Hasil untuk "Plasma engineering. Applied plasma dynamics"

M. Soulier, T. Vacek, K. Geraud et al.

Non-thermal atmospheric pressure plasma jets (APPJs) are increasingly used in biomedical applications due to their low temperatures and ability to generate reactive oxygen and nitrogen species (RONS), making them suitable for sensitive environments like medical therapies. The transferred plasma catheter (TPC), a variant of APPJ, shows promise for endoscopic applications but requires precise control of plasma dynamics in confined spaces to ensure safety and efficacy. Despite extensive studies on guided streamers in traditional APPJs, there is limited understanding of streamer behavior in TPC configurations, particularly in challenging scenarios involving grounded metallic surfaces. This study examines the spatiotemporal dynamics of guided streamers generated by TPCs under varying gap distances to establish a robust framework for safe and effective plasma delivery in endoscopic settings. Combining electrical and optical diagnostics, the study characterizes streamer propagation, electric field profiles, and plasma-induced currents in a helium-driven TPC delivering cold plasma to a grounded metal target across gaps of 2 to 18 mm. Results show that streamers maintain charge stability and effectively interact with the target for gap distances below 12 mm, producing significant therapeutic currents. Beyond this threshold, propagation deteriorates due to recombination and reduced electric field intensity. For shorter gaps, counter-propagating waves and secondary streamer interactions are observed, while larger gaps lead to charge dissipation and reduced efficacy. These findings highlight the importance of optimizing gap distances for plasma-assisted endoscopic procedures and demonstrate the TPC's robustness in adverse conditions.

S. Ratynskaia, M. Hoelzl, E. Nardon et al.

This Roadmap article addresses the critical and multifaceted challenge of plasma-facing component (PFC) damage caused by runaway electrons (REs) in tokamaks, a phenomenon that poses a significant threat to the viability and longevity of future fusion reactors such as ITER and DEMO. The dramatically increased RE production expected in future high-current tokamaks makes it difficult to avoid or mitigate REs when a plasma discharge terminates abnormally. Preventing damage from the intense localised heat loads REs can cause requires a holistic approach that considers plasma, REs and PFC damage. Despite decades of progress in understanding the physics of REs and the thermomechanical response of PFCs, their complex interplay remains poorly understood. This document aims to initiate a coordinated, interdisciplinary approach to bridge this gap by reviewing experimental evidence, advancing diagnostic capabilities, and improving modelling tools across different scales, dimensionalities and fidelities. Key topics include RE beam formation and transport, damage mechanisms in brittle and metallic PFCs, and observations in major facilities such as JET, DIII-D, WEST and EAST. The Roadmap emphasises the urgency of predictive, high-fidelity modelling validated against well-diagnosed controlled experiments, particularly in the light of recent changes in ITER's wall material strategy and the growing importance of private sector initiatives. Each section of the article is written to provide a concise overview of one area of this multidisciplinary subject, with an assessment of the status, a look at current and future challenges, and a brief summary. The ultimate goal of this initiative is to guide future mitigation strategies and design resilient components that can withstand the loads imposed by REs, thus ensuring the safe and sustainable operation of the next generation of fusion power plants.

