Ray Attenuation Research Articles

Investigation of gamma ray attenuation features of bismuth oxide nano powder reinforced high-density polyethylene matrix composites

In this work, five samples of high-density polyethylene have been made by varying bismuth oxide (Bi2O3) concentration 0.5, 1.0, 1.5 and 2.0 wt%. Scanning electron microscopic (SEM) has been used to analysis of the samples to point out the changes in the surface morphology. Energy Dispersive X-ray (EDX) has been performed for evaluating chemical composition of the prepared samples. X-ray diffraction (XRD) spectra of the pure Bi2O3, pure high-density polyethylene (HDPE) and HDPE with different amount of Bi2O3 have been investigated. Additionally, the Raman spectroscopy of all synthesized polymer matrix were measured to explore the different molecular groups. Finally, the mass attenuation coefficients μ/ρ for the samples have been measured using narrow beam of gamma-ray at eight energies between from 30.8 to 383.8 keV. The effect of the photon energy and the addition of Bi2O3 on the gamma-ray shielding ability of the prepared sample have been discussed. In conclusion, the prepared samples showed good attenuation properties.

Comparison of estimated soil bulk density using proximal soil sensing and pedotransfer functions

Due to disadvantages of the core sampling method for determining soil bulk density (BD), many soil surveys lack data of BD. To meet extensive demands for BD in hydrology, agriculture, environment, etc., an approach based on a pedotransfer function (PTF) is often established using available data of soil properties such as texture, organic matter content, pH and soil depth. Recently, an approach based on proximal soil sensing (PSS) was also proposed to fulfill this purpose, i.e., subtracting volumetric water content (θ, %) estimated using visible and near infrared spectroscopy (vis-NIRS) from BD of wet soils determined using gamma ray attenuation. With 120 samples collected from 20 profiles and 38 topsoils in a hilly subtropical area in China, this study compared accuracy of the two approaches based on leave-one-out cross-validation (LOOCV) and repeated cross-validations with a wide range of randomly split samples. Texture, organic matter content, pH and depth of the samples were measured, and they were used within multiple linear regression to establish PTFs. Results showed that the approach based on PSS was at least 12% more accurate than the other and its estimated BD were close to those measured using the core sampling method. For instance, in LOOCV, estimated BD based on PSS had root mean square error (RMSE) of 0.082 g cm−3, coefficient of determination (R2) of 0.92 and residual prediction deviation (RPD) of 2.07, while estimated BD based on the best PTF had RMSE of 0.094 g cm−3, R2 of 0.70 and PRD of 1.82. The results also showed that accuracy of the approach based on PSS was determined by accuracy of estimated θ using vis-NIRS. However, it is limited to improve accuracy of estimated BD using the approach based on PSS further by improving accuracy of estimated θ. This study demonstrated that the approach based on PSS is promising for estimating BD in future soil surveys.

Measurement of the gamma ray background in the Davis cavern at the Sanford Underground Research Facility

Deep underground environments are ideal for low background searches due to the attenuation of cosmic rays by passage through the earth. However, they are affected by backgrounds from γ-rays emitted by 40K and the 238U and 232Th decay chains in the surrounding rock. The LUX-ZEPLIN (LZ) experiment will search for dark matter particle interactions with a liquid xenon TPC located within the Davis campus at the Sanford Underground Research Facility, Lead, South Dakota, at the 4850-foot level. In order to characterise the cavern background, in-situ γ-ray measurements were taken with a sodium iodide detector in various locations and with lead shielding. The integral count rates (0–3300 keV) varied from 596 Hz to 1355 Hz for unshielded measurements, corresponding to a total flux from the cavern walls of 1.9 ± 0.4 γ cm−2s−1. The resulting activity in the walls of the cavern can be characterised as 220 ± 60 Bq/kg of 40K, 29 ± 15 Bq/kg of 238U, and 13 ± 3 Bq/kg of 232Th.

