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.
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A comparative study of the gamma transmission technique and Raman spectroscopic method for quantifying solution concentrations
Nguyen Thanh Dat, Tran Trung Nguyen, Tran Vu Thien An, Vo Diep Trung Tin, Nguyen Huynh Duy Khang, Huynh Dinh Chuong, Tran Thien Thanh, Hoang Thi Kieu Trang, Hoang Duc Tam
Measurement 122961
Abstract:
This paper presents a comparative study of two analytical techniques – gamma transmission (GT), using photon energies of 59.54 keV (241Am) and 661.7 keV (137Cs), and Raman spectroscopy (RS) – for quantifying the concentrations of aqueous sodium chloride and aqueous glucose solutions. To assess the accuracy and reliability of concentration determination using GT and RS, two evaluation metrics were adopted: relative uncertainty (RU) and relative deviation (RD) between measured and reference concentrations. For sodium chloride, measurements based on the 661.7 keV peak exhibited inconsistent behavior, whereas the 59.54 keV peak demonstrated robust performance, with RU and RD values below 6.8% and 7.0%, respectively, and a limit of detection (LOD) of 0.62 wt%. In contrast, Raman spectroscopy yielded acceptable RD values (<6.0%) only at concentrations above 12.5 wt%. However, the corresponding RU reached 13.0%, indicating that this approach is not well suited for accurate quantification of sodium chloride solutions. For glucose, consistent results were obtained exclusively using the 59.54 keV peak, enabling reliable measurements at concentrations ≥10 wt%, with RU and RD values below 10.4% and 4.0%, respectively, and an LOD of 3.0 wt%. Raman spectroscopy supported stable quantification of glucose at concentrations ≥10 wt%, achieving RU and RD values below 7.3% and 5.2%, respectively, with an LOD of 1.4 wt%. Overall, gamma transmission using low-energy photons demonstrated reliable quantitative performance for both the investigated sodium chloride and glucose solutions, whereas Raman spectroscopy exhibited superior precision for the investigated glucose solution.
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A comparative study of machine learning and conventional methods for determining the dead layer thickness of an HPGe detector
N.D. Thong, N.H.K. Vi, L.N.D. Uyen, N.V. Thiem, T.T. Thanh, V.T. Minh, P.L. Ho, C.T. Tai, C.V. Tao
Radiation Physics and Chemistry 249(2026)114162
Abstract:
The dead layer of p-type HPGe detectors grows progressively due to lithium diffusion, degrading detection efficiency at low gamma-ray energies. This study compares four regression approaches for dead layer estimation— conventional G4-scan interpolation, single-source Linear Regression (LR), single-source Random Forest (RF), multi-source LR and multi-source RF combining 241Am and 109Cd — applied to an ORTEC GEM50P4-83 detector at two epochs separated by eight years. A single Geant4 simulation campaign (N = 107 events/run, 1301 points) trained all models, with GUM-compliant uncertainties throughout. All four ML predictions agree with the G4-scan reference (1.323 ± 0.019 mm) within 0.006 mm for the 2018 dataset. When Beer–Lambert linearity is confirmed (R2 > 0.998) and features are restricted to 𝑙𝑛(𝜖), Linear Regression achieves a crossvalidated MAE of 0.009 mm, outperforming all tree-based benchmarks (MAE = 0.010 mm), consistent with the Gauss–Markov theorem. A quantitative threshold analysis shows that multi-source LR reduces total uncertainty by 27% when 𝛿𝜖Cd ∕𝜖Cd < 2.04% — a condition satisfied by the present measurements. Dead layer growth rates of 0.208 mm/year (2015–2018) and 0.009 mm/year (2018–2026) are consistent with nonlinear lithium diffusion deceleration.
More detail: https://doi.org/10.1016/j.radphyschem.2026.114162
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.
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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.
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210Po in Paddy Soils and Rice Grains in Chau Doc, An Giang, Vietnam: Activity Concentration, Soil-to-Rice Transfer, and Health Hazard
Van Thang Nguyen, Nguyen Phong Thu Huynh, Cong Hao Le
Science & Technology Development Journal, 24(4):1-10
Abstract:
Introduction: Soil-to-rice transfer factors (TF) are widely used to predict radionuclides' activity concentrations in rice plants. Since rice (Oryza sativa L.) is one of the most popular crops in Vietnam, the radiological risks due to 210Po contaminating rice grains and the TF must be concerned.
Methods: Alpha spectrometry measured the activity concentration of 210Po in rice and soil samples collected in Chau Doc, An Giang province. TF for the uptake of 210Po from soil to rice plant has been calculated the ratio of the dry weight concentration in the plants to the dry weight concentration in the specified soil layer. Assessment of radiological risks due to ingestion of rice grains was based on estimation of the effective dose.
Results: The activity concentrations of 210Po were in the ranges of 63.77 – 117.75 Bq kgdry weight-1 and 7.38 – 14.16 Bq kgdry weight-1 in soils and rice grains, respectively. Based on the radiation dose assessment, the accumulation of 210Po in rice grains was not considered for public health. The average TF values of 210Po were 0.12, 0.11, and 0.37 for grains, straws, and roots, respectively. Our TF values for rice were higher than the corresponding values found by other studies and the IAEA TRS-472 report.
Conclusion: The analytical method for 210Po determination using alpha spectrometry can be applied for further studies in the field of environmental radioactivity. The measured TF values can be used to predict the radioactivity level of 210Po in rice plants cultivated in other fields in the Mekong Delta region.
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