Microwave reflections from a VUV laser produced plasma sheet

Summary form only given. A 20 ns vacuum Ultra-Violet (VUV) laser pulse is used to create a plasma sheet in an organic gas. A bistatic antenna system is used for transmitting and receiving X-band microwaves which interact with the plasma. Reflected signals are measured for amplitude and phase analysis. Amplitude and phase shifts are compared to an aluminum conducting sheet placed in the same position as the plasma. The working gas is tetrakis (dimethylamino) ethylene (TMAE) with an ionization energy of 6.1 eV. The ionizing source is an excimer laser (W/sub max/=300 mJ) operating at 193 nanometers (6.4 eV). The laser beam is transformed into a sheet using VUV thin-film matched lenses. A plasma sheet with a peak density of 2.5/spl times/10/sup 13/ cm/sup -3/ and T/sub e/=0.3 eV is formed with dimensions 0.7-5 cm/spl times/7.8 cm/spl times/30 cm. Additional measurements of transmitted signals are utilized to determine plasma density and collision frequency. A finite-element computer model of the plasma profile to determine microwave transmission and reflection levels has been developed to optimize reflected signal levels as a function of density and thickness and to interpret experimental results. Comparison between the experimental results and the model show that this system is attractive for use as a microwave reflector. In addition, studies are being carried out to explore plasmas created with air components with this microwave.