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Plasma, Volume 8, Issue 3 (September 2025) – 6 articles

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11 pages, 950 KiB

Open AccessArticle

Numerical Investigation on the Thomas–Fermi Model and Its Quantum and Exchange Corrections

by Yangyang Ma, Wenle Song, Junlei Zhao, Lei Wang, Shenghui Mu and Kun Wang

Plasma 2025, 8(3), 31; https://doi.org/10.3390/plasma8030031 - 7 Aug 2025

Viewed by 183

Abstract

The Thomas–Fermi model and its quantum and exchange corrections with mathematic manipulations and numerical approaches are primarily investigated. The reduced ideal electron chemical potential is adopted as the initial value for the iterative solution of the Thomas–Fermi model. A new transformation for the quantum and exchange equations is proposed to apply the boundary conditions easily. Both the Thomas–Fermi equation and correction equations are solved with the Runge–Kutta algorithm. The mathematical difficulties in controlling the computing accuracy of the equations containing the Fermi–Dirac integral are settled. The equation of state, based on the Thomas–Fermi model with its quantum and exchange corrections, is constructed and compared with relevant data. Full article

(This article belongs to the Special Issue New Insights into Plasma Theory, Modeling and Predictive Simulations)

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24 pages, 8575 KiB

Open AccessArticle

Space Charge Structures on Spherical Hollow Electrodes

by Florin Enescu, Codrina Ionita, Dan Gheorghe Dimitriu and Roman Schrittwieser

Plasma 2025, 8(3), 30; https://doi.org/10.3390/plasma8030030 - 25 Jul 2025

Viewed by 234

Abstract

In this article, we present an overview of our investigations on the formation and behavior of space charge structures in an argon discharge plasma on gridded and smooth spherical hollow electrodes with and without orifices. Four experiments are described, in which we have used the following: (1) one spherical gridded sphere with one orifice, (2) one hollow smooth stainless steel sphere with two opposing orifices, (3) two smooth polished stainless steel spherical electrodes without orifices, (4) two smooth polished stainless steel spherical electrodes with opposing orifices. The experiments were conducted at the University of Innsbruck in a stainless steel cylindrical chamber (the former Innsbruck DP machine—IDP), and at the Alexandru Ioan Cuza University of Iaşi (Romania) in a Pyrex Vacuum Chamber (PCH). As diagnostics, we have used mainly optical emission spectroscopy to determine electron temperature and density. Full article

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

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19 pages, 7154 KiB

Open AccessArticle

A Heuristic Exploration of Zonal Flow-like Structures in the Presence of Toroidal Rotation in a Non-Inertial Frame

by Xinliang Xu, Yihang Chen, Yulin Zhou, Zhanhui Wang, Xueke Wu, Bo Li, Jiang Sun, Junzhao Zhang and Da Li

Plasma 2025, 8(3), 29; https://doi.org/10.3390/plasma8030029 - 22 Jul 2025

Viewed by 156

Abstract

The mechanisms by which rotation influences zonal flows (ZFs) in plasma are incompletely understood, presenting a significant challenge in the study of plasma dynamics. This research addresses this gap by investigating the role of non-inertial effects—specifically centrifugal and Coriolis forces—on Geodesic Acoustic Modes (GAMs) and ZFs in rotating tokamak plasmas. While previous studies have linked centrifugal convection to plasma toroidal rotation, they often overlook the Coriolis effects or inconsistently incorporate non-inertial terms into magneto-hydrodynamic (MHD) equations. In this work, we derive self-consistent drift-ordered two-fluid equations from the collisional Vlasov equation in a non-inertial frame, and we modify the Hermes cold ion code to simulate the impact of rotation on GAMs and ZFs. Our simulations reveal that toroidal rotation enhances ZF amplitude and GAM frequency, with Coriolis convection playing a critical role in GAM propagation and the global structure of ZFs. Analysis of simulation outcomes indicates that centrifugal drift drives parallel velocity growth, while Coriolis drift facilitates radial propagation of GAMs. This work may provide valuable insights into momentum transport and flow shear dynamics in tokamaks, with implications for turbulence suppression and confinement optimization. Full article

(This article belongs to the Special Issue New Insights into Plasma Theory, Modeling and Predictive Simulations)

