Plasma

30 pages, 705 KiB

Open AccessArticle

Strong, Weak and Merging Lines in Atomic Spectra

by Jean-Christophe Pain

Plasma 2025, 8(2), 17; https://doi.org/10.3390/plasma8020017 - 29 Apr 2025

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We present analytical estimates for the maximum line strength in a transition array, as well as for the numbers of strong and weak lines. For that purpose, two main assumptions are used as concerns the line strength distribution. The first one, due to [...] Read more.

J - J^{'}

sets, where J is the total atomic angular momentum, and the second one, based on a decreasing-exponential modeling of the line-amplitude distribution, is more relevant for an entire transition array. We also review the different approximations of overlapping and blanketing (band model), insisting on the computation and properties of the Elsasser function. We compare different approximations of the Ladenburg–Reiche function giving the equivalent width of an ensemble of lines in a frequency bin and discuss the possibility of using statistical indicators, such as the Chernoff bound or the Gini coefficient (initially introduced in economics for the measurement of income inequality), in the statistical characterization of transition arrays. Full article

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14 pages, 488 KiB

Open AccessArticle

A Theoretical Study of the Ionization States and Electrical Conductivity of Tantalum Plasma

by Shi Chen, Qishuo Zhang, Qianyi Feng, Ziyue Yu, Jingyi Mai, Hongping Zhang, Lili Huang, Chengjin Huang and Mu Li

Plasma 2025, 8(2), 16; https://doi.org/10.3390/plasma8020016 - 28 Apr 2025

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Abstract

Tantalum is extensively used in inertial confinement fusion research for targets in radiation transport experiments, hohlraums in magnetized fusion experiments, and lining foams for hohlraums to suppress wall motions. To comprehend the physical processes associated with these applications, detailed information regarding the ionization composition and electrical conductivity of tantalum plasma across a wide range of densities and temperatures is essential. In this study, we calculate the densities of ionization species and the electrical conductivity of partially ionized, nonideal tantalum plasma based on a simplified theoretical model that accounts for high ionization states up to the atomic number of the element and the lowering of ionization energies. A comparison of the ionization compositions between tantalum and copper plasmas highlights the significant role of ionization energies in determining species populations. Additionally, the average electron–neutral momentum transfer cross-section significantly influences the electrical conductivity calculations, and calibration with experimental measurements offers a method for estimating this atomic parameter. The impact of electrical conductivity in the intermediate-density range on the laser absorption coefficient is discussed using the Drude model. Full article

(This article belongs to the Special Issue Feature Papers in Plasma Sciences 2025)

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15 pages, 4340 KiB

Open AccessArticle

Voltage Dependent Effect of Spiral Wound Plasma Discharge on DBC1.2 Cellular Integrity

by Abubakar Hamza Sadiq, Md Jahangir Alam, Mahedi Hasan, Farhana Begum, Tomoki Yamano, Jaroslav Kristof and Kazuo Shimizu

