Target Atomic Number Research Articles

Compound nucleus formation probability of heavy and superheavy nuclei synthesized using heavy ion fusion reactions

The role of entrance channel parameters such as Z2/A, charge asymmetry αz, mass-asymmetry (ηA), charge product (Z1Z2), mean fissility χm, Coulomb interaction parameter and (N−Z)/(N+Z) on compound nucleus formation of actinide nuclei using heavy ion fusion reactions were investigated. For the formation of compound nuclei, the considered atomic number range of the projectile varies between 5≤Z≤14 and the mass number lies between 10≤A≤34. Similarly, the studied target atomic number varies between 78≤Z≤92 and the mass number range is 197≤A≤238. Among these entrance channel parameters, PCN is more systematic for (N−Z)(N+Z), Z2/A and αz. In addition to entrance channel parameters, the Ecm and EBass also play a significant role in the prediction of PCN. The proposed empirical formulae are applicable to the compound nuclei from Fr to Sg. These findings are significant for the PCN prediction from Fr to Sg.

A comprehensive open-access database of electron backscattering coefficients for energies ranging from 0.1KeV to 15MeV.

The characterization of electron backscattering is essential in medical physics for accurately assessing dose deposited around inhomogeneities where backscattering alters the spatial energy distribution pattern and for determining Monte-Carlo code's ability to effectively describe electron scattering and does calculation in a target volume. Recent machine learning advances have provided physicists with powerful tools for effectively extracting information and trends from extensive experiment observations if sufficiently sizeable datasets are available for data mining. We report on the development of a publicly accessible database on electron backscattering coefficients for solid targets. The first database on electron-solid interactions was assembled in 1995. Data for bulk materials, limited to normal incidence and energies up to 100keV, were primarily focusing on electron microscopy. To accommodate broad high-energy applications and include the most recent publications we have created a comprehensive database of electron backscattering coefficients, listed as a function of target atomic number and thickness, electron energy, and incidence angle. These additions resulted in a database of 3566 data points, compared to the previous database of 1430. The data collection includes only published experimental observations (no calculations or results fitting) with no attempt to judge their accuracy or quality. A limited number of data points were compared to recently published Monte-Carlo results. The presented database provides values of electron backscattering coefficients for 50 elements and 19 compounds at electron energies ranging from 0.1keV to 15MeV, presented in ASCII files. Each file contains the electron energy and backscattering coefficient with target thickness or electron incidence angle included where available, and the reference number shown in the last column. Additionally, the presented data were shown in the graphs for better visualization. The online database can be accessed from the website https://doi.org/10.5281/zenodo.7810951. The database provides the most up-to-date source of experimentally obtained electron backscattering coefficients that can be used in theoretical and MC calculations and modeling validations. The data availability is still very limited for many solids and almost non-existent for compounds. Novel machine learning methods should be well adapted to predict these unknown values for various targets, thicknesses, energies, and incident angles utilizing the presented cleaned dataset.

Exploring the influence of target atomic number (Z2) on mean equilibrium charge state (q¯: A comprehensive study

We have investigated the effect of the target atomic number Z2 on the mean charge state (q¯ using various model predictions such as the Shima–Ishihara –Mikumo, Ziegler–Biersack–Littmark, Schiwietz, Schiwietz–Grande , Fermi-gas-models and theoretical codes with experimental data available in the literature. This investigation makes it possible to determine the best-fit model to calculate q¯. In this work, we discuss the post-collision charge state distribution in different targets used as thin films and projectile beams (Fq+, Siq+, Clq+, and Cuq+) with different charge states (available in literature). A detailed overview of such collision experiments has been explored over a wide energy range of 1.07–3.93 MeV/u. In this contribution, an overview of the mean charge state dependence on the Fermi velocity of target materials is provided. Finally, the influence of the non-radiative electron capture at the target exit surface on the projectile charge state distribution for fast projectiles in different targets is shown, and a comparison is made with experimental data.