The Astrochemical Impact of Cosmic Rays in Protoclusters. II. CI-to-H2 and CO-to-H2 Conversion Factors

We utilize a modified astrochemistry code which includes cosmic ray attenuation in-situ to quantify the impact of different cosmic-ray models on the CO-to-H$_2$ and CI-to-H$_2$ conversion factors, $X_{\rm CO}$ and $X_{\rm CI}$, respectively. We consider the impact of cosmic rays accelerated by accretion shocks, and show that clouds with star formation efficiencies greater than 2\% have $X_{\rm CO} = (2.5 \pm 1)\times10^{20}$ cm$^{-2}$(K km s$^{-1}$)$^{-1}$, consistent with Milky Way observations. We find that changing the cosmic ray ionization rate from external sources from the canonical $\zeta \approx 10^{-17}$ to $\zeta \approx 10^{-16}$ s$^{-1}$, which better represents observations in diffuse gas, reduces $X_{\rm CO}$ by 0.2 dex for clusters with surface densities below 3 g cm$^{-2}$. We show that embedded sources regulate $X_{\rm CO}$ and decrease its variance across a wide range of surface densities and star formation efficiencies. Our models reproduce the trends of a decreased $X_{\rm CO}$ in extreme cosmic ray environments. $X_{\rm CI}$ has been proposed as an alternative to $X_{\rm CO}$ due to its brightness at high redshifts. The inclusion of internal cosmic ray sources leads to 1.2 dex dispersion in $X_{\rm CI}$ ranging from $2\times10^{20} < X_{\rm CI} < 4\times10^{21}$ cm$^{-2}$ (K km s$^{-1}$)$^{-1}$. We show that $X_{\rm CI}$ is highly sensitive to the underlying cosmic ray model.

Impact of Cosmic-Ray Feedback on Accretion and Chemistry in Circumstellar Disks

Abstract We use the gas-grain chemistry code uclchem to explore the impact of cosmic-ray feedback on the chemistry of circumstellar disks. We model the attenuation and energy losses of the cosmic rays as they propagate outward from the star and also consider ionization due to stellar radiation and radionuclides. For accretion rates typical of young stars of M ⊙ yr−1, we show that cosmic rays accelerated by the stellar accretion shock produce an ionization rate at the disk surface ζ ≳ 10−15 s−1, at least an order of magnitude higher than the ionization rate associated with the Galactic cosmic-ray background. The incident cosmic-ray flux enhances the disk ionization at intermediate to high surface densities (Σ &gt; 10 g cm−2), particularly within 10 au of the star. We find that the dominant ions are C+, S+, and Mg+ in the disk surface layers, while the ion dominates at surface densities above 1.0 g cm−2. We predict the radii and column densities at which the magnetorotational instability (MRI) is active in T Tauri disks and show that ionization by cosmic-ray feedback extends the MRI-active region toward the disk midplane. However, the MRI is only active at the midplane of a minimum-mass solar nebula disk if cosmic rays propagate diffusively (ζ ∝ r −1) away from the star. The relationship between accretion, which accelerates cosmic rays, the dense accretion columns, which attenuate cosmic rays, and the MRI, which facilitates accretion, creates a cosmic-ray feedback loop that mediates accretion and may produce variable luminosity.

Bioactive glasses and direct effect of increased K2O additive for nuclear shielding performance: A comparative investigation

This study aimed to provide a large-scale investigation on direct effect of K2O additive nuclear radiation shielding properties of calcium phosphate based bioactive quaternary P2O5–CaO–Na2O–K2O glasses. A gamma ray attenuation setup has been modeled in MCNPX (v-2.6–0) simulation code using Monte Carlo simulation technique. Next, all the bioactive glasses have been defined considering their chemical properties and material densities, respectively. The mass attenuation coefficients (MAC) have been calculated by using MCNPX code and obtained results have been used for determination of another vital gamma-ray shielding parameters. Moreover, a detailed calculation has been done for determination of exposure buildup factor (EBF) and energy absorption buildup factor (EABF) of investigated bioactive glasses which should be considered as important parameters for interaction properties of ionizing radiation with material environment. In addition, effective removal cross sections for fast neutrons have been calculated. To compare our results, obtained HVL values of the present investigation have been compared with copper oxide and cobalt oxide substituted bioactive glasses. Among the investigated bioactive glasses, the maximum MAC values were reported for PCNK60 sample with higher K2O additive. It can be concluded that chemical structure of additive materials in the bioactive glasses is strongly related with the radiation attenuation properties of bioactive glasses.

