Gamma-ray Energy Research Articles

Investigation of Some Properties of Chemical Fertilizers Using Gamma-ray Spectrometry and Energy Dispersive X-ray Fluorescence Spectrometry

Investigation of Some Properties of Chemical Fertilizers Using Gamma-ray Spectrometry and Energy Dispersive X-ray Fluorescence Spectrometry

Gamma-rays attenuation by mineralized siltstone and dolostone rocks: Monte Carlo simulation, theoretical and experimental evaluations

Radiation shielding performance against gamma rays for four mineralized natural rock samples collected from Um Bogma area, Southwestern Sinai, Egypt was determined by Monte-Carlo simulation, theoretical calculations and confirmed by experimental evaluations. The Monte Carlo simulation was utilized to investigate the shielding capacity of the investigated rock samples in the energy range between 0.015 and 15 MeV. According to the Monte Carlo simulation the best shielding properties were achieved for sample siltstone S22 which contains (Fe–Mn) mineralization and density of 3.85 (g/cm3), where the simulated linear attenuation coefficient decreased from 71.30 cm−1 to 0.09 cm−1, increasing the incident gamma photon energy between 0.015 and 15 MeV. On the other hand, the lowest gamma ray shielding capacity achieved for sample siltstone S24 which rich in iron sulfate, with linear attenuation coefficient decreased from 37.50 cm−1 to 0.05 cm−1, increasing the incident gamma ray energy between 0.015 and 15 MeV, respectively. The gamma ray shielding properties for sample siltstone S22 were examined experimentally to confirm the simulated results. Both of experimental and simulated results are close together, with a difference of ±0.5%. Moreover, the siltstone S22 sample shows a thin half-value layer, high effective and equivalent atomic numbers as well as low EBF and EABF values.

Proton-Induced Activation of New Scintillator Materials: SrI, GAGG, CLLB, CLLBC, TLYC, CLYC-7

In recent years, a number of new scintillator materials with improved energy resolution for gamma-ray detectors have become commercially available for use in terrestrial-based homeland security applications, and some are being incorporated into instrumentation for space. Unlike terrestrial applications, the harsh environment of space—in particular, energetic trapped particles, cosmic rays, and neutrons—often activates these materials, and any improvement in sensitivity as a result of improved energy resolution could be offset by the additional background due to activation. The purpose of this work was to measure potential backgrounds due to trapped and cosmic-ray proton-induced activation in the new materials: SrI₂:Eu (SrI), ⁷Li-enriched Cs₂LiYCl₆:Ce (CLYC-7), Cs₂LiLaBr₆:Ce (CLLB), Cs₂LiLa(Br,Cl)₆:Ce (CLLBC), Tl₂LiYCl₆:Ce (TLYC), and Gd₃(Al,Ga)₅O₁₂:Ce (GAGG). Using a large-diameter 64-MeV proton beam, detectors were irradiated with a total dose of 100 rad (Si), roughly equivalent to the annual dose in a typical low earth orbit. Measurements were made with a single 100% relative efficiency high-purity germanium (HPGe) (0.05–3 MeV) and the irradiated detector. Two multichannel analyzers (MCAs) operating in the event mode were used to collect the data. Time-tagged events were processed into various spectral integration times for analysis, and characteristic gamma-ray energies and decay times were used to identify activation products. Most of the identified activation products were the result of (p, xn) reactions, with a few exceptions. This work identifies the primary radioisotopes generated by energetic proton activation in six different scintillator materials.

