Nanosecond timescale plasma formation in pressurized gases in the presence of high-intensity electromagnetic field

TYPEPlasma Physics
Speaker:Leonid Beilin
Affiliation:Physics Department, Technion
Date:09.12.2014
Time:10:30
Location:Lidow 620
Remark:PhD seminar
Abstract:The main objectives of the present research were to conduct experimental and numerical studies of plasma formation during microwave energy release from high-power microwave pulse compressors with interference plasma switches. It was found that the plasma has the form of filaments with initial length of ~1 mm and diameters of 0.2-0.6 mm expanding along the RF electric field with the typical velocity ~5×107 cm/sec. Nanosecond-scale dynamics of plasma density was obtained by analyzing the shape of He I spectral lines, triplet 2p-4d (4471.5 Å) and triplet 2s-3p (3888.65 Å). Experimental data showed an evident correlation between the rise time of the plasma density and the peak power of the microwave output pulse: the density rise is steeper when the compressor output power is higher. Numerical simulations yielded a good agreement with measured output pulse peak power and waveform and showed that the rise of the output power in time correlates with the rise of the plasma density. In addition, the compressor operation with an alternative, Magic-tee based plasma switch was studied. It was shown that such compressor allows for the frequency variation without mechanical tuning.