Transport Properties Of Plasma Research Articles

Modeling and Simulation of Vacuum Arc Plasma Transport Properties Under the Influence of Anode Melting Pool

Modeling and Simulation of Vacuum Arc Plasma Transport Properties Under the Influence of Anode Melting Pool

Nonlinear electrostatic kelvin-helmholtz shock waves in a viscous electron-positron-ion plasma with non-maxwellian distribution

A theoretical investigation is carried out for nonlinear electrostatic Kelvin-Helmholtz (K-H) shock waves in a magnetized electron-positron-ion viscous plasma in the presence of transport equations and non-Maxwellian particles by following the generalized (r, q) distribution function. The propagation of electrostatic K-H modes are studied both in the presence of trapped and free electrons. The nonlinear analysis with inclusion of plasma transport properties (magnetic viscosity and heat conduction) lead to nonlinear electrostatic K-H mode in the form of shock like waves by solving the modified Burgers’ equation. The electrostatic K-H shocks are investigated numerically with effect of different plasma parameters such as shear velocity and non-Maxwellian distributed particles. It is observed that the striking features (viz., amplitude and width of dissipative shock through the solution of Burgers’ equation) of the K-H mode are significantly modified by the effects of non-thermality of electrons and positrons both at shoulder and tails along with shear velocity due to viscosity. The relevancy of our work to the observations in space (viz., cometary comae and earth’s ionosphere), astrophysical (viz., pulsars) and laboratory (viz., solid-high intense laser plasma interaction experiments) plasmas is highlighted.

Energy and mass transport properties in the near-cathode region of atmospheric thermal plasma

As the main region where charged particles are accelerated by the electric field and accumulated near the cathode, the near-cathode region has significant non-local equilibrium characteristics and plays a crucial role in exploring the energy and mass transport properties of the thermal plasma from the arc column region to the hot cathode surface. However, there is a lack of universally adopted models and accepted theories for the study of the near-cathode region due to the complexity of the physical mechanisms involved in the sheath. According to the physical characteristics of the arc discharge, an external circuit is usually used to regulate the total current applied to the electrodes to maintain stable discharge. Therefore, the energy and mass transport properties of atmospheric thermal plasma driven by a current source coupled to an external circuit are investigated in this work to explore the transport mechanism of charged particles in the near-cathode region based on an implicit particle-in-cell Monte Carlo collision method. Firstly, the current-driven model in this work is compared with the present voltage-driven model and fluid model to verify the correctness of this model. Then, the collisions between charged particles and gas atoms inside the sheath are analyzed, and the spatial distributions of particle current density and particle heating rate inside the sheath are also studied. Finally, the variations of typical parameters of thermal particles under different current densities (106–107 A m−2) are analyzed, including maximum particle number density, maximum particle spatially-averaged temperature, sheath thickness, charge density and electric field strength in the cathode.

Transport cross sections and collision integrals for C+(2P)–H(2S), C(3P)–H+(1S), C(1D)–H+(1S), and C+(4P)–H(2S) interactions

Transport collision integrals of interacting atoms or ions play a crucial role in modeling transport properties of high-temperature gases and plasmas. Here, we obtained the potential energy curves (PECs) of CH+ using the internally contracted multireference configuration interaction method with the Davidson correction (icMRCI+Q) method. The PECs were then used to investigate the transport cross sections and transport collision integrals for the C+(2P)–H(2S), C(3P)–H+(1S), C(1D)–H+(1S), and C+(4P)–H(2S) interactions using the classical mechanical approach and a quantum mechanical treatment of the scattering with Wentzel–Kramers–Brillouin approximations of the scattering phase shifts. The transport cross sections were obtained in the collision energy of 10−6–1 hartree, which were used to compute transport collision integrals for C–H+ and C+–H systems over the temperature range of 500–40 000 K. The C(1D)–H+(1S) and C+(4P)–H(2S) interactions are considered for the first time. Our transport collision integrals can provide data references for computing transport properties of high-temperature plasmas involving C and H atoms/ions.

