Non-equilibrium conditions in plasma are often achieved by pulsed power delivery, where the pulse shape and repetition rate determine the properties of the plasma constituents and thus its chemical reactivity. The evaluation of the latter is becoming increasingly important to understand the observed effects, especially when new application fields are targeted. The composition of the plasma and the occurring chemical reactions can be calculated using various models. Thereby, the temperature of the electrons, the electron number density, as well as the heavy particle temperature are usually required as the basis of such calculations. In this work, the influence of pulse amplitude and repetition rate on these plasma parameters is determined by laser scattering for a low-current, high-voltage discharge operated with nitrogen at atmospheric pressure. In particular, the characteristic parameters regarding the plasma free electrons in such discharges have not yet been experimentally determined to this extent. The results are validated by spectroscopic measurements, i.e., the electron density is estimated from the Stark broadening of the hydrogen beta line and the heavy particle temperature is estimated by fitting the spectrum of nitrogen molecular transitions. Depending on the operating frequency, a pure nitrogen discharge with an input power of about 650 W displays an electron density between $1.7\times {10}^{21}{\mathrm{m}}^{-3}$ and $2.0\times {10}^{21}{\mathrm{m}}^{-3}$ with electron temperatures in the range of 40,000 K and heavy particle temperatures of about 6000 K in the core of the discharge channel. Furthermore, a relatively slow electron recombination rate in the range of 20 µs is observed. Full article

We study pentane depletion using a hybrid plasma system based on a surface dielectric barrier discharge (SDBD), with and without a catalyst, and as a function of plasma power and alkane concentration. We evaluate pentane decomposition efficiency based on plasma power and quantify the role of the catalyst in the resulting depletion of intermediate products. Analyses of the temporal evolution of pentane and the intermediate decomposition products allow us to estimate the corresponding decomposition rates according to the plasma parameters. We find that depletion efficiency increases as a function of pentane concentration. Furthermore, it is shown that the catalytic processes are responsible for a significant increase in the depletion rates of the intermediate reaction products, thus contributing to the total abatement process of pentane. Full article

In most negative hydrogen ion sources, an external magnet is installed near the extraction region to reduce the electron temperature. In this paper, the self-developed CHIPIC code is used to simulate the mechanism of a magnetic filter system, in the expansion region of the negative hydrogen ion source, on “hot” electrons. The reflection and the filtering processes of “hot” electrons are analyzed in depth and the energy distribution of electrons on the extraction surface is calculated. Moreover, the effects of different collision types on the density distribution of “cold” electrons along the X-axis and the spatial distribution of “cold” electrons on the X−Z plane are discussed. The numerical results show that the electron reflection is caused by the magnetic mirror effect. The filtering of “hot” electrons is due to the fact that the magnetic field constrains most of the electrons from reaching the vicinity of the extraction surface, being that collisions cause a decay in electron energy. Excitation collision is the main decay mechanism for electron energy in the chamber. The numerical results help to explain the formation process of “cold” electrons at the extraction surface, thus providing a reference for reducing the loss probability of $H^{-}$. Full article

Presently, plasma-treated solutions (PTS) are widely introduced into medicine. Plasma-activated solutions contain various reactive forms of oxygen and nitrogen which provide the desired biological effects. Yet it remains unclear exactly which components of the treated solution are the most important and what the difference is between the plasma-treated solution and a chemically prepared solution composed of the same components. In this work, we show that the chemically prepared mixture of nitrites, nitrates, and hydrogen peroxide with concentrations similar to the plasma-treated solution exerts a fundamentally different effect on a cell culture. The chemically prepared solution has higher cyto- and genotoxicity and causes necrosis, while under the action of the plasma-treated solution, apoptotic processes develop in the cells slowly. Full article

In this paper, the packed bed dielectric barrier discharge (DBD) with needle-plate electrode configuration is presented to study the effects of electrical parameters, such as pulse duration and pulse rising and falling time, on discharge characteristics under air and nitrogen. The waveforms of the voltage and the discharge current, discharge evolution images, and the emission spectral of N₂ (C³П_u → B³П_g) and N₂⁺ (B²Σ_u⁺ → X²Σ_g⁺) are collected to investigate the discharge current, as well as the spatial distribution of the discharge modes and the reactive species in the packed bed reactor specifically. It is found that the pulse duration and pulse rising and falling time can regulate the discharge current. Firstly, increasing the pulse duration and the pulse rising and falling time can both increase the discharge duration. Secondly, the peak value of the discharge current has an obvious increasing trend with the pulse duration. Finally, the discharge start time can be delayed by increasing the pulse rising and falling time. A bright discharge channel is distributed at the top of the reactor, while the discharge is diffused at the bottom of the reactor. The generation of N₂⁺ (B²Σ_u⁺) tends to depend on the existence of the streamer channel, and N₂ (C³П_u) can be generated in the entire discharge area. In addition, the discharge operated in pure nitrogen can reach higher current values, a stronger discharge intensity, and longer existence time for the reactive species than in the air. Full article

Improving the transdermal delivery efficiency of medicine is a crucial measure to improve the treatment efficiency of psoriasis. This paper developed a low-cost, highly active, and large-action-area low-temperature plasma (LTP) jet array. The two components of plasma—the high concentration of reactive oxygen and nitrogen species and the strong electric field—easily changed the structural integrity of the stratum corneum, which enhanced the transdermal delivery of the medicine. Tripterygium wilfordii Hook F (TwHF) is a medicine used to treat autoimmune and inflammatory conditions. The enhanced transdermal delivery of TwHF significantly alleviated the severed psoriasiform dermatitis induced by the imiquimod. Unlike the TwHF treatment alone, the LTP + TwHF treatment was more efficient at suppressing epidermal thickening and inhibiting systemic inflammation without noticeable side effects. LTP + TwHF treatment provides a potential new solution for psoriasis treatment. Full article

This article presents a parametric study using full-wave simulations about the potential use of cold plasma discharges to achieve frequency reconfiguration on a Sievenpiper mushroom metasurface. The study was done by inserting plasma tubes in between the patches of the mushroom structure, in three different positions with respect to the top of the metasurface, and varying the electronic density while keeping the plasma collision frequency. The obtained results show that it is possible to shift the stop-band generated by the metasurface around 25% towards lower frequencies for an electron density value inside the tubes of ${10}^{14}$ cm${}^{-3}$, when they are placed in between the top patches of the metasurface. Additional insertion losses are exhibited when operating near the plasma frequency. Full article

Terahertz functional devices are essential to the advanced applications of terahertz radiation in biology and medicine, nanomaterials, and wireless communications. Due to the small size and high plasma frequency of microplasma, the interaction between terahertz radiation and microplasma provides opportunities for developing functional terahertz devices based on microplasma. This paper reviews the applications of microplasma in terahertz sources, terahertz amplifiers, terahertz filters, and terahertz detectors. The prospects and challenges of the interdisciplinary research between microplasma and terahertz technology are discussed. Full article