Propagation of Microwave Discharge Sustained by Surface Wave in Quartz Tube Filled with Low-Pressure Air

Plasma Physics Reports - Propagation was studied of the ionization front of the gas discharge sustained by the microwave surface wave in a quartz tube filled with low-pressure air. In a wide...     

Dynamics of Focused Pulsed Microwave Discharge in Air

Plasma Physics Reports - The formation dynamics of the parameters of a microwave discharge in air localized at electric field maxima created by a specially developed focusing system is investigated...     

Microwave Electromagnetic Field Affects the Corona Discharge Pattern of Water

We investigated the influence of microwave irradiation (cw; 10 GHz) on water by means of corona discharge electrography. Water drops from previously irradiated and control water were exposed to a high-voltage, high-frequency electric field on a photographic plate. Electrographs of the corona discharge around control and irradiated drops were taken simultaneously, and the images obtained were analyzed by computer. Several parameters relating to the luminosity, shape, and streamers of the image were calculated and tested nonparametrically. The results show a distinct, nonlinear behavior of corona discharge patterns (both radially and angularly) in water drops exposed to different microwave power densities (5 × 10^?1-5 × 10^?8 mWcm^?2).     

Characteristics of the Electrode Plasma of an Electrode Microwave Discharge in Hydrogen

The electrode region of an electrode microwave discharge in hydrogen at pressures of 0.5–4 torr and absorbed powers of up to 12 W is studied using emission spectroscopy and actinometry. It is shown that the gas temperature is at most 700 K and the degree of dissociation does not exceed several percent. Direct electron impact is shown to be the main factor governing all the processes in the electrode region of the discharge, including the excitation of the recorded emission. In particular, the Balmer-series H_α line emission is related to the dissociative electron-impact excitation of hydrogen molecules in the ground state.     

Non-equilibrium Kinetics of Dissociation of Molecular Hydrogen in Microwave Discharge in Liquid Hydrocarbons

Plasma Physics Reports - A semi-empirical level-based model is developed that describes the detailed kinetics of the formation and decay of hydrogen atoms during relaxation of the vibrational...     

Microwave and Optical Gas Discharges in Superstrong Pulsed Fields

A review is given of theoretical papers on gas breakdown in high-power pulsed microwave and optical fields under conditions such that the electron oscillatory energy in the wave field is much higher than the ionization energy of gas atoms. In microwave fields, which are much weaker than the atomic field, the ionization mechanism for gas atoms is governed by electron-impact avalanche ionization. In high-power optical fields that are comparable in strength to the atomic field, the gas atoms are ionized via the tunneling of the bound electrons. It is shown that, in both cases, the electrons obey similar, highly anisotropic distributions, thereby strongly affecting the stability of the discharge plasma.     

Analytical Model of a Surface Barrier Discharge Development

Plasma Physics Reports - The propagation of the front of a single surface dielectric barrier microdischarge is studied using an analytical model based on the charge balance equation. The model...     

UV Radiation of High-Voltage Multi-Electrode Surface Discharge in Gaseous Medium

Plasma Physics Reports - UV radiation of high-voltage pulsed multispark surface discharge in atmospheric-pressure air in the spectral range of 200–380 nm was investigated. The discharge was a...     

Simulation of an Inductive Discharge in Argon with the Gas Flow and Inhomogeneous Gas Temperature

Plasma Physics Reports - With the purpose to create new methods for monitoring the parameters of low-temperature nonequilibrium plasma, a numerical drift-diffusion model of an inductive RF...     

Time-Resolved Optical Diagnostics of the Microwave Discharge in Liquid Hydrocarbons with Argon Bubbling

Plasma Physics Reports - The methods of emission spectroscopy, shadow photography, and integral radiation of a discharge with time resolution are used to study the initial stages of the development...     

Discharge in a Subthreshold Microwave Beam as an Unusual Type of Ionization Wave

Plasma Physics Reports - Ionization−overheating instability of a non-self-sustained discharge in air in a subthreshold microwave field creates a self-sustained discharge with a fine cellular...     