E. Lotfy, M. Bakry, Hassan Sherif Elplpese

M. I. Baranov

Goal. Calculation and experimental determination of middle speed vL of advancement of plasma leader channel of a pulse spark discharge in the long air interval of the double-electrode discharge system (DEDS) «tip-plane». Methodology. Bases of the theoretical electrical engineering and electrophysics, electrophysics bases of technique of ultra- and high-voltage and high pulse currents, bases of high-voltage pulse technique and measuring technique. Results. The close calculation and experimental method of determination of middle speed vL of advancement of plasma leader channel of an electric pulse spark discharge is offered in the long air interval of DEDS «tip-plane». This method is based on the offered calculation empiric formula for finding of the indicated speed vL and results of decoding of oscillograms of process of cut of in-use standard interconnect аperiodic pulse of over- and high-voltage of temporal shape of Tm/Тd≈200 μs/1990 μs of positive polarity at an electric hasp in indicated DEDS of long air intervals with their minimum length of lmin, numeral making 1,5 m (first case) and 3 m (second case). It is shown that middle speed vL of advancement in atmospheric air of front of plasma channel of positive leader of an electric pulse spark discharge in probed DEDS «tip-plane» for two considered applied cases at lmin=1,5 m of lmin=3 m numeral makes approximately vL≈(1±0,03)∙105 m/s. The found numeral value of this speed vL well coincides with the known experimental information for speed of advancement of vL≈105 m/s in atmospheric air of plasma channel of negative leader for a long storm spark discharge in DEDS «charged cloud-earth». It is set that for the standard interconnect аperiodic pulse of high- and ultra- voltage of temporal shape of Tm/Тd≈200 μs/1990 μs of positive polarity middle value of aggressive strength Ed of high pulse electric field in the air interval of probed DEDS «tip-plane» numeral makes minimum length of lmin=1,5 m near Ed1≈360,8 kV/m, and for his minimum length of lmin=3 m of − Ed2≈313,4 kV/m. Originality. The comfortable is developed in the use and reliable in practical realization technicians-and-engineers calculation and experimental method of research in the conditions of high-voltage electrophysics laboratory of difficult electro-discharge processes of development of leader hasp of long air intervals and determination of minimum electric durability of air insulation of electrical power engineering and electrophysics equipment on working voltage of classes of 330-1150 kV. Practical value. Application in area of industrial electrical power engineering and high-voltage pulse technique of the got numeral electrophysics results and offered calculation and experimental method of determination of middle speed vL of advancement in atmospheric air of plasma channel of leader of a long spark discharge will allow, from one side, to deepen our scientific knowledges about a long electric pulse spark discharge in an air dielectric, and, from other side, to develop high-voltage electrical power engineering and electrophysics devices with enhanceable reliability of their work both in normal operation and malfunctions.

F. M. Marega, L. A. Klok, T. T. Steffen et al.

The increase in bone fractures has been driving the development of materials for bone repair with better mechanical and biological properties. This work reports the development of poly (lactic acid) (PLA)‐zinc oxide (ZnO) biocomposites for 3D printing of scaffolds to be applied in bone tissue engineering. The ZnO surface was functionalized with maleic anhydride (ZnOMA) by applying radio frequency plasma treatment as an alternative to control the catalytic effects of ZnO on the degradation of the PLA during the molten state processing. PLA and ZnOMA powders were processed using a heated internal mixer and the resulted biocomposites were used to manufacture scaffolds by 3D printing. The scaffolds were characterized by their rheological, thermal, microstructural, mechanical, and biological properties. Compositions containing ZnOMA presented higher viscosities, evidencing the control of degradation by surface functionalization, and achieved an elastic modulus near 1 GPa, suitable for bone applications, unlike the untreated samples. In relation to cell functions, PLA‐ZnOMA scaffolds exhibited cell viabilities at 160%, compared to 50% for untreated samples and stimulated mesenchymal stem cells toward osteoblast. Therefore, ZnO's negative thermal degradation effect on PLA was successfully overcome using plasma functionalization, enabling the 3D printing of bioactive scaffolds with great potential for application in tissue engineering.

Mangilal Choudhary

Dusty plasma is an admixture of electrons, ions, and massive charged solid particles of sub-micron to micron-sized in the background of neutral gas. The dust grain medium exhibits fluid (liquid) as well as solid-like characteristics at different background plasma conditions. It supports various linear and non-linear dynamical structures because of the external perturbation and internal instabilities. The vortical or coherent structure in the dusty plasma medium is a kind of self-sustained dynamical structure that is formed either by instabilities or external forcing. In this review article, the author discusses the past theoretical, experimental, and computational investigations on vortical and coherent structures in unmagnetized as well as in magnetized dusty plasma. The possible mechanisms to form vortices in dust grain medium are discussed in detail. The studies on the evolution of vortices and their correlation with turbulence are also reviewed.

