Streamer discharges that do not transition to a spark channel are now being widely investigated.One of these discharges is the apokamp discharge, in which streamers start from a diffuse spark channel having a curved shape at a high repetition rate of voltage pulse. In this work, to estimate the electron concentration in the plasma forming the apokamp a digital holographic laser scanning method is applied for the first time. The method is based on a comparison of the phases of two optical wavefronts, registered at different time instants in the form of digital holograms. The result of the phase comparison between the wavefronts is presented in the form of a numerically calculated map of the phase difference of the reconstructed wavefronts. A gas-discharge plasma is a phase(transparent) object, and the interference fringes are formed as a result of the change in the refractive index introduced by the plasma with respect to the original unperturbed medium. The obtained value of the refractive index allows estimation of the concentration of electrons in the spark channel plasma. It is shown that at as the voltage pulse repetition rate increases from 5 to 50 kHz the concentration of electrons in the plasma forming the apokamp decreases by an estimated four times.

Polyvinylidene fluoride (PVDF) has gained attention as a promising material for tissue engineering due to its biocompatibility and piezoelectricity. However, achieving proper cell adhesion to PVDF surfaces remains a challenge. This study focuses on the preparation and characterization of PVDF-based substrates, including PVDF thin films and nanocomposites incorporating CoFe2O4 magnetic nanoparticles. Helium plasma treatment is employed to modify the surface properties of these substrates. The plasma treatment induces significant changes in the topography of the PVDF-based nanocomposites. The roughness values of the samples increase from 2-3 nm to 14-17 nm after 90 s of plasma treatment, leading to enhanced hydrophilicity with an average contact angle below 60 degrees. Importantly, the helium plasma treatment preserves the magnetic and structural properties of the substrates, suggesting the retention of their magnetoelectric properties and, thus treated composites hold potential for remote stem cell activation. We provide evidence of cytocompatibility and improved adhesive properties of plasma-treated substrates using human mesenchymal stem cell cultures.

Magnetoelectric composites based on polymers with inclusions of magnetic nanoparticles have found novel applications in bone tissue engineering as growth-promoting substrates for stem cells. Current research focuses on the surface properties of composite materials, in particular their topographical features, as these have a significant impact on the behavior of stem cells and can promote their differentiation. In this paper, helium-plasma modification is proposed as a method to effectively modify the surface roughness and wettability of polyvinylidene fluoride (PVDF)-based films. It is demonstrated that this modification method facilitates the development of a topography and increases the surface roughness of PVDF substrates; it also contributes to a reduction in the contact angle, which is due to surface functionalization through defluorination and chemical oxidation. Such surface properties make it possible to use these nanocomposites as functional substrates for bone tissue engineering.

In this study, we investigated the effects of generating a cold plasma jet emanating from the surface of an arc in air at atmospheric pressure. This type of plasma was obtained relatively recently and is called apokamp. Apokamp plasmas are formed by applying short-pulsed high positive polarity voltages, which is provided when the second electrode is weakly capacitive coupled with the ground. The prospect of using apokamp plasmas in biomedical applications is also discussed.

In this paper, we consider the method for observing and detecting of high-frequency pulsed plasma spark discharge by means of stroboscopic digital holographic interferometry to demonstrate the feasibility of the electron concentration assessment in nonthermal plasma. A spark discharge with a 5 kHz frequency and 1250 ns duration has been exited between two electrodes in atmospheric pressure. The sequence of holograms acquired due to the proper synchronization between plasma pulses, laser radiation, and the camera's frame grabbing that ensure the recording of the plasma pulses at different moments of time, and the temporal optical scanning of plasma pulse were realized. We also show that the phase difference contrast variation corresponds to the plasma's instant and indicates a change in the electron concentration in the discharge. The concentration of electrons at different moments of plasma existence has been estimated. The limitations of the proposed method are considered, and its applicability for the study of low-temperature pulsed plasma are discussed.

