Fraction Of Ions Research Articles

Stripping features of 2-MeV/u sulfur-ion beams penetrating carbon foils

The dynamics of charge-state fractions of sulfur-ion beams stripped by carbon foils at 2.0 MeV/u is investigated as a function of the initial-ion charge state q0 of the incident beam using experimental data and theoretical calculations. Experimental dependencies of the ion fractions, mean charges and equilibrium foil thicknesses on q0 are explained using the BREIT code, based on the analytical solution of the balance rate equations, as well as the ETACHA code. Experimental equilibrium charge-state distribution is qualitatively reproduced by both codes, demonstrating the capability of their approaches to the density effect. It is shown experimentally and theoretically that the non-equilibrium charge-state fractions and equilibrium foil thicknesses strongly depend on the initial ion charge q0.

Parameters and ion mass-to-charge composition of a high-power impulse magnetron discharge with electron injection

We have explored the effect of electron injection on the burning conditions and parameters of a high-power impulse magnetron sputtering discharge, including the ion mass-to-charge composition of the discharge plasma. We find that with stabilized discharge burning voltage, electron injection leads to a significant increase in the discharge current and sustains discharge operation in the low pressure regime, but also leads to a lower fraction of metal ions in the plasma. By using a reflecting electrode, conditions are created that provide transport of the injected electron flux directly into the region of intense ionization, and one can preserve the fraction of metal ions in the plasma corresponding to the self-sputtering mode, and also decrease the limiting operating pressure.

Contribution of the metastable states to electron-impact single ionization for W7+

In this paper, we present the electron-impact single ionization cross sections for W7+. The level-to-level distorted-wave method implemented in the flexible atomic code (FAC) was used for calculation. Contributions from direct ionization (DI) and excitation-autoionization (EA) processes are taken into account. Comparison between the results of previous experimental measurements and the present calculations show a prominent contribution from metastable states in the W7+ ion. We extended the theoretical analysis including level-to-level calculations from long-lived levels of the [Cd]4f135p6 ground configuration and excited, metastable [Cd]4f145p5, [Cd]4f135p55d and [Cd]4f145p45d configurations. Calculated results are in good agreement with experimental data when, within a statistical model, a 56% fraction of parent ions in the ground configuration is assumed.

Ion beam composition in ion source based on magnetron sputtering discharge at extremely low working pressure.

In an ion source based on a pulsed planar magnetron sputtering discharge with gas (argon) feed, the fraction of metal ions in the ion beam decreases with decreasing gas pressure, down to the minimum possible working pressure of the magnetron sputtering discharge. The use of a supplementary vacuum arc plasma injector provides stable operation of the pulsed magnetron sputtering discharge at extremely low pressure and without gas feed. Under these conditions, the pressure dependence of the gaseous ion fraction displays a maximum (is nonmonotonic).

Mass Loss by Atmospheric Escape from Extremely Close-in Planets

Abstract We explore atmospheric escape from close-in exoplanets with the highest mass-loss rates. First, we locate the transition from stellar X-ray and UV-driven escape to rapid Roche lobe overflow, which occurs once the 10–100 nbar pressure level in the atmosphere reaches the Roche lobe. Planets enter this regime when the ratio of the substellar radius to the polar radius along the visible surface pressure level, which aligns with a surface of constant Roche potential, is X/Z ≳ 1.2 for Jovian planets (Mp ≳ 100 M ⊕) and X/Z ≳ 1.02 for sub-Jovian planets (M p ≈ 10–100 M ⊕). Around a Sun-like star, this regime applies to orbital periods of less than two days for planets with radii of about 3–14R⊕. Our results agree with the properties of known transiting planets and can explain parts of the sub-Jovian desert in the population of known exoplanets. Second, we present detailed numerical simulations of atmospheric escape from a planet like Uranus or Neptune orbiting close to a Sun-like star that support the results above and point to interesting qualitative differences between hot Jupiters and sub-Jovian planets. We find that hot Neptunes with solar-metallicity hydrogen and helium envelopes have relatively more extended upper atmospheres than typical hot Jupiters, with a lower ionization fraction and higher abundances of escaping molecules. This is consistent with existing ultraviolet transit observations of warm Neptunes, and it might provide a way to use future observations and models to distinguish solar-metallicity atmospheres from higher-metallicity atmospheres.

