Contributions to Plasma Physics最新文献

In the pedestal region, electromagnetic effects affect the evolution of micro-instabilities and plasma turbulence. The transport code Soledge3X developed by the CEA offers an efficient framework for turbulent 3D simulation on an electrostatic model with a fixed magnetic field. The physical accuracy of the model is improved with electromagnetic induction, driven by the local value of the parallel component of the electromagnetic vector potential $��A_{\parallel }�$, known from Ampère's law. It is solved implicitly in a coupled system with the vorticity equation on the electric potential $��\Phi �$. The consequence is a basic electromagnetic behavior in the form of shear Alfvén waves. A finite electron mass prevents unphysical speeds but requires solving for the time evolution of the parallel current density $��j_{\parallel }�$ in the generalized Ohm's law. This term can be analytically included with little computational overhead in the system on $��\Phi �$ and $��A_{\parallel }�$ and improves its numerical condition, facilitating the iterative solving procedure. Simulations on a periodic slab case let us observe the predicted bifurcation of the wave propagation speed between the Alfvén wave and the electron thermal wave speeds for varying perpendicular wavenumbers. The first results on a circular geometry with a limiter attest to the feasibility of turbulent electromagnetic scenarios.

In this work, we prepare a simulation framework for a high-accuracy numerical study of electron–ion temperature relaxation in nonideal (strongly coupled) plasmas. The existing relaxation rate theories require either parameter selection or some pre-knowledge of the electron–ion correlation functions and effective interaction potentials. This makes non-equilibrium classical and quantum molecular dynamics simulations a crucial stage in the study of energy transfer rates. We begin by revisiting the classical molecular dynamics simulations of a system of equally charged particles with different masses on a neutralizing background. We accurately simulate this simple ab-initio (parameterless) system with controlled precision in terms of number of particles, mass ratio, and energy convergence. The predictions for the equally charged system are compared to the previous simulations and theories, which are reproduced with higher accuracy. We also perform a series of classical molecular dynamics simulations of the system of oppositely charged particles with the corrected Kelbg potential based on the quantum statistical approach. We analyze the differences and similarities between the same-charge and opposite-charge systems. Some remarks about the forthcoming application of quantum simulations with the help of WPMD or WPMD-DFT methods are given.

PIV images of a dusty plasma (obtained after averaging 50 images) flow in a horizontal plane at different vertical locations of confined dust grains in a potential well. (a) Topmost dust grains (b) 2mm below the topmost dust grains plane, (c) 4mm lower than the topmost dust grains plane, (d) 6mm lower than the topmost dust grains plane. Fig. 5 of the paper by Mangilal Choudhary. https://doi.org/10.1002/ctpp.202300072

This study monitored the growth, biochemical, and developmental responses of Datura seedlings to the cold plasma. The effectiveness of different methods was explored to break seed dormancy. Germinating seeds were exposed to corona discharge plasma for different durations, including 0, 60, 120, 180, and 300 s. A procedure consisting of illumination with a red light (20 min), soaking in water (4°C for 48 h), and removing a part of Testa was the best method for breaking seed dormancy. The plasma treatments of 60, 120, and 180 s improved the plant growth performance, while this trait was declined in response to the plasma treatment of 300 s. The proline concentrations in both root and leaves displayed a linear significant upward trend in response to the plasma treatments. The plasma for 180 s was the most effective method to increase tropane alkaloids. With increasing the exposure time from 60 to 300 s, the leaf soluble phenols were linearly enhanced. The plasma application for 60, 120, and 180 s significantly augmented total protein concentration, while the exposure of seeds for 300 s significantly diminished it. The highest amounts of photosynthetic pigments (chlorophylls and carotenoids) were recorded in the seedlings treated with plasma for 120 and 180 s. The activities of enzymatic antioxidants (catalase and peroxidase) showed a similar upward trend to that of proline. The plasma priming also improved the phenylalanine ammonia-lyase activity (a secondary metabolism index). Further investigations are needed to optimize plasma parameters and understand the involved mechanisms to maximize its benefits while minimizing potential risks.

In this article, we would like to pay tribute to Gabor Kalman, outlining his contribution to a model widely used in dense plasma physics: the high-temperature Thomas–Fermi model. The approach of Ruoxian Ying and Kalman relies on the separation of the bound and free electrons, a physically reasonable definition of the bound electrons, a description of the source density in the Poisson equation through the electron–ion and ion–ion pair correlation functions and a determination of the degree of ionization from the minimization of the total free energy. We also report on different approximations of the function $��\Phi �$, which is a cornerstone of the original Thomas-Femi model.

