Non-equilibrium transport of charged particles in a wall-confined decaying plasma under an externally applied electric field

Abstract

In this work, non-equilibrium transport processes of the charged particles in a plasma confined between two parallel plates with externally applied electric fields are analyzed with the charged-particle transport of laser-induced plasma as the major research background. The theoretical analyses of the transient responses of the electrons to the externally applied electrostatic fields are conducted under different initial distributions of the plasma parameters including the loss and the oscillation frequency of the electrons in the transient oscillation process, and the critical value of the electron number density for the initial electron temperature effect of the ion transport. The particle-in-cell (PIC) modeling results are consistent well with the theoretical predictions. Based on the preceding results, the PIC simulations of the ion extraction process by imposing a radio-frequency (RF) electric field on the electrostatic field are conducted. The modeling results indicate that there exists an obvious resonance phenomenon in the ion extraction process, in which the ion extraction flux is significantly increased. Under a certain operating condition, the ion extraction time at the RF resonance point is reduced to 5.8% of its original value with only an electrostatic field. Further analysis shows that, on the one hand, the electrons will be heated by the externally applied RF electric field, and thus, the propagation velocity of the ion rarefaction wave will be increased; on the other hand, the electron oscillations will be enhanced, resulting in losing more electrons in the electron oscillation process and a higher plasma potential, which ultimately leads to a higher ion extraction flux and a shorter ion extraction time.