Self-channeling of a powerful microwave beam in a preliminarily formed plasma

Abstract

The self-channeling of a high power ( 500 MW) sub-nanosecond microwave beam in the plasma formed by a neutral gas (>10 3 Pa) ionization was demonstrated by Shafir et al. [Phys. Rev. Lett. 120, 135003 (2018)]. In the present research, this effect is observed and studied in detail in a plasma, preliminarily formed by an rf discharge, in a low (<150 Pa) pressure gas. The results of analytical modeling and numerical particle-in-cell simulations show that ionization-induced channeling can be realized at a significantly lower power of the microwave beam and gas pressure if the preliminarily formed plasma is radially non-uniform with minimal on axis density. Published by AIP Publishing. https://doi.

Experiments Designed to Study the Non-Linear Transition of High-Power Microwaves through Plasmas and Gases

“…A matrix of Neon lamps placed on plane perpendicular to the microwave beam axis inside or outside the chamber, is also used to produce a two-dimensional spatial integrated distribution of the electromagnetic beam power. All our experiments so far have been performed in this chamber [35,[42][43][44].…”

Wakefield excitation by a powerful sub-nanosecond 28.6 GHz microwave pulse propagating in a plasma filled waveguide

“…Theoretical research and numerical modeling [2][3][4][5][6][7][8][9][10][11][12] predict that wakefields, ionization selfchanneling, acceleration of electrons, positively charged plasma, etc., may result from such interactions. Indeed, our recent research on high power ( 500 MW) and ultra-short ($0.6 ns) X-band (9.6 GHz) focused microwave beam interactions with gas 13,14 and preliminarily formed plasma 15 showed beam propagation along a distance of several Rayleigh lengths inside a channel with an over-dense plasma boundary. The latter is the result of the enhanced impact ionization of neutrals at the periphery of the beam compared to the ionization on the beam axis where the electron's oscillatory energy can exceed 10 keV.…”

“…20 For instance, the ponderomotive force, produced by a 1 GW, 28 GHz microwave pulse propagating in a circular $0.7 cm radius waveguide, is almost 40 times larger than that realized in earlier experiements. [13][14][15] In the present paper, the experimental study of a recently built SR-BWO, which generates a 28.6 GHz, $0.4 ns, 1.2 GW microwave pulse, is presented. The parameters of a flashboard plasma source 21 and a cylindrical waveguide with walls transparent to plasma are experimentally determined and used in numerical simulations of the pulse propagation along this plasma filled waveguide.…”