H.-D. Huang, J. Chen, Z.-B. Wang

Capacitively coupled radio frequency (CCRF) discharge is widely applied in industry to generate large-area plasmas by the excellent performance of the controllability and discharge uniformity. Such kind of plasma exhibits a filamentation instability when the uniformly-discharging plasmas are subjected to an parallel magnetic field, with the formation of the parallel filamentary plasma patterns. Yet, the instability mechanism and dynamical process have not been well revealed until now. In this study, a kinetic approach using 2D PIC/MCC method is employed to explore the formation process of the filaments in CCRF discharge with magnetic field. The simulation results show how initial temporal perturbations, purely excited by RF pumping, evolve into stronger spatially inhomogeneous filaments with roughly constant diameter, accompanied by nonlinear phenomenon (such as wave modulation). The presence of modulational instability (MI) can be inferred from the results, elucidating the underlying mechanism through initial exploration of the nonlinear wave interactions. The results suggest the presence of the analogue-sheath structures surrounding each filament, constructing strong ambipolar electric field, thereby enhancing heating efficiency. Furthermore, fluid dynamics effects, including thermal pressure force and effective Lorentz force, are utilized to elucidate the emergence and evolution of filaments. It is indicated that the DC component of the effective Lorentz force serves as the primary driving force for the growth of the instability.

H. Zhu, H. Dong

In this work we present an air discharge stratification phenomenon in DC discharge tube in low pressure. We found that the addition of magnetic field can significantly produce discharge stratification. This discharge stratification was probably attributed to change in electronic dynamics processes, particularly variation in the electron energy distribution function due to the addition of a magnetic field. The number of striations is highly sensitive to the magnetic field configuration, discharge current, and gas pressure. This discharge stratification is considered as one of the manifestation of discharge instabilities [1–3]. These instabilities are usually considered undesirable because they disturb the homogeneity of the plasma column. For instance, for luminescent lamps, this means their failure [4]; for plasma etching in microelectronic industry, they destroy the homogeneity of plasma bulk region, and even affect the key process parameters such as electron energy distribution function and charged particle flux [5]; in particular, for high-power gas lasers, from an engineering point of view, they directly affect the optical pumping process, thus degrade or lose the efficiency of the laser [6]. Therefore, the investigation on the instabilities of gas discharge plasma is of great significance for these practical applications.

Xiaowen Wu, Haomin Li, Meng Zhang et al.

With the increasing demand for transformer overload capacity in high percentage renewable energy power grids, higher requirements for high temperature resistance and high thermal conductivity of insulating materials for transformer windings have been put forward. However, most of the existing researches have achieved the homogenization of ceramic film by longer oxidation time, and the homogeneity of ceramic film produced by short-time oxidation is poor, which cannot meet the voltage resistance requirements of transformer windings. In response to this need, the aim is to study the uniform growth in different timing and spatial location environments. For the longitudinal growth characteristics of the film under different oxidation time and the lateral growth characteristics under different spatial positions, the growth process of the ceramic film is explained from both time and space dimensions. The growth and insulation characteristics of plasma electrolytic oxidation ceramic aluminum foil film are investigated and applied to dry-type transformers. The research in this paper provides a theoretical basis and engineering guidance for the development and application of ceramic insulated conductors in power equipment.

J. A. González-Cuevas, R. Argüello, M. Florentin et al.

Escherichia coli bacterium is a rod-shaped organism composed of a complex double membrane structure. Knowledge of electric field driven ion transport through both membranes and the evolution of their induced permeabilization has important applications in biomedical engineering, delivery of genes and antibacterial agents. However, few studies have been conducted on Gram-negative bacteria in this regard considering the contribution of all ion types. To address this gap in knowledge, we have developed a deterministic and stochastic Brownian dynamics model to simulate in 3D space the motion of ions through pores formed in the plasma membranes of E. coli cells during electroporation. The diffusion coefficient, mobility, and translation time of Ca^2+, Mg^2+, Na^+, K^+, and Cl^− ions within the pore region are estimated from the numerical model. Calculations of pore’s conductance have been validated with experiments conducted at Gustave Roussy. From the simulations, it was found that the main driving force of ionic uptake during the pulse is the one due to the externally applied electric field. The results from this work provide a better understanding of ion transport during electroporation, aiding in the design of electrical pulses for maximizing ion throughput, primarily for application in cancer treatment.

Pepijn Heirman, Ruben Verloy, Jana Baroen et al.

