An investigation of mechanisms of initiation of Laser Supported Absorption (LSA) waves

Additional experimental results of a study of LSA-wave initiation processes are reported. The first measurements of delay time to initiation on nonmetallic materials are presented. In metallic studies, target emission of electrons from aluminum 2024, lead, and tungsten surfaces were recorded at atmospheric pressure prior to LSA-wave initiation. No surface damage was observed on the tungsten surface at 2000X in SEM inspections after irradiation, while lead and aluminum exhibited defect-oriented damage. Time-resolved spectroscopy experiments with aluminum 2024 revealed a dramatic drop in the ionized aluminum vapor emissions above the air pressure threshold for LSA-wave initiation (5-10 torr at 3.2 x 10 to the 8th power watt/cm squared).