Dictionary Learning-Cooperated Matrix Decomposition for Hyperspectral Target Detection

Hyperspectral target detection is one of the most challenging tasks in remote sensing due to limited spectral information. Many algorithms based on matrix decomposition (MD) are proposed to promote the separation of the background and targets, but they suffer from two problems: (1) Targets are detected with the criterion of reconstruction residuals, and the imbalanced number of background and target atoms in union dictionary may lead to misclassification of targets. (2) The detection results are susceptible to the quality of the apriori target spectra, thus obtaining inferior performance because of the inevitable spectral variability. In this paper, we propose a matrix decomposition-based detector named dictionary learning-cooperated matrix decomposition (DLcMD) for hyperspectral target detection. The procedure of DLcMD is two-fold. First, the low rank and sparse matrix decomposition (LRaSMD) is exploited to separate targets from the background due to its insensitivity to the imbalanced number of background and target atoms, which can reduce the misclassification of targets. Inspired by dictionary learning, the target atoms are updated during LRaSMD to alleviate the impact of spectral variability. After that, a binary hypothesis model specifically designed for LRaSMD is proposed, and a generalized likelihood ratio test (GLRT) is performed to obtain the final detection result. Experimental results on five datasets have shown the reliability of the proposed method. Especially in the Los Angeles-II dataset, the area under the curve (AUC) value is nearly 16% higher than the average value of the other seven detectors, which reveals the superiority of DLcMD in hyperspectral target detection.

Study of radiation-stimulated structural phase transformations in iradiated Zr by Mössbauer spectroscopy

The article considers the study of the influence of high-energy singly charged 57Fe ions with energy of 1 MeV, a beam current on the target of ~100 nA, a dose of 5x1016 ion/cm2, on the structural-phase state of zirconium. Using the methods of Mössbauer spectroscopy in transmission geometry (MS), conversion electron Mössbauer spectroscopy (CEMS), and scanning electron microscopy (SEM), we studied the effect of high-energy singly charged 57Fe ions on the structural-phase state of zirconium. The projective ranges of 57Fe ions in zirconium were determined, the number of target atoms subjected to irradiation was calculated, and the number of displacements caused by these ions was estimated. Radiation damage to zirconium materials was simulated by irradiating samples at a charged particle accelerator with probe Mössbauer atoms to obtain nuclear physical data from the zone of influence of these atoms on the structural and phase state of irradiated samples under conditions close to reactor conditions. The electronic state of the implant in these materials was evaluated. The concentration of implanted atoms in the near-surface layer and the volume of samples was calculated. In particular, it was shown that the projective range of 57Fe ions in zirconium was 497 nm, the total number of displaced atoms was 3.4х1020, and the number of displacements per atom (dpa) was 159. The solubility of Fe in Zr is 0.03%. However, when zirconium is irradiated with 57Fe ions, as a result of thermal recombination of vacancies and interstitial atoms within the cascade of displacements caused by thermal peaks, intermetallic compounds Zr3Fe, ZrFe2 and a Zr (Fe) solid solution are formed.

Measuring magnetic flux suppression in high-power laser–plasma interactions

Biermann battery magnetic field generation driven by high power laser–solid interactions is explored in experiments performed with the OMEGA EP laser system. Proton deflectometry captures changes to the strength, spatial profile, and temporal dynamics of the self-generated magnetic fields as the target material or laser intensity is varied. Measurements of the magnetic flux during the interaction are used to help validate extended magnetohydrodynamic (MHD) simulations. Results suggest that kinetic effects cause suppression of the Biermann battery mechanism in laser–plasma interactions relevant to both direct and indirect-drive inertial confinement fusion. Experiments also find that more magnetic flux is generated as the target atomic number is increased, which is counter to a standard MHD understanding.

