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.
The early expansion of the plasma produced by the laser irradiation of a polyethylene foil in vacuum has been studied by making time resolved observations at right angles to the target normal. Spectral line emission has been scanned to give the spatial distribution of the ion species carbon I-VI. The lines observed are Doppler broadened by the ion streaming motion, and this broadening has been interpreted to give velocity as a function of time and of distance from the target normal. For one ion species (carbon V) a reconstruction has been made of the ion trajectories. Velocities of 2-3*107 cm s-1 have been deduced from Doppler shifts observed parallel to the target normal and are in agreement with previous time of flight measurements.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.