Transport collision integrals for C(5S)-H(2S), C(1S)-H(2S), C(1D)-H(2S), and C(3P)-H(2S) interactions

Transport collision integrals of interacting atoms or ions are essential in modeling transport properties of high-temperature gases and plasmas. Here, we obtained the potential energy curves (PECs) of CH using the state-of-the-art ab initio methods. The PECs were also extrapolated to investigate the transport collision integrals for C(3P)-H(2S), C(5S)-H(2S), C(1S)-H(2S), and C(1D)-H(2S) interactions, in which the interactions between the excited C(5S), C(1S), and C(1D) atoms and the ground H(2S) atoms were calculated for the first time. The resulting transport collision integrals were fitted to simple functional forms for ease of use in plasma modeling. Our transport collision integrals can provide data references for computing transport properties of high-temperature plasmas involving C and H atoms.

Scattering cross sections and collision integrals for N(4S)–N+(3P) and N(4S)–N+(1D) interactions

Collisions between nitrogen (N) and nitrogen ion (N+) are fundamental phenomena in the Earth and planetary atmospheres. In this work, we carried out a theoretical study of collision data for N(4S)–N+(3P) and N(4S)–N+(1D) interactions, including scattering cross sections and collision integrals. Potential energy curves of N2+ are obtained using the state-of-the-art ab initio method and then used to provide the input for calculations of resonant charge exchange and elastic cross sections. The inelastic (corresponding to the resonant charge exchange process), elastic, and total collision integrals for N(4S)–N+(3P) and N(4S)–N+(1D) interactions are computed at 500 − 50 000 K. An analysis of the collision integrals shows that the elastic collision process should not be neglected for odd-order collision interactions at low temperatures and still makes a small contribution at high temperatures. Note that this is the first time that the cross sections and collision integrals for the N(4S)–N+(1D) interaction are calculated using ab initio potential energy points. The obtained cross sections and collision integrals are essential to model the transport properties of the related plasmas.

A model for determining thermodynamic and transport properties of electric arc plasmas at elevated pressures and temperatures and its validations

A model for determining thermodynamic and transport properties of electric arc plasmas at elevated pressures and temperatures and its validations

Effect of feedstock solution concentration on the spectroscopic and electrical transport properties of thermal plasma synthesized ZnO nanoparticles

The structural, optical, spectroscopic, and electrical transport properties of zinc oxide (ZnO) nanoparticles prepared using the solution precursor plasma spray (SPPS) technique were investigated for different feedstock solution concentrations such as 1-mol and 4-mol. Rietveld refined powder X-ray diffraction and Raman spectra reveal that the prepared ZnO crystallizes in a hexagonal wurtzite structure with no secondary phase. The crystallite sizes for 1-mol and 4-mol samples are 27.5 nm and 31.3 nm, respectively. Analysis of UV–vis spectra shows that ZnO's band gap has increased from 3.19 eV to 3.23 eV as the mole concentration has increased. The spherical nature and nano size of the ZnO are confirmed by the pictures obtained using field emission scanning electron microscopy (FE-SEM) and transmission electron microscope (TEM). The presence of elements zinc and oxygen in the Zn2+ and O2− ionic states are revealed by X-ray photoelectron spectroscopy (XPS). Electrical study demonstrates that the initial mole concentration of ZnO powder affected both its electrical conductivity and dielectric constant. The activation energy value of electrical conductivity for 1-mol and 4-mol is 0.661 eV and 0.552 eV, respectively. The impedance analysis shows the electrode effect for the 1-mol sample whereas it is not observed for the 4-mol sample, which is further confirmed by modulus analysis. The presence of defect in the 1-mol sample results in a lower conductivity (3.68 × 10−12 S/cm at 1 Hz) than the 4-mol sample. The comprehensive analysis confirms that the structural, spectroscopic and electrical properties of the ZnO nanoparticle can be tunable to meet demand by changing the feedstock mole concentration in the SPPS process.

Simultaneous inference of multiple plasma parameter profiles by utilizing transport properties

AbstractNumerical techniques for the computation of posterior distribution ease restrictions on inference models, and multiple plasma parameters can be simultaneously inferred with detailed modelling of uncertainties. In addition, data that depend on multiple parameters in a complex manner can also be utilized. This paper discusses frameworks that further expand the inference capability by including transport properties in plasmas. A prior belief based on a transport equation helps to localize the posterior distribution, and when ample diagnostic capability is available, even unknown parameters in the transport model can be estimated. Furthermore, these transport parameters can be directly inferred when the profiles of the measurable plasma parameters can be easily calculated for the given transport properties.

