摘要: A photoinitiated pulsed chemical laser has been developed for laser effects studies. This laser has produced 292 joules at 2.8 micrometers (HF) and 144 joules at 3.8 micrometers (DF). The threshold conditions for forming absorbing... 展开 A photoinitiated pulsed chemical laser has been developed for laser effects studies. This laser has produced 292 joules at 2.8 micrometers (HF) and 144 joules at 3.8 micrometers (DF). The threshold conditions for forming absorbing plasmas at atmospheric pressure have been extensively studied for both wavelengths and for seven materials. These thresholds have been measured in terms of both irradiance and fluence requirements. After forming a laser-supported absorption wave, the resulting plasma couples energy back to the target itself. For the conditions studied, all metal targets absorb a nearly constant energy above the plasma threshold. The plasma does spread radially, however, and the resulting spatial heating profile has been measured by inverting the time-dependent temperature at r=0. These measurements largely agree with measurements of thermal coupling to several targets of varying diameter and with both HF/DF radiation. Measurements of mass loss and impulse show a threshold dependence. In addition, the specific impulse and mass loss always have a maximum value at a particular laser irradiance. at 10.6 microns (CO2), the plasma spreading magnitude has been measured as a function of laser delivered energy. A theoretical study of target melting and vaporization indicates that efficient melt removal can occur at high intensities. This occurs because high surface temperatures lead to vaporization. 收起