Measurement of the Gamma-Ray Energy Spectrum beyond 100 TeV from the HESS J1843–033 Region

HESS J1843–033 is a very high energy gamma-ray source whose origin remains unidentified. This work presents, for the first time, the energy spectrum of gamma rays beyond 100 TeV from the HESS J1843–033 region using the data recorded by the Tibet air shower array and its underground muon detector array. A gamma-ray source with an extension of 0.°34 ± 0.°12 is successfully detected above 25 TeV at (α, δ) = (281.°09 ± 0.°10, −3.°76 ± 0.°09) near HESS J1843–033 with a statistical significance of 6.2σ, and the source is named TASG J1844–038. The position of TASG J1844–038 is consistent with those of HESS J1843–033, eHWC J1842–035, and LHAASO J1843–0338. The measured gamma-ray energy spectrum in 25 TeV < E < 130 TeV is described with (E/40 TeV)−3.26±0.30 TeV−1 cm−2 s−1, and the spectral fit to the combined spectra of HESS J1843–033, LHAASO J1843–0338, and TASG J1844–038 implies the existence of a cutoff at 49.5 ± 9.0 TeV. Associations of TASG J1844–038 with SNR G28.6–0.1 and PSR J1844–0346 are also discussed in detail for the first time.

Optimizing the gamma-ray shielding behaviors for polypropylene using lead oxide: a detailed examination

In the current study, the PbO compound was used in order to optimize the gamma-ray shielding properties of the polypropylene polymers. A series of polypropylene doped PbO were performed using various PbO concentrations varied between 0 and 50 wt%. The experimental measurement for the density of the fabricated sample showed that the samples’ density varied between 0.902 ± 0.004 and 1.645 ± 0.007 g/cm3, raising the PbO doping concentration between 0 wt% and 50 wt%. Furthermore, the scanning electron microscope was utilized to illustrate the distribution and morphology of the fabricated polypropylene doped PbO concentrations. The gamma-ray shielding capacity of the fabricated polypropylene doped PbO was examined and evaluated experimentally using a sodium iodide scintillation detector and different point sources in the gamma-ray energy interval between 0.059 and 1.408 MeV. The experimental results were affirmed via the Geant4 code, which depended on the Monte Carlo simulation. The difference recorded between the experimental and Geant4 calculations for the fabricated samples shielding properties was lies in between ±4%. The recorded linear attenuation coefficient at gamma-ray energy of 0.244 MeV varied between 0.1148 and 0.5837 cm−1, raising the PbO doping concentration between 0 wt% and 50 wt%. Moreover, the half-value thickness decreased with increasing the PbO doping ratio.

Synthesis of transparent binary germanate glasses and determination of their shielding performance against the gamma radiation

ABSTRACT In this study, we synthesized binary germanate glasses with compositions of GeO2 – Bi2O3, GeO2 – PbF2, and GeO2 – V2O5. The traditional melt-quenching method was used for glass synthesis. The radiation shielding properties of the synthesized samples were calculated theoretically and measured experimentally as well. A narrow-beam transmission geometry, which uses a NaI(Tl) detector, was employed to measure linear attenuation coefficient, mass attenuation coefficient, half-value layer, and effective atomic number values of the glasses at gamma-ray energies of 662, 1173, and 1332 keV and, 137Cs, and 60Co radioactive point sources were used to produce gamma-ray photons of these energies. Additionally, all the above parameters were also calculated theoretically using the WinXCOM software in the 0.015-15 MeV energy range to confirm the accuracy of the measurements. A good agreement between theoretical and experimental findings was observed. It was also found that the increase in the concentrations of Bi2O3, PbF2, and V2O5 network modifiers improved the radiation shielding capacity of synthesized germanate glasses. The results revealed that the GeBi30 glass has superior shielding properties among the synthesized germanate glasses.

Valorization of nano-PbO as an additive to modify the properties and radiation shielding of alkali-activated slag mortar

