Pressure dependence of plasma structure in microwave gas breakdown at 110 GHz

Abstract

Recent studies of 110 GHz microwave discharges in air at atmospheric pressure have demonstrated formation of a large array of quarter-wavelength-spaced plasma filaments. Here we present measurements showing that as pressure is decreased from atmosphere to a few torr, the discharge transitions from a well-defined array to a smeared-out array and finally to a diffuse plasma. Despite the distinct nature of breakdown phenomena at high microwave frequencies, the pressure dependence of the breakdown threshold field is seen to follow a Paschen-type curve. Data for air and argon at 110 GHz are compared with previous low-frequency data.

Gyrotron Development for High Power THz Technologies at IAP RAS

“…As example, impressive results of microwave discharge investigation initiated by powerful 0.1 THz gyrotron are obtained at MIT group (Massachusetts Institute of Technology, USA) [23,24]. At the same time, the experiments at the Institute of Nuclear Physics (Novosibirsk, Russia) demonstrated the breakdown in air under atmospheric pressure, which was produced by radiation of a 1.2-2.5 THz FEL with peak power of up to 1 MW, pulse duration of~100 ps, and a pulse repetition rate of up to 12 MHz [25,26].…”

A possibility of remote detection of air breakdown in a focal spot of microwave beam using reflected signal

“…Two different frequencies f 1 = 110 GHz and f 2 = 670 GHz where considered in simulations which corresponds to the frequencies of gyrotrons used in MIT experiments [5] and in IAP-UMD experiments [6], respectively. Two different scenarios of breakdown were studied.…”

Joule-heating-supported plasma filamentation and branching during subcritical microwave irradiation

“…[1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17][18][19][20] In recent years, a plasma filamentation was reported to occur during microwave irradiations. Hidaka et al 1 experimentally obtained a filamentary plasma by lens focusing of the microwaves generated by a pulsed 1.5 MW, 110 GHz gyrotron.…”