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15 pages, 6388 KiB

Open AccessArticle

Anodization Time Effect on Silver Particles Deposition on Anodic Oxide Coating over Al Produced by Plasma Electrolytic Oxidation

by Francisco Trivinho-Strixino, Adriana O. Delgado-Silva, Janaina S. Santos, Andressa Rodrigues, Giovanni P. Mambrini and Mariana S. Sikora

Plasma 2023, 6(2), 235-249; https://doi.org/10.3390/plasma6020018 - 23 Apr 2023

Viewed by 1668

Abstract

In this study, 6061 Al alloy was galvanostatically anodized under the Plasma Electrolytic Oxidation (PEO) condition. A factorial design of 2² was carried out using two variables (anodization time and presence of silver in the electrolyte) on two levels, i.e., 20 and [...] Read more.

In this study, 6061 Al alloy was galvanostatically anodized under the Plasma Electrolytic Oxidation (PEO) condition. A factorial design of 2² was carried out using two variables (anodization time and presence of silver in the electrolyte) on two levels, i.e., 20 and 60 min of anodization and the absence/presence of silver ions in the electrolyte. The Al anodization was performed in sodium silicate electrolyte, applying a constant current density of 20 mA cm⁻². The oxide characterization was performed by Scanning Electron Microscopy (SEM), surface roughness analysis (RMS), Energy Dispersive Spectroscopy (EDS), Rutherford Backscattered Spectroscopy (RBS), and Grazing Incidence X-ray Diffraction (GIXRD). The SEM micrographs revealed an irregular porous structure with cracks on the oxide surface composed of a thin crystalline layer of γ-Al₂O₃ over the Al substrate. From EDS and RBS analysis, it was possible to identify the elements Al, O, Si, Ag, and Na, demonstrating that a shorter anodization time (20 min) led to a significant amount of silver deposits on the outer layer of the oxide coating, mainly deposited in the surroundings of the pores. Conversely, the silver content on the PEO film anodized for 60 min was meager. These results demonstrated that the anodization time was the critical control variable for the amount of silver deposited over the oxide film. The shorter the anodizing time, the higher the silver content on the PEO coating. Full article

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

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10 pages, 3201 KiB

Open AccessArticle

Combinatorial Synthesis of AlTiN Thin Films

by Ferrine Gianne G. Reyes, Jason P. Licerio, Aian B. Ontoria and Magdaleno R. Vasquez, Jr.

Plasma 2023, 6(2), 225-234; https://doi.org/10.3390/plasma6020017 - 3 Apr 2023

Cited by 3 | Viewed by 2022

Abstract

Nitrides of aluminum (Al) and titanium (Ti) mixtures have long been studied and used as commercial coatings because of their high hardness and high oxidation resistance due to the formation of an alumina layer on the coating surface. To fully understand the contribution [...] Read more.

Nitrides of aluminum (Al) and titanium (Ti) mixtures have long been studied and used as commercial coatings because of their high hardness and high oxidation resistance due to the formation of an alumina layer on the coating surface. To fully understand the contribution of Al and Ti to the properties of the film, a combinatorial deposition approach was employed using half-disk targets. Film growth was carried out using a magnetron sputtering system powered by a 13.56 MHz radio frequency power supply with varying argon (Ar) and nitrogen (N₂) gas ratios. Depending on the location of the substrate relative to the target, atomic percent gradients of 0.60–0.70 Al and 0.30–0.40 Ti across the substrate surface were obtained from energy dispersive X-ray spectral analysis. X-ray diffraction peaks at 43.59°, 74.71° (face-centered cubic), and 50.60° (wurtzite) confirmed the presence of aluminum titanium nitride (AlTiN) mixtures, with an increasing amount of wurtzite phase at higher Al concentrations. For all samples, cauliflower-like nanograins were obtained and samples of the 80:20 Ar:N₂ gas pressure ratio showed the smallest grain size among the three gas ratio combinations. The 80:20 Ar:N₂ films revealed a relatively high hardness compared to the other gas ratios. All thin films exhibited good adhesion to 304 stainless steel substrates. Full article

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

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14 pages, 7428 KiB

Open AccessArticle

Geometrical Analysis of the Stagnation Zone in Laterally Colliding Plasmas: Effects of Plasma Plume Separation and Ablating Target Material

by Haider M. Al-Juboori and Tom McCormack

Plasma 2023, 6(2), 198-211; https://doi.org/10.3390/plasma6020015 - 30 Mar 2023

Viewed by 1837

Abstract

The influence of an ablating target’s atomic mass on the development and growth of the interaction zone in laterally colliding plasmas has been investigated. As diagnostic tools, fast imaging and optical emission techniques were used to evaluate the characteristics of the seed plasma [...] Read more.

The influence of an ablating target’s atomic mass on the development and growth of the interaction zone in laterally colliding plasmas has been investigated. As diagnostic tools, fast imaging and optical emission techniques were used to evaluate the characteristics of the seed plasma as well as the interaction zone created by different target materials (i.e., aluminum and silicon). The current findings show that the dynamical, spectral, and geometrical properties of the generated interaction zone are affected by the features of the ablated species and the geographical separation of the interacting plumes. The interaction of aluminum plume species results in a sharper, more intense, and more directed stagnation zone than that reported for silicon targets using a 450 nm filter. Furthermore, the investigation of the interaction area emission from both regions for aluminum (Al) and silicon (Si) plasma explains the variation in plasma properties in the stagnation zone. As a part of this work’s description, a comparative study of the dynamics and characteristics of the homogenous interaction region produced by colliding plasma plumes by laser ablation of flat Al and Si targets has been presented, which can provide deep insight into the characterization of colliding laser-produced plasma expansion and related physical and technical properties. Full article

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

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17 pages, 2243 KiB

Open AccessArticle

The Post-Shock Nonequilibrium Relaxation in a Hypersonic Plasma Flow Involving Reflection off a Thermal Discontinuity

by Anna Markhotok

Plasma 2023, 6(1), 181-197; https://doi.org/10.3390/plasma6010014 - 6 Mar 2023

Cited by 1 | Viewed by 1570

Abstract

The evolution in the post-shock nonequilibrium relaxation in a hypersonic plasma flow was investigated during a shock’s reflection off a thermal discontinuity. It was found that within a transitional period, the relaxation zone parameters past both the reflected and transmitted waves evolve differently [...] Read more.

The evolution in the post-shock nonequilibrium relaxation in a hypersonic plasma flow was investigated during a shock’s reflection off a thermal discontinuity. It was found that within a transitional period, the relaxation zone parameters past both the reflected and transmitted waves evolve differently compared to that in the incident wave. In a numerical example for the non-dissociating N₂ gas heated to 5000 K/10,000 K across the interface and M = 3.5, the relaxation time determined for the transmitted wave is up to 50% shorter and the relaxation depth for both waves is significantly reduced, thus resulting in a weakened wave structure. The results of the extension into larger values of heating strength and the shock Mach numbers are discussed. The findings can be useful in the areas of research involving strong shocks interacting with optical discharges or other heated media on the scale where the shock structure becomes important. Full article

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

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23 pages, 7129 KiB

Open AccessEditor’s ChoiceArticle

Application of Plasma Bridge for Grounding of Conductive Substrates Treated by Transferred Pulsed Atmospheric Arc

by Dariusz Korzec, Markus Hoffmann and Stefan Nettesheim

Plasma 2023, 6(1), 139-161; https://doi.org/10.3390/plasma6010012 - 5 Mar 2023

Cited by 1 | Viewed by 2321

Abstract

An atmospheric pressure plasma jet (APPJ) sustained by a pulsed atmospheric arc (PAA) transferred on an electrically conducting surface was operated with a mean power of 700 W, a pulse frequency of 60 kHz, and a gas mixture of N

_{2}

and H [...] Read more.

An atmospheric pressure plasma jet (APPJ) sustained by a pulsed atmospheric arc (PAA) transferred on an electrically conducting surface was operated with a mean power of 700 W, a pulse frequency of 60 kHz, and a gas mixture of N

_{2}

and H

_{2}

with up to 10% H

_{2}

, flowing at 30 to 70 SLM. It was shown that the plasma bridge ignited between the grounded injector and electrically conducting and floating substrates can be used for electrical grounding. This allowed for arc transfer on such substrates. The plasma bridge was stable for Argon flow through the injector from 3 to 10 SLM. Its length was between 5 and 15 mm. The plasma bridge current was 350 mA. The copper contact pads on an alumina electronic board were treated using the plasma bridge sustained by Ar injection for grounding. First, an oxide film of about 65 nm was grown by a compressed dry air (CDA) plasma jet. Then, this film was reduced at a speed of 4 cm

^{2}

/s by forming gas 95/5 (95% of N

_{2}

and 5% of H

_{2}

) plasma jet. Full article

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

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12 pages, 2207 KiB

Open AccessArticle

Electrocoalescence of Water Droplets

by A. V. Shavlov, V. A. Dzhumandzhi and E. S. Yakovenko

Plasma 2023, 6(1), 127-138; https://doi.org/10.3390/plasma6010011 - 1 Mar 2023

Viewed by 2281

Abstract

An experimental setup has been created to study the electrocoalescence of submillimeter- and millimeter-sized water droplets on a hydrophobic dielectric surface. The dependences of the interdroplet distance on the droplet radius are studied. It is shown that drops on a hydrophobic surface exhibit [...] Read more.

An experimental setup has been created to study the electrocoalescence of submillimeter- and millimeter-sized water droplets on a hydrophobic dielectric surface. The dependences of the interdroplet distance on the droplet radius are studied. It is shown that drops on a hydrophobic surface exhibit patterns of spatial arrangement that are characteristic of drops of a droplet cluster and fog. The electric field strengths at which mass coalescence of droplets begin are measured. A new model of electrocoalescence based on the state diagram of a drop-ion plasma is proposed. The possible role of electrocoalescence in the problem of rapid rain formation in atmospheric clouds is discussed. Full article

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

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12 pages, 3859 KiB

Open AccessArticle

CO₂ Decomposition in Microwave Discharge Created in Liquid Hydrocarbon

by Timur S. Batukaev, Igor V. Bilera, Galina V. Krashevskaya, Yuri A. Lebedev and Nurlan A. Nazarov

Plasma 2023, 6(1), 115-126; https://doi.org/10.3390/plasma6010010 - 27 Feb 2023

Cited by 5 | Viewed by 2278

Abstract

The task of CO₂ decomposition is one of the components of the problem associated with global warming. One of the promising directions of its solution is the use of low-temperature plasma. For these purposes, different types of discharges are used. Microwave discharge [...] Read more.

