A theoretical analysis of the line broadening of localized atomic transitions in liquid helium is presented. It is shown that accurate information can be derived on the long-range part of the He*-He interaction as well as on the local structure near the He* emitters. The analysis confirms that in corona discharges in liquid helium the emitting He* atoms reside in cavities and that for known He*-He interaction the size of the cavities can be deduced from the line profile. The He*-He interaction was calculated using the full configuration interaction (CI) method as implemented in the Molpro package. The widths of atomic lines due to fluorescent transitions between different excited states of helium atoms were calculated as a function of external pressure in the range from 0.1 and 3.5 MPa using the static approximation method, and the input from the results of the CI calculation and cavity diameters calculated using the bubble model. The calculated widths showed excellent agreement with experimental data of liquid helium excited by corona discharges. A second, analytical analysis using a power function to represent the He*-He interaction showed qualitative agreement with the experimental data.

Proton transfer reaction-mass spectrometry (PTR-MS) offers many advantages for trace gas analysis, including no sample preparation, real-time analysis, high selectivity and sensitivity, ultra-low detection limits and very short response times. These characteristic features have made it an ideal tool for many applications in science, technology and society. Here we will discuss recent developments, in particular advances concerning sensitivity, selectivity and general applicability.

This document gives an overview of a power supply construction suitable for dielectric barrier discharge (DBD) reactor excitation. The influence of temperature and voltage change on DBD reactor parameters is discussed. A power electronic supply system topology allowing for continuous resonant frequency tracking is proposed together with simulation and test stand results of operation. An additional feature of proposed topology is the output peak to peak voltage control.

In the present study, Fe2O3 was used as catalyst for the removal of NO in a hybrid plasma- catalytic reactor. The catalyst was located either directly inside the hybrid plasma-catalytic reactor or in a separate catalytic reactor, which followed ozone producing and injecting plasma reactor. Ozone production in such a reactor was dependent on the state of the electrode surface. The fresh catalyst ensured an order of magnitude smaller ozone concentration in the outlet of the hybrid reactor. After a short treatment of the catalyst with NO2, its ability to destroy ozone diminished but was regained after heating of the reactor up to 100 °C. Similarly to earlier results obtained with TiO2, the removal of NO in the hybrid reactor with Fe2O3 was enhanced compared to that in an ordinary plasma reactor. In the ozone injection reactor, oxidation of NO to NO2 took place with considerably higher efficiency compared to the hybrid reactor. The use of catalyst in the ozonation stage further improved the oxidation of NO2 to N2O5. The time-dependence effects of NO removal during plasma and ozone oxidation were explained by reactions between NO2 adsorbed on surface, with surface-bound NO3 and gas phase NO as the reaction product.

Cold air plasmas of DC and pulsed corona discharges: positive streamers and negative Trichel pulses were used for bio-decontamination of Streptococci biofilm and Bacillus cereus spores on polypropylene plastic surfaces. The reduction of bacterial population (evaluated as log10) in the biofilm on plastic surfaces treated by DC corona reached 2.4 logs with 10 min treatment time and 3.3 logs with 2 min treatment time with water spraying. The enhancement of plasma biocidal effects on the biofilm by electro-spraying of water through a hollow needle high-voltage electrode was investigated. No significant polarity effect was found with DC corona. Pulsed corona was demonstrated slightly more bactericidal for spores, especially in the negative polarity where the bacterial population reduction reached up to 2.2 logs at 10 min exposure time.

A dielectric barrier discharge was used for the oxidative coupling of methane (OCM) with oxygen at the pressure of 1.2 bar. A dielectric barrier discharge (DBD) reactor was powered at the frequency of about 6 kHz. Molar ratio CH4/O2 in the inlet gas containing 50% or 25% of argon was 3, 6 and 12. The effects of temperature (110, 150 and 340 ◦C), gas flow rate, molar ratio of methane to oxygen on the overall methane and oxygen conversion and methane conversion to methanol, ethanol, hydrocarbons, carbon oxides and water were studied. In the studied system the increase of the temperature decreases the conversion of methane to methanol. The increase of the molar ratio of methane to oxygen increased the methane conversion to hydrocarbons and strongly decreased the methane conversion to alcohols. The conversion of methane to hydrocarbons increased and the conversion of methane to methanol decreased with the decrease of the gas flow rate from 2 to 1 NL/h.

