Theoretical analyses on the one-dimensional charged particle transport in a decaying plasma under an electrostatic field

Abstract

The spatiotemporal evolutions of a one-dimensional collisionless decaying plasma bounded by two electrodes with an externally applied electrostatic field are studied by theoretical analyses and particle-in-cell (PIC) simulations with the ion extraction process in a laser-induced plasma as the major research background. Based on the theoretical analyses, the transport process of the charged particles including electrons and ions can be divided into three stages: electron oscillation and ion matrix sheath extraction stage, sheath expansion and ion rarefaction wave propagation stage and the plasma collapse stage, and the corresponding criterion for each stage is also presented. Consequently, a complete analytical model is established for describing the ion extraction flux at each stage during the decaying of the laser-induced plasmas under an electrostatic field, which is also validated by the PIC modeling results. Based on this analytical model, influences of the key physical parameters, including the initial electron temperature and number density, plasma width and the externally applied electric voltage, on the ratio of the extracted ions are predicted. The calculated results show that a higher applied electric potential, smaller initial plasma number density and plasma width lead to a higher ratio of the extracted ions during the first stage; while in this stage, the initial electron temperature shows little effect on it. Meanwhile, more ions will be extracted before the plasma collapse once a higher electric potential is applied. The theoretical model presented in this paper is helpful not only for a deep understanding to the charged particle transport mechanisms for a bounded decaying plasma under an applied electrostatic field, but also for an optimization of the ion extraction process in practical applications.