Revealing the supercritical dynamics of dusty plasmas and their liquidlike to gaslike dynamical crossover

Dusty plasmas represent a powerful playground to study the collective dynamics of strongly coupled systems with important interdisciplinary connections to condensed matter physics. Due to the pure Yukawa repulsive interaction between dust particles, dusty plasmas do not display a traditional liquid-vapor phase transition, perfectly matching the definition of a supercritical fluid. Using molecular dynamics simulations, we verify the supercritical nature of dusty plasmas and reveal the existence of a dynamical liquid-like to gas-like crossover which perfectly matches the salient features of the Frenkel line in classical supercritical fluids. We present several diagnostics to locate this dynamical crossover spanning from local atomic connectivity, shear relaxation dynamics, velocity autocorrelation function, heat capacity, and various transport properties. All these different criteria well agree with each other and are able to successfully locate the Frenkel line in both 2D and 3D dusty plasmas. In addition, we propose the unity ratio of the instantaneous transverse sound speed $C_T$ to the average particle speed $\bar{v}_{p}$, i.e., $C_T / \bar{v}_{p} = 1$, as a new diagnostic to identify this dynamical crossover. Finally, we observe an emergent degree of universality in the collective dynamics and transport properties of dusty plasmas as a function of the screening parameter and dimensionality of the system. Intriguingly, the temperature of the dynamical transition is independent of the dimensionality, and it is found to be always $20$ times of the corresponding melting point. Our results open a new path for the study of single particle and collective dynamics in plasmas and their interrelation with supercritical fluids in general.

Collision integrals for N(4S)–N(4S), N(4S)–N(2D), and N(4S)–N(2P) interactions

Collision integrals for the scattering of nitrogen (N) atoms are essential to model transport properties of air plasmas, which can be highly dependent on the species involved. At high temperatures, N atoms may exist in their excited states. Therefore, collision integrals for N atoms are computed at the temperature range of 500–50 000 K, in which the interactions between the excited [N(2D) and N(2P)] atoms and ground N(4S) atom are considered. The interaction between the excited N(2P) atom and ground N(4S) atom is considered for the first time. A comparison of the collision integrals from our combined-hyperbolic-inverse-power-representation (CHIPR) potential energy function with those obtained using other analytical potential energy functions in the literature is given. The results show that the trend of potential energy curves (PECs) in dissociated asymptotic and short-range regions has an important effect on the collision integrals. These regions are difficult to cover in experiments. Here we seek the state-of-the-art ab initio methods for a theoretical guideline to compute the PECs of N2, which are then modeled by the CHIPR function. PECs of some low-lying states are also refined by available experimental spectroscopic data. Overall, our collision integrals are reliable.

Yukawa-Friedel-tail pair potentials for warm dense matter applications.

Accurate equationsof state (EOS) and plasma transport properties are essential for numerical simulations of warm dense matter encountered in many high-energy-density situations. Molecular dynamics (MD) is a simulation method that generates EOS and transport data using an externally provided potential to dynamically evolve the particles without further reference to the electrons. To minimize computational cost, pair potentials needed in MD may be obtained from the neutral-pseudoatom (NPA) approach, a form of single-ion density functional theory (DFT), where many-ion effects are included via ion-ion correlation functionals. Standard N-ion DFT-MD provides pair potentials via the force matching technique but at much greater computational cost. Here we propose a simple analytic model for pair potentials with physically meaningful parameters based on a Yukawa form with a thermally damped Friedel tail (YFT) applicable to systems containing free electrons. The YFT model accurately fits NPA pair potentials or the nonparametric force-matched potentials from N-ion DFT-MD, showing excellent agreement for a wide range of conditions. The YFT form provides accurate extrapolations of the NPA or force-matched potentials for small and large particle separations within a physical model. Our method can be adopted to treat plasma mixtures, allowing for large-scale simulations of multispecies warm dense matter.