In this paper, a new model of the parallel transport in 2D drift-fluid turbulence codes is formulated as a 3-point model and benchmarked against SOLPS-ITER. The model allows for the existence of parallel temperature gradients and local recycling near the target. To realize this, the volume of the flux tube is split into two zones: (1) a connection zone extending from the outer midplane to the ionization zone entrance and (2) an ionization zone covering the remaining space until the sheath edge. By assuming a linear increase of the parallel particle and conductive heat fluxes in the connection zone, and assuming an ad-hoc relation for the electron pressure evolution, expressions for the plasma fields at the entrance of the ionization zone are obtained. The evaluation of the integral balances over the ionization zone leads to an implicit system in terms of the parallel fluxes. To benchmark the model, we compare with reference data from density, current and recycling scans for a flux tube with SOLPS-ITER. From these scans, one observes that the model predicts well the parallel particle flux in the density and recycling scans. Discrepancies that arise at higher densities for both the conductive heat fluxes and the required floating upstream potential are analyzed and partly explained by the superlinear evolution of the heat fluxes in the SOLPS-ITER simulations. It is concluded that the model can be used to construct the effective volumetric sink terms in 2D drift-fluid turbulence models.

In a fusion DEMOnstration reactor (DEMO)-relevant scrape-off layer plasma (SOL), whose collisionality is lower than in the SOLs of present-day tokamaks, kinetic effects are predicted to reduce the plasma heat conductivity along the magnetic field below the value obtained with the classical Spitzer–Harm model. As a part of ongoing efforts to improve the predictive capability of SOL heat transport calculations, we have implemented the non-local heat flux model proposed by [Luciani, Mora and Virmont, Phys. Rev. Lett. 51 (1983) 1664–1667] (here referred to as the LMV model) in the integrated SOL–divertor simulation code SONIC in order to account for the kinetic effect on the heat conduction due to the parallel streaming of rapidly moving particles. Our transport simulations for the Japanese demonstration tokamak reactor concept, JA DEMO, show that the LMV model yields a significantly reduced ion parallel conductive heat flux density both on the low- and high-field side of the upstream SOL. The heat flux obtained with the LMV model seems to be consistent with earlier kinetic simulations of tokamak ion transport. As a consequence of the reduced heat flux, a significant increase in the ion temperature and a decrease in the density have also been found over a broad area of the upstream SOL.

The collisions between neutral particles and plasma in the divertor region determine divertor detachment and heat flux to the target. However, the diagnostic of neutral particle information in the tokamak experiment is very lacking. To study the behavior of neutral particles in the boundary region flexibly and comprehensively, a two-dimensional kinetic neutral transport code based on Monte Carlo method is developed in this work. The code is applied to simulate the neutral particles in the boundary of EAST device. Firstly, the simulation results are compared with EIRENE using an identical plasma background, and good agreement is obtained. Secondly, the transport of methane and the corresponding hydrocarbon compounds is simulated using the developed code. The methane injection case is compared with the injection of carbon and deuterium molecule mixture gas (ratio 1:2) to investigate their impact on detachment and fueling. The simulation reveals that, compared to the direct carbon atom injection case, charge-exchange collision is the dominant collision of neutral methane (hydrocarbons), which suppresses divertor power radiation and plasma detachment while promoting the improvement of fueling efficiency.

Dust acoustic waves (DAWs) in plasmas are influenced by many plasma parameters, such as, ion temperature, electron number density, nonthermal and nonextensive parameters, and dust cyclotron frequency. The plasma system is described by plasma fluid equations. The Zakharov–Kuznetsov equation and instability growth rate of DAWs have been obtained by reductive perturbation method and small-$��k�$ expansion method, respectively. The effects of plasma parameters on the linear dispersion relation, phase velocity, amplitude, width, soliton energy, and three-dimensional instability of DAWs have been carried out. It is obvious that the incremental nonextensive (nonthermal) parameter leads to the shrinking (incremental) soliton energy and phase velocity. These results are useful for understanding dusty plasma dynamics with Cairns–Tsallis electrons in planetary rings.