XUV 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 XUV (/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 XUV coated (98% 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. An examination of the far and near zone 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 a homodyne system 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. The electron-neutral collision frequency and electron density are calculated from the amplitude and phase of the transmitted and reflected signals.