The influence of PbO on the radiation attenuation features of tellurite glass

Tellurite based glasses have been of considerable interest in the last decades due to their interesting mechanical, physical and chemical features. Presently, different investigators and engineers are being devoted for developing the Tellurite based glasses to be used as effective radiation shielding materials. Our aim is to study the energy as well as PbO content dependence on the gamma rays attenuation behavior of lead tellurite glasses when the PbO content changes from 0 to 30 mol% between 0.356 and 2.506 MeV photon energies. This was achieved by considering the lead tellurite glass system with the composition x(PbO)-(100-x)(TeO2). The photon attenuation factors of the lead tellurite glasses were evaluated at five energies utilizing Monte Carlo simulation (Geant4 code). The reative difference values between Geant4 and XCOM data for the six glasses are less than 7% and this validates the accuracy of the obtained results. The mass attenuation coefficient (μ/ρ) reduces with an increase in the energy whereas it increases when TeO2 is replaced by PbO. The influence of PbO on the μ/ρ is significant only at 0.356 and 0.511 MeV, but at the other energies it is found that PbO slightly affects the attenuation factor. The linear attenuation coefficient of 30PbO–70TeO2 (coded as TePb6) is higher than the other samples. The effective atomic number has the maximum value at 0.356 MeV (in the range of 27.76–41.25). We compared the mean free path for the tellurite glasses with RS-520 and RS-360, Osmani, nasir and PHP glasses. The results reveal that the lead tellurite glasses (especially the samples with high PbO content) are a candidate as protection materials from hazardous radiation and have better attenuation in comparison to some nuclear engineering materials.

Comparison between MCNP5, Geant4 and experimental data for gamma rays attenuation of PbO–BaO–B2O3 glasses

Monte Carlo simulations, MCNP5 and Geant4 codes were developed to investigate radiation shielding properties of xPbO–(50-x) BaO–50B2O3 (where 5 ≤ x ≤ 45 mol%) consider to be glass systems. The mass attenuation coefficients were evaluated for different PbO concentration in the glass samples for varies photon energies of 0.356, 0.662, 1.173 and 1.332 MeV. The obtained mass attenuation coefficient values used to calculate half-value layer, effective atomic number, and electron density. The simulation parameters were compared with experimental data. Results show that the simulation results of mass attenuation coefficients for all PbO concentrations were generally in good agreement with experimental results, however, mass attenuation coefficient values calculated using Geant4 were slightly lower than MCNP5 and experimental data on the low energy of 0.356 MeV. The results obtained from MCNP5 and Geant4 codes might be able to assessment mass attenuation for different glass systems. Furthermore, gamma ray, fast neutron and charged particle interaction for the glass systems were studied using buildup factors, fast neutron removal cross sections and ranges respectively.

Precise volume fraction measurement for three-phase flow meter using 137Cs gamma source and one detector

Abstract The ability to precisely predict the volume fraction percentage of the different phases flowing in a pipe plays an important role in the oil, petroleum and other industries. In this research, the volume fraction percentage was measured precisely in water-gasoil-air three-phase flows by using a single pencil beam gamma ray attenuation technique and multilayer perceptron (MLP) neural network. The volume fraction percentage determination in three-phase flows requires least two gamma radioactive sources with different energies while in this study, we used just a 137Cs source (with the single energy of 662 keV) and a NaI detector. Also, in this work, the MLP neural network in MATLAB software was implemented to predict the volume fraction percentage. The experimental setup provides the required data for training and testing the network. Using this proposed method, the volume fraction was predicted in water-gasoil-air three-phase flows with mean relative error percentage less than 6.95 %. Also, the root mean square error was calculated 2.60. The set-up used is simpler than other proposed methods and cost, radiation safety and shielding requirements are minimized.