Health benefits of using air purifier to reduce exposure to PM2.5-bound polycyclic aromatic hydrocarbons (PAHs), heavy metals and ions

In this study, the efficiency of air cleaners in removal of chemical components of PM2.5 (PAHs, heavy metals, and ions) in the indoor air of dormitories of Tehran University of Medical Sciences, Iran were assessed. 12 rooms were selected and randomly divided into two groups: sham air purifier system deployed room (SR) vs. true air purifier system deployed room (TR). 24-h PM2.5 samples were simultaneously collected in both TR and SR on PTFE filter papers at a flow rate of 5 L/min. The results showed overall removal efficiency of 76.5 ± 15.5%, 63.1 ± 22.5%, and 66.2 ± 24.8% for PAHs, heavy metals and ions, respectively. Moreover, the fraction of positive ions decreased when air purifiers were used in the rooms. The results showed that the smoking is an important influencing factor on the indoor air quality; smoking can leads to reduction in removal efficiency of PAHs, heavy metals and ions by 26%, 40%, and 51%, respectively. An air purifier could decreased the PM2.5 even lower than the WHO annual guideline level in non-smoker rooms. The present study revealed that use of indoor air purifiers can significantly reduce the risk of carcinogenicity and non-carcinogenicity attributed to heavy metals and PAHs, especially in places without a smoker.

Single-Ion Conducting Polymer Electrolytes Based on Random Polyurethane–Urea with Different Diisocyanate Structures for Lithium Batteries

Polyurethane–urea ionomers based on poly(ethylene oxide) (PEO) with various hard segment contents were synthesized from diisocyanates with different symmetries and planarities. The influence of the random copolymer microphase structure (including the phase separation morphology and hydrogen bonding behavior) on the ion states and ion migration was investigated. The soft phase could maintain a low glass transition temperature to yield samples with good ionic conductivity when the hard segment was less than 48 wt %. Furthermore, the hard phase and hydrogen bonds could provide good mechanical strength. Fourier transform infrared spectroscopy and small-angle X-ray scattering confirmed that ionomers with a smaller degree of phase separation had a high fraction of ions in isolated ion pairs. Coupled with faster segmental dynamics and ion mobility from the depressed Tg, the polyurethane–urea ionomer simultaneously showed high strength and ionic conductivity. After plasticization, the prepared single-ion conductor was successfully tested in lithium cells, demonstrating outstanding discharge capacity (166 mAh g–1), Coulombic efficiency (96.5%), and retention (92.6% after 100 cycles) at 0.1 C and high temperature.

Some aspects of rotation and magnetic-field morphology in the infrared dark cloud G34.43+00.24

ABSTRACT The infrared dark clouds (IRDCs) are molecular clouds with relatively greater values in their magnetic-field strengths. For example, the IRDC G34.43+00.24 (G34) has magnetic-field strength of the order of a few hundred micro-Gauss. In this study, we investigate if the dynamic motions of charged particles in an IRDC such as G34 can produce this magnetic-field strength inside it. The observations show that the line-of-sight velocity of G34 has global gradient. We assume that the measured global velocity gradient can correspond to the cloud rotation. We attribute a large-scale current density to this rotating cloud by considering a constant value for the incompleteness of charge neutrality and the velocity differences between the positive and negative particles with very low ionization fractions. We use the numerical package fishpack to obtain the magnetic-field strength and its morphology on the plane-of-sky within G34. The results show that the magnetic-field strengths are of the order of several hundred micro-Gauss, and its morphology in the plane-of-sky is somewhat consistent with the observational results. We also obtain the relationship between magnetic-field strength and density in G34. The results show that with increasing density, the magnetic-field strength increases approximately as a power-law function. The amount of power is approximately equal to 0.45, which is suitable for molecular clouds with strong magnetic fields. Therefore, we can conclude that the dynamical motion of IRDCs, and especially their rotations, can amplify the magnetic-field strengths within them.