The task of CO₂ decomposition is one of the components of the problem associated with global warming. One of the promising directions of its solution is the use of low-temperature plasma. For these purposes, different types of discharges are used. Microwave discharge in liquid hydrocarbons has not been studied before for this problem. This paper presents the results of a study of microwave discharge products in liquid Nefras C2 80/120 (petroleum solvent, a mixture of light hydrocarbons with a boiling point from 33 to 205 °C) when CO₂ is introduced into the discharge zone, as well as the results of a study of the discharge by optical emission spectroscopy and shadow photography methods. The main gas products are H₂, C₂H₂, C₂H₄, CH₄, CO₂, and CO. No oxygen was found in the products. The mechanisms of CO₂ decomposition in the discharge are considered. The formation of H₂ occurs simultaneously with the decomposition of CO₂ in the discharge, with a volumetric rate of up to 475 mL/min and energy consumption of up to 81.4 NL/kWh. Full article

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

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12 pages, 3294 KiB

Open AccessEditor’s ChoiceArticle

Understanding the Role of Plasma Bullet Currents in Heating Skin to Mitigate Risks of Thermal Damage Caused by Low-Temperature Atmospheric-Pressure Plasma Jets

by Shunya Hashimoto, Hideo Fukuhara, Endre J. Szili, Chiaki Kawada, Sung-Ha Hong, Yuta Matsumoto, Tatsuru Shirafuji, Masayuki Tsuda, Atsushi Kurabayashi, Mutsuo Furihata, Hiroshi Furuta, Akimitsu Hatta, Keiji Inoue and Jun-Seok Oh

Plasma 2023, 6(1), 103-114; https://doi.org/10.3390/plasma6010009 - 27 Feb 2023

Cited by 4 | Viewed by 2723

Abstract

Low-temperature atmospheric-pressure plasma jets are generally considered a safe medical technology with no significant long-term side effects in clinical studies reported to date. However, there are studies emerging that show plasma jets can cause significant side effects in the form of skin burns [...] Read more.

Low-temperature atmospheric-pressure plasma jets are generally considered a safe medical technology with no significant long-term side effects in clinical studies reported to date. However, there are studies emerging that show plasma jets can cause significant side effects in the form of skin burns under certain conditions. Therefore, with a view of developing safer plasma treatment approaches, in this study we have set out to provide new insights into the cause of these skin burns and how to tailor plasma treatments to mitigate these effects. We discovered that joule heating by the plasma bullet currents is responsible for creating skin burns during helium plasma jet treatment of live mice. These burns can be mitigated by treating the mice at a further distance so that the visible plasma plume does not contact the skin. Under these treatment conditions we also show that the plasma jet treatment still retains its medically beneficial property of producing reactive oxygen species in vivo. Therefore, treatment distance is an important parameter for consideration when assessing the safety of medical plasma treatments. Full article

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

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14 pages, 504 KiB

Open AccessArticle

Investigation of Machine Learning Techniques for Disruption Prediction Using JET Data

by Joost Croonen, Jorge Amaya and Giovanni Lapenta

Plasma 2023, 6(1), 89-102; https://doi.org/10.3390/plasma6010008 - 24 Feb 2023

Cited by 2 | Viewed by 2120

Abstract

Disruption prediction and mitigation is of key importance in the development of sustainable tokamak reactors. Machine learning has become a key tool in this endeavour. In this paper, multiple machine learning models are tested and compared. A focus has been placed on the [...] Read more.

Disruption prediction and mitigation is of key importance in the development of sustainable tokamak reactors. Machine learning has become a key tool in this endeavour. In this paper, multiple machine learning models are tested and compared. A focus has been placed on the analysis of a transition to dimensionless input quantities. The methods used in this paper are the support vector machine, two-tiered support vector machine, random forest, gradient-boosted trees and long-short term memory. The performance between different models is remarkably similar, with the support vector machine attaining a slightly better accuracy score. The similarity could indicate issues with the dataset, but further study is required to confirm this. Both the two-tiered model and long-short term memory performed below expectations. The former could be attributed to an implementation which did not allow error propagation between tiers. The latter could be attributed to high noise and low frequency of the input signals. Dimensionless models experienced an expected decrease in performance, caused by a loss of information in the conversion. However, random forest and gradient boosted trees experienced a significantly lower decrease, making them more suitable for dimensionless predictors. From the disruption detection times, it was concluded that several disruptions could be predicted at more than 600 ms in advance. A feature importance study using the random forest indicated the negative impact of high noise and missing data in the database, suggesting improvements in data preparation for future work and the potential reevaluation of some of the selected portable features due to poor performance. Full article

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

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14 pages, 3890 KiB

Open AccessEditor’s ChoiceArticle

Analysis and Mitigation of Pulse-Pile-Up Artifacts in Plasma Pulse-Height X-ray Spectra

by Taosif. Ahsan, Charles P. S. Swanson, Chris Galea, Sangeeta P. Vinoth, Tony Qian, Tal Rubin and Samuel A. Cohen

Plasma 2023, 6(1), 58-71; https://doi.org/10.3390/plasma6010006 - 2 Feb 2023

Cited by 1 | Viewed by 2612

Abstract

Pulse pile-up in pulse-height energy analyzers increases when the incident rate of pulses increases relative to the inverse of the dead time per pulse of the detection system. Changes in the observed energy distributions with incident rate and detector-electronics-formed pulse shape then occur. [...] Read more.

Pulse pile-up in pulse-height energy analyzers increases when the incident rate of pulses increases relative to the inverse of the dead time per pulse of the detection system. Changes in the observed energy distributions with incident rate and detector-electronics-formed pulse shape then occur. We focus on weak high energy tails in X-ray spectra, important for measurements on partially ionized, warm (50–500 eV average electron energy), pure hydrogen plasma. A first-principles two-photon pulse-pile-up model is derived specific to trapezoidal-shaped pulses; quantitative agreement is found between the measurements and the model’s predictions. The model is then used to diagnose pulse-pile-up tail artifacts and mitigate them in relatively low count-rate spectra. Full article

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

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13 pages, 2975 KiB

Open AccessEditor’s ChoiceArticle

Physical Properties of Plasma-Activated Water

by Mobish Shaji, Alexander Rabinovich, Mikaela Surace, Christopher Sales and Alexander Fridman

Plasma 2023, 6(1), 45-57; https://doi.org/10.3390/plasma6010005 - 30 Jan 2023

Cited by 8 | Viewed by 4538

Abstract

Recent observations of plasma-activated water (PAW)’s surfactant behavior suggest that the activation of water with non-equilibrium plasma can decrease the surface tension of the water. This suggested change to the surface tension also indicates that the addition of plasma can lead to changes [...] Read more.

Recent observations of plasma-activated water (PAW)’s surfactant behavior suggest that the activation of water with non-equilibrium plasma can decrease the surface tension of the water. This suggested change to the surface tension also indicates that the addition of plasma can lead to changes in the physical properties of the water, knowledge of which can expand existing PAW applications and open new ones. While the chemical behavior of PAW has been extensively analyzed, to the best of our knowledge the physical properties of PAW have not been investigated. This study focuses on the need for experimental determination of PAW’s physical properties—namely, surface tension, viscosity, and contact angle. The experimental results of this study show that the addition of plasma lowers the surface tension of water at room temperature, increases the viscosity of water at high temperatures, and lowers the contact angle of droplets on glass surfaces at room temperatures. Potential factors influencing these changes include plasma alteration of the mesoscopic structure of water at low temperatures and plasma additives acting as foreign particles in water at higher temperatures. Ultimately, this investigation demonstrates that the physical properties of water change due to plasma activation, which could lead to potential industrial applications of PAW as a surfactant or as a washing-out and cleaning agent. Full article

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

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9 pages, 1099 KiB

Open AccessArticle

Pulsed Plasma Accelerator

by Alexander Karimov, Svyatoslav Terekhov and Vladimir Yamschikov

Plasma 2023, 6(1), 36-44; https://doi.org/10.3390/plasma6010004 - 28 Jan 2023

Cited by 1 | Viewed by 2128

Abstract

In this paper, we consider the acceleration of plasma fluxes in crossed electromagnetic fields. The possible technical approach to a prospective plasma accelerator is discussed. A simple hydrodynamic model describing the dynamics of the plasma ring in these fields is proposed. Based on [...] Read more.

In this paper, we consider the acceleration of plasma fluxes in crossed electromagnetic fields. The possible technical approach to a prospective plasma accelerator is discussed. A simple hydrodynamic model describing the dynamics of the plasma ring in these fields is proposed. Based on this model, the estimations of basic characteristics for the accelerated flux are calculated for typical experimental conditions. Full article

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

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7 pages, 1366 KiB

Open AccessArticle

Laser–Plasma Wake Velocity Control by Multi-Mode Beatwave Excitation in a Channel

by Alexander Pukhov, Nikolay E. Andreev, Anton A. Golovanov, Ivan I. Artemenko and Igor Yu Kostyukov

Plasma 2023, 6(1), 29-35; https://doi.org/10.3390/plasma6010003 - 20 Jan 2023

Cited by 4 | Viewed by 1914

Abstract

The phase velocity of a laser-driven wakefield can be efficiently controlled in a plasma channel. A beatwave of two long laser pulses is used. The frequency difference between these two laser pulses equals the local plasma frequency, so that the slow resonant excitation [...] Read more.

The phase velocity of a laser-driven wakefield can be efficiently controlled in a plasma channel. A beatwave of two long laser pulses is used. The frequency difference between these two laser pulses equals the local plasma frequency, so that the slow resonant excitation of the plasma wave is possible. Because the driver energy is spread over many plasma periods, the interference pattern can run with an arbitrary velocity along the channel and generate the wakefield with the same phase velocity. This velocity is defined by the channel radius and the structure of laser transverse modes excited in the channel. The wake velocity can be matched exactly to the witness velocity. This can be the vacuum speed of light for ultra-relativistic witnesses, or subluminal velocities for low-energy, weakly relativistic witnesses such as muons. Full article

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

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26 pages, 690 KiB

Open AccessEditor’s ChoiceArticle

Hydrogen-, Helium-, and Lithium-like Bound States in Classical and Quantum Plasmas

by Werner Ebeling and Gerd Röpke

Plasma 2023, 6(1), 1-26; https://doi.org/10.3390/plasma6010001 - 28 Dec 2022

Cited by 3 | Viewed by 2249

Abstract

We study the effective interactions and the mass action constants for pair and triple associations in classical and quantum plasmas. Avoiding double counting, we derive new expressions for the mass action constants. The calculations resulted in values that were substantially smaller than the [...] Read more.

We study the effective interactions and the mass action constants for pair and triple associations in classical and quantum plasmas. Avoiding double counting, we derive new expressions for the mass action constants. The calculations resulted in values that were substantially smaller than the standard ones in relevant temperature ranges by up to 50 percent. On this basis, we determine the pressure of H, He and Li plasmas and the osmotic coefficient of electrolytes with higher charges such as, e.g., seawater. Classical and quantum Coulomb systems show strong similarities. The contributions in low orders with respect to the interaction

e^{2}

are suppressed by thermal and screening effects. The contributions of weakly bound states, near the continuum edge, to the mass action constants are reduced, replacing the exponential functions with cropped exponentials. The new mass action constants are consistent with well-known extended limiting cases of screening effects. We analyze classical examples including the salts CaCl

_{2}

and LaCl

_{3}

, and a model of seawater including multiple associations. In the case of quantum systems, we follow the work of Planck–Brillouin–Larkin for H plasmas and study He and Li plasmas. The equation of state (EoS) for wide-density regions is obtained through the concatenation of the EoS for the low-density region of partial ionization with the EoS of degenerate plasmas, where all bound states are dissolved and Fermi, Hartree–Fock and Wigner contributions dominate. Full article

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

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14 pages, 4069 KiB

Open AccessArticle

Plasma Electrolytic Polishing of Porous Nitinol Structures

by Kristina Navickaitė, Karl Roßmann, Klaus Nestler, Falko Böttger-Hiller, Michael Penzel, Thomas Grund, Thomas Lampke and Henning Zeidler

Plasma 2022, 5(4), 555-568; https://doi.org/10.3390/plasma5040039 - 30 Nov 2022

Cited by 4 | Viewed by 2137

Abstract

In this study, for the first time, the application of plasma electrolytic polishing (PEP) of porous Nitinol structures, mimicking a trabecular bone structure, that were additively manufactured, is reported. The cube-shaped samples were polished in a diagonal position three different times. The effect [...] Read more.

