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- MakaleYalnız künye2026Optimizing compton suppression systems: A parametric monte carlo study of NaI scintillator geometry
Kaya, Ali; Çelik, Necati; Kaya, Selim
Compton suppression systems are widely used to enhance gamma-ray spectral quality in applications such as nuclear safeguards and environmental radioactivity measurements. Although optimization of high-purity germanium (HPGe) detectors has been extensively reported, the geometric optimization of secondary sodium iodide [NaI(Tl)] scintillation detectors remains less studied. This work investigates the influence of annular and plug NaI(Tl) detector geometry—length, thickness, and radius—on Compton suppression performance using Monte Carlo simulations. Performance is evaluated in terms of the peak Compton suppression factor (CSFpeak) and total Compton suppression factor (CSFtotal). The results show that CSFpeak and CSFtotal increase with plug length (2–10.2 cm) and annular thickness (1–5.85 cm), with saturation observed beyond approximately 8–10 cm and 4–5 cm, respectively, due to reduced incremental photon absorption. The plug detector radius (3.72–5.1 cm) exhibits a nonlinear effect, with optimal performance achieved at 4.55–4.83 cm, beyond which gains are marginal (<5%). Suboptimal geometries (plug length <6 cm, annular thickness <3 cm, plug radius <4.28 cm) result in 20–60% lower suppression performance, increasing Compton continuum contributions in 662 keV spectra. The optimal configuration—plug length of 8–10 cm, plug radius of 4.55–4.83 cm, and annular thickness of 4–5 cm—achieves more than 90% of maximum CSFpeak and CSFtotal while maintaining a balance between performance and detector volume. These results provide quantitative design guidelines for optimizing NaI(Tl)-based Compton suppression systems for improved gamma-ray spectrometry performance.
- MakaleAçık Erişim2026Monte Carlo calculation of geometry-dependent true coincidence summing correction factors for the gamma-rays of 214Bi in HPGe detectors
Çelik, Necati
True coincidence summing (TCS) effects in gamma-ray spectrometry introduce significant systematic uncertainties in activity determinations, particularly for radionuclides with complex decay schemes such as 214Bi. This study presents a comprehensive Monte Carlo investigation of TCS correction factors (CFs) for seven major gamma-ray lines of 214Bi. The primary contribution of this study is the systematic decoupling of detector geometry effects: nine distinct HPGe detector configurations were simulated with varying crystal dimensions, dead layers, and hole geometries, followed by an isolated analysis of crystal radius versus crystal length contributions for both point and extended source geometries. The decay scheme of 214Bi was meticulously modeled using Nucleide 2000 data, incorporating all beta branches, gamma transitions, internal conversion coefficients, and cascade probabilities to ensure high-fidelity representation of the decay scheme. Results demonstrate that crystal radius exerts a substantially stronger influence on TCS CFs than crystal length, with point source values at 609.3 keV increasing by 18.2% across the radius range of 2.1–4.5 cm, compared to only 3.7% variation across the length range of 3–11 cm. Extended source geometries reduce TCS CFs by 5%–11% compared to point sources across all configurations, highlighting the mitigating effect of distributed sources. Energy-dependent behavior is also evident: the 609.3 keV line exhibits strong summing-in (CF > 1.3 for large detectors), while the 1377.7 keV line shows dominant summing-out (CF < 0.86). These findings provide gamma-ray spectrometrists with insight into the relative importance of detector dimensions for TCS effects, suggesting that crystal radius is the primary geometric parameter influencing coincidence summing corrections. The observed trends illustrate how TCS corrections vary with detector dimensions, offering spectrometrists a basis for understanding the relative sensitivity of these corrections to different geometric parameters.
- MakaleAçık Erişim2026A combined Monte Carlo, analytical, and experimental study of true coincidence summing correction factors for 152Eu
Çelik, Necati; Ali, Ahmed H.; Apaydin, Gokhan; Çevik, Ugur; Açikel, Selami
The radionuclide 152Eu presents a significant challenge in gamma-ray spectrometry due to its complex decay scheme and significant true coincidence summing (TCS) effects, especially in close-measurement geometries. This study presents a comprehensive investigation into TCS correction factors for the principal gamma-ray lines of 152Eu using tripartite methodology: a custom Monte Carlo (MC) simulation based on the EGS4 system, an established analytical method, and direct experimental measurements. The MC simulation explicitly models the complete decay process, including branching ratios, gamma emissions, internal conversion, and subsequent X-ray emissions for both decay branches (beta-minus to 152Gd and EC to 152Sm). Experimentally, correction factors were derived using a well-characterized point source measured at multiple distances with a coaxial HPGe detector. The analytical, method based on probabilistic analysis of the decay scheme, served as an examination. Results demonstrate that the analytical method underestimated the TCS correction factors, particularly for low-energy lines such as 121.78 keV, where it predicted a mere 0.78 % correction compared to 25.5 and 23.5 % from MC and experiment, respectively. This discrepancy is attributed to the analytical method's neglect of gamma-X ray coincidences and the internal conversion effects. In contrast, the MC simulation showed remarkable agreement with experimental results across all energies, validating its capability to accurately model the full complexity of TCS effects. The study concludes that while analytical methods offer rapid estimates, MC simulations, especially when experimentally validated, are essential for achieving metrological accuracy in the gamma-ray spectrometric analysis of complex radionuclides like 152Eu.
- MakaleAçık Erişim2022Investigation of natural radionuclide variations and the possible uranium migration by testing with gamma-ray spectrometer: An example from Tuğlu Tepe and Deliler Sites in Şefaatli/Yozgat, Central Anatolia Region, Turkey
Altundaş, Suna
The in-situ gamma-ray spectrometry measurements are performed to define and map natural radionuclide variations and the possible uranium migration on the sandstone in the Central Anatolia Region and Deliler sites in Yozgat, Turkey. The concentrations of radionuclide (eU, eTh, K%) and dose rate values were measured totally on 384 points in both areas with a duration of 5 min at each measurement point. The radionuclide ratios (eTh/K, eU/K, and eU/eTh), geochemical indicators (Ume, F parameter and eU-(eTh/3,5) rate) of uranium remobilization in the rocks, and the hazard parameters were calculated and evaluated by using measured data. The separation of uranium-rich or poor areas was made easily and associated with lithological formations by evaluating all the maps produced together. While the highest concentrations of radionuclide, and dose rate values were recorded in the sandstone units under the cover layer that are Eocene neritic limestones, the lowest concentration values and dose rate were measured on siltstone and claystone in the northern part of the Tuğlu Tepe area. At the Deliler study area, the lower anomaly zones are coincide with the soils used for the cultivation of chickpeas consists of loosely cemented sandy clay siltstone, claystone, gravel, sand, silt, and clay whereas the highest concentrations observed in the outcropped sandstone and limestones. It can be seen that the study areas have variable radioactivity levels as a result of both the weathering from the surrounding granitic rocks and the transport and accumulation of sediments through different factors. On sandstones serving as reservoir rock for uranium mineralization in both Tuğlu Tepe and Deliler sites, there is a uranium migration from the granitic rocks towards these masses and sandstones have been enriched by uranium. As a result of the evaluations, it has been seen that the areas showing uranium enrichment originated from migration can be determined very easily by radioactivity measurements, which is a fast, economical and effective method.