ALKALINITY CONTROL PROPERTIES OF THE SOLIDIFIED/STABILIZED SLUDGE BY A LOW ALKALINITY ADDITIVE

Several chemical reactions controlling the alkalinity of solidified/stabilized sludge using a low alkalinity additive (mainly composed of gypsum and slag) are investigated experimentally. The influence of curing conditions (open air or sealed) on the alkali leaching characteristics of the treated sludge was evaluated from the viewpoint of carbonate uptake and leaching properties of cations (Ca, K, Na, Mg, Al and Si). Modified batch leaching tests were conducted for the treated sludge cured in both open air and sealed conditions to characterize the alkali and cation leaching behaviour. Mineralogical characterization was performed through X-ray diffraction (XRD) analysis, and the Calcimeter test traced the variation of carbonate amount in the treated sludge under curing. In addition, the type of hydration products in treated sludge was also estimated by the acid neutralization capacity (ANC) tests. Experimental results showed that open air curing has an effect to decrease the pH of solutions from batch leaching tests compared to sealed curing, since the sludge cured in open air contained more carbonate and less hydroxide than those cured in sealed condition. Promoting the carbonation of Ca(OH) 2 by contact with carbon dioxide could reduce the alkalinity of treated sludge. In addition, the amount of magnesium carbonates (e.g. MgCO 3 ) and the fraction of Mg ions in treated sludge could affect the pH of leached water.

Modeling of beam ions loss and slowing down with Coulomb collisions in EAST

This paper uses the implicit Monte–Carlo full-orbit-following parallel program ISSDE to calculate the prompt loss and slowing down process of neutral beam injection (NBI)-generated fast ions due to Coulomb collisions in the equilibrium configuration of Experimental Advanced Superconducting Tokamak (EAST). This program is based on the weak equivalence of the Fokker–Planck equation under Rosenbluth MacDonald Judd (RMJ) potential and Stratonovich stochastic differential equation (SDE). The prompt loss with the LCFS boundary and the first wall (FW) boundary of the two co-current neutral injection beams are studied. Simulation results indicate that the loss behavior of fast ions using the FW boundary is very different from that of the LCFS boundary, especially for fast ions with a large gyration radius. According to our calculations, about 5.11% of fast ions generated by perpendicular injection drift out of the LCFS and then return inside the LCFS to be captured by the magnetic field. The prompt loss ratio of fast ions and the ratio of orbital types depend on the initial distribution of fast ions in the Pζ –Λ space. Under the effect of Coulomb collisions, the pitch-angle scattering and stochastic diffusion happens, which will cause more fast ion loss. For short time scales, among the particles lost due to collisions, the fraction of banana ions reaches 92.31% in the perpendicular beam and 58.65% in the tangential beam when the fraction of banana ions in the tangential beam is 3.4% of the total ions, which means that the effect of Coulomb collisions on banana fast ions is more significant. For long time scales, the additional fast ion loss caused by Coulomb collisions of tangential and perpendicular beams accounted for 16.21% and 25.05% of the total particles, respectively. We have also investigated the slowing down process of NBI fast ions.

Critical field analysis and magnetic properties of perovskite manganese oxide La0.8Ca0.2Mn1-xNixO3(x = 0.0,0.1,0.2)

Critical field analysis and the magnetocaloric effect of the polycrystalline perovskite manganese oxide samples, La0.8Ca0.2Mn1-xNixO3 (x = 0.0,0.1,0.2), which were prepared using a traditional solid phase reaction method, were explored. The data obtained from X-ray diffraction (XRD) measurements of the polycrystalline samples show good single-phase properties. The replacement of a given Mn3+ ion fraction by Ni2+ions decreased the crystal parameters and unit cell volume, Curie temperature (Tc), and the magnetic and the magnetic entropy change. These property changes originate from the partial substitution of Mn3+ ions by Ni2+, which changes the Mn3+/Mn4+ ratio and consequently weakens the double exchange (DE) effect. At an applied magnetic field of 7 T, the maximum difference in magnetic entropy of the undoped sample is 6.15 J/kg•K, and the refrigeration efficiency is 422.94 J/kg. The critical parameters of the parent material and the doped sample fit well to the Tricritical model. The La0.8Ca0.2Mn1-xNixO3 samples with x = 0.0 exhibit crossover of the phase transitions, which can be first or second order. The observed phase transitions of samples with x = 0.1 and 0.2 are exclusively second order. Around the TC of La0.8Ca0.2Mn1-xNixO3 (x = 0.0, 0.1 and 0.2) compounds, the correlation of the magnetic field with the maximum change in magnetic entropy follows a power law.

