Atomic Number Density Research Articles

Investigation of mechanical and radiation shielding characteristics of novel glass systems with the composition xNiO-20ZnO-60B2O3-(20-x) CdO based on nanometal oxides

Novel glass systems with the compositions xNiO-20ZnO-60B2O3-(20-x) CdO (0 ≤ x ≤ 5 mol%) have been designed and assembled by the melt quenching technique from different nanometal oxides (NiO, ZnO, B2O3, and CdO) to serve as competitive candidates for radiation shielding. The X-ray diffraction technique was utilized to confirm the amorphous character of the samples. The target metal oxides (ZnO, NiO, CdO and B2O3) were synthesized in the nanoscale, as confirmed by SEM analysis. The mechanical properties of the new composites have been studied and their elastic moduli have been estimated. Enhancement in the elastic moduli, density and physical properties were achieved by the assembled systems. The density was varied between 3.72 and 4.27 g/cm3, whereas molar volume decreased from 22.51 to 19.53 cm3 mol−1, as the loading of NiO NPs increased from 0 to 5 mol% in the composite. The mass attenuation coefficients (µm) have been measured at different γ-ray photon energies (662, 1173 and 1332 keV) using narrow beam transmission geometry and the results have been compared with those obtained by XCOM simulation code to confirm a good match between the values. Measurements referred to the increase in some parameters of the new glasses, including the mass attenuation coefficient (µm), effective atomic number (Zeff) and effective electron density (Nel) due to the increase in NiO content from 0 to 5 mol%. Additionally, the half value layer (HVL) and the mean free path (MFP) were decreased with increasing NiO percent content. The achieved results denote that 5NiO-20ZnO-60B2O3-15CdO exhibited the best radiation shielding characteristics among the tested glasses. Finally, the radiation shielding characteristics of the new glass systems have been compared with the previously studied standard glasses to refer to the superiority of the assembled systems.

The interaction of gamma radiation with drugs used in cholinergic medications

Purpose: Pharmacological medications can reduce the radiation damage in the organism when applied in the stage before or after exposure to radiation. Cholinergic drugs are a category of pharmaceutical agents acting on the neurotransmitter acetylcholine, the primary neurotransmitter in the parasympathetic nervous system. In this investigation, some gamma radiation interaction parameters namely mass attenuation coeffıcients (μρ), effective atomic number (Zeff) and electron densities (Nel) of 12 cholinergic system drugs have been calculated in the energy range 1 KeV–100 GeV. In addition, gamma-ray energy absorption (EABF) and exposure (EBF) of buildup factors have been computed using the five-parameter geometric progression (G-P) fitting formula for investigated drugs in the energy range 0.015–15 MeV, and for penetration depths up to 40 mean free path (mfp).Materials and methods: In order to perform these calculations, data obtained from WinXCom computer program were used. The computed μρ values were then used to calculate the effective atomic numbers and electron density of the investigated drugs. To compute the buildup factors, the G-P fitting parameters were determined by the method of interpolation from the equivalent atomic number, ‘Zeq’Results and Conclusions: It has been concluded that effective atomic number and electron density of malathion is bigger than the other drugs and the variations in values of Zeff and Nel for all drugs depend on chemical compositions and photon energy where the K-absorption edge of elements may affect the energy dependence of Zeff and Nel. It should also be noted that the buildup of photons is less in malathion and carbachol and is more in tabun and parathion compared with other drugs. Photon interaction parameters evaluated in the present study may be beneficial in radiation dosimetry and therapy.

