VUV laser plasma formation and microwave agile mirror/absorber

Summary form only given, as follows. Agile microwave reflectors are of interest as potential replacements for large phased arrays on mobile crafts. Preliminary measurements of microwave reflection from a VUV (/spl lambda/=193 nm) excimer laser produced plasma (W=20 mJ, /spl tau/=17 ns) in an organic gas (TMAE). This work investigates the reflection of X-band microwaves at oblique incidence by a planar TMAE sheet of dimensions: 8 cmW/spl times/4-15 mm H/spl times/20-cm L, produced by a new (W=300 mJ) excimer laser. Fast Langmuir probes are used to determine the laser produced plasma density and temperature profiles, at TMAE neutral pressures in the 25-60 m Torr range. 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. 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 temperature and density is obtained with Langmuir probes and compared with measurement based on microwave transmission through the plasma. Reflected and transmitted signals are compared with those from a calibration aluminum sheet of the same dimensions as the plasma.