atomic numbers from 1 to 20, thicknesses between 1 and 4 cm, and densities from 0.6 to 3.0 g cm−3. The Zeff of a material was determined by exploiting the ratio of logarithmic attenuations measured at 59.5 keV and 661.7 keV, using a calibration curve established from the simulation data, without requiring any prior knowledge of the sample thickness, density, and elemental composition. In addition, an analytical model was constructed to describe the dependence of the MAC on both atomic number and photon energy, for atomic numbers from 1 to 20 and photon energies in the range 50 keV to 20 MeV. This model enables the MAC of a material to be estimated at various photon energies directly from its previously determined Zeff. The proposed method was validated for several lightweight materials, including graphite, aluminum, polymers, pine wood, brick, glass, concrete, and stone, using both simulated and experimental data. The results show that the Zeff values obtained by this method are well correlated with the elemental composition of the materials. For materials that either do not contain hydrogen or contain it only in low concentrations, the MAC values estimated by the proposed method exhibit generally good agreement with reference XCOM data, whereas for materials with a high hydrogen content the discrepancies of up to approximately 16.8% are observed.
More detail >>
A benchmark for Monte Carlo simulations in gamma-ray spectrometry Part II: True coincidence summing correction factors
M.-C. Lépy, C. Thiam, M. Anagnostakis, C. Cosar, A. de Blas, H. Dikmen, M.A. Duch, R. Galea, M.L. Ganea, S. Hurtado, K. Karfopoulos, A. Luca, G. Lutter, I. Mitsios, H. Persson, C. Potiriadis, S. Röttger, N. Salpadimos, M.I. Savva, O. Sima, T.T. Thanh, R.W. Townson, A. Vargas, T. Vasilopoulou, L. Verheyen, T. Vidmar
Applied Radiation and Isotopes, 2023
Abstract:
The goal of this study is to provide a benchmark for the use of Monte Carlo simulation when applied to coincidence summing corrections. The examples are based on simple geometries: two types of germanium detectors and four kinds of sources, to mimic eight typical measurement conditions. The coincidence corrective factors are computed for four radionuclides. The exercise input files and calculation results with practical recommendations are made available for new users on a dedicated webpage.
More details >>
A benchmark for Monte Carlo simulation in gamma-ray spectrometry
M.C. Lépy, C. Thiam, M. Anagnostakis, R. Galea, D. Gurau, S. Hurtado, K. Karfopoulos, J. Liang, H. Liu, A. Luca, I. Mitsios, C. Potiriadis, M.I. Savva, T.T. Thanh, V. Thomas, R.W. Townson, T. Vasilopoulou, M. Zhang
Abstract:
Monte Carlo (MC) simulation is widely used in gamma-ray spectrometry, however, its implementation is not always easy and can provide erroneous results. The present action provides a benchmark for several MC software for selected cases. The examples are based on simple geometries, two types of germanium detectors and four kinds of sources, to mimic eight typical measurement conditions. The action outputs (input files and efficiency calculation results, including practical recommendations for new users) are made available on a dedicated webpage.
More detail >>