Gliding arc discharge is one of the unique plasmas of which the dynamic behavior is extremely complex in time and space. In this work, we report on time-resolved dynamic behavior of gliding arc discharge plasma in He and Ar using comparison of obtained results between high-speed camera (54 000 fps) photographs and the corresponding electrical properties. Both measurements were synchronized via an external trigger. For a gliding arc discharge in Ar 20 L/min, gliding of serpentine plasma was observed due to turbulent gas flow and reconnections of plasma path were observed. It was revealed that the applied voltage was decreased and small pulsed current flowed at the moment of the reconnection.

This work was aimed at experimental investigations of deactivation of different types of microorganisms by using atmospheric pressure low-temperature microwave microplasma source (MmPS). The MmPS was operated at standard microwave frequency of 2.45 GHz. Its main advantages are simple and cheap construction, portability and possibility of penetrating into small cavities. The microplasma deactivation concerned two types of bacteria (Escherichia coli, Bacillus subtilis) and one fungus (Aspergillus niger). The quality as well as quantity tests were performed. The influence of the microorganism type, oxygen concentration, absorbed microwave power, microplasma treatment time and MmPS distance from the treated sample on the microorganism deactivation efficiency was investigated. All experiments were performed for Ar microplasma and Ar/O2 microplasma with up to 3% of O2. Absorbed microwave power was up to 50 W. The Ar flow rate was up to 10 L/min. The sample treatment time was up to 10 s.

The phase modulation of transparent gas can be detected using Fraunhofer diffraction technique, which we call optical wave microphone (OWM). The OWM is suitable for the detection of sonic wave from audible sound to ultrasonic wave. Because this technique has no influence on sound field or electric field during the measurement, we have applied it to the sound detection for the electric discharges. There is almost no research paper that uses the discharge sound to examine the electrical discharge phenomenon. Two-dimensional visualization of the sound field using the OWM is also possible when the computerized tomography (CT) is combined. In this work, coplanar dielectric barrier discharge sin different gases of Ar, N2, He were characterized via the OWM as well as applied voltage and discharge current. This is the first report to investigate the influence of the type of the atmospheric gas on the two-dimensional sound field distribution for the coplanar dielectric barrier discharge using the OWM with CT.

The article presents the plasma synthesis method of carbon nanotubes using an electric arc discharge. In this method different carbon nanotubes are produced as a cathode deposit growth or are deposed on various substrates such as silicon, metals and other materials. The examples of applications of carbon nanotubes in medical applications were presented. Conditions required for the synthesis of carbon nanotubes and process parameters were mentioned. Applications of carbon nanotubes for cancer treatment were discussed. The method of temperature measurement of the arc was described.

Results of experimental investigation of a dielectric barrier surface discharge over barriers with different films deposited on their surface show evident dependence of the microdischarge structure, their intensity and their charge on the surface structure and chemical composition of the barrier surface. Measured profiles of barrier surface structures by means of a laser scanning microscope are used to calculate the electric field distribution in air in the vicinity of the barrier surface. The local electric field near the surface is shown to have strong dependence on the surface profile elements (highness of protrusions, curvature radii of their peaks and the distance between neighbor protrusions). It is shown that the values of local fields are sufficient for ionization processes in air and it is supposed that such additional ionization is one of the main factors to change the discharge behavior.

The secondary ionization coefficient γ of a CaO film electrode is investigated taking into account the difference in breakdown voltage obtained by repeated voltage applications. Such measurement is performed under a sinusoidal voltage of 0.5 Hz. If the CaO film electrode acts as the cathode, breakdown voltage gradually decreases and converges to an almost constant value after several breakdowns. From the obtained results, the γ of the CaO film electrode is determined for each breakdown using Townsend’s criterion. The γ in the first breakdown is lower than those in subsequent breakdowns, particularly in the steady state. The difference in γ is considered to originate from accumulated charges on the CaO film electrode.

Plasma aided materials conversion is the use of charged particles for producing new materials with unusual and superior properties or to convert unwanted materials such as waste into environmentally friendly products. The near LTE plasma (in atmospheric or reduced pressure) is a nice tool for engineering of materials which in consequence upgrades the performance of most of the consumer goods. The paper presents a few samples of the own research results related to the design and use of some plasma reactors for synthesis of nanomaterials and hazardous materials destruction with their conversion into valuable products.