In this study, for the first time, the application of plasma electrolytic polishing (PEP) of porous Nitinol structures, mimicking a trabecular bone structure, that were additively manufactured, is reported. The cube-shaped samples were polished in a diagonal position three different times. The effect of PEP was evaluated in terms of the polishing depth, the effect on sample chemical composition and a possible shift of the phase transition temperature using microscopy, the energy dispersive X-ray spectroscopy (EDX), and the differential scanning calorimetry (DSC) techniques, respectively. The obtained results demonstrated that the PEP technique is suitable for polishing porous structures up to a certain depth into the sample inner structure and does not have any influence on the chemical composition and the phase transformation temperatures. However, small changes in the specific enthalpy were observable among the investigated samples. These changes could be attributed to the sample chemical inhomogeneity, measurement error, and/or differences in sample size and shape. Full article

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

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15 pages, 43902 KiB

Open AccessArticle

Simulation as a Tool for Understanding Experimental Observations—Ion Beam Extraction from an ECRIS

by Peter Spädtke

Plasma 2022, 5(4), 540-554; https://doi.org/10.3390/plasma5040038 - 24 Nov 2022

Viewed by 1924

Abstract

A model for the simulation of ion beam extraction from an electron-cyclotron resonance ion source is proposed. It is based on the simple fact that charged particles follow magnetic field lines. Therefore, magnetic field lines are used to generate initial conditions for ray-tracing. [...] Read more.

A model for the simulation of ion beam extraction from an electron-cyclotron resonance ion source is proposed. It is based on the simple fact that charged particles follow magnetic field lines. Therefore, magnetic field lines are used to generate initial conditions for ray-tracing. This model reproduces in simulation experimentally obtained results. The importance of correlations in phase-space caused by the magnetic field is shown in the simulation. This model also describes the physics of space-charge and its compensation in the extracted (fast) ion beam by low-energy electrons. Simulation provides the possibility to test theoretical assumptions, as well as to optimize technical designs. Full article

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

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17 pages, 573 KiB

Open AccessArticle

Tolerable Stationary Heat Loads to Liquid Lithium Divertor Targets

by Aleksey A. Mavrin and Andrey A. Pshenov

Plasma 2022, 5(4), 482-498; https://doi.org/10.3390/plasma5040036 - 15 Nov 2022

Cited by 1 | Viewed by 1474

Abstract

An 0D model is proposed that makes it possible to estimate the limiting stationary heat loads to the targets covered with liquid lithium (LL) layer, taking into account the effects of vapor shielding by sputtered and evaporated LL and hydrogen recycling. Several models [...] Read more.

An 0D model is proposed that makes it possible to estimate the limiting stationary heat loads to the targets covered with liquid lithium (LL) layer, taking into account the effects of vapor shielding by sputtered and evaporated LL and hydrogen recycling. Several models of cooled target substrates are considered in which the LL layer facing the plasma is placed. For the considered substrate models, a parametric analysis of the tolerable stationary heat loads to the target on the substrate thickness, the effective cooling energy per particle of sputtered lithium, and the lithium prompt redeposition factor was carried out. It is shown that, at a small substrate thickness, the choice of the substrate model has a significant impact on the tolerable heat loads. It is also shown that even at unrealistically large values of the effective cooling energy, the dissipation of lithium remains modest. This means that in regimes with a high power coming from the core plasma to the edge, the injection of an additional radiator is required. Finally, it is shown that one of the most effective ways to increase the tolerable stationary heat loads would be to reduce the thickness of the target substrate. Full article

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

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12 pages, 15731 KiB

Open AccessArticle

Vacuum Arc Plasma Coating for Polymer Surface Protection— A Plasma Enhanced In-Orbit Additive Manufacturing Concept

by Marina Kühn-Kauffeldt, Marvin Kühn, Michael Mallon, Wolfgang Saur and Fabian Fuchs

Plasma 2022, 5(4), 470-481; https://doi.org/10.3390/plasma5040035 - 9 Nov 2022

Cited by 1 | Viewed by 2003

Abstract

In-orbit additive manufacturing (AM) is a promising approach for fabrication of large structures. It allows to expand and accelerate human space exploration possibilities. Extrusion-based AM was demonstrated in zero gravity, while the realization of such a process in orbit-like vacuum conditions is currently [...] Read more.

In-orbit additive manufacturing (AM) is a promising approach for fabrication of large structures. It allows to expand and accelerate human space exploration possibilities. Extrusion-based AM was demonstrated in zero gravity, while the realization of such a process in orbit-like vacuum conditions is currently under exploration. Still, a solution for protection of the UV and IR radiation sensitive polymers is needed in order to prevent their early mechanical failure under space conditions. Vacuum arc plasma based process is widely applied on earth for thin protective coating deposition. Its major advantage is its scalability—from tiny size used in electric propulsion to large scale coating devices. The usability of the vacuum arc process in space conditions was shown in electric propulsion applications in nano-satellites. In this work we discuss and demonstrate the integration of vacuum arc process as a post processing step after Fused Filament Fabrication (FFF) for additive manufacturing and functionalization of long polymer structures. Here we address the concept for technical realization, which integrates the vacuum arc into additive manufacturing process chain. More over we present a laboratory prototype, which implements this concept together with a use case, where a previously printed PEEK structure is coated with aluminum based coating suitable for UV radiation protection. Full article

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

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8 pages, 411 KiB

Open AccessEditor’s ChoiceArticle

Effects of Plasma on Physical Properties of Water: Nanocrystalline-to-Amorphous Phase Transition and Improving Produce Washing

by Jinjie He, Alexander Rabinovich, Dmitri Vainchtein, Alexander Fridman, Christopher Sales and Mikhail N. Shneider

Plasma 2022, 5(4), 462-469; https://doi.org/10.3390/plasma5040034 - 3 Nov 2022

Cited by 2 | Viewed by 1979

Abstract

Washing fresh produce using Plasma-activated water recently became a promising eco-friendly alternative to using chemical additives such as Chlorine. We discuss the produce-washing experiments that illustrate that addition of plasma to washing water is a multi-faced phenomena. Not only it increases the sterilization [...] Read more.

Washing fresh produce using Plasma-activated water recently became a promising eco-friendly alternative to using chemical additives such as Chlorine. We discuss the produce-washing experiments that illustrate that addition of plasma to washing water is a multi-faced phenomena. Not only it increases the sterilization ability of water by killing pathogens, but it also has improved washibility: the ability to remove pathogens from the cleaning surface. We propose an explanation of these features based on the recently discoveries that many physical and chemical properties of water change their temperature dependence between about 35 and 60 degrees Celsius. In particular, heat conductance, light absorption, and surface tension all change their temperature dependence. These drastic changes were associated with water gradually changing its mesoscopic structure: while at the higher temperatures water is a uniform media (amorphous state), at the temperatures below transition it consists of many nano-to-micro-scale clusters (crystalline state). This transition is similar to the second order phase transition. In the present paper we propose that treating water with non-thermal plasma (adding plasma-created active compounds) can lower the temperature of the transition and thus cause a significant change in such physical quantities as surface tension, viscosity, freezing rate, and wettability and washability. Full article

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

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11 pages, 9040 KiB

Open AccessEditor’s ChoiceArticle

Plasma Deposition to Improve Barrier Performance of Biodegradable and Recyclable Substrates Intended for Food Packaging

by Espedito Vassallo, Matteo Pedroni, Marco Aloisio, Hao Chen, Giuseppe Firpo, Silvia Maria Pietralunga and Dario Ripamonti

Plasma 2022, 5(4), 451-461; https://doi.org/10.3390/plasma5040033 - 28 Oct 2022

Cited by 4 | Viewed by 2197

Abstract

The extensive application of biodegradable polymers in the food packaging industries was partially limited due to poor barrier performances. In the present work, we investigated the improvement of oxygen barrier performances by means of the deposition of a few nanometres of SiOx coatings [...] Read more.

The extensive application of biodegradable polymers in the food packaging industries was partially limited due to poor barrier performances. In the present work, we investigated the improvement of oxygen barrier performances by means of the deposition of a few nanometres of SiOx coatings on Poly(butylene succinate) (PBS) films. The coated samples produced by the plasma-enhanced chemical vapor deposition technique were tested in terms of morphology and composition of the surface and barrier properties. Barrier performances studied as a function of SiOx thickness were greatly improved and a reduction of at least 99% was achieved for oxygen transmission rate. In order to reduce the formation of residual stress between PBS substrate and SiOx coatings, a proper buffer layer (silicon organic SiO_xC_yH_z) was used. Full article

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

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15 pages, 2723 KiB

Open AccessArticle

Design and Construction of a New Plasma Applicator for the Improved Disinfection and Activation of Large Surfaces

by Cristian D. Tudoran and Maria Coroș

Plasma 2022, 5(4), 436-450; https://doi.org/10.3390/plasma5040032 - 21 Oct 2022

Cited by 2 | Viewed by 2741

Abstract

This paper describes the design and operation of a low-cost plasma applicator based on a patented, swirled-type dielectric barrier discharge configuration with a treatment width up to 300 mm. Differences from earlier plasma applicators include: blown cylindrical dielectric barrier discharge, combining the functional [...] Read more.

This paper describes the design and operation of a low-cost plasma applicator based on a patented, swirled-type dielectric barrier discharge configuration with a treatment width up to 300 mm. Differences from earlier plasma applicators include: blown cylindrical dielectric barrier discharge, combining the functional properties of the plasma jet systems, arc and corona discharge blown in a single type of universal applicator, and the possibility of treating large areas of samples with cold plasma generated in a certain type of specific process gas mixture chosen according to the type of desired effect. We tested the effect of the plasma on a few materials such as cotton and linen fabrics, glass wafers and printing cardboard, proving that the generated plasma can easily make hydrophilic or hydrophobic surfaces. We also tried the plasma’s sterilizing effect on Escherichia coli (E. coli) bacteria. The results suggest that our plasma system can be successfully applied to medical and biological fields as well, where the removal of bacteria and their fragments is required. Full article

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

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13 pages, 4991 KiB

Open AccessArticle

On Plasma Activated Acetyl Donors: Comparing the Antibacterial Efficacy of Tetraacetylethylenediamine and Pentaacetate Glucose

by Endre J. Szili, Bethany L. Patenall, Adrian Fellows, Dharmit Mistry, A. Toby A. Jenkins, Robert D. Short and Bhagirath Ghimire

Plasma 2022, 5(4), 423-435; https://doi.org/10.3390/plasma5040031 - 13 Oct 2022

Cited by 2 | Viewed by 2143

Abstract

The study compares how acetyl donor molecules tetraacetylethylenediamine (TAED) and pentaacetate glucose (PAG) improve the antibacterial efficacy of solutions activated with a low-temperature atmospheric-pressure argon plasma jet. Plasma activation of solubilised TAED and PAG produce solutions with different chemical compositions and oxidative potentials. [...] Read more.

