Hasil untuk "Plasma physics. Ionized gases"

R. T. P., Aishik Basu Mallick, Vimod Kumar et al.

In this work, we present a systematic experimental study on the physics of helical plume formation in a cross-field atmospheric pressure plasma jet (APPJ) by comparing plume dynamics under continuous and pulsed radio frequency (RF) excitation. While continuous RF discharge predominantly produces a stable conical plume, pulsed operation (500 Hz with 50% duty cycle, identified as the minimum threshold condition) results a self-organized helical plume with enhanced spatial reactivity. Schlieren imaging revealed a significant modification of background gas dynamics after plasma ignition, including accelerated mixing of argon with ambient air. A key finding is the appearance of swirl-like flow structures at the laminar-to-turbulent transition in the continuous case. This was unexpected, since a direct transition was anticipated. In the pulsed case, however, the swirling begins directly at the nozzle exit. It then couples strongly with the ionization wave front and produces a helical plume morphology. Dimensionless analysis using the Strouhal number confirmed the frequency scaling of flow instabilities, while the role of Kelvin–Helmholtz instability and baroclinic torque was identified as the dominant mechanism driving the swirling of the plasma plume. These results provide experimental evidence supporting our proposed physics-based theory for helical plume formation in pulsed RF APPJs. In addition, optical emission spectroscopy and molecular beam mass spectrometry reveal the enhanced reactivity of helical plumes, highlighting their superior mixing, longer interaction path, and broader application potential in plasma–surface processing and biomedical treatments.

Samjhana Dahal, R. Chalise, R. Khanal

Plasma, often called the fourth state of matter, is an ionized gas with wide applications in physics ranging fromastrophysical phenomena and nuclear fusion research to material processing, biomedical technologies, and modernagricultural practices. This study investigates the application of cold atmospheric pressure plasma (CAPP) forimproving the wettability, seedling growth, and chlorophyll content in the leaves of Timur seeds (Zanthoxylumarmatum), a medicinally and culinarily valuable Himalayan plant. We have employed gliding arc discharge fordirect seed treatment, while the plasma-activated water (PAW) was generated using dielectric barrier discharge.The results reveal that direct plasma exposure had limited germination enhancement under laboratory conditions,whereas PAW significantly improved seedling growth, chlorophyll, and root–shoot development. Plasma diagnosticsconfirmed the formation of reactive oxygen and nitrogen species, with favorable physicochemical changes in PAW.The findings demonstrate the promising potential of CAPP for sustainable agrotechnological applications.

Lixin Yang, Yahong Xie, Sheng Liu et al.

Neutral beam injection serves as the effective auxiliary heating method in tokamak fusion research. Positive ion source with single radio frequency driver has been developed at the Institute of Plasma Physics, Chinese Academy of Sciences. To reduce plasma loss on the inner surface of the vacuum chamber, permanent magnets installed on the back plate are essential. Two configurations of cusp magnetic field (checkerboard type and symmetric type) have been carried out with an approach of finite element and experimental performance. The simulation results showed that the distribution of electron for the checkerboard type (type I, type II, and type III) was more uniformity. Heat loading on the inner surface of faraday shield was the lowest with type III. Hence, the checkerboard type III was the useful method to protect the faraday shield. Electron flux would move toward the bottom of the chamber with magnets from the simulation results. It was beneficial to increase the degree of gas ionization on the extracted area and improve the extracted current. Experimental results indicated that the checkerboard type of cusp magnetic field has little influence on reducing the heat loading. The heat loading on the faraday shield and the back plate decreased from 132.97 to 130 kJ because the majority of heat loading was from eddy current. However, the efficiency of radio frequency (RF) ion source increased from 0.36 A/kW to 0.43 A/kW with magnets. The checkerboard type of the cusp magnetic field was useful to improve the extracted current. The results were helpful to optimize the structure of RF ion source.

