Hasil untuk "Plasma physics. Ionized gases"

Iu. P. Raizer

S. Nijdam, J. Teunissen, U. Ebert

In this review we describe a transient type of gas discharge which is commonly called a streamer discharge, as well as a few related phenomena in pulsed discharges. Streamers are propagating ionization fronts with self-organized field enhancement at their tips that can appear in atmospheric air, or more generally in gases over distances larger than order 1 cm times N 0/N, where N is gas density and N 0 is gas density under ambient conditions. Streamers are the precursors of other discharges like sparks and lightning, but they also occur in for example corona reactors or plasma jets which are used for a variety of plasma chemical purposes. When enough space is available, streamers can also form at much lower pressures, like in the case of sprite discharges high up in the atmosphere. We explain the structure and basic underlying physics of streamer discharges, and how they scale with gas density. We discuss the chemistry and applications of streamers, and describe their two main stages in detail: inception and propagation. We also look at some other topics, like interaction with flow and heat, related pulsed discharges, and electron runaway and high energy radiation. Finally, we discuss streamer simulations and diagnostics in quite some detail. This review is written with two purposes in mind: first, we describe recent results on the physics of streamer discharges, with a focus on the work performed in our groups. We also describe recent developments in diagnostics and simulations of streamers. Second, we provide background information on the above-mentioned aspects of streamers. This review can therefore be used as a tutorial by researchers starting to work in the field of streamer physics.

Nils T. Basse

Turbulent flow in neutral fluids and fusion plasmas is known to have many commonalities, one example being the application of energy and enstrophy cascades. In this review, we discuss a cyclic process which may also be common to both fluids and plasmas: this includes exact coherent states (or magnetic islands), Reynolds stress-driven (zonal) flows and internal interface layers (or internal transport barriers). We connect this picture to the broader literature on layered “staircase” states in both magnetized plasmas and stratified/rotating fluids, where sharp interfaces separate well-mixed regions. We briefly review the current understanding of internal interface layers in fluids, summarize a minimal set of driving/damping relations for mean flows and transport suppression, and discuss open questions and possible research directions. The main objective is to create awareness of shared mechanisms to motivate further interdisciplinary research in this field, by both the fluid mechanics and plasma physics communities.

Petre Cornel Min

Nuclear and radiological emergency preparedness and response (EPR) including decision-support systems and emergency management frameworks operate at the intersection of advanced technical modelling, organizational processes, human decision-making, and societal dynamics. This review is based on a critical synthesis of the scientific and institutional literature addressing dispersion modelling, decision-support systems, emergency management frameworks, and large-scale exercise practice in nuclear and radiological emergencies. By examining how modelling outputs are generated, interpreted, and operationalized across preparedness and response contexts, the review identifies persistent gaps between analytical capabilities and real-world decision-making under uncertainty, time pressure, and multi-actor coordination. The analysis reveals that while significant progress has been achieved in modelling and computational tools, their integration into adaptive management and governance structures remains limited. Existing decision-support approaches often emphasize predefined scenarios and procedural compliance, offering limited support for exploratory reasoning and trade-off analysis in complex and evolving emergencies. Building on these findings, the review advances the concept of Hybrid Emergency Operations Centers (Hybrid EOCs) as an integrative operational and governance framework that connects modelling, decision-support, organizational workflows, and human-in-the-loop decision-making. Rather than prescribing optimal decisions, the proposed approach positions advanced modelling to structure decision spaces, enhance transparency, and support adaptive judgement within complex emergency response ecosystems.

Shi Chen, Qishuo Zhang, Qianyi Feng et al.

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.

Akhilesh Kumar Singh, Rajesh Prakash Guragain, Keshav Raj Sigdel et al.