Tuning the structure and transport properties of complex plasmas using electric field

In this work, we explored the effects of uniaxial (M z ) and biaxial (M xy ) ac electric fields on the structure and transport properties of complex (dusty) plasmas (CDPs) using molecular dynamics simulations. Structures are analyzed using two diagnostic methods, one is lattice correlation function ψ(τ) and the second is radial distribution function g(r) under the influence of M z and M xy , respectively. The Green–Kubo (G-K) method has been used to compute the shear viscosity (η xy ) in the M xy ac electric field. The diffusive behavior of dust particles is investigated using G-K and Einstein methods in M z . In the limits of the varying electric field, these properties of CDPs are accounted for an appropriate range of plasma Coulomb coupling (Γ) and constant Debye screening strength (κ = 0.50) parameters with different system sizes. The simulation outcomes of ψ(τ) and g(r) indicate that the phase transition phenomena occur in CDPs with the variations of M z , M xy and Γ. The η xy and diffusion coefficients significantly increase with increasing parallel electric fields. The subdiffusion motion for short-time behavior and superdiffusion motion for long-time behavior is observed in the presence of moderate to strong electric field strengths. It is revealed that the phase transition and changes in the transports properties of CDPs significantly depend on the strength of the external electric field and plasma parameter (Γ). Novel regimes are observed where CDPs quickly respond to the external electric field. Simulation results are outstanding in the combined effects of Yukawa and anisotropic wake potential on CDPs structural and transport properties. Simulation results demonstrate that the CDPs have electrorheological characteristics. Due to these unique properties, electrorheological CDPs may be used as a platform to study the electrorheological aspects of soft matter. There is a possibility that CDPs will be used as electrorheological material in the near future.

Data-driven electrical conductivities of dense plasmas

A wide range of theoretical and computational models have been developed to predict the electrical transport properties of dense plasmas, in part because dense plasma experiments explore order-of-magnitude excursions in temperature and density; in experiments with mixing, there may also be excursions in stoichiometry. In contrast, because high pressures create transient and heterogeneous plasmas, data from experiments that isolate transport are relatively rare. However, the aggregate of our datasets continues to increase in size and plays a key role in the validation of transport models. This trend suggests the possibility of using the data directly to make predictions, either alone or in combination with models, thereby creating a predictive capability with a controllable level of agreement with the data. Here, such a data-driven model is constructed by combining a theoretical model with extant data, using electrical conductivity as an example. Discrepancy learning is employed with a theoretical model appropriate for dense plasmas over wide ranges of conditions and a dataset of electrical conductivities in the solid to expanded warm dense matter regimes. The resulting discrepancy is learned via a radial basis function neural network. Regularization of the network is included through centers chosen with silhouette scores from k-means clustering. The covariance properties of each cluster are used with a scaled Mahalanobis distance metric to construct anisotropic basis functions for the network. The scale is used as a hyperparameter that is used to optimize prediction quality. The resulting predictions agree with the data and smoothly transition to the theoretical model away from the data. Detailed appendices describe the electrical conductivity model and compare various machine-learning methods. The electrical conductivity data and a library that yields the model are available at GitHub.

New constraints for QCD matter from improved Bayesian parameter estimation in heavy-ion collisions at LHC

The transport properties of quark-gluon plasma created in relativistic heavy-ion collisions are quantified by an improved global Bayesian analysis using the CERN Large Hadron Collider Pb–Pb data at sNN=2.76 and 5.02 TeV. The results show that the uncertainty of the extracted transport coefficients is significantly reduced by including new sophisticated collective flow observables from two collision energies for the first time. This work reveals the stronger temperature dependence of specific shear viscosity, a lower value of specific bulk viscosity, and a higher hadronization switching temperature than in the previous studies. The sensitivity analysis confirms that the precision measurements of higher-order harmonic flow and their correlations are crucial in extracting accurate values of the transport properties.

Impact of the mass isotope on plasma confinement and transport properties in the HL-2A tokamak

The impact of the mass isotope on plasma confinement and transport properties has been investigated in Ohmically-heated hydrogen and deuterium plasmas in the HL-2A tokamak. Experimental results show that under similar discharge parameters the deuterium plasma has better confinement and lower turbulent transport than the hydrogen one, and concomitantly, it is found that the magnitude of geodesic acoustic mode zonal flows, the tilting angle of the Reynolds stress tensor and the turbulence correlation lengths are all larger in the edge region of the deuterium plasma. The results provide direct experimental evidence on the importance of the nonlinear energy coupling between ambient turbulence and zonal flows for governing the isotope effects in fusion plasmas.

