High-power microwave energy coupling to nitrogen during breakdown

Abstract

A numerical solution of the Boltzmann equation for highpowered short pulse microwave breakdown in nitrogen Phys.Microwave energy coupling to nitrogen for breakdown conditions has been investigated. The experiments were performed in 25-Torr nitrogen using a 35-GHz l-,us microwave pulse focused to 33 kW /cm 2 . The plasma created during breakdown was observed to travel towards the source with a velocity of 4.6 X 10 6 cm/s. Spectroscopic measurements using a nitrogen-helium mixture indicate the average electron density over a 2-cm chord to be 4.4 X 10 12 cm~3, and the electron temperature to be 3.8 eV. Microwave cutoff was observed photographically, and suggests the peak electron density to be the collisional critical density. Computer simulations were also performed, and their results are in accord with the experimental results.

Spectroscopic temperature measurements of air breakdown plasma using a 110 GHz megawatt gyrotron beam

“…13,14 In particular, OES has been used to measure electron density and temperature when equilibrium models were assumed for discharges using a focused beam from a gyrotron in nitrogen. 15 However, to our knowledge, no measurements of plasma parameters using OES in nonequilibrium air plasmas using a gyrotron have been previously reported. OES measurement techniques do not perturb external electromagnetic fields and so can be used in situations where plasma dynamics are fast or electric fields are strong and are crucial to the spatial evolution of the plasma, as is the case in streamer formation in high frequency microwave breakdown.…”

Laser-driven vacuum breakdown waves

“…2 and Supplemental Material 38 ). Similarly to ionization waves in the gas discharge physics 8,9 , the interface propagation can be considered as a vacuum breakdown shock wave. The cushion plasma density eventually exceeds the relativistic critical density and the plasma screens the seed particles from the incident wave.…”

“…The cascade development is very similar to another physical phenomenon, namely, an avalanche ionization in a gas discharge 7 . Extensive studies of microwave breakdown in gases revealed complex discharge dynamics accompanied by plasma production and generation of gas breakdown waves 8,9 . The analogy between a vacuum pair production and a gas ionization, as well as between a vacuum breakdown via QED cascading and a gas breakdown has a deep physical origin 10-12 . Similar to gas discharges, where the self-sustained and non-self-sustained regimes are possible, there are also two types of QED cascades: the self-sustained QED cascades (or A (Avalanche)-type cascades 13 ), where the laser field provides the energy for cascading, there are also 'shower-like' cascades (or S-type cascades 13 ), where the cascade energy does not exceed the energy of the seed particles.…”

Active photometry of atmospheric compositions by microwave breakdown plasma spectroscopy

“…These models and techniques have been applied to more realistic environmental problems such as mitigation of ozone destruction in the stratosphere, removal of halocarbons from air, and decomposition of hazardous air pollutants [ Wong et al , 1989; Nusinovich et al , 1996; Akhmedzhanov et al , 1997; Gurevich et al , 2000]. More sophisticated techniques for plasma generation and spectroscopy using high‐power pulsed microwaves that gave some hints on our present experiments were also put to the test to confirm their feasibility [ Bollen et al , 1983; Vikharev et al , 1984; Armstrong et al , 1990].…”