Comprehensive Second-Order Adjoint Sensitivity Analysis Methodology (2nd-ASAM) Applied to a Subcritical Experimental Reactor Physics Benchmark: II. Effects of Imprecisely Known Microscopic Scattering Cross Sections

This work continues the presentation commenced in Part I of the second-order sensitivity analysis of nuclear data of a polyethylene-reflected plutonium (PERP) benchmark using the Second-Order Adjoint Sensitivity Analysis Methodology (2nd-ASAM). This work reports the results of the computations of the first- and second-order sensitivities of this benchmark’s computed leakage response with respect to the benchmark’s 21,600 parameters underlying the computed group-averaged isotopic scattering cross sections. The numerical results obtained for the 21,600 first-order relative sensitivities indicate that the majority of these were small, the largest having relative values of O (10−2). Furthermore, the vast majority of the (21600)2 second-order sensitivities with respect to the scattering cross sections were much smaller than the corresponding first-order ones. Consequently, this work shows that the effects of variances in the scattering cross sections on the expected value, variance, and skewness of the response distribution were negligible in comparison to the corresponding effects stemming from uncertainties in the total cross sections, which were presented in Part I. On the other hand, it was found that 52 of the 21600 × 180 mixed second-order sensitivities of the leakage response with respect to the scattering and total microscopic cross sections had values that were significantly larger than the unmixed second-order sensitivities of the leakage response with respect to the group-averaged scattering microscopic cross sections. The first- and second-order mixed sensitivities of the PERP benchmark’s leakage response with respect to the scattering cross sections and the other benchmark parameters (fission cross sections, average number of neutrons per fission, fission spectrum, isotopic atomic number densities, and source parameters) have also been computed and will be reported in subsequent works.

Reactive sites on the surface of polycyclic aromatic hydrocarbon clusters: A numerical study

The surface growth of soot is a key process in its mass growth, depending crucially on surface properties. In this work, we directly extract the detailed surface properties, such as surface area, number density of reactive sites on a particle and parameter α, from the microscopic configuration of polycyclic aromatic hydrocarbon (PAH) clusters. Five representative PAHs, including pyrene (C16H10), coronene (C24H12), ovalene (C32H14), hexabenzocoronene (C42H18) and circumcoronene (C54H18), are used to build the model configurations of nascent soot. We develop a numerical scheme to determine the detailed surface properties based on the approximation of solvent-excluded surface. The assumption of spherical particles is found to introduce a large uncertainty in the estimation of the surface area, and the error can be a factor of 2.5 in the worst case. The number density of atoms or sites on cluster surfaces does not depend on the chemical composition of a particle larger than 2 nm in diameter, and our study indicates that the number density of hydrogen atoms is overestimated by a factor of 3 in the literature. Finally, we propose a new equation for parameter α, which includes the effects of the size of gaseous species in surface reaction, local temperature, particle size and chemical composition.

Phy-X / PSD: Development of a user friendly online software for calculation of parameters relevant to radiation shielding and dosimetry

A user friendly online Photon Shielding and Dosimetry (PSD) software available at https://phy-x.net/PSD has been developed for calculation of parameters relevant to shielding and dosimetry. These parameters include linear and mass attenuation coefficients (LAC, MAC), half and tenth value layers (HVL, TVL), mean free path (MFP), effective atomic number and electron density (Zeff, Neff), effective conductivity (Ceff) energy absorption and exposure buildup factors (EABF, EBF). The software can generate data on shielding parameters in the continuous energy region (1 keV-100 GeV). Also, some well-known radioactive sources (22Na, 55Fe, 60Co, 109Cd, 131I, 133Ba, 137Cs, 152Eu and 241Am) along with their energies and some characteristic (K-shell) X-ray energies of Cu, Rb, Mo, Ag, Ba and Tb elements are available in the software and can be selected by the user. Thus, one can obtain the shielding parameters at photon energies available for the predefined energies. Moreover, another parameter relevant to shielding i.e. the fast neutron removal cross section (FNRCS) can be calculated for a compound or a mixture using this software. The software is freely available online after having registered to the Phy-X platform.

A study on determination of mass attenuation coefficient, effective atomic number and electron density of some materials using Monte Carlo method

This work aims to calculate the effective atomic number and electron density by Monte Carlo method. In previous studies, the most widely used solution is to use the transmission method with the narrow gamma-ray beam. In the approach of this work, the gamma-ray beam after going through material is uncollimated to recording by NaI(Tl) detector. To do this, the inner diameter of detector collimator was enlarged with the aim of decreasing the strengthen of radioactive source. The obtained results were compared with NIST data and the experimental values which yield the maximum deviation of 9.05% and 3.43%, respectively. These results show the promising approach in determining the features of material.

