One-dimensional theoretical analysis on charged-particle transports in a decaying plasma with an initial plasma–electrode gap

Abstract An analytical model for describing the charged-particle transport in a wall-confined laser-induced decaying plasma is established under an external electrostatic field, focusing on the effects of the initial plasma–electrode gap (IPEG) that exists in applications such as laser isotope separation. This newly developed analytical model is validated by particle-in-cell simulations and the experimental scaling relation, and can also be reduced to its previously published counterpart that did not consider IPEGs. Based on this analytical model, the influences of different IPEG spacings on the characteristics of the whole ion extraction process are studied. The results show that the ion extraction ratios at the endpoints of the first and second stages both decrease with increasing IPEG spacing, while the corresponding time durations for the first two stages show a non-monotonous variation trend. The specific ion extraction time, defined as the ion extraction time per unit mass to comprehensively characterize the ion extraction efficiency, increases generally with the increase of IPEG spacing. This study not only provides further insight into the fundamental physical processes in a wall-bounded decaying plasma under an externally applied electrostatic field, but also offers useful theoretical guidance for optimal designs of geometrical and operating parameters in laser isotope separation processes.