Abstract: The dynamics conditions of laser-produced plasmas have been analyzed and studied in detail using JB19 computer code, a non-LTE radiative hydrodynamic code of one-dimensional geometry. Using the code we can simulate the interactions of laser beams with targets. When a laser beam of 0.53μm with pulse duration of 450ps and intensity of 1014W/cm² for single-sided irradation (5×10¹³W/cm² for double-sided irradiation) is used to irradiate 750A selenium foil deposited on a 1500A formvar substrate, JB19 simulation predicts that the smooth electron density profile is over a distance of 100μm, the electron temperature Te and ion temperature T. are 0.9keV and 0.5keV respectively, electron density Ne, is about 3-5×10²⁰cm^-3. abundance of Ne-like ions is more than 25% and the lasting time of smooth density profile is over 100ps. When a laser beam of 1.06μm with a pulse duration of Ins, intensity of 7 ×1012W/cm² and total energy of 840J is used to irradiate Ge target of 500A deposited on 1000A formvar. JB 19 simulati o gives the results of ^N_t=2-3×1020cm^-3, T_t =7-8 × 10⁶K. When a laser beam of 1.06μm with a pulse duration of 2ns irradiates Cu target, we have the results of N_e = 1-2 × 1020cm^-3. T=5 × 10₆K and abundance of Ne-like ion 15-20%.
Computational results show that for a target of a medial Z element, irradiated by a laser beam of 1.06μm, a power density of 0.7-1.4× 10¹⁵W/cm² and a pulse duration of 1~2ns are necessary to demonstrate 3p-3s population inversion and certain gain of soft X-ray laser.