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14 pages, 2726 KiB

Open AccessArticle

Streamer Discharge Modeling for Plasma-Assisted Combustion

by Stuart Reyes and Shirshak Kumar Dhali

Plasma 2025, 8(3), 28; https://doi.org/10.3390/plasma8030028 - 10 Jul 2025

Viewed by 412

Abstract

Some of the popular and successful atmospheric pressure fuel/air plasma-assisted combustion methods use repetitive ns pulsed discharges and dielectric-barrier discharges. The transient phase in such discharges is dominated by transport under strong space charge from ionization fronts, which is best characterized by the streamer model. The role of the nonthermal plasma in such discharges is to produce radicals, which accelerates the chemical conversion reaction leading to temperature rise and ignition. Therefore, the characterization of the streamer and its energy partitioning is essential to develop a predictive model. We examine the important characteristics of streamers that influence combustion and develop some macroscopic parameters. Our results show that the radicals’ production efficiency at an applied field is nearly independent of time and the radical density generated depends only on the electrical energy density coupled to the plasma. We compare the results of the streamer model to the zero-dimensional uniform field Townsend-like discharge, and our results show a significant difference. The results concerning the influence of energy density and repetition rate on the ignition of a hydrogen/air fuel mixture are presented. Full article

(This article belongs to the Special Issue New Insights into Plasma Theory, Modeling and Predictive Simulations)

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28 pages, 8047 KiB

Open AccessArticle

Hybrid Dielectric Barrier Discharge Reactor: Production of Reactive Oxygen–Nitrogen Species in Humid Air

by Dariusz Korzec, Florian Freund, Christian Bäuml, Patrik Penzkofer, Oliver Beier, Andreas Pfuch, Klaus Vogelsang, Frank Froehlich and Stefan Nettesheim

Plasma 2025, 8(3), 27; https://doi.org/10.3390/plasma8030027 - 6 Jul 2025

Viewed by 816

Abstract

Reactive oxygen–nitrogen species (RONS) production in a Peltier-cooled hybrid dielectric barrier discharge (HDBD) reactor operated with humid air is characterized. Fourier-transform infrared spectroscopy (FTIR) is used to determine the RONS in the HDBD-produced gases. The presence of molecules

O_{3}

{NO}_{2}

[...] Read more.

O_{3}

{NO}_{2}

N_{2}

N_{2} O_{5}

, and

{HNO}_{3}

is evaluated. The influence of HDBD reactor operation parameters on the FTIR result is discussed. The strongest influence of Peltier cooling on RONS chemistry is reached at conditions related to a high specific energy input (SEI): high voltage and duty cycle of plasma width modulation (PWM), and low gas flow. Both PWM and Peltier cooling can achieve a change in the chemistry from oxygen-based to nitrogen-based.

N_{2} O_{5}

and

{HNO}_{3}

are detected at a low humidity of 7% in the reactor input air but not at humidity exceeding 90%. In addition to the FTIR analysis, the plasma-activated water (PAW) is investigated. PAW is produced by bubbling the HDBD plasma gas through 12.5 mL of distilled water in a closed-loop circulation at a high SEI. Despite the absence of

N_{2} O_{5}

and

{HNO}_{3}

in the gas phase, the acidity of the PAW is increased. The pH value decreases on average by 0.12 per minute. Full article

(This article belongs to the Special Issue Processes in Atmospheric-Pressure Plasmas—2nd Edition)

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18 pages, 995 KiB

Open AccessArticle

A Quasi-Spherical Fusion Reactor Burning Boron-11 Fuel

by Joel G. Rogers, Andrew A. Egly, Yoon S. Roh, Robert E. Terry and Frank J. Wessel

Plasma 2025, 8(3), 26; https://doi.org/10.3390/plasma8030026 - 30 Jun 2025

Viewed by 407

Abstract

In this study, particle-in-cell (PIC) simulation was used to validate a conceptual design for a quasi-spherical, net power, hydrogen-plus-boron-11-fueled fusion reactor incorporating high-temperature superconducting (HTS) magnets. By burning a fully thermalized plasma, our proposed MET6 reactor uses the principles of the 1980 magneto-electrostatic trap design of Yushmanov to improve the classic Polywell design. Because the input power consumed by the reactor will barely balance the waste bremsstrahlung radiation, future research must focus on reducing the bremsstrahlung losses to reach practical net power levels. The first step to reducing bremsstrahlung, explored in this paper, is to tune the reactor parameters to reduce the energies of trapped electrons. We assume the quality factor Q can be approximated as the ratio of fusion power output divided by bremsstrahlung power loss. Thus, assuming the particles’ power loss is negligible compared to bremsstrahlung power loss, the resulting quality factor is estimated to be Q ≈ 1.3. Full article

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

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