Plasma, Volume 4, Issue 4 (December 2021) – 7 articles

For relatively strong magnetic fields, hydrogen atoms can have delocalized bound states of almost macroscopic dimensions. Therefore, such states are characterized by a Giant Electric Dipole Moment (GEDM), thus making them very sensitive to an external electric field. We considered the manifestations of the GEDM states in hydrogen spectral line profiles in the presence of a quasimonochromatic electrostatic wave of a frequency ω in a plasma. We demonstrated that in this situation, hydrogen spectral lines can exhibit quasi-satellites, which are the envelopes of Blochinzew-type satellites. We showed that the distinctive feature of such quasi-satellites is that their peak intensity is located at the same distance from the line center (in the frequency scale) for all hydrogen spectral lines, the distance being significantly greater than the wave frequency ω. At the absence of the GEDM (and for relatively strong electrostatic waves), the maxima of the satellite envelopes would be at different distances from the line center for different hydrogen lines. We demonstrated that this effect would constitute a supersensitive diagnostic method for measuring the amplitude of electrostatic waves in plasmas down to ~10 V/cm or even lower. Full article

The behavior of corona discharge was investigated in wire–cylinder electrodes under the effect of a crossed magnetic field. Townsend’s formula was used commonly with a modified empirical formula to evaluate the different parameters of corona discharge in positive and negative discharge. By using a least-squares fitting, the dimensional constants A, K, and the exponent n displayed a significant dependence on the applied magnetic field. An improvement of pre-breakdown has been achieved by using a crossed magnetic field. For both polarities, while the magnetic field is present, breakdown voltage V_B and corona inception voltage V₀ increased, whereas the corona current decreases. In addition, the corona inception voltage was greater in positive corona in the absence of a magnetic field, while the opposite occurred regarding the crossed magnetic field. Furthermore, the breakdown streamer demonstrated significant triggering in the negative corona by applying the magnetic field. Full article

Surface dielectric barrier discharge (SDBD) was used to evaluate cylindrical plasma actuators for inactivation of Salmonella enterica. A cylindrical SDBD configuration was evaluated to determine if the inherent induced body force could be leveraged to impel plasma species, such as reactive oxygen and nitrogen species (RONS), as an apparatus to sterilize surfaces. The cylindrical structure is evaluated in this study to observe whether an increase in mixing is possible to efficiently distribute the plasma species, thereby improving bacterial inactivation efficiency. The increase in induced airflow of SDBD actuators with increased numbers of electrodes correlates with increased bacterial inactivation. These results suggest that improving the particle velocity, airflow mixing tendencies, and plasma volume for the same power inputs (same net power to the actuators) results in increased surface decontamination efficiency. Full article

Inductively Coupled Plasma (ICP) discharges are part of intense research. Predicting different plasma parameters, like the distribution and temperature of the present species, is of great interest for many applications. Iodine- or halide-containing plasmas in particular have an important function, for example, in the development of mercury-free UV radiation sources. Therefore, a 2D simulation model of a xenon- and iodine-containing ICP was created by using the Finite Element Method (FEM) software COMSOL Multiphysics^®. The included species and the used reactions are presented in this paper. To verify the simulation in relation to the plasma distribution, the results were compared with measurements from literature. The temperature of the lamp vessel was measured in relation to the temperature distribution and also compared with the results of the simulation. It could be shown that the simulation reproduces the plasma distribution with a maximal deviation of ≈6.5% to the measured values and that the temperature distribution in the examined area can be predicted with deviations of up to ≈24% for long vessel dimensions and ≈3% for shorter dimensions. However, despite the deviating absolute values, the general plasma behaviour is reproduced by the simulation. The simulation thus offers a fast and cost-effective method to estimate an effective geometrical range of iodine-containing ICPs. Full article

Intravenous catheter-related bloodstream infections are a cause of remarkable problems. Catheter lock solutions are used to keep catheter patency and prevent catheter-related bloodstream infections. The leakage of catheter lock solution to the bloodstream raises toxicity concerns. Plasma-treated liquids carry the potential to act as catheter lock solutions by virtue of their strong antimicrobial effects. The present study investigates the tolerance of the proposed solution in vitro and in vivo. N-acetylcysteine (NAC) solution was treated with atmospheric-air DBD plasma and antimicrobial assays were performed. The cytotoxicity of the plasma-treated NAC solution was evaluated on an EA.hy926 cell line. Intravenous administration of plasma-treated NAC solution in different doses was given to Sprague Dawley rats. One week after infusion with plasma-treated NAC solution, first, the blood samples were collected, and then liver, kidney, tail vein, heart, and lung tissue samples were collected from euthanized rats for histopathological examination. The cytotoxicity of plasma-treated NAC solution depended on plasma treatment time, contact time, and cell number. A strong antimicrobial effect with no cytotoxicity of plasma-treated NAC solution was observed in endothelial cells. Based on blood tests and histopathological examination, no signs of systemic toxicity were observed that can be correlated to the plasma-treated-NAC solution. This solution has the potential to be used as a catheter lock solution with strong antimicrobial properties, keeping catheter patency. Full article

Occurrence of electrostatic solitary waves (ESWs) is ubiquitous in space plasmas, e.g., solar wind, Lunar wake and the planetary magnetospheres. Several theoretical models have been proposed to interpret the observed characteristics of the ESWs. These models can broadly be put into two main categories, namely, Bernstein–Green–Kruskal (BGK) modes/phase space holes models, and ion- and electron- acoustic solitons models. There has been a tendency in the space community to favor the models based on BGK modes/phase space holes. Only recently, the potential of soliton models to explain the characteristics of ESWs is being realized. The idea of this review is to present current understanding of the ion- and electron-acoustic solitons and double layers models in multi-component space plasmas. In these models, all the plasma species are considered fluids except the energetic electron component, which is governed by either a kappa distribution or a Maxwellian distribution. Further, these models consider the nonlinear electrostatic waves propagating parallel to the ambient magnetic field. The relationship between the space observations of ESWs and theoretical models is highlighted. Some specific applications of ion- and electron-acoustic solitons/double layers will be discussed by comparing the theoretical predictions with the observations of ESWs in space plasmas. It is shown that the ion- and electron-acoustic solitons/double layers models provide a plausible interpretation for the ESWs observed in space plasmas. Full article

We experimentally investigated the accelerated proton beam characteristics such as maximum energy and number by varying the incident laser parameters. For this purpose, we varied the laser energy, focal spot size, polarization, and pulse duration. The proton spectra were recorded using a single-shot Thomson parabola spectrometer equipped with a microchannel plate and a high-resolution charge-coupled device with a wide detection range from a few tens of keV to several MeV. The outcome of the experimental findings is discussed in detail and compared to other theoretical works. Full article