Effect of Nitrogen Additive on Inhomogeneous Microwave Discharge in Hydrogen at Reduced Pressures

Plasma Physics Reports - The effect of a small nitrogen additive on a microwave discharge in hydrogen ignited near the antenna at a pressure of 1 Torr was studied by emission spectroscopy and...     

Discharge in a Subthreshold Microwave Beam as an Effective Means for Mercaptan Decomposition

Plasma Physics Reports - A subthreshold microwave discharge in atmospheric-pressure air is used to process mixtures of mercaptans (thiols) with air and with air and methane. It is found that, at...     

Synthesis of Nitrogen Oxides in a Subthreshold Microwave Discharge in Air and in Air Mixtures with Methane

Plasma Physics Reports - A subthreshold discharge excited by a microwave beam in air at pressures close to atmospheric is studied as a plasmachemical method of nitrogen oxide (NOx) production. It...     

Surface Decontamination in an Autoclave Chamber with Formaldehyde Gas

A simple device for the conversion of a standard steam autoclave into a formalde-hyde gas sterilization chamber is described.     

Physico-Chemical Investigation of Pulsed Discharge in CO2/O2 Gas Mixture

Plasma Physics Reports - In this research, the decomposition of CO2 in CO2/O2 pulsed discharge was studied. The developed model is based on the physical processes involved in the discharge with the...     

Community Structure of Archaea in the Water Column above Gas Hydrates in the Gulf of Mexico

Microorganisms play fundamental roles in the ecosystem of the Gulf of Mexico (GOM), yet their vertical distributions along the depth continuum of water column are not well known. In this study, we presented the 16S rDNA sequences and lipid profiles in the context of water chemistry to characterize the archaeal community structure above a gas hydrate mound (MC 118) in GOM. Our results showed that all archaeal sequences were related to unknown species of Crenarchaeota or Euryarchaeota. Phylogenetically, group II –β Euryarchaeota dominated the surface water and mid-depth (400-m) water (74% and 58% of total archaeal species, respectively) whereas the marine group I-γ Crenarchaeota dominated the bottom (869 m) water (61% of total archaeal species). Estimates of the Shannon index showed the highest diversity of planktonic Archaea at the 400 m depth. Glycerol dialkyl glycerol tetraether (GDGT) lipids were detected from the 400- and 869-m depths only and characterized by relatively high abundances of GDGT-5 (crenarchaeol) and GDGT-0. Our studies suggested a possible zonation of archaeal community in the water column, which did not seem to be affected by the possible venting of hydrocarbons from the hydrate location in GOM.     

A Subthreshold High-Pressure Discharge Excited by a Microwave Beam: Physical Basics and Applications

A new form of discharge excited by a microwave beam in a high-pressure (up to atmospheric and higher) gas in free space and in a closed chamber is discussed. For the first time, the discharge was implemented by means of a gyrotron with a pulse power of 200 ≤ P ≤ 600 kW, a pulse duration of 0.5 ≤ τ ≤ 20 ms, and a wavelength of λ = 0.4 cm. Under deeply subthreshold conditions in atmospheric-pressure air, a plasma column with a length of L = 50 cm was generated by a microwave beam formed with the help of a quasi-optical transmission line. With the use of the MIG-3 gyrotron complex with the above parameters, generation of a plasma column with a length of several meters is possible in principle. The parameters and structure of the formation of the plasma investigated make it possible to class it as a self-non-self-sustained (SNSS) discharge, discovered and described for the first time at the Prokhorov General Physics Institute, Russian Academy of Sciences. One of the important applications of this type of discharge is plasmachemical cleaning of the urban air environment of hazardous contaminants.     

Experimental Study of a Vacuum Spark Discharge over a Dielectric Surface

A decrease in the amplitude of the current of a vacuum spark discharge over a dielectric surface with increasing discharge gap length is established. It is shown that, in the presence of a longitudinal magnetic field, the leading edge of the discharge voltage pulse is extended, whereas the clearly pronounced current pulse transforms into a train of alternating current oscillations. The discharge is found to decelerate when the spark is preceded by a low-current discharge.