The light emitted spectra of air and air/argon plasmas at ambient pressure in a dielectric barrier discharge (DBD) operating at power supply frequency, 50 Hz, were recorded using an optical emission spectrometer (OES). The spectra cover the full wavelength range from 2000 A0 to 11,000 A0. It was found that air/argon plasma displays the radical composed of OH (A²Σ⁺(v′=0) → X²Π(v″=0)) at 3090 A0, a feature not observed in air plasma. The LIFBASE software suite was utilized to obtain the best fit between simulated and experimental spectra. At a voltage amplitude of 11.6 kV and a discharge gap of 0.3 cm, the plasma gas temperature, determined from the OH (3090 A0) line, was found to be 420 ± 10 K. Additionally, the intensity of the OH radical (3090A0) in air/argon plasma was studied in relation to the argon gas flow rate, applied voltage, and discharge gap. The results showed that, at a constant discharge gap, the OH intensity increases with higher argon flow and applied voltage. However, as the discharge gap increases, the OH intensity first rises and then decreases. The maximum OH intensity for a given applied voltage occurs at a discharge gap of 0.3 cm. Furthermore, the electrical diagnostics of air/argon plasma were done. Using the current density method, the electron concentration was found to be around 1017 m-3. Analysis of the current and voltage waveforms, along with the Lissajous figure approach, indicated that the reactor's power consumption was 6.2 watts. These findings contribute to a better understanding of DBD plasma's physical and chemical properties, and its potential applications in fields such as plasma agriculture, plasma chemistry and plasma medicine.

Dmitry Levko

This paper reviews the state of the art of our understanding of the mechanisms of runaway electron generation in pressurized gases from the numerical modeling perspective. Since the energy relaxation length of these electrons is comparable to the interelectrode spacing, these electrons can be captured only using the kinetic approach. Therefore, only the results from kinetic models are discussed here. Special attention is given to pulsed discharges, which play an important role in modern industry. It is concluded that the mechanisms of runaway electron generation are defined by the gap overvoltage and the discharge gap geometry. For small and moderate overvoltages, runaway electrons are primarily generated at the heads of fast ionization waves or streamers. Due to their long energy relaxation length, these electrons can pre-ionize the discharge gap far from their origin, accelerating ionization and starting new avalanches. At high overvoltages, cathode surface irregularities enhance the local electric field, leading to electron emission into the interelectrode space. These electrons, injected into the strong electric field, gain high energy and reach discharge walls with extremely high energies measuring tens and hundreds of electron volts. These electrons not only pre-ionize the gas but also stimulate the emission of high-energy photons, which can further contribute to the pre-ionization of the discharge gap.

Michael Okebiorun, Dalton Miller, Kenneth A. Cornell et al.

The study evaluates the efficacy of an image-guided CAP treatment method with a plasma device capable of rapid biofilm removal from chicken tissue. The plasma treatment operating configuration includes a gas mixture of Argon and H₂O at a flowrate of 1.5 lpm. An X-Y stage was used to move the chicken sample below the stationary plasma scalpel at a speed of 0.1 mm/s. The discharge voltage and current were maintained between 3.2 and 3.7 kV (AC 20 kHz), and at 3 mA, respectively. The electrode gap and sample distance were set to 0.6 mm and 4 mm. This configuration facilitated effective biofilm removal, as confirmed by CFU analysis and 3D microscopic analysis showing a >99% reduction in biofilm post treatment with an etch rate of 2.2–5.8 µm/s and an impact width of up to 300 µm. The plasma scalpel electrode temperature reached 94.7 °C, while the targeted biofilm area was heated to 36.3 °C, suggesting non-thermal biofilm disruption. Three-dimensional microscopic analysis revealed biofilm thickness on chicken tissues ranging from 20 to 180 µm, comparable to biofilm loads on mammalian tissues. In conclusion, the study highlights the potential of CAP devices as a promising solution for biofilm debridement.

Bandombele Marcel Mokili, Bandombele Marcel Mokili, Abdesselam Abdelouas

The sorption properties of I2 and CH3I on activated carbon were reviewed. The dependence of the sorption capacity on activated carbon of iodine and methyl iodide in air or effluent gas on the sampling operating conditions (temperature, relative humidity, linear velocity and bed length) was investigated. A compilation of experimental data on the sorption efficiency, penetration or decontamination factor of gaseous radioactive iodine species was carried out for nuclear-grade activated carbon. Non-linear surface fitting of experimental data of I2 and CH3I sorption efficiencies by activated carbon at different values of temperature and relative humidity shows that there are ranges of variation in both parameters where the removal capacity remains relatively constant. The values and associated uncertainties of the sorption efficiencies of I2 and CH3I by activated carbon cartridges with bed lengths of 25 and 50 mm were determined for different specified ranges of temperature, relative humidity and linear gas flow velocity. The Sorption Efficiency (SE) values can be used to determine the concentration of iodine radioisotopes in the gaseous effluent or ambient air in Bq/m3 from the results of radionuclide activity in the cartridge measured by gamma spectrometry.

