A spectroscopic study of the plasma generated by a laser from polyethylene

Abstract

This paper describes a spectroscopic study of the plasma produced when a giant pulse ruby laser of 5 J energy and 17 ns duration is focused into a 0.3 mm diameter spot on a polyethylene target in vacuum. Quantitative measurements of spectral intensities in the range from 20 Angstrom to 6000 Angstrom have yielded estimates of the electron and ion densities, the electron temperature and the streaming velocities of the ions. From these results it is estimated that the electron temperature, the ionization energy, the energy lost by radiation and the energy of recoil of the target account for only about 10% of the incident laser energy. The ion kinetic energy accounts for 70% of the incident energy with an experimental uncertainty of ± 70%. It is calculated that there are about 10¹⁶ ions produced by the laser beam striking the target. It is shown that the electrons contained in the plasma expanding away from the target cool adiabatically. In the course of the work there have been identified several new lines hitherto unclassified.