Fundamental Plasma Physics最新文献

In this paper we report on the dynamics of a plasma oscillator forced by a non-sinusoidal wave function, which is modeled by a six-parameter nonhomogeneous second-order ordinary differential equation. We keep four of these parameters constant, and investigate the dynamics of this system by varying other two parameters, namely $A$ and $\omega$, which are related to the amplitude and the angular frequency of the components of a Fourier series consisting of an expansion of cosine functions, that represents the external forcing. We investigate points in the two-dimensional $(\omega ,A)$ parameter-space of the forced plasma oscillator, with the dynamical behavior of each these points being characterized as regular or chaotic, depending on the magnitude of the largest Lyapunov exponent. Then we show that this parameter-space reveals regions of occurrence of the multistability phenomenon in the system. Properly generated bifurcation diagrams confirm this finding. Basins of attraction of coexisting periodic and chaotic attractors in the phase-space are presented, as well as the coexisting attractors themselves.

Ultra-intense laser-plasma wakefield accelerator possess several superior properties compared with the traditional radio-frequency accelerators. These characteristics include femtosecond duration, micro-source size, and ultra-dense beam density, result in highly advantageous for various important applications. In this paper, we reviewed the generation of ultra-intense and high charge electron beam based on laser-plasma acceleration and its nuclear applications in Shanghai Jiao Tong University, including the production of 10 s nC charge beams, the generation of ultra-high flux neutron source on the order of 10¹⁹ n/cm²/s, and the excitation of nuclear isomers with the peak efficiency on the order of 10¹⁵ particle/s. This laser driving ultra-dense electron source, in conjunction with the plasma environment, presents immense potential in addressing critical problems in astrophysics, and facilitating various nuclear applications. Based on above progress in nuclear astrophysics, a new research plateform about laboratory astrophysics with a 2.5 PW laser will be constructed in TDLI institute.

This work demonstrates the application of DBD plasma-based exciplex UV technology for surface modification of natural fibres. KrCl* (222 nm) and XeI* (253 nm) exciplex lamps have been developed and characterized in terms of the applied voltage, applied frequency, gas pressure, and absolute UV light intensity. The measured radiated intensities are 2.45 mW/cm² and 1.91 mW/cm² for 222 nm and 253 nm exciplex lamps, respectively. The change in physicochemical properties such as tensile strength, weight loss, wettability, surface morphology, and chemical composition, are evaluated using different characterization techniques ̶ like Contact Angle Goniometry, Thermogravimetric Analysis (TGA), Attenuated Total Reflectance-Fourier Transform Infrared Spectroscopy (ATR-FTIR), Field Emission Scanning Electron Microscopy (FE-SEM), and Energy Dispersive X-ray (EDX) analysis, etc. The results are compared with untreated fibres to see the effect of different doses of UV₂₂₂ and UV₂₅₃ on the different properties of fibres. It is inferred that the exciplex UV₂₂₂ treated fibres have a higher concentration of different polar groups (− OH, − COOH, etc.). Much improvement in the dyebath ability of the natural fibre is achieved using a 222 nm exciplex light source, which reduces the dye concentration in the textile effluents and improves the dye adhesion to the fibre. It has been found that the fibre's hydrophilicity and dye bath capabilities have improved significantly.

For a wide range of plasma applications across diverse fields, a comprehensive understanding of the plasma-wall interaction mechanism is indispensable due to its inherent connection with confined plasma. This work compilation delves into the Kinetic Trajectory Simulation (KTS) method for the interaction of multi-component magnetized plasma with wall, specifically focusing on its implications for the tungsten wall sputtering model. In the evolution of the 1d3v (one dimensional spatial coordinates and three dimensional velocity coordinates) KTS method, the coupled set of kinetic equations has been solved under specified boundary conditions which yields results of higher accuracy. At the particle injection boundary, we have assumed the velocity distribution function of particle species to be cut-off Maxwellians, meeting essential requirements for plasma-wall transition processes: quasineutrality, sheath edge singularity, continuity of macroscopic fluid variables, and the kinetic Bohm sheath condition. The kinetic Bohm sheath condition, a fundamental criterion for plasma sheath formation, is extended for multi-component plasmas, accounting for the cut-off Maxwellian distribution of negatively charged particles. A comparative study of the kinetic Bohm sheath condition for cut-off and Boltzmann distributions reveals a deviation of less than 2.0% in magnitude. The concentration ratio of positive or negative ion species and the presheath side electron temperature influence various plasma-wall transition characteristics, including wall potential, Debye sheath thickness, particle densities, potential distribution, particle fluxes towards the surface, particle drift velocity, phase-space trajectory evolution, and physical sputtering of the tungsten surface. Although lighter ions possess higher energy when striking the surface, the physical sputtering yield of the tungsten surface is greater for heavier ions due to their lower threshold energy and larger collision cross-section. Furthermore, a comparative study of plasma-wall transition properties using kinetic and fluid approaches demonstrates qualitative similarities, with a notable deviation of approximately 4.0% in the magnitude in the vicinity of the material surface.