The study compares how acetyl donor molecules tetraacetylethylenediamine (TAED) and pentaacetate glucose (PAG) improve the antibacterial efficacy of solutions activated with a low-temperature atmospheric-pressure argon plasma jet. Plasma activation of solubilised TAED and PAG produce solutions with different chemical compositions and oxidative potentials. Both acetyl donor molecules enhance the hydrogen peroxide (H₂O₂) concentration in solution with TAED being more effective compared to PAG. However, PAG is more effective at forming peracetic acid (PAA) from reaction of its acetyl donor groups with plasma generated H₂O₂. The enhanced oxidative potential of plasma activated TAED and PAG solutions were shown to significantly improve bactericidal activity against common wound pathogens Gram-negative Pseudomonas aeruginosa and Gram-positive Staphylococcus aureus compared to plasma activated water produced without acetyl donors. Furthermore, the oxidative capacity of plasma activated PAG was least affected by the bacterial oxidative defence enzyme catalase, attributed to the high concentration of PAA produced in this formulation. Overall, the above data show that acetyl donors may help improve next generation of antimicrobial formulations produced by plasma, which might help combat increasing problems of antimicrobial resistance. Full article

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

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15 pages, 3157 KiB

Open AccessArticle

Microsecond Discharge Produced in Aqueous Solution for Pollutant Cr(VI) Reduction

by Son Truong Nguyen, Nicolas Fagnon, Arlette Vega, Xavier Duten, Sébastien Forget, Arnaud Brugier, Hervé Rabat and Cathy Rond

Plasma 2022, 5(4), 408-422; https://doi.org/10.3390/plasma5040030 - 29 Sep 2022

Viewed by 1528

Abstract

This paper presents a detailed analysis of underwater electrical discharge parameters in the treatment of chromium (VI) used as a model pollutant to analyze the reduction process by plasma liquid interaction (PLI). Pin-to-pin microsecond discharges were performed in an aqueous Cr(VI) solution and [...] Read more.

This paper presents a detailed analysis of underwater electrical discharge parameters in the treatment of chromium (VI) used as a model pollutant to analyze the reduction process by plasma liquid interaction (PLI). Pin-to-pin microsecond discharges were performed in an aqueous Cr(VI) solution and the processes were characterized using electrical measurements, optical imaging and UV-Vis absorption measurements for [Cr(VI)] estimation. For the first time, the total reduction of Cr(VI) was successfully achieved by PLI process and a maximum energy yield of 4.7 × 10⁻⁴ g/kJ was obtained. Parametric studies on electrode geometry, applied voltage, electrodes gap and pulse duration are presented in detail. Finally, an analysis of the process is proposed by comparing our results of the energy yield calculation based on the injected energy with those of the literature and by providing an estimation of the global energy efficiency of the process. Full article

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

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24 pages, 482 KiB

Open AccessArticle

Multi-Configuration Calculation of Ionization Potential Depression

by Jean-Christophe Pain

Plasma 2022, 5(4), 384-407; https://doi.org/10.3390/plasma5040029 - 27 Sep 2022

Cited by 2 | Viewed by 2417

Abstract

The modelling of ionization potential depression in warm and hot dense plasmas constitutes a real theoretical challenge due to ionic coupling and electron degeneracy effects. In this work, we present a quantum statistical model based on a multi-configuration description of the electronic structure [...] Read more.

The modelling of ionization potential depression in warm and hot dense plasmas constitutes a real theoretical challenge due to ionic coupling and electron degeneracy effects. In this work, we present a quantum statistical model based on a multi-configuration description of the electronic structure in the framework of Density Functional Theory. We discuss different conceptual issues inherent to the definition of ionization potential depression and compare our results with the famous and widely-used Ecker-Kröll and Stewart-Pyatt models. Full article

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

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18 pages, 8699 KiB

Open AccessArticle

Simulation of the First Two Microseconds of an Ar CCP Cold Plasma Discharge by the PIC-MCC Method

by Pietro Mandracci

Plasma 2022, 5(3), 366-383; https://doi.org/10.3390/plasma5030028 - 16 Sep 2022

Viewed by 2497

Abstract

Most simulations of capacitively coupled radiofrequency cold-plasma discharges (RF-CCP) are focused on the steady state, but the initial discharge time is important for understanding the ignition process and the behavior of pulsed discharges. In this work, the time evolution of an RF-CCP Ar [...] Read more.

Most simulations of capacitively coupled radiofrequency cold-plasma discharges (RF-CCP) are focused on the steady state, but the initial discharge time is important for understanding the ignition process and the behavior of pulsed discharges. In this work, the time evolution of an RF-CCP Ar discharge was simulated, considering a pressure of 66.6 Pa, a distance between the electrodes of 20 mm, and RF (13.56 MHz) bias amplitudes in range 100–400 V, and the discharge evolution was observed for the first 2 μs. A 1d3v (1 dimension for particle positions and 3 dimensions for particle velocities) electrostatic particle in cell with montecarlo collisions (PIC-MCC) model was used, with separated particle weights for electrons and ions that varied with the particle density. During the simulations, the time evolution of the electron density, mean electron energy, Debye length, Debye number, and plasma frequency were observed. The spatial distribution of electric potential and the electron energy distribution function were also monitored. A transition between two regimes was observed; the first was characterized by strong oscillation of the mean electron energy and an exponential increase of the mean plasma density with time, while in the second the mean electron energy was lower, and the plasma density increased linearly. The time required for the transition between the two regimes increased as the RF amplitude was raised from 100 to 250 V, then decreased with a further increase of the RF amplitude to 300 and 350 V. Full article

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

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10 pages, 2874 KiB

Open AccessArticle

Recognizing Cold Atmospheric Plasma Plume Using Computer Vision

by Marisa Lazarus, Dayun Yan, Ruby Limanowski, Li Lin and Michael Keidar

Plasma 2022, 5(3), 341-350; https://doi.org/10.3390/plasma5030026 - 26 Aug 2022

Cited by 2 | Viewed by 2489

Abstract

Over the last three decades, cold atmospheric plasma (CAP) has been heavily investigated in a wide range of biological applications, including wound healing, microorganism sterilization, and cancer treatment. Atmospheric pressure plasma jets (APPJs) are the most common plasma sources in plasma medicine. An [...] Read more.

Over the last three decades, cold atmospheric plasma (CAP) has been heavily investigated in a wide range of biological applications, including wound healing, microorganism sterilization, and cancer treatment. Atmospheric pressure plasma jets (APPJs) are the most common plasma sources in plasma medicine. An APPJ’s size determines its application range and approach in treatment. In this study, we demonstrated the real-time recognition of an APPJ’s plasma plume output using computer vision (CV), dramatically improving the measurement speed compared to the traditional method of using the naked eye. Our work provides a framework to monitor an aspect of an APPJ’s performance in real time, which is a necessary step to achieving an intelligent CAP source. Full article

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

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17 pages, 2131 KiB

Open AccessArticle

A Global Model Study of Plasma Chemistry and Propulsion Parameters of a Gridded Ion Thruster Using Argon as Propellant

by Bernardo Magaldi, Júlia Karnopp, Argemiro da Silva Sobrinho and Rodrigo Pessoa

Plasma 2022, 5(3), 324-340; https://doi.org/10.3390/plasma5030025 - 28 Jul 2022

Cited by 6 | Viewed by 4307

Abstract

This work reports on the (zero-dimensional) global model study of argon plasma chemistry for a cylindrical thruster based on inductively coupled plasma (ICP) whose output has a system of two grids polarized with each other with direct current potential. The global model developed [...] Read more.

This work reports on the (zero-dimensional) global model study of argon plasma chemistry for a cylindrical thruster based on inductively coupled plasma (ICP) whose output has a system of two grids polarized with each other with direct current potential. The global model developed is based on particle and energy balance equations, where the latter considers both charged and neutral species. Thus, the model allows the determination of the neutral gas temperature. Finally, this study also investigated the role of excited species in plasma chemistry especially in the ions production and its implications for propulsion parameters, such as thrust. For this, the study was carried out in two different scenarios: (1) one taking into account the metastable species Ar^r and Ar^p (multi-step ionization), and (2) the other without these species (single-step ionization). Results indicates a distinct behavior of electron temperature with radiofrequency (RF) power for the investigated cases. On the other hand, the gas temperature is almost the same for investigated power range of up to 900 W. Concern propulsion analysis, a thrust of 40 mN at 450 W was verified for case (1), which represents a remarkable thrust value for electric thrusters. Full article

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

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18 pages, 5327 KiB

Open AccessEditor’s ChoiceArticle

Simple Parametric Model for Calculation of Lateral Electromagnetic Loads in Tokamaks at Asymmetric Vertical Displacement Events (AVDE)

by Sergey Sadakov, Fabio Villone, Guglielmo Rubinacci and Salvatore Ventre

Plasma 2022, 5(3), 306-323; https://doi.org/10.3390/plasma5030024 - 25 Jul 2022

Cited by 1 | Viewed by 1867

Abstract

This paper describes a family of relatively simple numerical models for calculation of asymmetric electromagnetic (EM) loads at all tokamak structures and coils at asymmetric vertical plasma displacement events (AVDE). Unlike currently known AVDE studies concentrated on plasma physics, these models have a [...] Read more.

This paper describes a family of relatively simple numerical models for calculation of asymmetric electromagnetic (EM) loads at all tokamak structures and coils at asymmetric vertical plasma displacement events (AVDE). Unlike currently known AVDE studies concentrated on plasma physics, these models have a practical purpose to calculate detailed time-dependent patterns of AVDE-induced EM loads everywhere in the tokamak. They are built to intrinsically assure good-enough EM load balance (opposite net forces and torques for the Vacuum Vessel and the Magnets with zero total for the entire tokamak), as needed for consequent simulation of the tokamak’s dynamic response to AVDE, as well as for the development of tokamak monitoring algorithms and tokamak simulators. To achieve these practical goals, the models work in a manner of parametric study. They do not intervene in details of plasma physics, but run at widely varied input assumptions on AVDE evolution and severity. Their outputs will fill a library of ready-for-use lateral EM loads for multiple variants of AVDE evolution and severity. The tokamak physics community can select any variant from the library, and engineers can pick ready-for-use AVDE loads. Investigated here, EM models represent one already known approach and one newly suggested. The latter attempts to reflect the helical pattern of halo currents in plasma and delivers richer outcomes and, thus, can be preferred as the single practical model for parametric calculations. Full article

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

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11 pages, 3472 KiB

Open AccessEditor’s ChoiceArticle

Chamber with Inverted Electrode Geometry for Measuring and Control of Ion Flux-Energy Distribution Functions

by Christian Schulze, He Li, Leonie Mohn, Martin Müller and Jan Benedikt

Plasma 2022, 5(3), 295-305; https://doi.org/10.3390/plasma5030023 - 23 Jun 2022

Cited by 2 | Viewed by 4251

Abstract

Measurements of ion flux-energy distribution functions at the high sheath potential of the driven electrode in a classical low-pressure asymmetric capacitively coupled plasma are technically difficult as the diagnostic device needs to float with the applied radio frequency voltage. Otherwise, the ion sampling [...] Read more.