Investigation of polymer-based BaO and rGO nanocomposites for application in low energy X ray attenuation

Polymeric materials can serve as a matrix for the dispersion of nanomaterials with good attenuation features, resulting in lightweight, conformable, flexible, lead-free and easy-to-process materials. Thus, some well-known radiation shielding materials could be used in low proportion as a filler, for the formation of new materials. On the other hand, nanostructured carbon materials, such as graphene oxide (GO) have been reported recently to show enhanced attenuation properties. For the present work, poly(vinylidene fluoride) [PVDF] homopolymers and its fluorinated copolymers were filled with metallic oxides and nanosized reduced graphene oxides (rGO) in order to produce nanocomposites with increased low energy X ray attenuation efficiency. We objective is to investigate the X ray shielding features of multilayered PVDF/rGO and P(VDF-TrFE)/BaO composites. PVDF/rGO overlapped with P(VDF-TrFE)/BaO thin films were sandwiched between two layers of kapton films of different thickness. The linear attenuation coefficients were measured for monochromatic X ray photons with energy of 8.1 keV. The samples were characterized by Scanning Electron Microscopy (SEM), Energy Dispersive Spectroscopy (EDS), Ultraviolet–visible (UV-vis) and Fourier-Transform Infrared (FTIR) Spectroscopy. The linear attenuation coefficient of the multilayered sample was evaluated and compared with the linear attenuation of the individual constituents. It was observed an increase in the attenuation coefficient of the overlapping samples. It is demonstrated that thin films of rGO nanocomposite with thickness of only 0.32 mm can attenuate up to 50% of X ray beams with energy of 8.1 keV, justifying further investigation of these nanocomposites as X ray or gamma radiation attenuators

Optimizing vertical profile measurements setup of gamma ray attenuation

Abstract: For undisturbed measurements of material properties, the gamma ray attenuation (GRA) method is a commonly used approach, e.g. in soil sciences. So far, various setups of the GRA method are applied depending on specific purposes. For accurate measurements, statistical error due to radioactive decay must be considered. In addition, a careful setting of the further involved parameters such as collimator size, the distance between source and detector as well as the measuring time need to be taken into account. In this study, a method to optimize GRA measurements is presented by relating measuring time and collimator selection to the statistical error of radiation. As a result, a method for choosing the optimum collimator size and a mathematical equation for optimizing the measuring time are derived, which is helpful for planning the vertical profile measurement in terms of required time and spatial resolution.

Comparative Study of Calculation Methods for Shield Thickness of Typical Materials against Gamma Rays

The paper aims to analyze the shielding properties of concrete and lead materials against gamma rays at different energies, and the relationships between the shield thickness of the two materials and gamma ray energy and attenuation factor have been obtained by using the method of attenuation multiple and the method of half-value-thickness, respectively. The results show that when the gamma ray energy and the attenuation factor are determined, the thickness of the concrete shield layer obtained by the method of attenuation multiple is greater than that obtained by the half-value-thickness method. The relative magnitude of thickness of lead shield obtained by the method of attenuation multiple and the method of half-value-thickness method is relate to the gamma ray energy. When the gamma ray energy is lower than 8 MeV, the thickness of lead shield calculated by the method of attenuation multiple is larger than that obtained by the half-value-thickness method, while when the gamma ray energy is higher than 8 MeV, the conclusion is opposite.

Radiation shielding, mechanical and tribological properties of treated AISI304L using H2/N2 rf plasma

The electro-slag re-melting technique was used to produce locally two standard stainless steel samples, AISI304L and AISI316L. The shielding properties of both neutrons and gamma radiations were determined using He-3 and NaI(Tl) detectors. A mixture of hydrogen and nitrogen gases (1:1) was used to investigate the effect of rf plasma surface engineering on properties of austenite stainless steel AISI304L which is used in many parts of nuclear power plant. The X-ray diffraction technique was used for recognizing the structural phases on the studied austenite stainless steel samples. The rf plasma process was performed for half an hour at stable gas pressure and water cooling rate. As a result of the rf plasma surface engineering process, enormous enhancement was achieved in surface microhardness, tribological properties and remarkable increase in the absorption cross section for slow neutrons. Moreover, the gamma ray attenuation properties for the HN304L sample is to great extent comparable with those of AISI316L and AISI304L austenite stainless steel samples. As a consequence, the obtained results give a further support in favor of the rf plasma engineering in the nuclear domain.