Environment regimes play an important role in structuring trait‐ and taxonomy‐based temporal beta diversity of riverine diatoms

Abstract A sound understanding of the community changes over time and its driving forces is at the centre of biodiversity conservation and ecology research. In this study, we examined: (i) the relative roles of turnover and nestedness components to trait‐ and taxonomy‐based temporal beta diversity of riverine diatoms; (ii) whether trait‐based temporal beta diversity provides complementary information to taxonomy‐based temporal beta diversity; (iii) the relative roles of hydrology (e.g. discharge, antecedent precipitation index), metal ions (e.g. Mg2+, Si2+) and nutrients (e.g. nitrogen, orthophosphate) to the both facets of temporal beta diversity and their components (i.e. total beta diversity, turnover and nestedness); and (iv) whether inclusion of environment regimes increase their explained variations. A total of 338 daily samples of riverine diatom communities were collected. We employed Mantel tests to evaluate the complementarities between trait‐ and taxonomy‐based temporal beta diversity. Using distance‐based redundancy analysis (db‐RDA) and variation partitioning, we investigated the relative roles of hydrology, metal ions and nutrients to each facet of temporal beta diversity and its components. Correlations between trait‐ and taxonomy‐based temporal beta diversity and their components were weak, which showed their complementary ecological information. Taxonomy‐based total beta diversity had a high contribution by turnover component, whereas trait‐based total beta diversity was largely driven by nestedness component. Results of variation partitioning demonstrated that the pure and shared fractions of hydrology, metal ions and nutrient differed among the components of trait‐ and taxonomy‐based temporal beta diversity. Furthermore, addition of environment regimes could dramatically increase the explained variation of temporal beta diversity and its components. Synthesis. Our results highlighted the importance of the two facets of temporal beta diversity as well as their decomposition for exploring diversity patterns of riverine diatoms in relation to abiotic factors, particularly the environment regimes. Although a high temporal taxonomic divergence was detected, the high level of temporal trait convergence indicated that species turnover with similar biological traits occurred during our study period. Our study, for the first time, provides a new perspective into temporal beta diversity of daily riverine diatom communities, which has not yet been documented by previous freshwater studies.

Ionization-Gasdynamic Simulations of Wind-Blown Nebulae around Massive Stars

Using a code that employs a self-consistent method for computing the effects of photo-ionization on circumstellar gas dynamics, we model the formation of wind-driven nebulae around massive stars. We take into account changes in stellar properties and mass-loss over the star’s evolution. Our simulations show how various properties, such as the density and ionization fraction, change throughout the evolution of the star. The multi-dimensional simulations reveal the presence of strong ionization front instabilities in the main-sequence phase, similar to those seen in galactic ionization fronts. Hydrodynamic instabilities at the interfaces lead to the formation of filaments and clumps that are continually being stripped off and mixed with the low density interior. Even though the winds start out as completely radial, the spherical symmetry is quickly destroyed, and the shocked wind region is manifestly asymmetrical. The simulations demonstrate that it is important to include the effects of the photoionizing photons from the star, and simulations that do not include this may fail to reproduce the observed density profile and ionization structure of wind-blown bubbles around massive stars.

Mesoscopic Inhomogeneities in Concentrated Electrolytes.

A mesoscopic theory for water-in-salt electrolytes combining density functional and field-theoretic methods is developed in order to explain the unexpectedly large period of the oscillatory decay of the disjoining pressure observed in recent experiments for the lithium bis(trifluoromethylsulfonyl)-imide (LiTFSI) salt [T. S. Groves et al., J. Phys. Chem. Lett.2021, 12, 1702]. We assumed spherical ions with different diameters and implicit solvent, inducing strong, short-range attraction between ions of the same sign. For this highly simplified model, we calculated correlation functions. Our results indicate that mesoscopic inhomogeneities can occur when the sum of the Coulomb and the water-mediated interactions between like ions is attractive at short and repulsive at large distances. We adjusted the attractive part of the potential to the water-in-LiTFSI electrolyte and obtained both the period and the decay rate of the correlations, in semiquantitative agreement with the experiment. In particular, the decay length of the correlations increases nearly linearly with the volume fraction of ions.