Geant4 X-ray fluorescence with updated libraries

We present the results concerning the development in Geant4 of a new data driven library, called here the ANSTO HF library. This X-ray fluorescence library is based on an approach of particular interest for PIXE simulation applications; however, it can be used in any Geant4 applications where X-ray fluorescence needs to be described. The X-ray fluorescence transition probabilities were calculated within the Hartree-Fock (HF) approach, which is recognised to better reproduce PIXE experimental values compared with the Hartree-Slater approach, adopted in the current default Geant4 EADL data library. These HF X-ray fluorescence transition probabilities were integrated into a new Geant4 library and will be released within Geant4 in the near future.In this paper, we compare the fluorescence X-ray spectra generated by the ANSTO HF library and by the currently available library (EADL-1991 [1]) within Geant4, for targets irradiated with protons and α particles with energies up to 10 MeV, a range of interest for PIXE applications. The comparisons were performed for a large set of sample materials spanning a broad range of target atomic numbers. These two approaches were compared to existing experimental measurements performed at the ANSTO heavy ion microprobe beamline using 2 MeV and 3 MeV proton and 10 MeV He2+ ion beams. This work represents a useful upgrade to the Geant4 atomic de-excitation package.

Screening parameter for elastic scattering of electrons

The present work, with its interest focusing on the elastic scattering of energetic electrons, provides a novel formulation that is demonstrated to give accurate values of the screening parameter. This is a matter considered vital in obtaining transport cross-sections, the work herein covering not only a wide range of electron energies popular in applications (1–3000 keV) but also a comprehensively wide range of target atomic numbers (Z: 1–94). Such ability has hitherto not been commonly available in making use of existing formulations. Results from the proposed formula together with comparisons made against previously published results are presented for seventeen representative elements, covering the energy range 1 keV to 3 MeV, providing a representative condensation from the 94 elements for which we have made comparable calculations. The new formulation is seen to offer a viable and accurate approximation, being both simple to apply and devoid of limitations within the bracketed electron energy and target atomic number ranges.

Folding model analysis of 28Si elastic scattering using different density distributions

The elastic scattering cross-sections of [Formula: see text]Si projectile by [Formula: see text]Al, [Formula: see text]Si, [Formula: see text]Ni, [Formula: see text]Ni and [Formula: see text]Pb targets are analyzed using the double folding model based on the effective M3Y interaction which is known as the most popular density independent form. In the calculations of the double folding model, 16 different density distributions of [Formula: see text]Si nucleus are examined. A very good agreement between experimental data and theoretical results is obtained, and also the literature results support our results. In addition, dependence on incident energy, target atomic number and target mass number of the imaginary potential depth is studied, and new and global equations are proposed.

UV and soft x-ray emission from gaseous and solid targets employing SiC detectors

A ns Nd:YAG pulsed laser has been employed to produce plasma from the interaction with a dense target, generating continuum and UV and soft x-ray emission depending on the laser parameters and target properties. The laser hits solid and gaseous targets producing plasma in high vacuum, which was investigated by employing a silicon carbide detector. The two different interaction mechanisms were studied, as well as their dependence on the atomic number. The photon emission from laser-generated plasma produced by solid targets, such as boron nitride (BN) and other elements (Al, Cu, Sn and Ta) and compounds such as polyethylene, has been compared with that coming from plasma produced by irradiating different gas-puff targets based on N2 and other gases (Ar, Xe, Kr, SF6). The experimental results demonstrated that the yields are comparable and, in both cases, increase proportionally to the target atomic number. The obtained results, focusing the attention on the advantages and drawbacks of the employed targets, are presented and discussed.

