acta physica slovaca

Abstract: An additional electrode was used to control the appearance and dynamics of a complex space charge structure (CSCS) in plasma. The potential threshold of the CSCS appearance, as well as the amplitude and the frequency of its oscillations, strongly depends on the negative bias of this electrode with respect to the plasma potential.

Abstract: We report on the barrier-multi-torch plasma-jet system - the novel plasma deposition system capable of working at atmospheric pressure in open air. This system can be operated in continuous-wave mode as well as in pulse regime. In the paper we describe time evolution of light intensity during single impulse in the multi-torch plasma jet system recorded by digital cine camera. Plasma jet impedance in the active part of the impulse was determined by direct voltage and current measurements using digital phosphor oscilloscope.

Abstract: This paper concerns the unusual hydrogen line broadening in electron paramagnetic  resonance (EPR) spectrum. We study hydrogen line in the afterglow of a microwave discharge in hydrogen with a small amount of oxygen admixture. A strong increase of the hydrogen EPR line width and concentration of H atoms with increasing amount of oxygen in the discharge was observed.

Abstract: The H3+, H2+ and H+ ion energy distributions (IEDs) were recorded in the 13.56 MHz hydrogen glow discharges with the energy dispersive quadrupole mass spectrometer (PPM 421) horizontally mounted between the discharge electrodes. The discharge was capacitively coupled with an asymmetric arrangement. The measurements were spatially resolved along the discharge axis, i.e. perpendicular to the electrodes, and reflected the ion flux to the grounded PPM extraction orifice 15 mm aside the electrodes. The IEDs of H3+ and H+ revealed a saddle structure that was suppressed by an effect of collisions in case of  H2+. The H+ with energies up to 10 eV higher than the maximum energy of the saddle structure were observed and explained by a dissociative ionization of H2. We proved an appreciable impedance of the plasma glow region from the width changes of the saddle structure. The effect of pressure and rf power on the IEDs was studied for a fixed position at the glow region.

Abstract: The dissociative electron attachment to chloro and fluoro derivatives of ethane have been measured using swarm technique. The rate coefficients have been estimated for first time for many of them and the values of the rate coefficients have been correlated to the DEA energies.

Abstract: The effect of the nitrogen pink afterglow quenching by hydrocarbon traces is studied in theflowing afterglow regime. The Pyrex wall temperature around the observation point was varied between the ambient and liquid nitrogen temperature. The spectra of nitrogen N2 1st positive, N2 2nd pos. and N2 1s negative bands and CN violet and red systems were observed. The strong quenching of the vibrational populations of the nitrogen N2(B3Pi_g),  N2(C3Pi_u) and N2+(B2Sigma_u+) was observed and this effect increases with the decreasing wall temperature. The vibrational populations of CN(A2Pi) and CN(B2Sigma+) states are more or less independent of the hydrocarbon concentration at the ambient wall temperature, but they increase with the decreasing temperature. A simplified kinetic model of the processes at our experimental condition is presented, too.

Abstract: We report on 2D Particle-In-Cell (PIC) simulations of dc magnetized plasma in cylindrical coordinates. Simulations aremade by XOOPIC code developed on the University of California, Berkeley. Results of the simulation are compared with experimental data obtained by Langmuir probe and emissive probe diagnostics in cylindrical magnetron device.

Abstract: A new method of using ozone generator to improve selective catalytic reduction of nitrogen oxides (NOx) was investigated. In most practical exhaust gases, NOx (NO plus NO2) consists mainly of NO. Injecting ozone into the exhaust gas as a means for the oxidation of NO to NO2, it was experimentally shown that the catalytic reduction of NOx was remarkably enhanced. For the present study, a dielectric barrier discharge device using ac high voltage was employed to produce ozone, which was continuously fed to the exhaust gas. The experiments were primarily concerned with the influence of the NO2/NOx ratio on the catalytic reduction of NOx. The effect of reaction temperature, water vapor content, oxygen content, initial NOx concentration, and ammonia concentration on the catalytic reduction of NOx under various NO2/NOX ratios were examined. The changes in the NO2/NOx ratio as a result of the ozone injection into the exhaust gas were found to largely improve the catalytic reduction of NOx, especially at low temperatures.

Abstract: Generation of the oxidants and decomposition of the organic compouds using pulsed electric discharge in the foaming column was investigated. Hydrogene peroxide, dissolved and gaseous ozone formations at various discharge power, pulse repetition rates, gas flow rates and substrate gases were evaluated. The potential of the system for the decomposition of methylene blue and humic acids was tested. The foaming reactor presents a promising method for simultaneous treatment of both gaseous and liquid pollutants.

Abstract: Plasma containing hexamethyldisilazane (HMDSZ) and nitrogen or amonia os often used to deposit silicon nitride-like films at low substrate temeprature. Kinetics of the reaction N + HMDSZ was studied by means of the electron paramagnetic resonance (EPR) method. Molecular nitrogen was partially atomised by a 13.56 MHz discharge in the quartz tube which passed through an EPR cavity. HMDSZ vapours were injected between the discharge and molecules was measured and the relevant rate coefficient k was determined The results could be used for the deposition process optimisation and modelling.