The treatment of a well plate by an atmospheric pressure plasma jet is common for in vitro plasma medicine research. Here, reactive species are largely produced through the mixing of the jet effluent with the surrounding atmosphere. This mixing can be influenced not only by the ambient conditions, but also by the geometry of the treated well. To limit this influence and control the atmosphere, a shielding gas is sometimes applied. However, the interplay between the gas shield and the well geometry has not been investigated. In this work, we developed a 2D-axisymmetric computational fluid dynamics model of the kINPen plasma jet, to study the mixing of the jet effluent with the surrounding atmosphere, with and without gas shield. Our computational and experimental results show that the choice of well type can have a significant influence on the effluent conditions, as well as on the effectiveness of the gas shield. Furthermore, the geometry of the shielding gas device can substantially influence the mixing as well. Our results provide a deeper understanding of how the choice of setup geometry can influence the plasma treatment, even when all other operating parameters are unchanged.

D. Nishimura, A. Fujisawa, K. Yamasaki et al.

This article presents a method to estimate the rotational velocity of a cylindrical plasma from its two-dimensional images by an extended use of the Fourier-rectangular function transform, which was proposed to analyze the structure and dynamics of a cylindrical plasma [K. Yamasaki etal., J. Appl. Phys. 126, 043304 (2019)]. The proposed method is applied to tomography images of plasmas produced in a linear cylindrical device and succeeds in obtaining the radial distribution of rotational velocity and its fluctuations, providing an interesting finding, that is, the existence of flow modulation associated with m=1 mode fluctuations.

R. Kaur, G. Slathia, M. Kaur et al.

V. Panov, Yu M. Kulikov, Sergey Vetchinin et al.

The motion of immiscible liquids and electrical breakdown at the interface of two horizontal layers of conducting water and transformer oil are studied under vertically oriented nonuniform pulsed electric field. The interface profile is tracked during experiments and shows the appearance and growth of a water cone inside the oil. After the water cone reaches the high voltage electrode located in the oil, three scenarios are observed depending on water conductivity and pulsed voltage amplitude: electrical current flows over the water without plasma formation; plasma onset occurs due to thermal breakdown in the water at the moment the cone tip touches the sphere; plasma onset occurs due to breakdown through a swarm of small water drops atomized from the cone tip under the action of electrical forces. From experiments and numerical simulations, the breakdown time is determined depending on applied voltage amplitude; the oil–water interface behavior in the electric field is analysed; and the electrical force distribution is studied. The experiment and simulation results show good agreement.

Zhiyong Huang, Ming Feng, Pengcheng Gao et al.

An inhomogeneous ionized plasma layer is generated around the hypersonic vehicle, which may cause radio blackout. In this paper, an innovative multi-physical method combining plasma fluid equations and Maxwell's equations is proposed. Numerical results indicate that the electron concentration can be significantly reduced via the applied magnetic field to create a magnetic window. In addition, this paper proposes a set of simulation methods to realize the process of receiving signals from hypersonic vehicle, avoiding complicated and expensive flight experiments. Providing theoretical basis and simulation data for solving the problem of radio blackout in engineering. This is also one of the innovations of this article, therefore, our research has an extensive application prospect.

E. Lavine, D. A. Lund, C. Seyler et al.

An experimental platform is being developed for the 1-MA, 220-ns rise time COBRA generator at Cornell University to investigate the nature of magnetically driven, self-organized, HED flows and their impact on plasma dynamics and stability by simulating astrophysical jets in a well-diagnosed laboratory experiment. In contrast to previous HED laboratory plasma jet experiments that use radial/conical foils or wire arrays, this experiment uses azimuthally symmetric gas-puff injection. This provides a continuous mass source and allows for free rotation of the jet foot points. Because there is no ablation phase from a dense solid target, the magnetically driven jets develop earlier in the current pulse and can be driven longer without depleting their mass source and disrupting. Flexibility in load design permits the generation of a poloidal dipole field (mimicking a magnetized accretion disk) using permanent magnets or dynamically through a helically twisted cathode. A polarity convolute allows for the reversal of the applied electric field to investigate extended MHD (XMHD) effects. Detailed measurements of flow velocities, temperatures, densities, and magnetic fields will be obtained using optical spectroscopy, laser interferometry, Thomson scattering, magnetic probes, and Faraday rotation imaging. Results will be interpreted using the framework of generalized or canonical helicity, which extends the physics of magnetic flux tubes to canonical flux tubes (a weighted sum of flow vorticity flux and magnetic flux). Here we present the design of the experiment, preliminary experimental observations, and 3D modeling using the PERSEUS XMHD code.