X-ray emission for Ar11+ ions impacting on various targets in the collisions near the Bohr velocity* *Project supported by the National Key R&D Program of China (Grant No. 2017YFA0402300), the National Natural Science Foundation of China (Grant Nos. 11505248, 11775042, 11875096, and 11605147) the Scientific Research Program Funded by Shaanxi Provincial Education Department, China (Grant No. 20JK0975), the Scientific Research

X-ray emission from the collisions of 3 MeV Ar11 + ions with V, Fe, Co, Ni, Cu, and Zn is investigated. Both the x-rays of the target atom and projectile are observed simultaneously. The x-ray yield is extracted from the original count. The inner-shell ionization cross section is estimated by the binary encounter approximation model and compared with the experimental result. The remarkable result is that the Ar K-shell x-ray yield is diminished with the target atomic number increasing, which is completely opposite to the theoretical calculation. That is interpreted by the competitive consumption of the energy loss for the ionization of inner-shell electrons between the projectile and target atom.

I L-shell X-rays from near Bohr-velocity I<sup>20+ </sup>ions impacting on various targets

The L-shell X-ray emissions of iodine are investigated as a function of target atomic number for 4.5-MeV I<sup>20+</sup> ions impacting on Fe, Co, Ni, Cu and Zn targets. Six distinct L-subshell X-rays are observed. The energy of the x-ray has a blue shift compared with the atomic data. The relative intensity ratio of Lβ<sub>1, 3, 4</sub> and Lβ<sub>2, 15</sub> to Lα<sub>1, 2</sub> almost increase linearly with the target atomic number increasing. The ratio of I(Lι) to I(Lα<sub>1, 2</sub>) and I (Lγ<sub>2, 3, 4, 4'</sub>) to I(Lγ<sub>1</sub>) are approximately proportional to the square of target atomic number. It is indicated that during the interaction of highly charged heavy ions with atom in the energy region near the Bohr velocity, the inner-shell process is mainly caused by the close-range collisions below the surface. There, the projectile not only has enough time to capture electrons from the target atom to be neutralized, but also has enough kinetic energy to ionize the inner-shell electron by coulomb interaction. At the balance between electron capture and ionization, the outer-shells of M, N, O etc. could be multiply ionized. The extent of multiple ionization increases with the target atomic number increasing. That leads to the energy shift, resulting in the change of the relative intensity ratio for the L-subshell X-ray. The smaller the atomic fluorescence, the larger the enhanced fluorescence caused by multiple ionization.

X-rays produced by interaction of Xe<sup>20+</sup> with different targets in Bragg peak energy region

<sec>The inner shell process produced by the collision of highly charged ion with medium atoms near the Bragg peak is an important frontier area of atomic physics under extreme conditions such as celestial plasmas and controlled nuclear fusion plasmas. Because of the special complexity of the inner shell process produced by the collision of ions with atoms in the Bragg peak energy region and the relevant experimental research is less, limited by the experimental conditions, there remain some interesting and unanswered questions.</sec><sec>We report the experimental data of X-ray spectra produced by the impact of Xe<sup>20+</sup> with 6.0 MeV kinetic energy on V, Fe, Ni, Cu, and Zn surface in the National Laboratory of Heavy Ion Research Facility in Lanzhou, China. The generation mechanism of X-ray with energy of 1.60 keV is analyzed. The results show that when Xe<sup>20+</sup> without initial holes interacts with different targets, the Mα X-ray of Xe is not observed, but X-ray with energy twice as great as that of Xe Mα X-ray is observed in the experiment, which is called Xe Mαα X-ray and considered to be generated by the two-electron-one-photon process of Xe on the upper surface of the target. The existence time of the first-generation hollow atoms on the upper surface is calculated by using the classical over-barrier model when Xe<sup>20+</sup> interacts with different targets, which is consistent with the variation of Mαα X-ray yield with the atomic number of target, therefore it is further proved that Mαα X-ray is formed by the two-electron one-photon process of Xe on the upper surface of the target. Of course, this conclusion needs further analyzing and verifying with more experimental data.</sec>

Experimental electronic stopping cross section of transition metals for light ions: Systematics around the stopping maximum

Electronic stopping cross sections of different transition metals (Nb, Pd, Ta, and Pt) for light ions have been experimentally determined in a wide energy range. We performed relative measurements using different backscattering geometries for protons (from 50 to 5000 keV) and helium (from 80 to 10 000 keV). Data are compared to values from the literature, as well as to the widely used semiempirical (srim) and modeling (dpass) approaches. The magnitude and energy dependence of the deduced stopping power at energies around the Bragg peak, as well as the different trends observed within individual periods, are analyzed with respect to target atomic number and electronic structure. We also compare the observed magnitude of electronic stopping to several different theoretical approaches.