The study of low-temperature plasma generated in pulsed mode at atmospheric pressure was carried out. The purpose of the presented research is to develop a method of digital holographic interferometry for registration and evaluation of parameters of low-temperature plasma at atmospheric pressure in pulsed mode. This type of plasma is currently applied in medicine and biology. Thus, there is a need to control the exposure dose and plasma environment formation regimes. As plasma parameters, it can be considered its electron concentration which can be calculated through the estimation of the refractive index of plasma pulse in relation to unperturbed state. The plasma pulses were activated in Helium. The plasma pulse frequency was 5 kHz and its duration was 750 ns. During an investigation a laboratory set-up for recording holographic images of plasma pulses was developed. Holograms are acquired on a digital camera and a pulsed laser INNOLAS SpitLight Hybrid II at a wavelength of 532 nm with pulse duration of 10 ns is used as a source of coherent radiation. In order to record plasma pulses, the laser, plasma generator and digital camera were strictly synchronized to each other. During the experiment, a series of about 500 holograms were acquired, and the reconstruction of the phase of the object field was calculated. Analysis of the sequence of holograms allowed calculations of phase difference (interferograms) related to the refractive index of low-temperature pulsed plasma in Helium. It is known that low-temperature plasma leads to low phase delay which forms low phase contrast of the evaluated interferograms. For this purpose, we carried out preliminary experiments with plasma-arc that has similar temporary parameters, however, with a higher phase contrast of the interferograms. The paper presents experimental results obtained by studying the phase contrast of the refractive index of pure Helium, plasma-arc and plasma pulses in Helium. Thus, the effectiveness of both the experimental set-up and the method to evaluate the interferograms related to the refractive index of the plasma pulse was verified. The data obtained can then be used to estimate the electron concentration of the plasma. However, it needs to increase the sensitivity of the method in order to enhance phase contrast. Increase of sensitivity can be done by means of extension of the spectral range, for example, toward to infra-red.

This article presents an experimental study of a DBD-driven plasma jet system. The aim of the study is to design a whole system (the jet reactor, its electrical power supply, and a gas-feeding apparatus) suitable for biomedical applications. The article describes the test bench developed for this purpose and discusses the parameters it controls. The measurements show that the studied solutions can be used to control critical parameters such as the jet temperature and dimensions. The best results were obtained for a bipolar short-pulse voltage power supply in the 10–20 kHz frequency range and for a series resonant inverter current power supply operated in “burst mode”, allowing low-frequency modulation.

Narrow-band ultraviolet B radiation is increasingly used in the therapy and recurrence prevention of autoimmune skin diseases. The popularity of this method stems from the relative safety and minimal impact on the human body during physical therapy. This paper reports on the development of a unique design of the excimer lamp equipped with a UVB dose control system, a sensor control unit with a ribbon software interface, a quick positioning system, and an electronic patient logbook. The excimer lamp is designed to provide safer and more effective UVB therapy for skin psoriasis, nail plate psoriasis, vitiligo and atopic dermatitis.

The results of a study of a plasma jet of atmospheric-pressure helium driven by a capacitive discharge using sine and pulsed modes of excitation are presented. The homogeneous discharge of a multi-channel plasma jet at gas temperature of 34 °C and helium flow rate of 0.5 L/min was achieved with short pulse excitation. A digital holography method is proposed to estimate a basic plasma parameter, i.e., its electron concentration. An automated digital holographic interferometry set-up for the observation and study of a nonthermal plasma jet in a pulse mode is developed and described. The synchronization features of recording devices with the generation of plasma pulses are considered. The electron concentration of the plasma jet is also estimated. The disadvantages of the proposed technique and its further application are discussed.

Our study describes effective techniques to transfer heat away from UV emitters based on dielectric barrier discharge excilamps. It presents findings from an investigation into the efficiency of excilamp radiation when cooled by air, inert gas, and liquid refrigerants. The devised cooling techniques were used to create radiation sources with a UV power density of up to 117 mW/cm(2). (C) The Authors. Published by SPIE under a Creative Commons Attribution 4.0 Unported License.

Intermediate ultraviolet (UVB) therapy is considered a relatively safe method of treating skin diseases with an autoimmune component in development compared to medical drug methods, including PUVA therapy. This is due to the small depth of penetration of the rays of this wavelength range into skin, which provides a purely local effect on the human body. Excimer lamps are an alternative to the expensive excimer laser for phototherapy of psoriasis or vitiligo. However, for effective phototherapy using UVB lamps, the distance from an emitter to a patient’s skin must be considered. In this paper, we report on treatment of patients using an excimer lamp, the control unit of which is equipped with an optical system for controlling of ultraviolet radiation dose, which allows automatically calculating the time for a set UVB dose. The article describes the results of phototherapy using an excimer lamp of several cases of psoriasis, vitiligo and other forms of dermatitis with a good therapeutic and cosmetic effect. When using an excimer lamp, not a single case of exacerbation of dermatological diseases was established.

