Comparative study of component erosion for electromagnetic and electrothermal launchers

The electrothermal launcher SIRENS has been used to study the erosion of critical components (rails and insulators) of plasma-driven launchers. SIRENS can produce high-density (>10/sup 25//m/sup 3/) low-temperature (1-3 eV) plasma, formed by the ablation of the insulator (Lexan), with currents up to 100 kA. The incident heat flux varies between 2 and 90 GW/m/sup 2/ over 100 mu s duration, for input energies of 1-10 kJ. Erosion studies have been performed on several insulators, pure and coated metals, alloys, and several graphite grades. The fraction of the total incident energy transmitted to the eroded surface varies from 12 to 30% for the materials tested and decreases to 5-7% as the incident energy fluence increases. Such reduction in erosion for a given incident fluence is due to the vapor shield effect. The scaling law for the energy transmission factor through the vapor shield layer was obtained for the exposed materials.<>