DocumentCode :
731270
Title :
Fast-frame optical imaging and time-resolved spectroscopy of plasma in a gas discharge-based switch of a microwave pulse compressor
Author :
Shlapakovski, Anatoli ; Beilin, Leonid ; Krasik, Yakov E.
Author_Institution :
Phys. Dept., Technion - Israel Inst. of Technol., Haifa, Israel
fYear :
2015
fDate :
24-28 May 2015
Firstpage :
1
Lastpage :
1
Abstract :
Summary form only given. Presently, mostly advanced microwave pulse compressors with plasma switches provide hundreds megawatt power in nanosecond pulses1. Nevertheless, in spite of significant progress in their development, no data existed on the nanosecond dynamics of the plasma formation under strong microwave fields in pressurized gases that ultimately determine a compressor´s output power. In this work, the evolution of the plasma formed in the S-band compressor was studied using fast-frame (2 ns) imaging and time-resolved spectroscopy. The compressor represented a rectangular waveguide-based cavity connected to an H-plane waveguide tee with a shorted side arm. The plasma discharge in the tee side arm was triggered by a Surelite laser. In experiments with optical imaging, the system was filled with dry air at up to 3·105 Pa pressure. It was found that the plasma appears as filaments with diameters of <;0.6 mm expanding along the RF electric field with the typical velocity of ~5·107 cm/s. For time-resolved spectroscopy, the system was filled with helium at 2-105 Pa pressure. The nanosecond dynamics of plasma density was obtained by analyzing the shape of He I spectral lines: triplet 2s-3p (3888.65 Å) and triplet 2p-4d (4471.5 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. The density reaches values of the order of 1016 cm3. Numerical simulations of the microwave energy release from the cavity with the appearance of the plasma yield a good agreement with measured output pulse peak power and waveform.
Keywords :
helium; numerical analysis; plasma density; plasma diagnostics; plasma filled waveguides; plasma simulation; plasma sources; plasma switches; time resolved spectra; H-plane waveguide tee; He; RF electric field; S-band compressor; Surelite laser; dry air; fast-frame optical imaging; gas discharge-based switch; helium spectral lines; microwave pulse compressor; nanosecond plasma density dynamics; nanosecond plasma formation dynamics; numerical simulations; plasma switches; rectangular waveguide-based cavity; time 2 ns; time-resolved spectroscopy; Microwave imaging; Microwave measurement; Microwave technology; Optical imaging; Optical waveguides; Plasmas; Spectroscopy;
fLanguage :
English
Publisher :
ieee
Conference_Titel :
Plasma Sciences (ICOPS), 2015 IEEE International Conference on
Conference_Location :
Antalya
Type :
conf
DOI :
10.1109/PLASMA.2015.7179776
Filename :
7179776
Link To Document :
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