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 P_a and the ablated mass rate, for a given pellet radius r_a, 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 P_a and r_a; consequently, if the time laws P_a(t) and r_a(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).