The oil and fat were treated at first by only ozone bubbling and it was confirmed that the collection efficiency of them became 98.4% when the aeration was used. It showed that the aeration method in a grease trap cleared the standard value of 90% and there was no worry on the oil and fat outflow from a grease trap. The characteristics of sonication process were studied for free fatty acids degradation. The free saturated fatty acids are the most hard-degradable compounds of the fats, oils and greases (FOGs) in the grease trap. The influence of various parameters such as immersion level of an ultrasound probe in the liquid and bubbling of various gases (Ar, O2, air, O3) on the sonochemical and energy efficiency of the sonication process was investigated. The most effective degradation treatment method for saturated free fatty acids was the combination of sonication and low flow rate argon bubbling.

Organic materials used for packing food products prevent the access of microorganisms or gases, like oxygen or water vapor. To prolong the stability of products, preservatives such as sulfur dioxide, sulfites, benzoates, nitrites and many other chemical compounds are used. To eliminate or limit the amount of preservatives added to food, so-called active packaging is sought for, which would limit the development of microorganisms. Such packaging can be achieved, among others, by plasma modification of a material to deposit on its surface substances inhibiting the growth of bacteria. In this work plasma modification was carried out in barrier discharge under atmospheric pressure. Sulfur dioxide or/and sodium oxide were used as the coating precursors. As a result of bacteriological studies it was found that sulfur containing coatings show a 16% inhibition of Salmonella bacteria growth and 8% inhibition of Staphylococcus aureus bacteria growth. Sodium containing coatings show worse (by 10%) inhibiting properties. Moreover, films with plasma deposited coatings show good sealing properties against water vapor.

We succeeded in generating an atmospheric pressure Townsend discharge (APTD) in air by using a simple DBD device that consists of alumina barriers and plane electrodes. So far, we applied the APTD to an ozonizer and found that the ozone generation efficiency was higher by the APTD mode than by the conventional DBD mode in larger specific input energy region. It is well known that an operation under an optimized high gas pressure is advantageous for efficient ozone generation from air. In this paper, we investigated whether the Townsend discharge (TD) in dry air in high pressure up to 0.17 MPa can be generated or not. From the observation results of current waveforms and discharge photographs, we found that (1) the discharge currents flow continuously and have only one peak in every half cycle in all gas pressure and (2) filamentary discharges are not recognized between barriers in all gas pressure. These features completely agree with the features of the APTD we reported. Therefore, we concluded that our TD can be generated even in dry air in the pressure range of 0.1 and 0.17 MPa.

We developed a portable ozone-mist sterilization system to exterminate pests (harmful insects) in agricultural field and greenhouse. The system is composed of an ozone generator, an ozone-mist spray and a small container of ozone gas. The ozone generator can supply highly concentrated ozone using the surface dielectric barrier discharge. Ozone-mist is produced using a developed nozzle system. We studied the effects of ozone-mist spray sterilization on insects and agricultural plants. The sterilization conditions are estimated by monitoring the behavior of aphids and observing the damage of the plants. It was shown that aphids were exterminated in 30 s without noticeable damages of the plant leaves. The reactive radicals with strong oxidation potential such as hydroxyl radical (*OH), hydroperoxide radical (*HO2), the superoxide ion radical (*O2‒) and ozonide radical ion (*O3‒) can increase the sterilization rate for aphids.

Changes of the gas temperature in a single microdischarge channel and inside the entire discharge gap of dielectric barrier discharge were analyzed. It was shown that the initial temperature of the gas in the microdischarge channel is tens of degrees higher than the average gas temperature in the gap. The gas expanding effect which causes the gas mixing in the reaction space is presented. It has been explained why and in which part of the gap the ozone is decomposed.

Formation of negative ions initiated by interaction of thermal electrons and in the corona discharge (CD) in N2 with small admixture of SF6; was studied using the ion mobility spectrometry- orthogonal acceleration time-of-flight mass spectrometry (IMS-oaTOF) at atmospheric pressure. The negative ions have been analyzed by the ion mobility spectrometry and mass spectrometry (IMS-MS) and two-dimensional spectra (2D IMS-MS) have been recorded. We discuss the mechanisms of the negative ion formation in the N2/SF6 mixtures (0.003-0.018%) as well as the transport parameters of the ions in these mixtures. The values of the reduced ion mobilities of negative ions formed in these mixtures were determined (2.43 cm2/V s for HF2– (HF)n, 2.32 cm2/V s for NO3– (HF)n, 2.08 cm2/V s for SF5–, 2.01 cm2/V s for SOF5–, 2.00 for SOF4– 1.99 cm2/V s for SF6–, 1.83 cm2/V s for SOF5–(H2O)n and 1.73 for SOF5–(H2O)n(HF)m). The assignment of the ion mobility peaks was performed on the basis of the 2D IMS-MS spectra.