Feedforward and cascade forward networks for viscosity prediction for binary mixtures of ammonium-based ionic liquids and water

Ionic liquids have been attracting great interest due to some properties, such as low vapor pressure, thermal and chemical stability, non-flammability and the possibility of designing ionic liquids for specific purposes. The development of new processes and the substitution of traditionally used solvents, however, depend on the availability of data for the substances involved, either experimental or modeling data. Neural networks are robust models that can be used for optimization, pattern classification and recognition, property prediction and many other applications. They can use experimental data to, after enough training, learn functional relationships between variables and then generalize them for unseen cases. In this work, neural networks were trained and applied in the prediction of viscosity for binary mixtures of ammonium-based ionic liquids and water using a group contribution approach. The input variables were the temperature, the ionic liquid mass fraction and the amount of each group used to describe the ionic liquids structures. The influence of the hidden neuron number and the addition of an extra hidden layer was investigated. Furthermore, 13 training algorithms were tested. Feedforward and cascade forward networks were compared. The average absolute relative deviations for the testing set varied from almost 200% to 0.1999% depending on the selected parameters. The results showed neural networks can be used successfully to predict viscosity data, but a careful selection of architecture and training algorithm is required.

Effect of geometric position on the film properties for a complex-shaped substrate in HiPIMS discharge: Experiment and simulation

The purpose of this paper is to explore the effect of geometric position on the film properties for a complex-shaped substrate in high-power impulse magnetron sputtering (HiPIMS) discharge. The substrate is a trapezoidal prism, whose base has four inner corners of 60°, 120°, 75°, and 105°. A negative bias is added to this trapezoidal prism during the high-density discharge to deposit TiAlSiN films. The chemical compositions, microstructures and mechanical properties of the films at different area of the substrate are analyzed using the energy dispersive spectroscopy, X-ray diffraction, scanning electron microscope, nano-indentor and Vickers indentation tester. Systematic investigations demonstrate that the films properties have prominent differences on various planes of the trapezoidal-prism sample, due to the so-called shadowing effect. Compared with the measurements on the plane perpendicular to the target surface, there is a higher average hardness and stronger toughness on the plane facing to the target surface. However, the values of both the hardness and toughness are the lowest on the plane facing away from the target surface. Moreover, even for the same plane, the enhanced mechanical properties as well as a smoother surface and denser microstructure appear in the edge regions, with respect to that in the planar center regions. To understand these interesting phenomena, a two-dimensional particle-in-cell/Monte Carlo collision simulation (2D PIC-MCC) and Transport of Ions in Matter method (TRIM) are employed to explore the ion dynamics at the different sites of the sample. Simulation results suggest that a higher ion flux density and larger re-sputtering rate may contribute to the improved film properties in the edge regions. These results in this paper are important for broadening the industrial applications of high ion fraction plasma sources in irregular structures, especially for cutting tools.

Compositional design, structure stability, and microwave dielectric properties in Ca3MgBGe3O12 (B = Zr, Sn) garnet ceramics with tetravalent cations on B-site

Two garnet-structured Ca3MgBGe3O12 (B = Zr, Sn) ceramics with tetravalent cations at B-site were prepared by conventional solid state reaction. The crystal structure, microstructure evolution, and microwave dielectric performance were investigated using X-ray powder diffraction, Rietveld refinement, scanning electron microscopy, Raman spectroscopy, and infrared spectroscopy techniques. Dense Ca3MgZrGe3O12 and Ca3MgSnGe3O12 ceramics were obtained at sintering temperatures of 1420 and 1400 °C, respectively. The dielectric constant, unloaded quality factor, and temperature coefficient of resonance frequency of Ca3MgZrGe3O12 were 10.80 ± 0.2; 79,600 ± 1000 GHz (f = 12.61 GHz); and −66.8 ± 1 ppm/°C, respectively, and the corresponding values for Ca3MgSnGe3O12 were 9.68 ± 0.2; 83,400 ± 1000 GHz (f = 14.19 GHz); and −57.9 ± 1 ppm/°C, respectively. The dielectric performances of the two ceramics were compared by analyzing the ionic polarizability, packing fraction, and bond valence. The intrinsic dielectric properties were predicted by fitting the infrared reflectivity spectra.