Harry Jang, Frederic Poineau

This perspective explores recent advancements in the synthesis and application of uranium fluoride micromaterials, emphasizing their role in the nuclear industry. Uranium micromaterials, including oxides, fluorides, and carbides, are crucial for applications ranging from high-temperature gas-cooled reactors to nuclear forensics and medical isotope production. The perspective highlights a novel chemical transformation process for synthesizing uranium fluoride micromaterials, in which uranium oxides are fluorinated in an autoclave using HF gas (generated from the decomposition of silver bifluoride) or ammonium bifluoride while preserving their original morphologies. This transformation produces various uranium fluoride microstructures, including UF4, UO2F2, and (NH4)3UO2F5, in the form of microrods, microplates, and microspheres. The perspective discusses challenges in maintaining controlled morphologies during fluorination and explores future directions, such as the synthesis of actinide fluoride micromaterials and the development of uranium chloride and other uranium compounds. The continued advancement of these materials holds significant potential for innovations in nuclear fuel cycles, actinide material chemistry, and nuclear forensics.

Zhaohui Wu, Hao Peng, Xiaoming Zeng et al.

We present the first experimental realization of a four-dimensional (4D) plasma hologram capable of recording and reconstructing the full spatiotemporal information of intense laser pulses. The holographic encoding is achieved through the interference of a long object pulse and a counter-propagating short reference pulse, generating an ionized plasma grating that captures both spatial and temporal characteristics of the laser field. A first-order diffractive probe enables the retrieval of encoded information, successfully reconstructing the spatiotemporal profiles of Gaussian and Laguerre-Gaussian beams. The experiment demonstrates the ability to encode artificial information into the laser pulse via spectral modulation and retrieve it through plasma grating diffraction, high-lighting potential applications in ultraintense optical data processing. Key innovations include a single-shot, background-free method for direct far-field spatiotemporal measurement and the obser-vation of laser focus propagation dynamics in plasma. The plasma grating exhibits a stable lifetime of 30-40 ps and supports high repetition rates, suggesting usage for high-speed optical switches and plasmatic analog memory. These advancements establish plasma holography as a robust platform for ultrafast laser manipulation, with implications for secure optical communication, analog computing,and precision spatiotemporal control of high-intensity lasers.

Osama A. Marzouk

This study explores the suitability of hydrogen-based plasma in direct power extraction (DPE) as a non-conventional electricity generation method. We apply computational modeling and principles in physics and chemistry to estimate different thermal and electric properties of a water-vapor/nitrogen/cesium-vapor (H2O/N2/Cs) gas mixture with different levels of cesium (Cs) at a fixed temperature of 2300 K ( $2026.85~^{\circ }$ C). This gas mixture and temperature are selected because they resemble the stoichiometric combustion of hydrogen with air, followed by the addition of the alkali metal element cesium to allow ionization, thus converting the gas mixture into electrically conducting plasma. We vary the cesium mole fraction in the gas mixture by two orders of magnitude, from a minute amount of 0.0625% (1/1600) to a major amount of 16% (0.16). We use these results to further estimate the theoretical upper limit of the electric power output from a unit volume of a high-speed magnetohydrodynamic (MHD) channel, with the plasma accelerated inside it to twice the local speed of sound (Mach number 2) while subject to an applied magnetic field of 5 T (5 teslas). We report that there is an optimum cesium mole fraction of 3%, at which the power output is maximized. Per 1 m3 of plasma volume, the estimated theoretical electric power generation at 1 atm (101.325 kPa) pressure of the hydrogen-combustion mixture is extraordinarily high at 360 MW/m3, and the plasma electric conductivity is 17.5 S/m. This estimated power generation even reaches an impressive level of 1.15 GW/m3 (11500 MW/m3) if the absolute pressure can be decreased to 0.0625 atm (6.333 kPa), at which the electric conductivity exceeds 55 S/m (more than 10 times the electric conductivity of seawater). Our interdisciplinary study combines principles from various fields (gas dynamics, thermodynamics, physics, and chemistry) while analyzing thermochemical and electric properties of weakly-ionized plasma. The study’s findings may raise interest in the utilization of hydrogen (particularly green hydrogen) in magnetohydrodynamic direct power extraction (MHD-DPE).