This paper presents a new Monte Carlo algorithm intended for use in orbit following Monte Carlo codes (OFMC) to describe resonant interaction of ions with Radio Frequency (RF) waves in axi-symmetric toroidal plasmas. The algorithm is based on a quasi-linear description of the wave–particle interaction and its effect on the distribution function of a resonating ion species. The algorithm outlined in the present paper utilises a two-step approach for the evaluation of the Monte Carlo operator that has better efficiency and a stronger convergence than the standard Euler–Maruyama scheme. The algorithm preserves the reciprocity of the diffusion process. Furthermore, it simplifies how the displacement of the resonance position, as a result of wave–particle interaction, is accounted for. Such displacements can have a noticeable effect on the deterministic part of the Monte Carlo operator. The fundamental nature of guiding centre displacements of resonant ions as a result of wave–particle interaction is reviewed.

Magneto-inertial range dominated by magnetic helicity has been studied using results of the numerical simulations, laboratory measurements, solar, solar wind, and the Earth’s and planets’ magnetosphere observations (spacecraft measurements). The spectral data have been compared with the theoretical results based on the distributed chaos notion in the frames of the Kolmogorov–Iroshnikov phenomenology. The transition from magnetohydrodynamics to kinetics in the electron and Hall magnetohydrodynamics, and in a fully kinetic 3D approach, as well as in the solar wind, solar photosphere, and at the special events (reconnections, Kelvin–Helmholtz instability, isolated flux tube interchanges, etc.) in the magnetosphere of Earth, Saturn, Jupiter, and Mercury has been also discussed.

A unified linear theory that includes forced reconnection as a particular case of Alfvén resonance is presented. We consider a generalized Taylor problem in which a sheared magnetic field is subject to a time-dependent boundary perturbation oscillating at frequency ${\omega }_0$. By analyzing the asymptotic time response of the system, the theory demonstrates that the Alfvén resonance is due to the residues at the resonant poles, in the complex frequency plane, introduced by the boundary perturbation. Alfvén resonance transitions towards forced reconnection, described by the constant-psi regime for (normalized) times $t\gg S^{1/3}$, when the forcing frequency of the boundary perturbation is ${\omega }_0\ll S^{-1/3}$, allowing the coupling of the Alfvén resonances across the neutral line with the reconnecting mode, as originally suggested in Uberoi and Zweibel, (1999). Additionally, it is shown that even if forced reconnection develops for finite, albeit small, frequencies, the reconnection rate and reconnected flux are strongly reduced for frequencies ${\omega }_0\gg S^{-3/5}$.

The famous Hill’s solution describing a spherical vortex with nested toroidal pressure surfaces, bounded by a sphere, propelling itself in an ideal Eulerian fluid, is re-derived using Galilei symmetry and the Bragg–Hawthorne equations in spherical coordinates. The correspondence between equilibrium Euler equations of fluid dynamics and static magnetohydrodynamic equations is used to derive a generalized vortex type solution that corresponds to dynamic fluid equilibria and static plasma equilibria with a nonzero azimuthal vector field component, satisfying physical boundary conditions. Separation of variables in Bragg–Hawthorne equation in spherical coordinates is used to construct further new fluid and plasma equilibria with nested toroidal flux surfaces, featuring respectively boundary vorticity sheets and current sheets. Finally, the instability of the original Hill’s vortex with respect to certain radial perturbations of the spherical flux surface is proven analytically and illustrated numerically.