V. A. Panarin

Phenomenon of apokamp discharge

A new phenomenon has been discovered where a bend of a plasma channel becomes of a source of one or several diffuse jets that have a length (at a given voltage) up to 4–6 cm and are directed across the plasma channel at a pulse-periodic spark discharge in air under normal conditions. The phenomenon is called apokamp discharge (apokamp). The spectrum of radiation of the apokamp includes primarily the bands of electron-vibrational transitions of the second positive system of molecular nitrogen. The conditions of the formation of apokamp have been experimentally revealed and it has been established that it consists of plasma bunches moving from the plasma channel at each pulse at a velocity of about 220 km/s.

Source of an atmospheric-pressure plasma jet formed in air or nitrogen under barrier discharge excitation

We analyzed the atmospheric pressure plasma jet excited in air and nitrogen by a barrier discharge. The source forming stable plasma jets of length up to 4 cm in air and nitrogen is constructed, and its energy and spectral characteristics are measured.

Ministarters and mini blue jets in air and nitrogen at a pulse-periodic discharge in a laboratory experiment

Miniature analogs of starters and blue jets that are observed in the upper atmosphere of the Earth and have dimensions of tens of kilometers are formed and studied in air and nitrogen at pressures of tens and hundreds of Torr. Ministarters and mini blue jets have been obtained in laboratory experiments owing to the application of a pulse-periodic discharge with a plasma jet referred to as apokamp. The velocities of propagation of apokamps have been measured at various pressures. It has been found that the average values of these velocities are about the velocities of propagation of starters and blue jets in the atmosphere of the Earth. It has been shown that jets (apokamps) with the maximum length are observed in the pressure range corresponding to the altitudes of appearance and propagation of starters and blue jets.

Dynamics of apokamp-type atmospheric pressure plasma jets initiated in air by a repetitive pulsed discharge

This paper presents the research data on the dynamics of a repetitive pulsed discharge as a source of plasma jets in atmospheric pressure air and on the conditions under which the discharge produces apokamp–plasma jets ejected from the bending point of the discharge channel with no gas supply through the discharge region. The data suggest that the formation of apokamps requires the application of a large number of voltage pulses to sharp-ended electrodes at a repetition frequency of several to tens of kilohertz. Before an apokamp starts developing, the apokamp-initiating discharge passes through a spark stage and then becomes diffuse. Next, at the site of electric field amplification, the discharge channel gives rise to a bright branch from which plasma bullets escape with a velocity of ∼200 km/s. The images of different discharge and apokamp stages are presented.

Acoustic characteristics of a barrier-discharge XeCl excilamp

The generation of an acoustic signal by means of voltage pulses (f = 15 kHz) applied to the electrodes of a barrier-discharge excilamp based on a Xe/Cl2 = (50–500)/1 mixture kept at a pressure of 5–500 Torr is studied. It is shown that, from the time variation of the acoustic signal intensity, one can judge the time instant the excilamp starts operating in a steady mode. Optimal (in power and efficiency) operating conditions of the excilamp are found (Xe/Cl2 = 240/1, p = 98 Torr, η ≈ 9.5%). It is experimentally demonstrated that the discharge energy at a low pressure is spent largely on heating the gas. This is indicative of the volume heat release and volume glow discharge (as the pressure grows, the efficiency of this source of energy consumption drops and more and more energy is spent on acoustic vibration excitation). Under higher pressures, the Fourier spectrum of the acoustic signal becomes richer, the intensity of the spectrum rises, and the dispersion of the signal grows. At very high pressures, the intensity of the acoustic signal drops to a level corresponding to the natural vibrations of the excilamp envelope without the discharge (when the discharge is quenched, the Fourier spectrum of the signal becomes depleted and contains only harmonics corresponding to the carrier frequency of voltage pulses from the power source).