Huasheng Xie, Haojie Ma, Yukun Bai

Although an accurate description of wave propagation and absorption in plasmas requires complicated full-wave solutions or kinetic simulations, local dispersion analysis can still be helpful to capture the main physics of wave properties. Plasma wave propagation conditions or accessibility informs whether a wave can propagate to a region, which usually depends on the wave frequency, wave vector, the local plasma density, and magnetic field. We demonstrate a warm multi-fluid eigenvalue model and a matrix approach to rapidly calculate plasma wave accessibility diagrams, where thermal effects are also included via an isotropic pressure term. All cold plasma waves, from high-frequency electron cyclotron waves, intermediate-frequency lower hybrid waves, to low-frequency ion cyclotron waves, are presented. By comparing with the kinetic model, it is interesting to find that the warm multi-fluid model, though incapable of reproducing the Bernstein modes, can provide a quick way to determine whether thermal effects are important.

Emily De Stefanis, Kemal Ramic, Judith Vidal et al.

Ionic liquid materials are viable candidates as a heat transfer fluid (HTF) in a wide range of applications, notably within concentrated solar power (CSP) technology and molten salt reactors (MSRs). For next-generation CSP and MSR technologies that strive for higher power generation efficiency, a HTF with wide liquid phase range and energy storage capabilities is crucial. Studies have shown that eutectic chloride salts exhibit thermal stability at high temperatures, high heat storage capacity, and are less expensive than nitrate and carbonate salts. However, the experimental data needed to fully evaluate the potential of eutectic chloride salts as a HTF contender are scarce and entail large uncertainties. Considering the high cost and potential hazards associated with the experimental methods used to determine the properties of ionic liquids, molecular modeling can be used as a viable alternative resource. In this study, the eutectic ternary chloride salt MgCl2–NaCl–KCl is modeled using ab-initio molecular dynamics simulations (AIMDs) in the liquid phase. Using the simulated data, the thermophysical and transport properties of eutectic chloride salt can be calculated: density, viscosity, heat capacity, diffusion coefficient, and ionic conductivity. For an initial model validation, experimental pair-distribution function data were obtained from X-ray total scattering techniques and compared to the theoretical pair-distribution function. Additionally, theoretical viscosity values are compared to experimental viscosity values for a similar system. The results provide a starting foundation for a MgCl2–NaCl–KCl model that can be extended to predict other fundamental properties.

Sergey N. Grigoriev, Alexander S. Metel, Marina A. Volosova et al.

Mechanical polishing of a product makes it possible to decrease the roughness of its surface to Ra = 0.001 µm by rubbing it with a fine abrasive contained in a fabric or other soft material. This method takes too much time and is associated with abrasive particles and microscopic scratches remaining after the processing. As such, a non-contact treatment with plasma and accelerated particles has been chosen in the present work to study polishing of ceramic samples. The small angular divergence of fast argon atoms made it possible to obtain the dependence of the sample roughness on the angle α of the atom’s incidence on its surface. It was found that the roughness weakly depends on the angle α, if not exceeding the threshold value α_o ~ 50°, and rapidly decreases with increasing α > α_o. Polishing with fast argon atoms leads to a noticeable decrease in friction of ceramic samples.

Jan Weiland, Tariq Rafiq, Eugenio Schuster

As it turns out, both isotope scaling and density limits are phenomena closely linked to fluid closure. The necessity to include ion viscosity arises for both phenomena. Thus, we have added ion viscosity to our model. The experimental isotope scaling has been successfully recovered in our fluid model through parameter scans. Although ion viscosity typically exerts a small effect, the density limit is manifested by increasing the density by approximately tenfold from the typical experimental density. In our case, this increase originates from the density in the Cyclone base case. Notably, these phenomena would not manifest with a gyro-Landau fluid closure. The isotope scaling is nullified by the addition of a gyro-Landau term, while the density limit results from permitting ion viscosity to become comparable to the gyro-Landau term. The mechanism of zonal flows, demonstrated analytically for the Dimits upshift, yields insights into the isotope scaling observed in experiments. In our approach, ion viscosity is introduced in place of the Landau fluid resonances found in some fluid models. This implies that the mechanism of isotope scaling operates at the level of fluid closure in connection with the generation of zonal flows. The strength of zonal flows in our model has been verified, particularly in connection with the successful simulation of the nonlinear Dimits shift. Consequently, a role is played by our approach in the temperature perturbation part of the Reynolds stress.

Pierpaolo Iovane, Carmela Borriello, Giuseppe Pandolfi et al.