In this work, for the first time, the possibility of employing nano-lead oxide (nPbO) in alkali-activated slag (AAS) mortar as a modifier agent for its properties was studied. Different ratios of nPbO (0 wt%, 1 wt%, 3 wt% and 5 wt%) were added to the plain AAS mortar. The effects of these ratios on flowability, mechanical strength, water absorption, total porosity, aging resistance, gamma-ray radiation shielding, crystalline phases, thermal analysis and microstructure were investigated. The gamma-ray attenuation coefficients were determined as a function of the additive percentages of lead oxide for gamma-ray energies of 1332, 1173 and 662 keV using Co-60 and Cs-137 sources. Different techniques were used to analyze the results. The results showed higher flowability of the mixtures with introducing nPbO. The flowability increased with increasing nPbO ratio. The mechanical strength and aging resistance increased with introducing 1% and 3% nPbO, then slightly decreased with including 5% nPbO. Water absorption and total porosity decreased with introducing 1% and 3% nPbO, then slightly increased with including 5% nPbO. Introducing nPbO in the AAS system improved the radiation properties, of which the attenuation coefficients increased with including nPbO. In a word, using suitable ratios of nPbO improved the fresh, hardened, durability and radiation properties of AAS mortar and can provide it for wider applications.

Effect of iron and ferrosilicon materials to enhance the radiation shielding ability of bentonite clay

This study focuses on enhancing the attenuation properties of bentonite clay using powdered iron and ferrosilicon. Scanning electron microscopy and X-ray diffraction analysis were used to characterize the prepared samples. The linear attenuation coefficient was calculated experimentally for the prepared samples using a NaI scintillation detector and four radioactive point sources (Am-241, Cs-137, Co-60, and Eu-152). These results were in good agreement with the compared with the XCOM results. Other radiation shielding parameters, such as the half-value layer, mean free path, and radiation protection efficiency, were determined. Furthermore, at a photon energy of 0.06 MeV, the half-value layers were 0.276 and 0.628 cm for bentonite–iron and bentonite–ferrosilicon, respectively. The results indicate that the radiation shielding efficiency of bentonite–iron composites is better than that of bentonite–ferrosilicon composites at low and intermediate gamma-ray energies.

Reflection symmetry in the folded light curve of the Crab pulsar from NICER

ABSTRACT The rotation powered pulsars Crab, Vela, and Geminga have double peaked folded light curves (FLC) at gamma-ray energies that have an approximate reflection symmetry. Here, this aspect is studied at soft X-ray energy by analysing a high-resolution FLC of the Crab pulsar obtained at 1–10 keV, using the Neutron star Interior Composition Explorer observatory. The rising edge of the first peak of the FLC and the reflected version of the falling edge of the second peak are compared in several ways, and phase ranges are identified where the two curves are statistically similar. The best matching occurs when the two peaks are aligned, but only in a small phase range of ≈0.0244 just below their peaks; their mean difference is −0.78 ± 1.8 photons s−1 with a reduced χ2 of 0.93. If the first curve is convolved by a Laplace function, the corresponding numbers are phase range of ≈0.0274, mean difference of −1.23 ± 1.30 and χ2 of 0.76. These phase ranges are much smaller than those over which the reflection symmetry has been perceived. Therefore, the only way the two edges can have a mirror relation over a substantial phase range is if one invokes a broad and faint emission component of amplitude ≈100 photons s−1 and width ≈0.1 in phase, centred at phase ≈0.1 beyond the second peak.

Gamma-ray energy spectrum unfolding of plastic scintillators using artificial neural network

In this study, the unfolding of the plastic scintillator spectrum was undertaken using the artificial neural networks tools of MATLAB. To this purpose, the response matrix of the plastic scintillator was generated for 145 energy groups and in 512 pulse-height channels using the MCNPX2.6 code. The results confirmed that the relative error in the gamma-ray energy unfolding with artificial neural networks is less than 3.8%.

Impact of mask thickness on the imaging performance of the coded-aperture gamma camera

