Contributions to Plasma Physics最新文献

Effects of rippled electron density, the intensity of the laser beam, and the refractive index on the second harmonic generation of super-Gaussian pulses in inhomogeneous plasmas are investigated. Using the magnetic field of the laser beam and the quiver velocity of the electrons, the second harmonic nonlinear ponderomotive force is obtained. This nonlinear force pushes electrons which generates a space-charge force and nonlinear electron velocity. This leads to the nonlinear current density. Using the linear and nonlinear current densities and Maxwell's equations, the equation of the second harmonic electric field is obtained. Results show that by increasing the laser intensity and the amplitude of the ripped electron density, the absolute value of the second harmonic electric field amplitude increases. By increasing the refractive index of the plasma, the amplitude of the second harmonic wave decreases.

EMEC waves driven by kinetic anisotropies and suprathermal particles are expected to play an important role at dissipative scales in the solar wind and planetary magnetospheres. Moreover, the correlation of EMEC waves with electric field magnitude and direction can be a tool to probe the inner magnetosphere. Thus, in this manuscript, we present the study of EMEC waves driven by temperature anisotropy in bi-Kappa distributed space plasmas in the presence of a parallel DC electric field. The dispersion equation bearing the influence of electric field and suprathermal particles followed by the analytical expressions for wave frequency and wave growth rate is derived. The general dispersion equation is solved numerically to unveil the effect of suprathermal particles, temperature anisotropy, and the magnitude of the electric field on growth rate as well as the domain of unstable wave numbers, and the obtained numerical outcomes are compared with those of the bi-Maxwellian model. Moreover, the maximum growth rates for EMEC waves have also been obtained.

The hydraulic-electric pulsed discharge(HEPD) rock-breaking technology is a new high-efficiency technology that generates plasma shock waves to rupture rocks. Since the plasma channel formation mechanism involved in HEPD rock-breaking technology is difficult to describe, there are fewer theoretical models of this technology. This paper establishes a HEPD plasma model, which integrally considers the mutual coupling between five physical fields. The multi-physical field model realizes the whole process of plasma channels, breakdown channels, plasma shock waves, and plasma shock wave rock-breaking during the HEPD. The changes in mass fraction, density, and diffusion flux of relevant elements in the electrochemical reaction equation of the plasma channel are comprehensively analyzed. The obtained plasma multiphysics field model shows that the interpenetration of charged ions forms the breakdown channel and plasma channel. The anion number density is related to the H- number density, and the decrease in H- number density is due to the fact that the energy in the plasma channel is not sufficient to satisfy the relevant chemical equations to continue the collision reaction. The damage to the rock by the plasma shock wave takes the form of a gradual spreading of the plasma shock wave from the center of the rock to the edges, which leads to rock fragmentation. The model has the potential to establish a link between HEPD rock-breaking parameters and the efficiency of HEPD rock-breaking, which could provide a practical way for the development and parameter optimization of hydraulic-electric pulsed discharge rock-breaking tools.

This paper examines the impact of different $��L�-�\pi �$ type external matching networks on the discharge characteristics of dual-frequency capacitively coupled plasma. A nonlinear global model is employed to analyze the discharge of dual-frequency capacitively coupled argon plasma, with a low frequency of 8 MHz and 60 W and a high frequency of 100 MHz at 10–80 W. Discharge voltage waveforms, current waveforms, and emission spectra of the plasma were measured, while electron density and electron temperature were determined using the Boltzmann method. The electron density and electron temperature are utilized as input parameters for the nonlinear global model, while the plasma discharge is simulated with a fixed low-frequency radio frequency (RF) source power (60 W) and a varied high-frequency RF source power ranging from 10 to 80 W. The results indicate that the plasma discharge current, sheath capacitance, plasma resistance, plasma inductance, and the ratio of stochastic heating to Ohmic heating increase, while the sheath thickness decreases with increasing power. It is also found that the fundamental frequency current as well as 12th and 13th harmonic currents in the plasma are caused by the matching network and the nonlinear interaction between the sheath and the plasma. An optimal matching network can be designed to eliminate the effects of the harmonics and to meet industrial requirements for discharge uniformity.