Measurements of ion flux-energy distribution functions at the high sheath potential of the driven electrode in a classical low-pressure asymmetric capacitively coupled plasma are technically difficult as the diagnostic device needs to float with the applied radio frequency voltage. Otherwise, the ion sampling is disturbed by the varying electric field between the grounded device and the driven electrode. To circumvent such distortions, a low-pressure plasma chamber with inverted electrode geometry, where the larger electrode is driven and the smaller electrode is grounded, has been constructed and characterized. Measurements of the ion flux-energy distribution functions with an energy-selective mass spectrometer at the high sheath potential of the grounded electrode are presented for a variety of conditions and ions. The potential for suppressing low-energy ions from resonant charge transfer collisions in the sheath by the dilution of the working gas is demonstrated. Additionally, the setup is supplemented by an inductively coupled plasma that controls the plasma density and consequently the ion flux to the substrate while the radio frequency bias controls the ion energy. At high ion energies, metal ions are detected as a consequence of the ionization of sputtered electrode material. The proposed setup opens a way to study precisely the effects of ion treatment for a variety of substrates such as catalysts, polymers, or thin films. Full article

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

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15 pages, 1241 KiB

Open AccessEditor’s ChoiceArticle

Impact of Internal Faraday Shields on RF Driven Hydrogen Discharges

by David Rauner, Dominikus Zielke, Stefan Briefi and Ursel Fantz

Plasma 2022, 5(3), 280-294; https://doi.org/10.3390/plasma5030022 - 21 Jun 2022

Cited by 3 | Viewed by 4042

Abstract

At RF plasma reactors operated at high power, internal Faraday shields are required to shield dielectric vessel or windows from erosion due to isotropic heat and particle fluxes. By utilizing a flexible and diagnostically well-equipped laboratory setup, crucial effects that accompany the application [...] Read more.

At RF plasma reactors operated at high power, internal Faraday shields are required to shield dielectric vessel or windows from erosion due to isotropic heat and particle fluxes. By utilizing a flexible and diagnostically well-equipped laboratory setup, crucial effects that accompany the application of internal Faraday shields at low-pressure hydrogen (and deuterium) RF discharges are identified and quantified in this contribution. Both an inductively coupled plasma (ICP) utilizing a helical coil and a low-field helicon discharge applying a Nagoya-type III antenna at magnetic fields of up to 12 mT are investigated. Discharges are driven at 4 MHz and in the pressure range between 0.3 and 10 Pa while the impact of the Faraday shields on both the RF power transfer efficiency and spectroscopically determined bulk plasma parameters (electron density and temperature, atomic density) is investigated. Three main effects are identified and discussed: (i) due to the Faraday shield, the measured RF power transfer efficiency is globally reduced. This is mainly caused by increased power losses due to induced eddy currents within the electrostatic shield, as accompanying numerical simulations by a self-consistent fluid model demonstrate. (ii) The Faraday shield reduces the atomic hydrogen density in the plasma by one order of magnitude, as the recombination rate of atoms on the metallic (copper) surfaces of the shield is considerably higher compared to the dielectric quartz walls. (iii) The Faraday shield suppresses the transition of the low-field helicon setup to a wave heated regime at the present conditions. This is attributed to a change of boundary conditions for wave propagation, as the plasma is in direct contact with the conductive surfaces of the Faraday shield rather than being operated in a laterally fully dielectric vessel. Full article

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

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15 pages, 2439 KiB

Open AccessArticle

Indigo Carmine Degradation in Water Induced by a Pulsed Positive Corona Discharge in Air: Discharge and Postdischarge Effects

by Matías G. Ferreyra, Brenda L. Fina, Natalio J. Milardovich, Juan C. Chamorro, Brenda Santamaría, Karina Balestrasse and Leandro Prevosto

Plasma 2022, 5(2), 265-279; https://doi.org/10.3390/plasma5020021 - 30 May 2022

Cited by 4 | Viewed by 2703

Abstract

In recent years, one of the fastest growing technological applications in the field of nonthermal plasmas is the degradation of organic contaminants of water. In this work, the degradation of indigo carmine (IC) in water induced by a pulsed positive corona discharge operating [...] Read more.

In recent years, one of the fastest growing technological applications in the field of nonthermal plasmas is the degradation of organic contaminants of water. In this work, the degradation of indigo carmine (IC) in water induced by a pulsed positive corona discharge operating in ambient air is reported. Degradation levels in different volumes of IC in solution with distilled water treated with different plasma exposure times immediately after discharge (0 h), and in the postdischarge up to 24 h were examined. To explain the IC discoloration in the postdischarge phase, a chemical model was developed. The stability of the reactive species in solution nitrate (NO₃⁻), nitrite (NO₂⁻) and hydrogen peroxide (H₂O₂), as well as the properties of the solution (electrical conductivity, pH) were also measured. The results suggest that the hydroxyl radical (OH˙) as well as ozone (O₃) are the main oxidizing species during the discharge phase, being primarily formed in the gas phase through plasma-mediated reactions and then transferred to the liquid by diffusion, while the OH˙ production in the bulk liquid through the decomposition of peroxinitrous acid (O=NOOH) plays a major role in the IC degradation during the postdischarge. These results are associated with a noticeably increase in the energy-yield values observed at 24 h post-treatment. Full article

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

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11 pages, 1601 KiB

Open AccessEditor’s ChoiceArticle

Pulsed Spherical Tokamak—A New Approach to Fusion Reactors

by Mikhail Gryaznevich, Valery A. Chuyanov and Yuichi Takase

Plasma 2022, 5(2), 247-257; https://doi.org/10.3390/plasma5020019 - 18 May 2022

Cited by 5 | Viewed by 3636

Abstract

Traditionally, spherical tokamak (ST) reactors are considered to operate in a steady state. This paper analyses the advantages of a pulsed ST reactor. The methodology developed for conventional tokamak (CT) reactors is used and it is shown that advantages of a pulsed operation [...] Read more.

Traditionally, spherical tokamak (ST) reactors are considered to operate in a steady state. This paper analyses the advantages of a pulsed ST reactor. The methodology developed for conventional tokamak (CT) reactors is used and it is shown that advantages of a pulsed operation are even more pronounced in an ST reactor because of its ability to operate at a higher beta, therefore achieving a higher bootstrap current fraction, which, together with a lower inductance, reduces requirements for magnetic flux from the central solenoid for the plasma current ramp-up and sustainment. Full article

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

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14 pages, 4875 KiB

Open AccessArticle

Oxidative Stress Pathways Linked to Apoptosis Induction by Low-Temperature Plasma Jet Activated Media in Bladder Cancer Cells: An In Vitro and In Vivo Study

by Hideo Fukuhara, Endre J. Szili, Jun-Seok Oh, Kawada Chiaki, Shinkuro Yamamoto, Atsushi Kurabayashi, Mutsuo Furihata, Masayuki Tsuda, Hiroshi Furuta, Howard D. Lindsay, Robert D. Short, Akimitsu Hatta and Keiji Inoue

Plasma 2022, 5(2), 233-246; https://doi.org/10.3390/plasma5020018 - 27 Apr 2022

Cited by 6 | Viewed by 3457

Abstract

Current methods used to treat non-muscle invasive bladder cancer are inadequate due to a high recurrence rate after surgery and the occurrence of adverse events such as interstitial pneumonia following intravesical instillation therapy. Low-temperature plasma is a new form of physical therapy that [...] Read more.

Current methods used to treat non-muscle invasive bladder cancer are inadequate due to a high recurrence rate after surgery and the occurrence of adverse events such as interstitial pneumonia following intravesical instillation therapy. Low-temperature plasma is a new form of physical therapy that provides a rich source of reactive oxygen species (ROS). Oxidative solutions, created by pre-treatment of aqueous media with plasma before application to target cells, lead to the destruction of cancer cells through oxidative stress pathways. This study focuses on the effects of plasma-activated media (PAM) in bladder cancer cells. PAM treatment increases oxidative stress that leads to cell cycle arrest and concomitantly depolarises the mitochondrial membrane leading to increased mitochondrial ROS production. Cell cycle arrest and increased mitochondrial ROS production led to an increase in caspase 3/cytochrome c activity, which might explain the induction of apoptosis in bladder cancer cells in vitro and in a bladder cancer tumour in vivo. These observations highlight the potential of plasma activated solutions as a new adjuvant therapy in the clinical treatment of bladder cancer. Full article

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

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12 pages, 3160 KiB

Open AccessArticle

ElectroCatalytic Activity of Nickel Foam with Co, Mo, and Ni Phosphide Nanostructures

by Morteza Saghafi Yazdi, Mohammad Rezayat and Joan Josep Roa Rovira

Plasma 2022, 5(2), 221-232; https://doi.org/10.3390/plasma5020017 - 27 Apr 2022

Cited by 14 | Viewed by 3609

Abstract

In this study, the electrocatalytic activity of nickel foam, which is activated by cobalt, molybdenum, and nickel phosphide nanostructures, is prepared by the plasma hydrothermal method for use in the release of hydrogen and oxygen. The morphology and crystallographic structure of the synthesized [...] Read more.

In this study, the electrocatalytic activity of nickel foam, which is activated by cobalt, molybdenum, and nickel phosphide nanostructures, is prepared by the plasma hydrothermal method for use in the release of hydrogen and oxygen. The morphology and crystallographic structure of the synthesized phosphide specimens were examined by means of scanning electron microscopy, Fourier-transform infrared spectroscopy, and X-ray diffraction. Moreover, the electrolysis activity for these sets of specimens was investigated using the Tafel polarization curve or linear sweep voltammetry, cyclic voltammetry, as well as by means of the electrochemical impedance spectroscopy technique. Preliminary results show that nickel phosphide presents the highest electrocatalytic activity than the other phosphides developed in this research. In this regard, it presents an electrocatalytic activity to release hydrogen and oxygen of around −1.7 and 0.82 mV, which is measured at a current density of 100 mA·cm⁻², respectively. Full article

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

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10 pages, 2621 KiB

Open AccessEditor’s ChoiceArticle

Poly (O-Aminophenol) Produced by Plasma Polymerization Has IR Spectrum Consistent with a Mixture of Quinoid & Keto Structures

by Natalie M. Stuart and Karl Sohlberg

Plasma 2022, 5(2), 196-205; https://doi.org/10.3390/plasma5020015 - 14 Apr 2022

Viewed by 2349

Abstract

A vibrational analysis of various poly(o-aminophenol) structures has been undertaken using first principles methods. It is shown that a mixture of quinoid and keto forms of poly(o-aminophenol) gives rise to a simulated spectrum that replicates the experimental infrared spectra of plasma-produced poly(o-aminophenol) better [...] Read more.