Coded-aperture gamma imaging techniques have been applied widely in several radiation monitoring fields. However, in terms of the design of the coded-aperture mask, the category and rank of the mask are generally considered, but there is a lack of detailed research on selection of the appropriate mask thickness. Concretely, the imaging performance is affected by the mask thickness in terms of two factors: the full-field image quality of the overall field of view (FOV), which represents the background noise tolerance of the radioactive source; and the image brightness consistency, which represents consistency of the imaging efficiency. We have studied and analyzed these two imaging performance indexes in relation to the mask thickness based on the model of our custom-made gamma camera. Specifically, the full-field image quality initially improves and later deteriorates with the mask thickness increases from 0.1 mm to 30 mm because of the competition and the tradeoff between the transmission background and the oblique irradiation effect; the image brightness consistency initially descends, then improves, and finally decreases again under the same conditions as a result of the tradeoff between the improvement of the transmission background ratio and deterioration of the oblique irradiation coefficient ratio. Furthermore, these two indexes change trends are both related to gamma-ray energy. Finally, based on a comprehensive analysis of the imaging performance, the optimal thicknesses for the customized W-Cu alloy modified uniformly redundant array masks for 59.5 keV, 662 keV, 1250 keV gamma-ray imaging are 0.5 mm, 10 mm, and 16 mm, respectively.

Simulation study of gamma-ray spectroscopy on MYRRHA spent fuel located in lead–bismuth eutectic

A concept model of a measurement station for gamma-ray spectroscopy for safeguards verification of spent fuel from the future MYRRHA facility has been developed using MCNP6.2. The measurement station consists of a collimator and a lanthanum bromide detector which are placed adjacent to a cylindrical container with the fuel assembly submerged in lead–bismuth eutectic for cooling. The total count rate as well as the peak-area uncertainties for several gamma-ray peaks have been studied for a number of measurement geometries to determine the optimal collimator dimensions and assess how the performance depends on the lead–bismuth container geometry. Finally, the contribution from each fuel pin in the assembly to the detected signal has been determined as a function of gamma-ray energy to determine if the inner parts of the fuel assembly can be assayed with gamma-ray measurements. The results show that the dimensions of the lead–bismuth container will have a considerable effect on both the total count rate and the peak-area uncertainties, but that gamma-ray spectroscopy could be used for verification of spent fuel from MYRRHA.

Holmium(III) oxide and its significant effects on the radiation shielding performance of P2O5 + B2O3 + ZnSO4 optical glasses

Glasses are versatile materials whose uses span across a wide technological spectrum. The application of glasses in radiation protection directly depends on their chemical description. In the present study, we investigate the influence of Ho2O3 on the gamma-ray shielding performance of P2O5-B2O3-ZnSO4 glasses for selected gamma energies between 0.284 and 2.506 MeV. Three glass samples with the chemical composition: (40-x)P2O5 + 30B2O3 + 30ZnSO4 + xHo2O3, where x = 0.0, 0.5, and 1.0 mol% represents PBZH1–3 accordingly. The computation of the photon shielding parameters started with photon transmission simulation using GEANT4 simulation code and validated by XCOM. The mass attenuation coefficient MAC obtained via both methods were very close with deviations between 0.72% and 1.79%. The MAC of the glasses varied from 0.039 to 0.109 cm2 g−1 for PBZH1, 0.039 to 0.111 cm2 g−1 for PBZH2, and 0.039 to 0.113 cm2 g−1 for PBZH3. The mass attenuation coefficient exhibits strong dependence on the energy of gamma-ray and the changes in the chemical composition of the glasses. The half value layer values of the PBZH1, and PBZH3 samples ranged from 2.21 cm to 6.22 cm and 2.00 cm to 5.87 cm, respectively. The values of the effective atomic number for PbZH3 ranged from 10.80 to 10.30 within the selected incident photon energy. On the other hand, the effective atomic number of PbZH1 samples ranged from 10.29 to 10.19. Generally, PbZH samples with higher Ho2O3 content gave a composition with higher density, linear attenuation coefficient, and effective atomic number; but lower half value layer and mean free path within photons with energies of 0.284–2.506 MeV. The PbZH glass samples had better shielding efficiencies than commercial RS-253-G18 glass and ordinary concrete thus making them applicable for gamma-ray absorption purposes.