Studying the thermodynamic processes in excilamps by the pressure jump method (Review)

A review of studies of thermodynamic processes in KrBr (207 nm), KrCl (222 nm), and XeBr (282 nm) barrier-discharge excilamps and XeBr (282 nm) and XeCl (222 nm) microwave-discharge excilamps is presented. Using various pressure gauges, it was experimentally shown that a pressure jump that occurs upon excilamp switching-on (-off) contains a fast (with a characteristic time of ∼100 ms) and a slow (∼100 s) component. The fast pressure-jump component is associated with gas heating during the discharge and allows evaluation of the fraction of the discharge power that is thermalized in the gas. From the analysis of the pressure decay after the jump, it follows that the gas is heated as a result of two processes: direct gas heating during the discharge (∼100 ms) and the energy dissipation of acoustic waves in the gas (∼10 ms). The slow component of the pressure jump is caused by the general heating of the excilamp and can be used to determine the fraction of the discharge power that is converted to thermal energy and to study various excilamp cooling modes.

Characteristics of a Pulse-Periodic Corona Discharge in Atmospheric Air

Pulse-periodic corona discharge in atmospheric air excited by applying a voltage pulse with a subnanosecond or microsecond rise time to a point electrode is studied experimentally. It is shown that, at a voltage rise rate of dU/dt ~1014 V/s, positive and negative ball-shaped streamers with a front velocity of ≥2 mm/ns form near the point electrode. As dU/dt is reduced to 1010−1011 V/s, the streamer shape changes and becomes close to cylindrical. The propagation velocity of cylindrical streamers is found to be ~0.1 mm/ns at dU/dt ~ 2 × 1010 V/s. It is shown that the propagation direction of a cylindrical streamer can be changed by tilting the point electrode, on the axis of which the electric field strength reaches its maximum value. It is established that, for the negative polarity of the point electrode and a microsecond rise time of the voltage pulse, a higher voltage is required to form a cylindrical streamer than for the positive polarity of the point electrode.

Dynamics and Structure of Nonthermal Atmospheric-Pressure Air Plasma Jets: Experiment and Simulation

Results of experimental and computational study of the dynamics and structure of atmospheric-pressure air plasma jets formed by barrier discharge in a thin dielectric tube are presented. Formation of plasma bullet-guided streamers, moving along the jet with velocity varying in the range (1-3) × 107 cm s-1, is observed. Simulation, for conditions of the experiment, gives the streamer radius, velocity, and propagation length in reasonable agreement with the experimental data.

On the Question of the Source of the Apokamp

The object of this work is the apokamp—a new type of plasma jet, which is formed from a bright offshoot emerging at the bending point of a channel of a high-voltage pulse-periodic discharge under conditions where the electrodes have a capacitive decoupling with the ground. The aim of this work is the identification of distinctive properties of the offshoot in comparison with the apokamp. The differences in the spectra of the offshoot and plasma jet (apokamp) were detected experimentally in air under normal conditions. The results of the previous studies, according to which the apokamp is a wave of ionization, were confirmed. The launch of a helium plasma jet from the offshoot of the pulse-periodic discharge in a mode of the apokamp forming was demonstrated experimentally. It was shown that the offshoot of high-voltage pulsed discharge in the mode with the apokamp is a medium that is strongly heated and conducting electric current.

A Planar Source of Atmospheric-Pressure Plasma Jet

In a single-barrier discharge with voltage sharpening and low gas consumption (up to 1 L/min), plane atmospheric pressure plasma jets with a width of up to 3 cm and length of up to 4 cm in air are formed in the slit geometry of the discharge zone. The energy, temperature, and spectral characteristics of the obtained jets have been measured. The radiation spectrum contains intense maxima corresponding to vibrational transitions of the second positive system of molecular nitrogen N2 (C3Πu → B3Πg) and comparatively weak transition lines of the first positive system of the N2+ ion (B2Σu+ → X2Σg). By an example of inactivation of the Staphylococcus aureus culture (strain ATCC 209), it is shown that plasma is a source of chemically active particles providing the inactivation of microorganisms.