Production of Energetic Highly Ionized Plasma by Laser Irradiation of Lithium Hydride Pellets

Abstract

Spherical LiH pellets have been utilized as targets for high‐power, fast‐rising, nanosecond laser pulses. Using different pulse lengths, $\tau$ , it has been shown that the pellets behave as a continuous source of energetic plasma during a time $t_l$ (called “interaction time”) depending on the pellet size and on the laser flux density. For pellets 50$\mu$ in diameter and flux densities of ${\text{1.5\hspace{0.17em}×\hspace{0.17em}10}}^{12}{\mathrm{W/cm}}^2{\mathrm{,\hspace{0.17em}t}}_l$ is 20 nsec; the degree of ionization approaches 100% (about ${10}^{16}$ ions in the plasma) and the root‐mean‐square expansion velocity is ${10}^7\hspace{0.17em}\mathrm{cm/sec;}$ the total plasma energy is about 0.5 J with an energy transfer efficiency of 10%. The general behavior of the burning process agrees with the extension to small pellets of the theoretical model developed for the case of massive targets.