Interaction chamber for laser Compton slant-scattering in SLEGS beamline at Shanghai Light Source

Energy-variable gamma-rays are produced in the laser Compton slant-scattering in the Shanghai laser electron gamma source (SLEGS) beamline of the Shanghai Light Source. An interaction chamber composed of the rotating laser optical system, shielding finger, and reference-target insertion device was developed to ensure slant scattering in the angular range of 20–160°, producing gamma-rays in the energy range of 0.66–21.1 MeV with a flux of 4.8 × 105–1.5 × 107 photons/s. SLEGS is the first slant-scattering beamline which systematically produces energy-variable gamma-ray beams and continuously tune the gamma-ray energy in the laser Compton slant-scattering. We report on designed performance of the slant-scattering and results of a test run.

Latest growth of large diameter Tl-based elpasolite scintillation crystals

Elpasolite scintillators play an important role in radiation detection and imaging. Novel Tl-based elpasolite scintillators such as Ce-doped Tl2LiYCl6 (TLYC) have been developed as excellent Tl-based dual mode gamma and neutron detectors. This paper presents a successful high yield growth and γ-ray characterization of large diameter (1-inch to 1.5-inch diameter) single, crack-free, and transparent TLYC crystals at Fisk University. Energy resolution of 4.2% (FWHM) at 662 keV and light yield of 26,000 photons/MeV are measured. As-processed and hermetically packaged TLYC samples are characterized for their gamma-ray energy resolutions, light yields, non-proportionality behaviors and decay times. Successful growth of 1-inch diameter (Cs,Tl)2LiLaBr6:Ce crystals are also shown. The best result is obtained when the content of Cs+ is larger than Tl+. Energy resolution of 3.4% (FWHM) at 662 keV is measured for (Cs,Tl)2LiLaBr6:Ce for 75% Cs-to-25% Tl ratio.

Fabrication, characterization, and gamma-ray shielding performance for the lead-based Iraqi white silicate glasses: A closer examination

A novel lead-based silicate glass was manufactured throughout the Iraqi white sand rich with silica. The collected sand was separated into different grain sizes, and then the grain size between 200 and 615 µm was used in glass manufacturing. The clean Iraqi sand was other metal oxides as well as a concentration of 35 wt% from the PbO compounds. The mixture was transferred into an aluminum crucible placed in an electric muffle under a high temperature that reaches 1580 °C. The obtained molten was molded at room temperature and then annealed under an annealing temperature of 509 °C. Moreover, XRD was used to confirm the amorphous phase for the fabricated lead-based Iraqi sand. The fabricated lead-based Iraqi silica glass's density was measured using the MH-300A densimeter as well as dispersive energy X-ray spectrometry was utilized to measure the chemical composition and the IRF-454B2M refractometer was used to measure the refractive index for the fabricated lead-based silica glass. Moreover, the Monte Carlo simulation was applied in order to investigate the radiation shielding properties for the fabricated lead-based Iraqi sand in the gamma-ray energy interval between 0.015 and 15 MeV, including the experimental energies of 0.662, 1.173, and 1.332 MeV emitted Cs-137 and Co-60. At 0.662 MeV, the linear attenuation coefficient of the fabricated glass sample reaches 0.266 cm−1 while it is 0.165 cm−1 at 1.25 MeV. The theoretical Phy-X/PSD program also was utilized to report the buildup factors for the fabricated glasses.

Experimental verification of real-time gamma-ray energy spectrum and dose monitor

The purpose of this study is to develop a portable monitor that can measure the energy spectrum and dose of gamma-rays simultaneously in real time for the benefit of medical staff who must work in clinical radiation environments. For this purpose, we have developed a prototype monitor using a CsI (Tl) scintillator combined with a multi-pixel photon counter (MPPC). For real-time measurement, we employed an improved sequential Bayesian estimation (k-α method) to convert the measured pulse height spectrum into an energy spectrum. Then we confirmed that reconstruction of the energy spectrum and dose estimation could simultaneously be carried out in real time by the k-α method in a radiation field composed of mixed standard gamma-ray sources. In this study, we carried out measurements in a background gamma-ray field to confirm applicability of the prototype monitor to the weakest type of radiation field. In addition, we conducted measurements in front of a nuclear fuel storage room (∼2 μSv/h) in the authors’ laboratory to evaluate practicality of the monitor for measuring fields with a complex energy spectrum. As a result, it was found that the dose could be estimated in about 20 s after start of measurements even in the background field. For the energy spectrum, it was instantly reconstructed within 60 s in front of the fuel storage room. On the other hand, it could successfully be estimated within 10 min in the background gamma-ray field. Currently, the convergence of the energy spectrum is determined visually from time dependent change of the spectrum and dose. As a next step, we will attempt to develop a more quantitative procedure for determining the convergence.

