VUV laser plasma formation and microwave agile mirror/absorber

Summary form only given. Agile microwave reflectors are of interest as potential replacements for large phased arrays on mobile crafts. Microwave reflection from an VUV(/spl lambda/=193 nm) excimer laser produced plasma (W=20 mJ, /spl tau/=17 ns) in an organic gas (TMAE: tetrakis-dimethylamino-ethylene) contained in a 22 mm/spl times/7 mm rectangular column, has been demonstrated. This work investigates the reflection of X-band microwaves at normal and oblique incidences by a planar TMAE sheet of dimensions: 9 cm W/spl times/2-7 mm H/spl times/10-20 cm L, produced by the same excimer laser. Suprasil VUV coated (96% transparent) lenses are used to generate the sheet laser beam profile. Both triple probes and reference probes are used to determine the 3-D laser produced plasma density and temperature profiles, at TMAE neutral pressures in the 25-150 mTorr range. The plasma diffusion during its lifetime is very small. Densities and temperatures in the ranges of n=5/spl times/10/sup 12/-2/spl times/10/sup 13/ cm/sup -3/ and T/sub e/=0.5-0.7 eV are obtained. An examination of the microwave reflection is carried out using X-band horns and rectangular guide apertures. The amplitude and phase of the transmitted and reflected microwave signals are measured using both homodyne and heterodyne systems with hybrid-tee mixers. A time history of the plasma and temperature density is obtained with Langmuir probes and compared with. a measurement based on microwave transmission through the plasma. Reflected and transmitted signals are compared with those from an aluminum sheet of the same dimensions as the plasma. Future plans for the agile mirror reflector and absorber are discussed.