Plasma 2025, 8(2), 15; https://doi.org/10.3390/plasma8020015 - 12 Apr 2025

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Abstract

Low temperature plasmas (LTPs) generated at atmospheric pressure and room temperature have gained increasing attention in biomedical research due to their ability to control cellular behavior through the production of reactive oxygen and nitrogen species (RONS), electric fields, and UV radiation. Among several LTP configurations, dielectric barrier discharge (DBD) plasma has been extensively studied for its ability to stimulate controlled biological effects while maintaining low gas temperature, making it suitable for cell-based applications. This study designed a novel spiral-wound DBD plasma device to investigate the voltage-dependent effects of plasma discharge on DBC1.2 epithelial cells. Plasma was applied at 2 kV_p-p, 3 kV_p-p, and 4 kV_p-p to evaluate its effect on cellular permeability, mitochondrial activity, viability, and apoptosis. FITC-dextran-70 (FD-70, MW: 70 kDa) was used as a model permeation marker to assess cellular uptake. The results showed a voltage-dependent increase in FD-70 uptake, suggesting improved plasma-assisted drug delivery. The cell mitochondrial activity, evaluated with a MT-1 MitoMP detection kit, revealed that plasma exposure at 2 kV_p-p and 3 kV_p-p slightly enhanced mitochondrial membrane potential (MMP), signifying increased metabolic and mitochondrial activity, whereas exposure at 4 kV_p-p led to a reduction in MMP, suggesting oxidative stress and early apoptosis. Early and late apoptosis was further assessed using FITC Annexin-V and propidium iodide (PI). The results showed enhanced cell viability and a reduced apoptotic cell at 2 kV_p-p and 3 kV_p-p plasma exposure when compared to the control. However, at 4 kV, there was a decline in cell viability and an increase in apoptosis, suggesting a shift towards plasma-induced cytotoxicity. This study established a safe plasma exposure threshold for DBC1.2 cells and explored the potential use of a spiral-wound DBD plasma device for biomedical applications, particularly in drug delivery and cell modulation. Full article

(This article belongs to the Special Issue Recent Advances of Dielectric Barrier Discharges)

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15 pages, 3975 KiB

Open AccessArticle

Decomposition Mechanisms of Lignin-Related Aromatic Monomers in Solution Plasma

by Takaki Miyamoto, Jeanielle Amurao, Eiji Minami and Haruo Kawamoto

Plasma 2025, 8(2), 14; https://doi.org/10.3390/plasma8020014 - 10 Apr 2025

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Abstract

Lignin is a natural aromatic macromolecule present in wood and an abundant resource on Earth, yet it is hardly used. In this study, an aqueous solution plasma treatment was investigated for the catalyst-free production of valuable chemicals from lignin. To elucidate the decomposition mechanism, the aqueous solution plasma treatment was applied to the fundamental lignin aromatic model compounds—phenol, guaiacol, and syringol. The results showed that the decomposition rate followed the order syringol > guaiacol > phenol, indicating that electron-donating methoxy groups enhance reactivity. These aromatic model compounds underwent hydroxylation at the ortho and para positions, oxidative ring cleavage, and fragmentation, leading to the formation of various dicarboxylic acids, primarily oxalic acid. All these reactions were promoted by hydroxyl radicals generated from water. Ultimately, decarbonylation and decarboxylation of carboxyl groups resulted in gasification, mainly producing H₂, CO, and CO₂. These results provide fundamental insights into lignin decomposition and demonstrate that aqueous solution plasma is a promising method for producing dicarboxylic acids from lignin under mild conditions without catalysts. Full article

(This article belongs to the Special Issue Feature Papers in Plasma Sciences 2025)

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17 pages, 3091 KiB

Open AccessReview

A Tutorial on One-Dimensional Numerical Simulation of Virtual Cathode Oscillation

by Weihua Jiang

Plasma 2025, 8(2), 13; https://doi.org/10.3390/plasma8020013 - 1 Apr 2025

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Abstract

This review article is the continuation of a previous publication, by the same author, on one dimensional theory of space charge effect and virtual cathode. The virtual cathode is known to be unstable. However, the process of virtual cathode oscillation is very complicated both physically and mathematically. No satisfactory theoretical model exists that can fully describe the oscillatory behavior of the virtual cathode. On the other hand, computer simulations allow us to numerically observe this phenomenon and establish certain relations between the electron beam parameters and the virtual cathode characteristics. This article explains the detailed procedure of numerical modeling by dealing with the one-dimensional case as an example. A sample code written in the C language is attached at the end following the main text. This article is expected to serve as a reference for young researchers and students who are interested in computer simulations of intense particle beams and high-power microwave generation. Full article

(This article belongs to the Special Issue Latest Review Papers in Plasma Science 2025)

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Plasma, Volume 8, Issue 2 (June 2025) – 5 articles

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