A vibrational analysis of various poly(o-aminophenol) structures has been undertaken using first principles methods. It is shown that a mixture of quinoid and keto forms of poly(o-aminophenol) gives rise to a simulated spectrum that replicates the experimental infrared spectra of plasma-produced poly(o-aminophenol) better than either the quinoid or keto poly(o-aminophenol) spectra alone. An unassigned peak in the spectrum is attributed to hydrogen bonding to the silica substrate. Full article

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

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12 pages, 1762 KiB

Open AccessArticle

Features of Pinch Plasma, Electron, and Ion Beams That Originated in the AECS PF-1 Plasma Focus Device

by Mohamad Akel, Sharif AL-Hawat, Muthanna Ahmad, Yamen Ballul and Soliman Shaaban

Plasma 2022, 5(2), 184-195; https://doi.org/10.3390/plasma5020014 - 25 Mar 2022

Cited by 5 | Viewed by 3016

Abstract

The measured current traces of alow energy AECS PF-1 plasma focus device are used for studying of the formed plasma, and the produced ion and electron beams. Anadapted version of the Lee model (RADPFV5.15FIB&REB) is applied, taking into account the fitting procedures between [...] Read more.

The measured current traces of alow energy AECS PF-1 plasma focus device are used for studying of the formed plasma, and the produced ion and electron beams. Anadapted version of the Lee model (RADPFV5.15FIB&REB) is applied, taking into account the fitting procedures between the measured and computed current waveforms for each shot. The experiments on AECSPF-1 were performed with three different gases—helium, nitrogen, and argon—for studying the effect of the atomic number on the properties of the generated beams. For numerical experiments using the Lee model, 36 successful shots for each gas were selected. The peak values of the total discharge current I_peak were 50–55 kA, the pinch currents I_pinchwere34–36 kA, and the final pinch radius reached a minimum value of 0.03 cm for argon. The ion mean energy ranged from 35 keV (for He) to 223 keV (for Ar). The beam energy also had an extreme value of 1.34 J (0.05%E₀) for argon. The results presented the highest values of 2.4 × 10¹⁴Wm⁻² for the power flow density, and adamage factor of around 3.1 × 10¹⁰ Wm⁻²s^0.5 for argon. For electron beams, the results also showed that the fluence and flux increased with the higher atomic number and reached a peak of 9.7 × 10²² m⁻² and 5.9 × 10³⁰ m⁻² s⁻¹ for argon, respectively. The results presented the highest values of 2.2 × 10¹⁶Wm⁻² for the power flow density (heat flux), and adamage factor of around 3 × 10¹² Wm⁻²s^0.5 for argon. The kinetic energy of the relativistic electrons was found to be within the range of 18–23 keV. The results show that the ion and electron beam properties (energy, flux, fluence, ion and electron numbers, current, power flow density, and damage factor) emitted from the plasma focus had wide ranges based on the operational plasma focus parameters. Thus, these results could be used for selection of the suitable plasma focus parameters for desired material processing applications. Full article

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

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8 pages, 791 KiB

Open AccessEditor’s ChoiceArticle

Enhancement of Nuclear Fusion in Plasma Oscillation Systems

by Alfred YiuFai Wong and Chun-Ching Shih

Plasma 2022, 5(1), 176-183; https://doi.org/10.3390/plasma5010013 - 17 Mar 2022

Cited by 2 | Viewed by 3806

Abstract

Concepts of dynamic oscillations of positive and negative ions to enhance fusion reactions are examined in this paper. Collective oscillations of positive and negative ions produce large oscillating electrostatic fields and could provide a significant reduction of the Coulomb potential barrier between the [...] Read more.

Concepts of dynamic oscillations of positive and negative ions to enhance fusion reactions are examined in this paper. Collective oscillations of positive and negative ions produce large oscillating electrostatic fields and could provide a significant reduction of the Coulomb potential barrier between the two interacting species (such as hydrogen anion H− and B+ in the hydrogen-boron fusion reaction). The negative hydrogen ions can be produced by populating low-temperature electrons around the neutral hydrogen atoms in a rotation chamber. The existence of H− ensures the stability of the plasma and the effectiveness of fusion interactions between H− and B+. In this paper, theoretical analyses of such oscillations systems will be presented and the conditions for fusion enhancement are discussed. Full article

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

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22 pages, 544 KiB

Open AccessEditor’s ChoiceArticle

Adaptive Algorithm for the Generation of Superconfigurations in Hot-Plasma Opacity Calculations

by Jean-Christophe Pain

Plasma 2022, 5(1), 154-175; https://doi.org/10.3390/plasma5010012 - 4 Mar 2022

Cited by 5 | Viewed by 2898

Abstract

In hot plasmas, such as the ones encountered in astrophysics or laser-fusion studies, the number of ionic excited states may become huge, and the relevant electron configurations cannot always be handled individually. The Super Transition Array approach enables one to calculate the massic [...] Read more.

In hot plasmas, such as the ones encountered in astrophysics or laser-fusion studies, the number of ionic excited states may become huge, and the relevant electron configurations cannot always be handled individually. The Super Transition Array approach enables one to calculate the massic photo-absorption cross-section (or radiative opacity) in a statistical manner consisting of grouping configurations close in energy into superconfigurations. One of the main issues of the method, beyond its spectral resolution, is the determination of the most relevant configurations that contribute to opacity. In this work, we discuss different aspects of the generation of superconfigurations in a hot plasma and propose a new adaptive algorithm. Full article

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

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8 pages, 1332 KiB

Open AccessArticle

Bulk Polymerization of PEGDA in Spruce Wood Using a DBD Plasma-Initiated Process to Improve the Flexural Strength of the Wood–Polymer Composite

by Matthew Mieles, Callie Stitt and Hai-Feng Ji

Plasma 2022, 5(1), 146-153; https://doi.org/10.3390/plasma5010011 - 28 Feb 2022

Cited by 2 | Viewed by 2914

Abstract

The chemical treatment of wood has been shown to increase its mechanical strength by forming composites with a variety of polymers. Polyethylene glycol diacrylate (PEGDA) has commonly been used as a polymer reinforcement to increase the strength and resistance of spruce wood for [...] Read more.

The chemical treatment of wood has been shown to increase its mechanical strength by forming composites with a variety of polymers. Polyethylene glycol diacrylate (PEGDA) has commonly been used as a polymer reinforcement to increase the strength and resistance of spruce wood for various applications, such as protection from weathering. In this study, PEGDA was impregnated into wood samples and polymerized by dielectric barrier discharge (DBD) plasma to form wood–polymer composites (WPCs). The kinetic rate order of PEGDA was explored using FT-IR quantitative analysis and the DBD plasma-initiated polymerization was determined to be second order. The strength of the wood samples was then determined by a three-point flexural test. The PEGDA-treated spruce wood samples showed improved flexural strength versus the untreated wood samples. The WPCs were also made using a UV treatment method and were then compared to the DBD plasma-treated samples. The results showed that the DBD plasma-treated samples yielded superior flexural strength relative to the UV-treated samples. We accredited this difference in strength to the plasma process and its ability to penetrate into the various layers of the wood and initiate polymerization, as opposed to UV light that can only penetrate superficially, initiating polymerization in only the first few layers of the wood surface. Full article

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

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16 pages, 6043 KiB

Open AccessArticle

Effect of Electrode Profile and Polarity on Performance of Pressurized Sparkgap Switch

by Vinod Kumar Gandi, Rishi Verma, Manoj Warrier and Archana Sharma

Plasma 2022, 5(1), 130-145; https://doi.org/10.3390/plasma5010010 - 13 Feb 2022

Cited by 6 | Viewed by 4739

Abstract

Sparkgap are most widely used closing switches in various high-voltage pulsed power systems and its reliable operation at desired voltage level is very essential. Conventionally by adjusting the filling gas pressure inside sparkgap switch, breakdown voltage level is altered but switching characteristics such [...] Read more.

Sparkgap are most widely used closing switches in various high-voltage pulsed power systems and its reliable operation at desired voltage level is very essential. Conventionally by adjusting the filling gas pressure inside sparkgap switch, breakdown voltage level is altered but switching characteristics such as stability in hold-off voltage at various pressures, breakdown delay, plasma channel formation, and erosion rate are mainly dictated by adopted electrode profile and its dimensions, inter-electrode gap length and polarity. In this paper, experimental results obtained on breakdown characteristics of four different electrode geometries—Plane Parallel, Hemi-spherical, Bruce, and Rogowski and also a generalized criterion for fixing major dimensions of electrode and inter-gap length to ensure uniform electric field in the inter-electrode region are reported. All electrodes are of brass material and have common radius and thickness of 25 mm and 18 mm, respectively (surface finish <1 µm). Experiments performed on various electrode profiles in gap lengths of 2 mm to 5 mm range with pure nitrogen (N₂) gas pressurization up to 50 psi reveal that among all profiles, Rogowski performs most reliably having stable hold-off voltage in wide operating range. Hold-off voltage magnitude and breakdown delay was commonly obtained higher for negative polarity in all trials. A comprehensive overview of experimental investigation reported herein compares suitability of various electrode profiles and polarity for reliable switching. Full article

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

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19 pages, 8889 KiB

Open AccessEditor’s ChoiceArticle

Application of Nitrogen Piezoelectric Direct Discharge for Increase in Surface Free Energy of Polymers

by Dariusz Korzec, Florian Hoppenthaler, Thomas Andres, Sophia Guentner and Simona Lerach

Plasma 2022, 5(1), 111-129; https://doi.org/10.3390/plasma5010009 - 9 Feb 2022

Cited by 6 | Viewed by 3224

Abstract

The subject of this study is the application of the piezoelectric direct discharge (PDD) operated with nitrogen to control the surface free energy (SFE) of polymers. The activation area, defined as the area of the zone reaching the SFE of 58 mN/m for [...] Read more.

The subject of this study is the application of the piezoelectric direct discharge (PDD) operated with nitrogen to control the surface free energy (SFE) of polymers. The activation area, defined as the area of the zone reaching the SFE of 58 mN/m for high-density polyethylene (HDPE) and poly (methyl methacrylate) (PMMA), is characterized. For HDPE, the activation area was characterized as a function of the distance from 1 to 16 mm, the nitrogen flow from 5 to 20 SLM, and the treatment time from 1 to 32 s. For larger distances, where SFE does not exceed 58 mN/m, the water contact angle is evaluated. The activation area for nitrogen PDD is typically a factor of 3 higher than for air with all other conditions the same. A maximum static activation area of 15 cm

^{2}

is reached. The plasma treatment of lens panels made of PMMA is presented as application example. Full article

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

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14 pages, 1132 KiB

Open AccessArticle

3D-Modulational Stability of Envelope Soliton in a Quantum Electron–Ion Plasma—A Generalised Nonlinear Schrödinger Equation

by Shatadru Chaudhuri, Asesh Roy Chowdhury and Basudev Ghosh

Plasma 2022, 5(1), 60-73; https://doi.org/10.3390/plasma5010005 - 17 Jan 2022

Cited by 2 | Viewed by 2599

Abstract

In physical reality, the phenomena of plasma physics is actually a three-dimensional one. On the other hand, a vast majority of theoretical studies only analyze a one-dimensional prototype of the situation. So, in this communication, we tried to treat the quantum electron–ion plasma [...] Read more.

