Quasi-steady expansion of plasma ablated from laser-irradiated pellets

Abstract

The ablative, quasi-steady expansion of the spherical coronal plasma produced by irradiating an overdense pellet by a high-intensity laser pulse, is studied for large ion charge number Z;. The entire structure of the flow and its changes as the laser power is increased, are determined. The instantaneous power W required to generate a given ablation pressure Pa and pellet radius rB at any time is determined in terms of Z,-, ion mass m,, and critical density; the mass ablation rate is also found. If the time law PB {t) and (consequently) ra {t) for a desired optimal compression of the pellet are determined independently, the results allow one to obtain the laser power history W[t) = W[Ptl\t),rtt\t),Zj,ml,ne]. For a critical radius much larger than ra, most of the energy flows outward; this seems to invalidate known simple estimates of the relation W[Pa).