The Ionization and Destruction of Polycyclic Aromatic Hydrocarbons in Powerful Quasars

Abstract We reanalyze the mid-infrared (5–40 μm) Spitzer spectra of 86 low-redshift (z < 0.5) Palomar–Green quasars to investigate the nature of polycyclic aromatic hydrocarbon (PAH) emission and its utility as a star formation rate (SFR) indicator for the host galaxies of luminous active galactic nuclei (AGNs). We decompose the spectra with our recently developed template-fitting technique to measure PAH fluxes and upper limits, which we interpret using mock spectra that simulate the effects of AGN dilution. While luminous quasars can severely dilute and affect the detectability of emission lines, PAHs are intrinsically weak in some sources that are otherwise gas-rich and vigorously forming stars, conclusively demonstrating that powerful AGNs destroy PAH molecules. Comparing PAH-based SFRs with independent SFRs derived from the mid-infrared fine-structure neon lines and the total infrared luminosity reveals that PAHs can trace star formation activity in quasars with bolometric luminosities ≲1046 erg s−1, but increasingly underestimate the SFR for more powerful quasars, typically by ∼0.5 dex. Relative to star-forming galaxies and low-luminosity AGNs, quasars have a comparable PAH 11.3 μm/7.7 μm ratio but characteristically lower ratios of 6.2 μm/7.7 μm, 8.6 μm/7.7 μm, and 11.3 μm/17.0 μm. We suggest that these trends indicate that powerful AGNs preferentially destroy small grains and enhance the PAH ionization fraction.

Magnetic field tailoring effects on ion beam properties in cylindrical Hall thrusters

The magnetic field is the most important element in designing a Hall thruster and improving thruster performance because it directly influences the behavior of electrons in the discharge channel. In this work, magnetic field tailoring, parallel magnetic fields to the thruster channel wall, has been attempted in a cylindrical Hall thruster, and the resultant ion beam properties are studied. The magnetic field tailored cylindrical Hall thruster demonstrated much higher ion current and propellant efficiencies than the conventional cylindrical Hall thruster, with an identical mass flow rate. A large fraction of multiply charged ions (>65%) was observed and reduced beam emission was demonstrated near the channel wall. Further, the channel wall is solely coated without erosion even at the end of the channel. Hence, tailoring of the magnetic field in cylindrical Hall thrusters could significantly enhance the potential of Hall thrusters in space applications owing to their higher propellant efficiency and reduced wall interaction.

The vertical shear instability in poorly ionized, magnetized protoplanetary discs

ABSTRACT Protoplanetary discs should exhibit a weak vertical variation in their rotation profiles. Typically, this ‘vertical shear’ issues from a baroclinic effect driven by the central star’s radiation field, but it might also arise during the launching of a magnetocentrifugal wind. As a consequence, protoplanetary discs are subject to a hydrodynamical instability, the ‘vertical shear instability’ (VSI), whose breakdown into turbulence could transport a moderate amount of angular momentum and facilitate, or interfere with, the process of planet formation. Magnetic fields may suppress the VSI, however, either directly via magnetic tension or indirectly through magnetorotational turbulence. On the other hand, protoplanetary discs exhibit notoriously low ionization fractions, and non-ideal effects, if sufficiently dominant, may come to the VSI’s rescue. In this paper, we develop a local linear theory that explores how non-ideal magnetohydrodynamics influences the VSI, while exciting additional diffusive shear instabilities. We derive a set of analytical criteria that establish when the VSI prevails, and then show how it can be applied to a representative global model of a protoplanetary disc. Our calculations suggest that within ∼10 au the VSI should have little trouble emerging in the main body of the disc, but beyond that, and in the upper regions of the disc, its onset depends sensitively on the size of the preponderant dust grains.