M. Cerepi, K. Hara

One of the key challenges of time-dependent (dynamic) plasma phenomena is the measurement of plasma properties due to the multiscale nature of the plasma flows. An extended Kalman filter (EKF), a state estimation technique that uses both a physics-based model and measurement data, was successfully coupled with a zero-dimensional (0D) plasma model to study the plasma dynamics in Hall effect thrusters (HETs) and pulsed inductively coupled plasma [1], [2]. In this work, we present a state estimation approach for 1D plasma phenomena to estimate the spatiotemporal evolution of plasma properties using a Kalman Filter. The Kalman filter is compared with stochastic differential equations and applied to discharge oscillations in HETs. The results show that the technique provides an effective and efficient estimation method that can be extended to a variety of plasma dynamics applications. This approach has the potential for increased understanding and control in plasma dynamics, leading to improved design and performance of plasma-based systems.

S. Langendorf, A. LaJoie, F. Chu et al.

The Plasma Liner Experiment (PLX) at Los Alamos National Laboratory is studying plasma-jet driven magneto-inertial fusion (PJMIF), an innovative fusion approach in which a magnetized target plasma is compressed and heated by a spherically imploding plasma liner. We report on experimental efforts towards target formation experiments using colliding magnetized plasma jets, formed by coaxial plasma guns with applied field. In the collision of high-beta magnetized jets, we observe aspects of collisional and collisionless plasma dynamics during the jet collision and stagnation, informed by Doppler ion spectroscopy measurements of ion bulk flow and thermalization. Implications for future integrated liner-on-target compression experiments are presented. We also describe a range of kinetic and fluid modeling efforts studying both the near-term experimental scale as well as scaling of the broader PJMIF concept.

M. Reza, F. Faraji, A. Knoll

Partially magnetized low-temperature plasmas (LTP) in an E × B configuration, where the applied magnetic field is perpendicular to the self-consistent electric field, have become increasingly relevant in industrial applications. Hall thrusters, a type of electrostatic plasma propulsion, are one of the main LTP technologies whose advancement is hindered by the not-fully-understood underlying physics of operation, particularly, with respect to the plasma instabilities and the associated electron cross field transport. The development of Hall thrusters with unconventional magnetic field topologies has imposed further questions regarding the instabilities' characteristics and the electrons' dynamics in these modern cross field configurations. Accordingly, we present in this effort a detailed parametric study of the influence of three factors on the plasma processes in the radial-azimuthal coordinates of a Hall thruster, namely, the magnetic field gradient, secondary electron emission, and plasma number density. The studies are carried out using the reduced-order particle-in-cell code developed by the authors. The setup of the radial-azimuthal simulations largely follows a well-defined benchmark case from the literature in which the magnetic field is oriented along the radius, and a constant axial electric field is applied perpendicular to the simulation plane. The salient finding from our investigations is that, in the studied cases corresponding to elevated plasma densities, a long-wavelength azimuthal mode with the frequency of about 1 MHz is developed. Moreover, in the presence of strong magnetic field gradients, this mode results from an inverse energy cascade and induces a significant electron cross field transport as well as a notable heating of the ions.

Antoine Bret, Ramesh Narayan

The properties of collisionless shocks, like the density jump, are usually derived from magnetohydrodynamics (MHD), where isotropic pressures are assumed. Yet, in a collisionless plasma, an external magnetic field can sustain a stable anisotropy. In \cite{BretJPP2018}, we devised a model for the kinetic history of the plasma through the shock front, allowing to self-consistently compute the downstream anisotropy, hence the density jump, in terms of the upstream parameters. This model dealt with the case of a parallel shock, where the magnetic field is normal to the front both in the upstream and the downstream. Yet, MHD also allows for shock solutions, the so-called switch-on solutions, where the field is normal to the front only in the upstream. This article consists in applying our model to these switch-on shocks. While MHD offers only 1 switch-on solution within a limited range of Alfvén Mach numbers, our model offers 2 kinds of solutions within a slightly different range of Alfvén Mach numbers. These 2 solutions are most likely the outcome of the intermediate and fast MHD shocks under our model. While the intermediate and fast shocks merge in MHD for the parallel case, they do not within our model. For simplicity, the formalism is restricted to non-relativistic shocks in pair plasmas where the upstream is cold.