Nano-structured natural bentonite clay coated by polyvinyl alcohol polymer for gamma rays attenuation

The main goal of this work is to find natural rock materials that can be used as effective gamma rays shielding at minimal cost, reliability and wide applications. It must be at particular weight and volume (lighter and more protection). Natural bentonite clay can be used as shelters from nuclear waste because of its large availability and low cost. Bentonite clay was used in two forms naturally as it is from its ores and in ground phase. Natural bentonite was cut into cylindrical pellets at different thicknesses; also, the other form pressed into cylindrical pellets with different thicknesses and different pressing pressures (50, 100 and 150 bar). The different samples are coated with polyvinyl alcohol polymer to prevent nuclear waste leakage through porosity of clay. Chemical analysis and density are measured for all samples. Bentonite clay was found naturally in nanometer scale because it is formed from volcanic ash deposits. The nanoparticle size was determined by dynamic light scattering and Williamson–Hall size analysis using XRD patterns and the help of X-powder program. The particle size of natural bentonite was found to be 59.79 nm. The microstructure was characterized by scanning electron microscope and transmission electron microscopy. The linear and mass attenuation coefficients of nano-structured bentonite clay (natural and pressed) were determined at 662 keV energy of 137Cs; at 1173 and 1332 keV energies of 60Co, gamma ray sources were determined by using NaI(Tl) scintillation detector. The experimental results showed that the ground bentonite pressed at 150 bar gave the highest linear and mass attenuation coefficients than other samples. The theoretical and the experimental calculations of mass attenuation coefficient were found to be in a good agreement.

Effect of Nano-ferrite addition on mechanical properties and gamma ray attenuation coefficient of steel fiber reinforced heavy weight concrete

Abstract Perfect pure Nano-ferrite (NF) powder with 29.6 nm particle size was prepared using citrate-gel method and added with (1 and 2)% of binder to barite concrete mixes incorporating 450 kg/m3 cement content, 15% silica fume (SF) of particle size (1 µm) as a cement replacement. Steel reinforced fibers (SRF) of hooked shape with specific gravity of 7.85, diameter of 1.12 mm, aspect ratio of 22.3 and strength of 1100 N/mm2, were added with (0.5, 1 and 1.5)% of concrete total volume. Their effects on mechanical properties, microstructure, gamma-ray attenuation coefficient (µ) and density were studied. All studied properties of mixes were improved using SFR and NF with increasing their percentages. The best results were obtained using 2% NF. The improvements of this mix with respect to the control mix at 7 and 28 days ages compressive strength were 71% and 66%, respectively while the splitting strength, µ of (Co60-1332.5) and density improvements were, 101%, 138.5% and 2.5%, respectively at 28 days age.

Gamma ray thickness measurement

Gamma ray attenuation coefficients are different in diverse condition after its penetration through different components. This character has been widely used in worldwide researches for kinds of measurement treatments in medicine, and industrial detection etc. This study is mainly about one of applications of gamma ray measurement which is called gamma ray thickness measurement. Moreover, this paper also introduces principles of gamma ray detection methods and attenuation principles as well as digging its best measurement condition of the correlations. Continually, the paper will state a derivation process of the best condition by calculations.

Mechanical and gamma ray attenuation properties of N316L steel treated by rf plasma as a nuclear material

The effect of plasma surface engineering on average surface roughness, wettability and gamma ray attenuation properties of AISI316L standard steel sample were carried out. The results showed an increase in surface roughness accompanied with an increase in the surface energy and a decrease in the contact angle of N316L sample treated by plasma carbonitriding. The experimental measurements of gamma ray attenuation properties of the investigated stainless steel alloys were carried out using gamma lines emitted from 232Th and 60Co gamma ray sources. The attenuation parameters such as linear and mass attenuation coefficients and half value layer were determined experimentally and theoretically. The obtained results indicated that the rf plasma surface treatment is an effective method for developing the surface tribological properties of treated stainless steel alloy without any change in the gamma ray attenuation properties. The obtained results suggest the suitability of N316L for in-core applications of nuclear reactor systems.