In physical reality, the phenomena of plasma physics is actually a three-dimensional one. On the other hand, a vast majority of theoretical studies only analyze a one-dimensional prototype of the situation. So, in this communication, we tried to treat the quantum electron–ion plasma in a full 3D setup and the modulational stability of envelope soliton was studied in a quantum electron–ion plasma in three dimensions. The Krylov–Bogoliubov–Mitropolsky method was applied to the three-dimensional plasma governing equations. A generalized form of the nonlinear Schrödinger (NLS) equation was obtained, whose dispersive term had a tensorial character, which resulted in the anisotropic behavior of the wave propagation even in absence of a magnetic field. The stability condition was deduced ab initio and the stability zones were plotted as a function of plasma parameters. The modulational stability of such a three-dimensional NLS equation was then studied as a function of plasma parameters. It is interesting to note that the nonlinear excitation of soliton took place again here due to the balance of nonlinearity and dispersion. The zones of contour plots are given in detail. Full article

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

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14 pages, 2015 KiB

Open AccessEditor’s ChoiceArticle

The Effect of Excited Species on the Collisional Energy of Argon Inductively Coupled Plasmas: A Global Model Study

by Júlia Karnopp, Bernardo Magaldi, Julio Sagás and Rodrigo Pessoa

Plasma 2022, 5(1), 30-43; https://doi.org/10.3390/plasma5010003 - 4 Jan 2022

Cited by 6 | Viewed by 5003

Abstract

Global modeling of inductively coupled plasma (ICP) reactors is a powerful tool to investigate plasma parameters. In this article, the argon ICP global model is revisited to explore the effect of excited species on collisional energy through the study of different approaches to [...] Read more.

Global modeling of inductively coupled plasma (ICP) reactors is a powerful tool to investigate plasma parameters. In this article, the argon ICP global model is revisited to explore the effect of excited species on collisional energy through the study of different approaches to particle and energy balance equations. The collisional energy loss is much more sensitive to modifications in the balance equations than the electron temperature. According to the simulations, the multistep ionization reduces the collisional energy loss in all investigated reaction sets and the inclusion of heavy species reactions has negligible influence. The plasma parameters obtained, such as total energy loss and electron temperature, were compared with experimental results from the literature. The simulated cases that have more excited species and reactions in the energy balance are in better agreement with the experimental measurements. Full article

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

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11 pages, 515 KiB

Open AccessArticle

Modulational Instability of Ion-Acoustic Waves in Pair-Ion Plasma

by Sharmin Jahan, Rubaiya Khondoker Shikha, Abdul Mannan and A A Mamun

Plasma 2022, 5(1), 1-11; https://doi.org/10.3390/plasma5010001 - 29 Dec 2021

Cited by 2 | Viewed by 2793

Abstract

The modulational instability (MI) of ion-acoustic waves (IAWs) is examined theoretically in a four-component plasma system containing inertialess electrons featuring a non-thermal, non-extensive distribution, iso-thermal positrons, and positively as well as negatively charged inertial ions. In this connection, a non-linear Schrödinger equation (NLSE), [...] Read more.

The modulational instability (MI) of ion-acoustic waves (IAWs) is examined theoretically in a four-component plasma system containing inertialess electrons featuring a non-thermal, non-extensive distribution, iso-thermal positrons, and positively as well as negatively charged inertial ions. In this connection, a non-linear Schrödinger equation (NLSE), which dominates the conditions for MI associated with IAWs, is obtained by using the reductive perturbation method. The numerical analysis of the NLSE reveals that the increment in non-thermality leads to a more unstable state, whereas the enhancement in non-extensivity introduces a less unstable state. It also signifies the bright (dark) ion-acoustic (IA) envelope solitons mode in the unstable (stable) domain. The conditions for MI and its growth rate in the unstable regime of the IAWs are vigorously modified by the different plasma parameters (viz., non-thermal, non-extensive q-distributed electron, iso-thermal positron, the ion charge state, the mass of the ion and positron, non-thermal parameter

α

, the temperature of electron and positron, etc.). Our findings may supplement and add to prior research in non-thermal, non-extensive electrons and iso-thermal positrons that can co-exist with positive as well as negative inertial ions. Full article

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

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9 pages, 1992 KiB

Open AccessArticle

A Supersensitive Method for Spectroscopic Diagnostics of Electrostatic Waves in Magnetized Plasmas

by Eugene Oks, Elisabeth Dalimier and Paulo Angelo

Plasma 2021, 4(4), 780-788; https://doi.org/10.3390/plasma4040040 - 10 Dec 2021

Cited by 1 | Viewed by 1950

Abstract

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 [...] Read more.

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

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

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10 pages, 2613 KiB

Open AccessArticle

On the Temperature and Plasma Distribution of an Inductively Driven Xe-I₂-Discharge

by Tim Gehring, Santiago Eizaguirre, Qihao Jin, Jan Dycke, Manuel Renschler and Rainer Kling

Plasma 2021, 4(4), 745-754; https://doi.org/10.3390/plasma4040037 - 16 Nov 2021

Viewed by 2714

Abstract

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 [...] Read more.

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

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

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9 pages, 474 KiB

Open AccessArticle

Electrostatic Ion-Acoustic Shock Waves in a Magnetized Degenerate Quantum Plasma

by Sharmin Jahan, Booshrat E. Sharmin, Nure Alam Chowdhury, Abdul Mannan, Tanu Shree Roy and A A Mamun

Plasma 2021, 4(3), 426-434; https://doi.org/10.3390/plasma4030031 - 26 Aug 2021

Cited by 8 | Viewed by 3347

Abstract

A theoretical investigation has been carried out to examine the ion-acoustic shock waves (IASHWs) in a magnetized degenerate quantum plasma system containing inertialess ultra-relativistically degenerate electrons, and inertial non-relativistic positively charged heavy and light ions. The Burgers equation is derived by employing the [...] Read more.

A theoretical investigation has been carried out to examine the ion-acoustic shock waves (IASHWs) in a magnetized degenerate quantum plasma system containing inertialess ultra-relativistically degenerate electrons, and inertial non-relativistic positively charged heavy and light ions. The Burgers equation is derived by employing the reductive perturbation method. It can be seen that under the consideration of non-relativistic positively charged heavy and light ions, the plasma model only supports the positive electrostatic shock structure. It is also observed that the charge state and number density of the non-relativistic heavy and light ions enhance the amplitude of IASHWs, and the steepness of the shock profile is decreased with ion kinematic viscosity. The findings of our present investigation will be helpful in understanding the nonlinear propagation of IASHWs in white dwarfs and neutron stars. Full article

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

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18 pages, 4023 KiB

Open AccessArticle

On the Effect of Electron Streaming and Existence of Quasi-Solitary Mode in a Strongly Coupled Quantum Dusty Plasma—Far and Near Critical Nonlinearity

by Shatadru Chaudhuri and Asesh Roy Chowdhury

Plasma 2021, 4(3), 408-425; https://doi.org/10.3390/plasma4030030 - 26 Aug 2021

Cited by 2 | Viewed by 2715

Abstract

A strongly coupled quantum dusty plasma consisting of electrons and dust with the ions in the background is considered when there is streaming of electrons. It is observed that the streaming gives rise to both the slow and fast modes of propagation. The [...] Read more.

A strongly coupled quantum dusty plasma consisting of electrons and dust with the ions in the background is considered when there is streaming of electrons. It is observed that the streaming gives rise to both the slow and fast modes of propagation. The nonlinear mode is then analyzed by the reductive perturbation approach, resulting in the KdV-equation. In the critical situation where non-linearity vanishes, the modified scaling results in the MKdV equation. It is observed that both the KdV and MKdV equations possess quasi-solitary wave solution, which not only has the character of a soliton but also has a periodic nature. Such types of solitons are nowadays called nanopteron solitons and are expressed in terms of cnoidal-type elliptic functions. Full article

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

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12 pages, 2942 KiB

Open AccessArticle

Dependence of Optical Emission Spectra on Argon Gas Pressure during Modulated Pulsed Power Magnetron Sputtering (MPPMS)

by Masaomi Sanekata, Hiroshi Nishida, Yuki Nakagomi, Yoshihiro Hirai, Nobuo Nishimiya, Masahide Tona, Naoyuki Hirata, Hiroaki Yamamoto, Keizo Tsukamoto, Keijiro Ohshimo, Fuminori Misaizu and Kiyokazu Fuke

Plasma 2021, 4(2), 269-280; https://doi.org/10.3390/plasma4020018 - 19 May 2021

Cited by 3 | Viewed by 3383

Abstract

Modulated pulsed power magnetron sputtering (MPPMS) of titanium was investigated as a function of argon gas pressure using optical emission spectroscopy (OES). Delays in discharge and the formation of comb-like discharge current waveforms due to splitting and pulsing were observed with a decrease [...] Read more.

Modulated pulsed power magnetron sputtering (MPPMS) of titanium was investigated as a function of argon gas pressure using optical emission spectroscopy (OES). Delays in discharge and the formation of comb-like discharge current waveforms due to splitting and pulsing were observed with a decrease in pressure. This observation corresponds to the evolution from MPPMS condition to deep-oscillation-magnetron-sputtering (DOMS)-like condition by changing discharge gas pressure. The optical emission intensities of the ionic species (Ar⁺ and Ti⁺) increased as the comb-like current waveforms were formed with decreasing Ar pressure. This behavior showed a marked contrast to that of the neutral species (Ar and Ti). The Ar pressure dependence of OES was revealed to be due to the plasma build-up stage, which is the initial generation process of plasma discharge in pulsed dc magnetron sputtering, from the temporal profile for the atomic-line intensities of the optically emitting species in MPPMS and DOMS-like plasmas. Full article

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

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17 pages, 365 KiB

Open AccessArticle

Beginnings of Developing Kinetic Scenarios of Plasma Evolution Due to Coulomb Collisions

by Vasily Erofeev

Plasma 2021, 4(2), 252-268; https://doi.org/10.3390/plasma4020017 - 23 Apr 2021

Cited by 2 | Viewed by 2041

Abstract

A new logic of reducing the two-time formalism to a highly informative scenario of redistribution of plasma particles in momentum due to Coulomb collisions is reported. Based on objective plasma evolution equations following from a properly reduced full plasma description, it has a [...] Read more.