Nuclear radiation shielding and mechanical properties of colemanite mineral doped concretes

ABSTRACTThe present research focused on the investigation of photon and fast neutron shielding parameters of colemanite mineral doped and undoped concretes. The fabricated concretes have been exposed to gamma rays at 59.5 and 81 keV energies and the measurements have been carried out with NaI(Tl) detector. The parameters of effective atomic number (Zeff) and electron density (Nel) have been determined experimentally and theoretically. The exposure buildup factor (EBF) and energy absorption buildup factor (EBF) have been computed utilizing the Geometric progression (G–P) fitting method. In addition to the photon shielding parameters, the macroscopic effective removal cross-section calculations for fast neutron (ΣR) were performed. As a result, it was observed that the concretes doped with colemanite mineral are not very effective in gamma radiation shielding. On the contrary, it was observed that concretes with colemanite were more effective in shielding fast neutrons and the fast neutron removal cross-section values increased with increasing colemanite concentration in the concrete. Additionally, compressive strength values (MPa) of concretes were tested using ALFA TESTING (B001-PC) 200 tons capacity device.

Influence of N2, O2, and H2 admixtures on the electron power balance and neutral gas heating in microwave Ar plasmas at atmospheric pressure

A combination of optical emission and absorption spectroscopy of argon 2p –1s transitions (Paschen notation) combined with collisional-radiative (CR) modelling of argon 2p states was used to characterize microwave argon plasmas at atmospheric pressure in presence of N2, O2, and H2 admixtures. In particular, the neutral gas temperature (obtained from the broadening of argon 2p 2–1s2 and 2p 3–1s2 emission lines), the number density of argon 1s5 atoms (obtained from absorption spectroscopy of the argon 2p 9–1s5 transition using a tunable laser diode), the electron temperature (obtained from the comparison between measured and simulated argon 2p -to-1s relative line emission intensities), and the electron density (obtained from the Stark broadening of the Hβ line and argon relative line emission intensities) were recorded as a function of the axial distance along the microwave plasma column. The results show that, for a given position in the plasma and a higher amount of admixture in the nominally pure argon plasma, the neutral gas temperature increases and the electron number density decreases, while the electron temperature and the population of argon metastable atoms first decreases and then increases at higher concentrations. With such information, a detailed analysis of the electron power balance was performed. It is found that less than 1% of the admixture in the argon plasma already absorbed more than 80% of the microwave power. Part of this energy is used for neutral gas heating, mostly through electron-impact excitation of rotational levels.

Resonant semiconductor laser absorption of atomic Rb in a pulsed Nd:YAG laser-induced plasma

ABSTRACTNanosecond laser pulses from a 1064 nm Nd:YAG laser were focused on the atomized spray of RbCl aqueous solution whose threshold energy of plasma ignition is around 550 mJ in atmosphere. A narrow-linewidth (100 MHz) vertical-cavity surface-emitting laser (VCSEL) has been used to probe the transient density of ground-state atomic Rb. The frequency of VCSEL probe beam was locked to the 87Rb transition |52S1/2, F = 2 → |52P1/2, F′ = 1 which corresponds to an absorption cross-section of up to 10−10 cm2. The atomic Rb number density was inferred from the extinction ratio of transmitted light intensity. The simple mathematical model developed to describe the density evolution n(t) conforms with the detected increase-peak-decline-vanish process well. It is a sensitive and real-time method used to diagnose the evolution process of generated plasma in air. The detection limit of RbCl concentration is lower than 1 gram per litre. Rb atoms have a mean lifetime of 250 µs in each pulsed plasma.

Study Effective Atomic Numbers and Attenuation Cross-Section of Caprylic Acid by Using Gamma Ray Sources.