The production of spherical powders has recently registered a boost due to the need to fabricate new printing materials for Additive Manufacturing applications, from polymers and resins to metals and ceramics. Among these materials, stainless steels powders play a leading role, since they are widely used in industry and everyday life; indeed, micron-sized spherical stainless steel powders have specific characteristics and are considered as one of the best candidates for Additive Manufacturing systems and for application in a wide range of sectors. In this paper, stainless steel 316 L powders were used to explore and identify the best process parameters of a thermal plasma process able to produce spherical powders for Additive Manufacturing applications. X-ray Diffraction, Scanning Electron Microscopy, Particle Size Distribution and Flowability analysis were performed to characterize reagents and products. Powders with a high circularity (>0.8) and improved flowability (<30 s/50 g) were successfully obtained. The collected results were compared with data available from the literature to identify the potential use of the spherical produced powders.

Susan Ortner, Paul Styman, Elliot Long

It is necessary to quantify the effects of flux on reactor pressure vessel steel embrittlement under neutron irradiation, if surveillance or high-flux test reactor data is used to predict vessel embrittlement occurring at lower fluxes. This is particularly important when considering embrittlement occurring during extended (60–80 years) operation for which there is no direct experience. Dedicated investigations are time-consuming and expensive even when only small flux-fluence ranges are investigated, so collating data from multiple campaigns is necessary to provide sufficient information to cover the wide range of fluxes required for vessel assessment in the long term. This paper collates and reviews such data. The review finds that flux dependences probably differ in sign and strength in different regimes (low flux and fluence, intermediate flux at low and high fluence, high flux at low and high fluence) with the regime limits affected by composition and temperature. The current understanding of diffusion processes and microstructural development are invaluable in interpreting the trends and limits. Many contradictory data sets were found, however, and not all contradictions could be dismissed as resulting from poor quality data. Suggestions are made for investigations to clarify the uncertainties. One wide-ranging model of flux effects, based on an extensive data set, is used to compare high-fluence data from different sources, to assess whether embrittlement rates accelerate after a high, threshold fluence. The model helps to identify experiments which investigated comparable flux-fluence-temperature regimes. The comparable data are split evenly between data sets supporting acceleration after a particular fluence and data sets contradicting it. The model identifies regimes in which further campaigns would clarify the causes of these contrasting observations.

Faisal J. Khan, M. Ikram, Mostafa Rashdan et al.

Electron cyclotron resonance heating method of Particle-in-Cell code was used to analyze heating phenomena, axial kinetic energy, and self-consistent electric field of confined electron plasma in ELTRAP device by hydrogen and helium background gases. The electromagnetic simulations were performed at a constant power of 3.8 V for different RF drives (0.5 GHz– 8 GHz), as well as for 1 GHz constant frequency at these varying amplitudes (1 V—3.8 V). The impacts of axial and radial temperatures were found maximum at 1.8 V and 5 GHz as compared to other amplitudes and frequencies for both background gases. These effects are higher at varying radio frequencies due to more ionization and secondary electrons production and maximum recorded radial temperature for hydrogen background gas was 170.41 eV. The axial kinetic energy impacts were found more effective in the outer radial part (between 0.03 and 0.04 meters) of the ELTRAP device due to applied VRF through C8 electrode. The self-consistent electric field was found higher for helium background gas at 5 GHz RF than other amplitudes and radio frequencies. The excitation and ionization rates were found to be higher along the radial direction (r-axis) than the axial direction (z-axis) in helium background gas as compared to hydrogen background gas. The current studies are advantageous for nuclear physics applications, beam physics, microelectronics, coherent radiation devices and also in magnetrons.

Y. Cao, Y. Bliokh, J. Leopold et al.

Over last ten years, ultra-intense (sub-gigawatt) ultra-short (sub-nanosecond) high-power microwave (HPM) sources (X- and K-band) were developed. These advancements have facilitated the exploration of microwave-plasma and microwave-gas interactions in nonlinear regimes that were previously unachievable. In this presentation, we will unveil findings from studies conducted over the past five years at the Technion - Israel Institute of Technology’s Plasma Physics and Pulsed Power Laboratory. We have discovered a range of novel phenomena, including the self-channeling of HPM pulses triggered by ionization [1], [2], the generation of plasma wakefields driven by HPM [3], the nonlinear total absorption of these pulses [4], and their propagation at superluminal speeds. [5]. These insights have been confirmed through experimental investigations and are buttressed by both theoretical and computational studies, significantly enhancing our comprehension of the dynamics involved in interactions between microwaves and plasma.