Cyclostratigraphy of the Late Miocene to Pliocene sediments at IODP sites U1425 and U1430 in the Japan Sea and paleoceanographic implications

High-resolution studies of sedimentary sequences have reconstructed paleoceanographic changes in the Atlantic and southern and equatorial Pacific Oceans during the Late Miocene and Pliocene, but comparable analyses are lacking for the North Pacific Ocean. However, continuous samples of hemipelagic sequences covering this time interval were obtained at Integrated Ocean Drilling Program sites U1425 and U1430 in the Japan Sea during expedition 346. Because the paleoceanography of the Japan Sea was sensitive to glacio-eustatic sea-level changes, changes in the sediment record are manifested as cyclic lithological changes. By using a gamma ray attenuation (GRA) density, which reflects biogenic silica content, as an indicator of sea-level changes, we developed an independent orbitally tuned chronology at each site to construct high-resolution, high-precision age models for the time span of 11.8 to 1.45 Ma. First, the 405-kyr-filtered GRA profile at each site was tuned to 405-kyr-filtered orbital eccentricity. Then, using the 405-kyr-tuned age model, the 100-kyr-filtered GRA profile was tuned to short-eccentricity cycles to adjust the 405-kyr-tuned age models. We used the resulting age models to revise the time intervals of previously published lithological units and paleoceanographic stages for the Japan Sea. Our profiles based on physical properties are a good match to the oxygen isotope record, except for 6.6–3.6 Ma, a time interval with small-amplitude fluctuations in the oxygen isotope record.

Application of Monte Carlo Method for Gamma ray Attenuation Properties of Lead Zinc Borate Glasses

This work aims to introduce an useful computational model, based in Monte Carlo simulation, which can be used in practical application, and this paper presents values determined using a Monte Carlo algorithm for linear attenuation coefficient of lead zinc borate glasses with different percentages of PbO. The simulation results have been verified with predictions from the XCOM program in the studied energy region from 1 keV to 2000 keV and experimental results. Thus, this verification indicated that this research method can be followed to determine the interaction and attenuation of gamma rays with the several energies in different materials. Also, the values of mean free path and the half-value layer were calculated using the values of the linear attenuation coefficient. The dependence of these radiation shielding parameters on the energy of impinging gamma ray and the ratio of substances changes has been examined.

Production of atomic hydrogen by cosmic rays in dark clouds

Context.Small amounts of atomic hydrogen, detected as absorption dips in the 21 cm line spectrum, are a well-known characteristic of dark clouds. The abundance of hydrogen atoms measured in the densest regions of molecular clouds can only be explained by the dissociation of H2by cosmic rays.Aims.We wish to assess the role of Galactic cosmic rays in the formation of atomic hydrogen, for which we use recent developments in the characterisation of the low-energy spectra of cosmic rays and advances in the modelling of their propagation in molecular clouds.Methods.We modelled the attenuation of the interstellar cosmic rays that enter a cloud and computed the dissociation rate of molecular hydrogen that is due to collisions with cosmic-ray protons and electrons as well as fast hydrogen atoms. We compared our results with the available observations.Results.The cosmic-ray dissociation rate is entirely determined by secondary electrons produced in primary ionisation collisions. These secondary particles constitute the only source of atomic hydrogen at column densities above ~1021cm−2. We also find that the dissociation rate decreases with column density, while the ratio between the dissociation and ionisation rates varies between about 0.6 and 0.7. From comparison with observations, we conclude that a relatively flat spectrum of interstellar cosmic-ray protons, such as suggested by the most recent Voyager 1 data, can only provide a lower bound for the observed atomic hydrogen fraction. An enhanced spectrum of low-energy protons is needed to explain most of the observations.Conclusions.Our findings show that a careful description of molecular hydrogen dissociation by cosmic rays can explain the abundance of atomic hydrogen in dark clouds. An accurate characterisation of this process at high densities is crucial for understanding the chemical evolution of star-forming regions.