Measured the effective atomic number(Zeff), effective electron density (Neff), atomic cross-section (бt)and electronic cross-section (бe)depending on the amount of mass attenuation coefficient, the mass attenuation coefficients (μm)measured for fatty acid “Caprylic” C8H16O2by using Gamma ray radiation(γ), emitted from sources Co57, Ba133, Na22, Cs137, Mn54, and Co60with energies from 122 to1330 keV. We used scintillation NaI(Tl) detector with resolution 8.2% (at 662keV ). The attenuation coefficient data were then used to obtain the effective atomic numbers (Zeff), and effective electron densities (Neff), atomic cross-section (бt)and electronic cross-section (бe) off atty acids. It was observed that the effective atomic number (Zeff) and effective electron densities (Neff) initially decrease and tend to be almost constant as a function of gamma-ray energy. Zeff and Neff experimental values showed good agreement with the theoretical. Data on interaction of photons of energy (below 1500 keV) with biological compounds are used in radiation therapy, especially for dose calculations.

Basic restrictions for theories of ion-induced track formation: ignored relationships between experimental data

Ion-induced track data is analyzed without the application of any model for revealing the existing relationships between them. Published data is completed with some new ones. Prethinned Y3Fe5O12 samples were irradiated by C60 ions with 3.5, 5 and 7 MeV energy. Track radii Re were measured by electron microscopy. It was derived from the data that the electronic (Se) and nuclear stopping (Sn) powers are combined as αSe + βSn when they have a simultaneous effect. α = 0.45 was derived from experiments on Y3Fe5O12. When using a larger database, α varies in the range 0.4 > α > 0.17 with increasing ion energy that is valid for monoatomic irradiations as well, and this is the origin of the reduction of Re with the increasing ion energy in insulators. A Gaussian relationship exists between melting temperatures Tm and track radii in track forming insulators for Se/N = constant (N—atomic number density). Due to this, Tm is the unique controlling materials parameter for the track size. Consequences for the parameters of the induced temperature distributions are discussed. The conclusions were deduced directly from the raw experimental data, therefore, the derived relationships should be followed by any theoretical model.

Na2Si3O7/BaO composites for the gamma-ray shielding in medical applications: Experimental, MCNP5, and WinXCom studies

The role of BaO in the glassy structured Na2Si3O7 was investigated in the context of gamma radiations shielding parameters in the study. The mass attenuation coefficient, half layer value, and mean free path of the Na2Si3O7/BaO composites were calculated experimentally for the photons with the energies of 81 keV and 356 kev emitted from 133Ba point radioactive source. The same parameters were also calculated by Monte Carlo N-particle simulation (MCNP5) for the gamma photons which are emitted from 133Ba, 241Am, 99mTc, 177Lu, 192Ir, and 137Cs radioactive sources. The effective atomic number and effective electron density were determined by WinXCom software. Additionally, the scattered gamma photon intensity of the composites was realized for the energy of 364 keV and compared with the most utilized radiation shielding material lead. It was concluded that the composite having the highest BaO additive exhibits the best gamma photon absorption ability at all energies investigated.

Radiative cooling due to NO at 5.3 [formula omitted]m emission as observed by TIMED/SABER over Asian sector

The effect of geomagnetic storms on the peak emission of NO Volume Emission Rate (NO VER) at 5.3 μm, in mesosphere and lower thermosphere (MLT) region, is studied over the Asian sector during 26–29 September 2011 (storm 1) and 18–21 February 2014 (storm 2). The data for peak emission of NO VER is obtained from SABER instrument onboard the NASA’s TIMED satellite. The SABER retrieved data along with the neutral densities obtained from NRLMSISE-00 model have been used to study the latitudinal and longitudinal variation of peak NO VER during the storm period. The variations induced in the peak emission of NO VER is understood with the help of fluctuations in neutral species and the resulting changes in chemistry. It has been found that the peak emission of NO VER is strongly influenced by the storm conditions. The peak emission of NO VER at 5.3 μm is found to be maximum at higher latitudes during the storms. However, the magnitude of peak NO VER gradually decreases towards the equator during the storms. The modeled atomic oxygen number density shows depletion at the higher latitudes corresponding to peak altitude of NO VER. There is a negative correlation between the peak emission of NO VER and Dst index during the main phase of the storm. The peak emission of NO VER and modeled atomic oxygen number density shows the positive correlation at the equator region, while negative correlation at the higher latitudes. At higher latitudes modeled atomic oxygen number density shows positive correlation with Dst index, while negative correlation at the equator. The correlation factors obtained between various parameters related to the storm time radiative cooling strongly support the existing understanding of the variation of NO VER during extreme space weather events.