Experimental and FLUKA evaluation on structure and optical properties and γ-radiation shielding capacity of bismuth borophosphate glasses

For 662, 1173, 1275, and 1333 keV gamma-ray energy, photon transmissions, linear attenuation coefficients, half value layer, tenth value layer, and mean free path values of bismuth-borophosphate glasses were measured experimentally. Then, the measured findings were compared to the FLUKA code. The FLUKA code findings agreed well with the experimental results. Furthermore, the findings show that adding Bi2O3 to the glass network improves the shielding properties. The current data reveal that when the Bi2O3 content rises, so does the absorbance. Furthermore, the optical constants of the present gasses, such as optical band gap, phonon energy, and tails of localized states, were examined. Fourier transform infrared (FTIR) spectrometer was used to analyze the Fourier transform infrared (FTIR) spectra of our samples at room temperature in the 4000–400 cm−1 wavenumber range. From a shielding standpoint, bismuth-borophosphate glasses offer excellent gamma-ray shielding properties.

Effect of the new photoatomic data library EPDL2017 to mass attenuation coefficient calculation of materials used in the nuclear medicine facilities using EpiXS software

The accuracy of the photoatomic cross-section data is of great importance in the field of radiation protection, particularly in the characterization of radiation shielding materials. With the release of the latest and probably the most accurate photoatomic data library, EPDL2017, the need to re-evaluate all the existing and already established mass attenuation coefficients (MACs) of all radiation shielding materials arises. The MACs of several polymers, alloy-based, glasses, and building materials used in a nuclear medicine facility were investigated using the EPDL2017 library embedded in EpiXS software and were compared to MACs available in the literature. The relative differences between MACEpiXS and MACXCOM were negligible, ranging from 0.02% to 0.36% for most materials. However, for material like a glass comprising of elements Te and La evaluated near their corresponding K-edge energies, the relative differences in MACs increased up to 1.46%. On the other hand, a comparison with MACs calculated based on EPDL97 (a predecessor of EPDL2017) revealed as much as a 6.61% difference. Also, it would seem that the changes in MACs were more evident in the materials composed of high atomic number elements evaluated at x-ray energies compared to materials composed of low atomic number elements evaluated at gamma-ray energies.

A rapid and direct method for half value layer calculations for nuclear safety studies using MCNPX Monte Carlo code

Half Value Layer calculations theoretically need prior specification of linear attenuation calculations, since the HVL value is derived by dividing ln(2) by the linear attenuation coefficient. The purpose of this study was to establish a direct computational model for determining HVL, a vital parameter in nuclear radiation safety studies and shielding material design. Accordingly, a typical gamma-ray transmission setup has been modeled using MCNPX (version 2.4.0) general-purpose Monte Carlo code. The MCNPX code's INPUT file was designed with two detection locations for primary and secondary gamma-rays, as well as attenuator material between those detectors. Next, Half Value Layer values of some well-known gamma-ray shielding materials such as lead and ordinary concrete have been calculated throughout a broad gamma-ray energy range. The outcomes were then compared to data from the National Institute of Standards and Technology. The Half Value Layer values obtained from MCNPX were reported to be highly compatible with the HVL values obtained from the NIST standard database. Our results indicate that the developed INPUT file may be utilized for direct computations of Half Value Layer values for nuclear safety assessments as well as medical radiation applications. In conclusion, advanced simulation methods such as the Monte Carlo code are very powerful and useful instruments that should be considered for daily radiation safety measures. The modeled MCNPX input file will be provided to the scientific community upon reasonable request.