Investigation of the influence of single‐particle oscillations on the transport properties of dense plasma

AbstractTransport properties of the ionic component of dense plasmas are investigated on the basis of effective potentials taking into account the presence of an external alternating electrical (laser) field. The latter generates single‐particle oscillations of electrons and significantly changes the screening of the test charge in plasma. Therefore, transport coefficients become non‐monotonic function of the oscillation frequency. The results for the diffusion and viscosity coefficients are presented. These transport coefficients are computed using the generalized Coulomb logarithm within the Chapman‐Enskog model for the fluid description. It was revealed that the oscillation of the electrons in the alternating external field with the frequency (with ωp being plasma frequency) results in the significant reduction of the ionic diffusion and viscosity coefficients. In contrast, at , the ionic diffusion and viscosity coefficients are larger compared to the case without the external field impact.

Modelling and experimental investigations of composition-dependent heat and mass transfer during Cu–Ni alloy nanoparticle synthesis in a transferred arc helium plasma

In the synthesis of alloy nanoparticles (NPs) via arc evaporation and fast quenching, the composition of the synthesized NPs differs significantly from that of the precursor. The properties of the NPs formed following evaporation of a copper–nickel anode by a helium arc are investigated using a nucleation model coupled to the thermal and flow fields derived from a magneto-hydrodynamic simulation of the arc, and experimentally. Results are obtained for three different Cu:Ni precursor compositions, 10:90, 50:50 and 90:10 at%. The synthesized particles are spherical with different size distributions and have a higher concentration of Cu than the precursor in all three cases, in contrast to previous observations, but in accordance with the predictions of the model. Emission spectroscopic measurements of copper and nickel lines indicate that the concentration of atomic copper in the plasma region near the anode is much higher than that of the nickel, in accordance with the predictions of the model. The higher vapour pressure of copper compared to nickel, and its higher activity in the alloy precursor (anode), immersed in a self-consistent thermal and flow field maintained by the transferred arc are found to play a critical role. The thermodynamic, radiative and transport properties of the helium plasma contaminated with evaporated precursor are important in determining the thermal and flow fields.

Study on Thermophysical Properties of Arc Plasma for Melting Magnesium Oxide Crystals at Atmospheric Pressure

The thermodynamic and transport properties of magnesium oxide crystal arc plasma have been researched under local thermodynamic equilibrium in this paper. The pure CO2 plasma in the arc initiation stage and Mg-CO mixtures plasma in the stable melting stage were selected. The parameter-variation method combined with Levenberg–Marquardt algorithm (PVM-LMA) is used to solve the plasma equilibrium compositions model established by mass action law from higher to lower temperature in sequence. Taking Mg50%-CO50% plasma as an example, the plasma number density of 7500 K is calculated according to 8000 K. The results show that the PVM-LMA algorithm has the advantages of fast and high precision. The comparisons to the results of pure CO2 in previous literature are displayed and our work shows better agreement with theirs. The results of Mg-CO mixtures indicate that the chemical properties of Mg atoms are more active and easier to ionize, which can effectively improve the electrical conductivity and thermal conductivity of plasma and reduce its viscosity.

Effects of magnetic field on thermal conductivity and shear viscosity of strongly coupled dusty plasma in presence of asymmetric ion flow

Thermal conductivity and shear viscosity are two important transport properties of dusty plasma. In dusty plasma asymmetric ion flow towards the sheath gives rise to a well known attractive oscillatory wake potential. The effect of ion flow induced wake potential and external magnetic field on thermal conductivity and shear viscosity in strongly coupled dusty plasmas have been reported in the present paper. Green-Kubo formalism along with Langevin dynamics simulation has been used to estimate thermal conductivity and shear viscosity of strongly coupled dusty plasma in presence of external magnetic field and attractive wake potential super-imposed with repulsive Debye-Hu¨ckel potential for a wide range of Coulomb coupling parameter (Γ), screening parameter (κ), neutral pressure (Nn) and magnetic field B. The study gives interesting results of transport properties of strongly coupled dusty plasma system.