Angular distribution of characteristic X-ray emission from Fe and V following photoionization

<sec> The de-excitation process of vacancy in the inner shell of the target atom caused by collision ionization produces the characteristic X-ray or Auger electrons. The precise measurement of ionization cross sections plays an important role in many basic research fields, as well as in practical fields, such as chemical analysis of Particle Induced X-ray Emission (PIXE), atomic and nuclear processes, and X-ray fluorescence (XRF) spectroscopy. As we know, when ionization cross sections are measured precisely, whether the emission of X-ray is isotropic in collision process must be considered. However, there have been few experimental results for angular dependence of <i>K</i><sub>β</sub>/<i>K</i><sub>α</sub> intensity ratios in the literature until now. Therefore, this study aims to verify that the <i>K</i><sub>α</sub> and <i>K</i><sub>β</sub> X-rays originated from filling of the <i>K</i> shell vacancies with total angular momentum quantum number 1/2 (<i>J</i> = 1/2) are isotropic.</sec><sec> In this work, the typical <i>K</i>-shell X-ray spectra for Fe and V, which induced by bremsstrahlung with central energy of 13.1 keV, have been measured at emission angles varied from 120° to 170° at intervals of 10°. The characteristic X-ray spectra obtained by the detector are fitted by Gauss function, where the absorption of incident X-rays by the detector, the absorption of emitted X-rays by the atmosphere and the self-absorption correction factor of incident and emitted X-rays by the target are all taken into account.</sec><sec> The experimental results of <i>K</i><sub>β</sub>/<i>K</i><sub>α</sub> intensity ratio in this experiment coincide with those of theoretical calculation, as well as the Ertuğral’s experimental result. The experimental results show that the intensity ratio of <i>K</i><sub>β</sub>/<i>K</i><sub>α</sub> is a constant at different detection angles. Therefore it can be concluded that the emission of <i>K</i><sub>α</sub> and <i>K</i><sub>β</sub> is isotropic in the detection range. Since the <i>K</i> shell has no sub-shell, there is no Coster-Kronig transition in the collision ionization process. In the process of photoionization, the vacancies in the <i>K</i> shell are produced by direct ionization. As a result, the cross section ratio of <i>K</i> shell X-ray generation is independent of the <i>K</i> shell photoionization cross section. In addition, the experimental results show that the <i>K</i><sub>β</sub>/<i>K</i><sub>α</sub> characteristic X-ray intensity ratio of target Fe is 8% higher than that of target V, which are consistent with the theoretical analysis results that the characteristic X-ray intensity ratio depends on the target atomic number <i>Z</i>.</sec>

COMPUTER SIMULATION OF VACANCY CLUSTERS CONCENTRATION IN TITANIUM IRRADIATED WITH IONS

Abstract. The process of irradiation of metals with ions is an effective method for changing various properties of materials, in particular titanium, as well as obtaining new materials. This work is devoted to modeling radiation processes in titanium irradiated with ions. Algorithms of cascade-probabilistic functions CPF) computation depending on the number of interactions and the particle penetration deep number for various incident particles of the Mendeleev's periodic table in titanium are presented. Approximate value expressions for cross-sections are chosen, patterns of cooperation cross-sections demeanor, CP-functions depending on observation profound, number of interactions, target atomic number, primary particle initial energy are noted. Algorithms for calculating the radiation imperfections concentration in ion radiation have been developed and computations in titanium in ion radiation have been carried out. With the calculating CPF and the depth distribution of vacancy clusters, it is necessary to find the region of the result in which these characteristics of the process of formation of radiation defects in solids are exists. Regularities obtained when finding this area are formulated. The calculation results in the form of graphs and tables are presented. Keywords: Modeling, algorithm, computation, ion, regularities, approximate value, CPF, cooperation cross-section, concentration, vacancy accumulations.