Spectral range of UVB is widely used for treating psoriasis and vitiligo. Portable and low-cost XeCl excimer lamps having the 308-nm wavelength are more suitable for dermatology than traditional excimer lasers. Unlike laser, excimer lamps have a significantly decreased radiation intensity which depends on the distance to the treated skin area. The authors explore a new prototype for skin treatment having an automated UV dose control system. The system makes measurements of the distance to the treated area of the skin and calculates the treatment time according to the required UV dose. If the distance is changed during the phototherapy, the control system corrects the treatment time in the online mode. The article describes other functional opportunities of the control system.

Low-temperature plasma has been successfully used in medicine for last 15 years. Cure of purulent wounds by means of discharge plasma with low gas temperature is a new method of medical drug-free treatment. A result of investigation of atmospheric pressure helium plasma-jet excited by capacitive discharges at various methods of excitation is presented. Homogenous discharge of multichannel plasma jet and 34 degrees C of gas temperature at helium flow 0.5L/min was achieved at short pulsed voltage excitation.

A Dielectric Barrier Discharge driven cold plasma jet is ignited using three different power supplies to experimentally study the impact of the electrical operating point over several jet characteristics. The characteristics under study are the homogeneity of the jet and the gas temperature. Additionally, the jet reactor is operated at different gas flow rates. The power injected into the jet is in the 0,2 - 5 Watts range. From the obtained results the operating conditions allowing to obtain a homogeneous low temperature jet, required for biomedical applications, are found.

The particle temperature distribution depending on the laser radiation power and the particle's trajectory and velocity were studied. The uneven heating of particles moving in the laser radiation field was identified. The regimes of laser heating without melting, with partial melting, and with complete particle melting were considered.

Three different electrical generators have been designed and used to supply an exciplex dielectric barrier discharge lamp in order to elucidate the influence of each one of these supplying strategies over the system performance; the first method consists on supplying the lamp with short bipolar voltage pulses; the second and third methods are based on semiresonant converters were current pulses, of controlled duration and magnitude, are injected into the lamp. For each one of the generators, measurements of the lamp and supply efficiency, are performed and analyzed, at different levels of power (up to 130 W) and operating frequencies (60-90 kHz). From the experimental results, the pulsed voltage-mode approach has allowed obtaining the highest lamp efficiency (7%), yet the maximum supply efficiency is offered by the resonant mode supplies. On the basis of the lamp and the supply efficiencies, the whole system performance is analyzed.

The proposed solution makes possible the transfer of high-voltage excitation pulses through the long coaxial cable with the minimum losses and the excilamp efficiency. Use of resonant topology of the pulse converter provides ZCS at switching-ON and ZVC at switching- OFF of the transistors. The values of efficiency of radiation of ∼ 9% at the feedline of 2.5 m in length obtained during the experiments are about twice as much as the efficiency at the XeCl- excilamp excitation by the quasi-square pulses power supply due to the decrease of losses at switching and the increase of electric efficiency of a resonant power supply with the long coaxial feedline.

We describe a mathematical model of electrophysical processes occurring in the system consisting of a transistor inverter, an oscillatory circuit, a step-up transformer, a long feedline, and a barrier-discharge lamp. We propose and test a method for effective transmission of a high-frequency voltage from a power supply to the barrier-discharge lamp via a long coaxial line in which the voltage was applied to the electrodes of the lamp in the form of harmonic voltage bursts at a frequency close to the self-resonant frequency of the excitation system.

The results of investigations of planar and coaxial barrier-discharge KrCl excilamps (λ ∼ 222 nm) are reviewed. Brief information on the developed structures of radiators and power-supply units and the results of life tests are presented. The kinetics of the processes in the working gaseous medium, the possible methods for improving the energy parameters of KrCl excilamps, and prospects of their applications are reported.

We have developed a module based on exciplex barrier-discharge lamps for irradiation by high-power narrow-band ultraviolet radiation. The module uses air cooling and is intended for irradiation of substrates such as those used in microelectronics. The module provides close to uniform irradiation on a flat surface with power density up to 35 and 25 mW/cm2 as a result of emission in B–X bands of the molecules XeBr* (282 nm) and XeCl* (308 nm) respectively.