A new logic of reducing the two-time formalism to a highly informative scenario of redistribution of plasma particles in momentum due to Coulomb collisions is reported. Based on objective plasma evolution equations following from a properly reduced full plasma description, it has a more sound foundation than that presented in the previous report on increasing the informativeness of scenarios of the phenomenon. The possibilities of adapting the approach to the further development of more informative scenarios of plasma collisional relaxation and the modelling of transport phenomena are discussed. Full article

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

13 pages, 1666 KiB

Open AccessEditor’s ChoiceArticle

Delayed Discharge Bridging Two Sputtering Modes from Modulated Pulsed Power Magnetron Sputtering (MPPMS) to Deep Oscillation Magnetron Sputtering (DOMS)

by Masaomi Sanekata, Hiroshi Nishida, Tatsuya Watabe, Yuki Nakagomi, Yoshihiro Hirai, Nobuo Nishimiya, Masahide Tona, Hiroaki Yamamoto, Naoyuki Hirata, Keizo Tsukamoto, Keijiro Ohshimo, Fuminori Misaizu and Kiyokazu Fuke

Plasma 2021, 4(2), 239-251; https://doi.org/10.3390/plasma4020016 - 21 Apr 2021

Cited by 4 | Viewed by 3236

Abstract

Delayed discharges due to electrical breakdown are observed in modulated pulsed pow er magnetron sputtering (MPPMS) plasma of titanium. The delayed discharge, which is remarkable with decreasing argon gas pressure, transforms the discharge current waveform from a standard modulated pulsed discharge current waveform [...] Read more.

Delayed discharges due to electrical breakdown are observed in modulated pulsed pow er magnetron sputtering (MPPMS) plasma of titanium. The delayed discharge, which is remarkable with decreasing argon gas pressure, transforms the discharge current waveform from a standard modulated pulsed discharge current waveform to a comb-like discharge current waveform consisting of several pulses with high power. In addition, the delay times, consisting of statistical times and formative times in the delayed MPPMS discharges, are experimentally measured with the help of Laue plot analysis. The pressure dependence of delay times observed indicates that the delayed discharge behavior matches the breakdown characteristics well. In the present study, the delayed discharge dynamics of the comb-like discharge current waveform, which can be the origin of deep oscillation magnetron sputtering, are investigated based on measurement of the delay times and the characteristics of discharge current waveforms. Full article

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

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9 pages, 863 KiB

Open AccessArticle

Electrostatic Dust-Acoustic Rogue Waves in an Electron Depleted Dusty Plasma

by Jebun Naher Sikta, Nure Alam Chowdhury, Abdul Mannan, Sharmin Sultana and A. A. Mamun

Plasma 2021, 4(2), 230-238; https://doi.org/10.3390/plasma4020015 - 16 Apr 2021

Cited by 7 | Viewed by 3032

Abstract

The formation of gigantic dust-acoustic (DA) rouge waves (DARWs) in an electron depleted unmagnetized opposite polarity dusty plasma system is theoretically predicted. The nonlinear Schrödinger equation (NLSE) is derived by employing the reductive perturbation method. It is found that the NLSE leads to [...] Read more.

The formation of gigantic dust-acoustic (DA) rouge waves (DARWs) in an electron depleted unmagnetized opposite polarity dusty plasma system is theoretically predicted. The nonlinear Schrödinger equation (NLSE) is derived by employing the reductive perturbation method. It is found that the NLSE leads to the modulational instability (MI) of DA waves (DAWs), and to the formation of DARWs, which are caused by to the effects of nonlinearity and dispersion in the propagation of DAWs. The conditions for the MI of DAWs and the basic properties of the generated DARWs are numerically identified. It is also seen that the striking features (viz., instability criteria, amplitude and width of DARWs, etc.) of the DAWs are significantly modified by the effects of super-thermality of ions, number density, mass and charge state of the plasma species, etc. The results obtained from the present investigation will be useful in understanding the MI criteria of DAWs and associated DARWs in electron depleted unmagnetized opposite polarity dusty plasma systems like Earth’s mesosphere (where the D-region plasma could suffer from electron density depletion), cometary tails, Jupiter’s magnetosphere, and F-ring of Saturn, etc. Full article

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

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Review

Jump to: Research

31 pages, 7359 KiB

Open AccessReview

Fundamentals and Applications of Nonthermal Plasma Fluid Flows: A Review

by Masaaki Okubo

Plasma 2023, 6(2), 277-307; https://doi.org/10.3390/plasma6020020 - 10 May 2023

Cited by 1 | Viewed by 2891

Abstract

A review is presented to integrate fluid engineering, heat transfer engineering, and plasma engineering treated in the fields of mechanical engineering, chemical engineering, and electrical engineering. A basic equation system for plasma heat transfer fluids is introduced, and its characteristics are explained. In [...] Read more.

A review is presented to integrate fluid engineering, heat transfer engineering, and plasma engineering treated in the fields of mechanical engineering, chemical engineering, and electrical engineering. A basic equation system for plasma heat transfer fluids is introduced, and its characteristics are explained. In such reviews, generally, the gap between fundamentals and application is large. Therefore, the author attempts to explain the contents from the standpoint of application. The derivation of formulas and basic equations are presented with examples of application to plasmas. Furthermore, the heat transfer mechanisms of equilibrium and nonequilibrium plasmas are explained with reference to the basic equation system and concrete examples of analyses. Full article

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

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41 pages, 4900 KiB

Open AccessEditor’s ChoiceReview

A Comprehensive Review on Amplification of Laser Pulses via Stimulated Raman Scattering and Stimulated Brillouin Scattering in Plasmas

by Renju Miriam Cheriyan, Nikhil Varghese, R. S. Sooraj, Kavya H. Rao and N. Smijesh

Plasma 2022, 5(4), 499-539; https://doi.org/10.3390/plasma5040037 - 24 Nov 2022

Cited by 1 | Viewed by 2768

Abstract

The demand for high-intensity lasers has grown ever since the invention of lasers in 1960, owing to their applications in the fields of inertial confinement fusion, plasma-based relativistic particle accelerators, complex X-ray and gamma-ray sources, and laboratory astrophysics. To create such high-intensity lasers, [...] Read more.

The demand for high-intensity lasers has grown ever since the invention of lasers in 1960, owing to their applications in the fields of inertial confinement fusion, plasma-based relativistic particle accelerators, complex X-ray and gamma-ray sources, and laboratory astrophysics. To create such high-intensity lasers, free-running lasers were either Q-switched or mode-locked to increase the peak power to the gigawatt range. Later, chirped pulse amplification was developed, allowing the generation of peak power up to

10^{12}

W. However, the next generation of high-intensity lasers might not be able to be driven by the solid-state technology alone as they are already operating close to their damage thresholds. In this scenario, concepts of amplification based on plasmas has the potential to revolutionize the laser industry, as plasma is already a broken-down medium, and hence does not pose any problems related to the damage thresholds. On the other hand, there are many other aspects that need to be addressed before developing technologies based on plasma-based amplification, and they are being investigated via theoretical and numerical methods and supported by several experiments. In this report, we review the prospects of employing plasma as the medium of amplification by utilising stimulated scattering techniques, such as the stimulated Raman scattering (SRS) and stimulated Brillouin scattering (SBS) techniques, to modulate high-power laser pulses, which would possibly be the key to the next generation of high-power lasers. The 1980s saw the commencement of research in this field, and possibilities of obtaining high peak powers were verified theoretically with the help of numerical calculations and simulations. The extent of amplification by these stimulated scattering schemes are limited by a number of instabilities such as forward Raman scattering (FRS), filamentation, etc., and here, magnetised plasma played an important role in counteracting these parasitic effects. The current research combines all these factors to experimentally realise a large-scale plasma-based amplifier, which can impact the high-energy laser industry in the near future. Full article

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

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221 pages, 61334 KiB

Open AccessEditor’s ChoiceReview

Update on the Scientific Status of the Plasma Focus

by Sunil Auluck, Pavel Kubes, Marian Paduch, Marek J. Sadowski, Vyacheslav I. Krauz, Sing Lee, Leopoldo Soto, Marek Scholz, Ryszard Miklaszewski, Hellmut Schmidt, Alexander Blagoev, Maurizio Samuelli, Yeow Sing Seng, Stuart Victor Springham, Alireza Talebitaher, Cristian Pavez, Mohammad Akel, Seong Ling Yap, Rishi Verma, Karel Kolacek, Paul Lee Choon Keat, Rajdeep S. Rawat, Ali Abdou, Guixin Zhang and Tõnu Laas Show full author list Hide full author list

Plasma 2021, 4(3), 450-669; https://doi.org/10.3390/plasma4030033 - 7 Sep 2021

Cited by 38 | Viewed by 7479

Abstract

This paper is a sequel to the 1998 review paper “Scientific status of the Dense Plasma Focus” with 16 authors belonging to 16 nations, whose initiative led to the establishment of the International Center for Dense Magnetized Plasmas (ICDMP) in the year 2000. [...] Read more.

This paper is a sequel to the 1998 review paper “Scientific status of the Dense Plasma Focus” with 16 authors belonging to 16 nations, whose initiative led to the establishment of the International Center for Dense Magnetized Plasmas (ICDMP) in the year 2000. Its focus is on understanding the principal defining characteristic features of the plasma focus in the light of the developments that have taken place in the last 20 years, in terms of new facilities, diagnostics, models, and insights. Although it is too soon to proclaim with certainty what the plasma focus phenomenon is, the results available to date conclusively indicate what it is demonstrably not. The review looks at the experimental data, cross-correlated across multiple diagnostics and multiple devices, to delineate the contours of an emerging narrative that is fascinatingly different from the standard narrative, which has guided the consensus in the plasma focus community for several decades, without invalidating it. It raises a question mark over the Fundamental Premise of Controlled Fusion Research, namely, that any fusion reaction having the character of a beam-target process must necessarily be more inefficient than a thermonuclear process with a confined thermal plasma at a suitably high temperature. Open questions that need attention of researchers are highlighted. A future course of action is suggested that individual plasma focus laboratories could adopt in order to positively influence the future growth of research in this field, to the general benefit of not only the controlled fusion research community but also the world at large. Full article

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

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23 pages, 4765 KiB

Open AccessReview

Pulsed Discharge Plasma in High-Pressure Environment for Water Pollutant Degradation and Nanoparticle Synthesis

by Wahyu Diono, Siti Machmudah, Hideki Kanda, Yaping Zhao and Motonobu Goto

Plasma 2021, 4(2), 309-331; https://doi.org/10.3390/plasma4020021 - 4 Jun 2021

Cited by 4 | Viewed by 5149

Abstract

The application of high-voltage discharge plasma for water pollutant decomposition and the synthesis of nanoparticles under a high-pressure argon gas environment (~4 MPa) was demonstrated. The experiments were carried out in a batch-type system at room temperature with a pulsed DC power supply [...] Read more.

The application of high-voltage discharge plasma for water pollutant decomposition and the synthesis of nanoparticles under a high-pressure argon gas environment (~4 MPa) was demonstrated. The experiments were carried out in a batch-type system at room temperature with a pulsed DC power supply (15.4 to 18.6 kV) as a discharge plasma source. The results showed that the electrode materials, the pulsed repetition rates, the applied number of pulses, and the applied voltages had a significant effect on the degradation reactions of organic compounds. Furthermore, carbon solid materials from glycine decomposition were generated during the high-voltage discharge plasma treatment under high-pressure conditions, while Raman spectra and the HRTEM images indicated that titanium dioxide with a brookite structure and titanium carbide nanoparticles were also formed under these conditions. It was concluded that this process is applicable in practice and may lead to advanced organic compound decomposition and metal-based nanoparticle synthesis technologies. Full article

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

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