The ablative, quasisteady expansion flow of a plasma generated by impinging a pellet by an intense light ion beam pulse is analysed. Profile of beam density and velocity and plasma density, velocity, and temperatures as functions of the radius are obtained from the analysis. The ablation pressure Pa and the ablated mass rate, for a given pellet radius ra, are found as functions of both the beam energy per nucleon E0 and the current intensity I0. The results may be used for determining the instantaneous E0 (or I0), for a given I0 (or E0), required to generate given values of Pa and ra; consequently, if the time laws Pa(t) and ra(t), for optimal pellet compression, are obtained independently, the results yield the light ion beam energy history E0(t) I0(t) for a given or (I0(t) for E0(t) given).