Comparative studies between the shielding parameters of concretes with different additive aggregates using MCNP-5 simulation code

In the present work, cementation concretes with different aggregates were produced. The mass attenuation coefficient (μm) for the produced concretes is simulated using MCNP 5 code between 0.047 MeV and 1.836 MeV. Besides, the μm is computed theoretically using XCOM database and the comparison showed an agreement between simulated and computed μm values. The simulated results revealed that the concretes with additive of barite minerals have the highest μm while the lowest μm reported for the concretes with additive hematite minerals. Moreover, we calculated the half value layer (HVL) for all concretes between 0.047 MeV and 1.836 MeV. The results showed that the lowest HVL achieved by concretes with barite minerals while the highest HVL achieved by hematite (this is at low energy). On other hand, at high energy the lowest HVL achieved for concretes with additive chalcocite minerals and the highest HVL achieved for concretes with barite minerals. The effective atomic number and effective electron density are calculated and they found to be maximum at energy 0.047 MeV and then decrease with further increasing in the energy.

Transport of light through a dense ensemble of cold atoms in a static electric field

We demonstrate that the transport of coherent quasiresonant light through a dense cloud of immobile two-level atoms subjected to a static external electric field can be described by a simple diffusion process up to atomic number densities of the order of at least $10^2$ atoms per wavelength cubed. Transport mean free paths well below the wavelength of light in the free space can be reached without inducing any sign of Anderson localization of light or of any other mechanism of breakdown of diffusion.

Resonance line in rotating accretion disc

We study the resonance line emission from the rotating plane optically thick accretion disc, consisting of free electrons and resonant atoms. We use the standard assumption that the source of continuum radiation is located near central plane of the accretion disc, where the temperature is the highest. This corresponds to the Milne problem consideration for continuum. We shortly discuss the impossibility of the Milne problem for the resonance radiation. We assume that the resonant atoms are located in a thin layer of an accretion disc near the surface. In this case the resonance line emission arises due to scattering of a continuum on the resonant atoms. In thin layer we can neglect the multiple scattering of the resonance radiation on the resonant atoms. We consider the axially symmetric problems, where the Stokes parameter U =0. We take into account the Doppler effect for the frequencies of the resonance line. The three types of the resonant atom sources are considered (see Figs.1-3). The first source is the axially symmetric continuous distribution of the resonant atoms along the circular orbit. The second spot-like source rotates in the orbit. The third type presents two spot-like sources located in the orbit contrary one to another. In the first and third cases the shape of the emitting resonance line is symmetric, i.e. the right and left wings have the similar shapes. In the second case the resonance line has asymmetric shape. The shape of the emerging line depends significantly on the ratio of the rotation velocity value to the velocity, characterizing the Doppler width. It also depends on the ratio of the electron number density to the number density of resonant atoms. The results of the calculations characterize the different observational effects of H$\alpha$ radiation in the accretion discs and can be used for estimations of the parameters mentioned above.

Radiation interaction parameters for blood samples of breast cancer patients: an MCNP study.