Dynamical versus statistical production of Intermediate Mass Fragments at Fermi Energies

The emission probability of Intermediate Mass Fragments (IMFs) in non-central reactions has been investigated in collisions of heavy $$^{124}\hbox {Xe}$$ projectiles with the two different medium-mass targets of $$^{64}\hbox {Ni}$$ and $$^{64}\hbox {Zn}$$ at the laboratory energy of 35 A MeV. The two colliding systems differ only for the target atomic number Z and, consequently, for the isospin N/Z ratio. The probability of IMFs emission from the projectile-like fragment has been measured, showing an enhancement of the IMFs emission for the neutron rich $$^{64}\hbox {Ni}$$ target. Most of the observed projectile break-up yield is associated with the production of only one IMF, that is, a quasi-binary splitting of projectile in two fragments in a broad range of charge asymmetry. For the events with one IMF, the relative contributions of the dynamical and statistical emissions have been evaluated. We find an enhancement of dynamical break-up probability for the neutron rich target with respect to the neutron poor one. The analysis suggests influence of the target isospin in inducing the dynamical break-up of projectile-like fragments. The new data have been also compared with previous published results of $$^{112,124}\hbox {Sn}$$ + $$^{58,64}\hbox {Ni}$$ systems, in order to disentangle between isospin effects against system-size effects on the emission probability. The comparisons between previous and new data suggest that the dynamical break-up is determined by the N/Z content of both projectile and target; for the cases here investigated, the influence of the system size on the dynamical emission probability can be excluded.

Calculation of Kstopped− absorption yields on light nuclei

This paper describes an atomic cascade model which is used to predict the absorption yields for a kaon at low orbits in [Formula: see text]Li,9Be,[Formula: see text]C and [Formula: see text]O nuclei. The calculations show that most of the absorptions occur in [Formula: see text] and [Formula: see text] states so that their contribution adds up to 100% for [Formula: see text]O. However, for all of the targets, absorption in the other states is nearly zero. Also by increasing atomic number of target [Formula: see text], the yield of [Formula: see text] states decreases while it increases for the [Formula: see text] states. The results also display a low sensitivity on the widths of 4[Formula: see text] state (0.1%), in which it is comparable with the natural width of the radiation transition [Formula: see text].

Multiple ionization state of Arq+ ions during collisions near the Bohr velocity

In order to clarify the mechanism and the influence of the initial charge state and target atomic parameters for the formation of L-shell multiple ionization state of Arq+ ions produced by the collisions near the Bohr velocity, the k-shell x-ray emission of Ar is measured for 1.2 MeV Arq+(q=4, 6, 8, 9, 11, 12) ions impacting on V target and 3 MeV Ar11+ ions interacting with selected targets (Z2 = 23, 26, 27, 28, 29, 30). It is found that the measured Ar Kα and Kβ x-ray energies shift to the high energy side, and the relative intensity ratios of Kβ/Kα are enlarged than the atomic data, owing to the presence of out-shell multiple vacancies. The multiple ionization is almost independence of the projectile charge state, but is diminished with increasing target atomic number.

Production of φ Mesons on Nuclear Targets in the Quark–Gluon String Model

Experimental data on the production of φ mesons in proton–nucleus and nucleus–nucleus collisions are considered. These data show unusually small shadowing corrections to the inclusive density for φ-meson production in the midrapidity region. It is found that the results of calculations based on the quark–gluon string model are in qualitative agreement with experimental data on the density of produced φ mesons as a function of both the initial energy ranging from the Collaboration NA49 energy to the LHC high energies and the target atomic number A.