The main goal of this study was to determine radiation interaction parameters such as mass attenuation coefficients, effective atomic numbers, and effective electron densities depending on element concentrations (Na, K, Cu, Zn, Al, Ca, Mg Cr, Fe, Se) in blood samples of patients with breast cancer. Eighty blood samples were collected and analyzed in this study (40 from breast cancer patients and 40 from healthy patients). The determination of element concentrations of the samples was performed with inductively coupled plasma-mass spectrometry (ICP-MS) and inductively coupled plasma-optical emission spectrometry (ICP-OES) after which the element concentrations were normalized to percentage. Mass attenuation coefficients were calculated by Monte Carlo simulation method. In addition, effective atomic numbers and effective electron density values of the blood samples were calculated with the ZXCOM program. One of the most important results of this study is that differences in radiation interaction parameters between the two groups were observed. More specifically, the mass attenuation coefficients of the healthy group's blood samples were higher than those of the cancerous group at photon energies of 50keV, 100keV, 250keV and 500keV, while they were lower at 1MeV. All the MCNP results were consistent with the results obtained from ZXCOM. As the main result of this study it is concluded that photon atomic parameters such as mass attenuation coefficient, effective atomic number and electron density may be considered in cancer diagnosis or treatment modalities.

Effective atomic number estimation by energy-resolved X-ray computed tomography with a current-mode detector system

We have developed a current-mode detector system, called a “transXend” detector, consisting of several segmented detectors aligned along the direction of X-ray incidence, for energy-resolved computed tomography (CT). The transXend detector measures X-rays as electric currents and after analysis gives the energy spectrum of the incident X-ray. In previous work, we measured the linear attenuation coefficients of resins as a function of X-ray energy with the energy-resolved CT using the transXend detector. This paper shows a method to estimate the effective atomic number and electron density of nine resins from the linear attenuation coefficients using a photon–atom cross-section lookup table. The estimated and agreed well with calibration lines with accuracies of about 2%.

Determination of proton stopping power ratio with dual-energy CT in 3D-printed tissue/air cavity surrogates.

To study the accuracy with which proton stopping power ratio (SPR) can be determined with dual-energy computed tomography (DECT) for small structures and bone-tissue-air interfaces like those found in the head or in the neck. Hollow cylindrical polylactic acid (PLA) plugs (3cm diameter, 5cm height) were 3D printed containing either one or three septa with thicknesses tsepta =0.8, 1.6, 3.2, and 6.4mm running along the length of the plug. The cylinders were inserted individually into a tissue-equivalent head phantom (16cm diameter, 5cm height). First, DECT scans were obtained using a Siemens SOMATOM Definition Edge CT scanner. Effective atomic number (Zeff ) and electron density (ρe ) images were reconstructed from the DECT to produce SPR-CT images of each plug. Second, independent elemental composition analysis of the PLA plastic was used to determine the Zeff and ρe for calculating the theoretical SPR (SPR-TH) using the Bethe-Bloch equation. Finally, for each plug, a direct measurement of SPR (SPR-DM) was obtained in a clinical proton beam. The values of SPR-CT, SPR-TH, and SPR-DM were compared. The SPR-CT for PLA agreed with SPR-DM for tsepta ≥3mm (for CT slice thicknesses of 0.5, 1.0, and 3.0mm). The density of PLA was found to decrease with thickness when tsepta <3mm. As tsepta (and density) decreased, the SPR-CT values also decreased, in good agreement with SPR-DM and SPR-TH. Overall, the DECT-based SPR-CT was within 3% of SPR-TH and SPR-DM in the high-density gradient regions of the 3D-printed plugs for septa greater than~3mm in thickness.

Unstable modes of oscillations of a tangential discontinuity in partly ionized plasma with charge exchange: long waves

An analytical study of linear unstable modes of oscillations of a tangential velocity discontinuity in partly ionized space plasma with charge exchange is carried out.The long-wave approximation is considered. In this approximation, the scale of perturbations is much larger than a certain characteristic size, which is determined by the charge-exchange cross-section and number density of neutral atoms. It is shown that along with the classical Kelvin – Helmholtz instability, there exists an unstable mode whose increment does not depend explicitly on the relative velocity of the two media separated by the discontinuity. The presence of this mode is entirely determined by the presence of the charge-exchange process.