K. Eder, A. Stegmeir, W. Zholobenko et al.

We report on developments in the edge and scrape-off layer turbulence code GRILLIX to self-consistently simulate plasma turbulence coupled to a fluid neutral gas model. The neutrals model is extended from a single fluid moment (neutrals density) to three moments, describing additionally the dynamics of neutrals parallel momentum and neutrals pressure. GRILLIX employs the flux-coordinate-independent (FCI) approach, wherein the mesh is neither conformal to the wall nor the magnetic field. A new flux evaluation method consistent with FCI allows for implementing plasma recycling at the boundaries that preserves particles to high precision. The improved plasma-neutrals model is applied to simulate an ASDEX Upgrade attached L-mode discharge. Diffusion and viscosity of neutrals parallel momentum introduce a loss channel for ion parallel momentum. This increases the plasma-neutrals interaction time, which is expected to facilitate detachment. Evolution of neutrals pressure leads to a smoother neutrals distribution. Through the charge-exchange coupling, fluctuation amplitudes of ion temperature filaments in the divertor region are reduced. When additionally applying self-consistent recycling boundary conditions, neutrals density and ionization rates at the strike-lines further increase, which impacts the heat load distribution on the target plates.

Muhammad Waqar Ahmed, Kainat Gul, Sohail Mumtaz

Cold atmospheric plasma (CAP) acts as a powerful antibacterial tool in the food industry, effectively eliminating <i>E. coli</i> and a wide range of pathogens, including bacteria, viruses, fungi, spores, and biofilms in meat and vegetables. Unlike traditional bactericidal methods, CAP leverages an arsenal of reactive species, including reactive oxygen species (ROS) such as ozone (O3) and hydroxyl radicals (OH•), and reactive nitrogen species (RNS) like nitric oxide (NO•), alongside UV radiation and charged particles. These agents synergistically dismantle <i>E. coli</i>’s cell membranes, proteins, and DNA, achieving high degradation rates without thermal or chemical damage to processed food. This non-thermal, eco-friendly technology preserves food’s nutritional and sensory integrity, offering a transformative edge over conventional approaches. It emphasizes the critical need to optimize treatment parameters (exposure time, gas composition, power) to unlock CAP’s full potential. This review explores CAP’s effectiveness in degrading <i>E. coli</i>, emphasizing the optimization of treatment parameters for practical food industry applications and its potential as a scalable food safety solution. It is crucial to conduct further studies to enhance its implementation, establishing CAP as a fundamental element of advanced food processing technologies and a key measure for protecting public health.

Anandam Choudhary, Laxman Prasad Goswami, C. Aparajit et al.

The interaction of intense linearly polarized (LP) femtosecond laser pulses with solids is known to generate azimuthal magnetic fields, while circularly polarized (CP) light has been shown to create axial fields. We demonstrate through experiments and particle-in-cell simulations that circularly polarized light can generate both axial and azimuthal fields of comparable magnitude in a plasma created in a solid. Angular distributions of the generated fast electrons at the target front and rear show significant differences between the results for the two polarization states, with circular polarization enforcing more axial confinement. The measurement of the spatial distribution of both types of magnetic fields captures their turbulent evolution.

Espedito Vassallo, Miriam Saleh, Matteo Pedroni et al.

A capacitively coupled radio-frequency argon plasma, used for tungsten sputtering deposition, is characterized using Langmuir probe measurements. Druyvesteyn’s method is used to evaluate plasma parameters through the integral of the Electron Energy Distribution Function (EEDF). In the pressure range analyzed (0.6–10 Pa), the obtained distributions are not Maxwellian, which suggests some depletion of electrons with higher energies. The obtained plasma parameters are compared with those derived from the graphical method. The electron temperature obtained via the graphical method is always lower than the effective temperatures derived from EEDFs, and vice versa, the electron density is overestimated by the graphical method. Optical Emission Spectroscopy is used to monitor the atoms sputtered in the plasma process. The behavior of excited species correlates with the plasma parameters.

Alfred YiuFai Wong, Chun-Ching Shih

An approach to achieve nuclear fusion utilizing the formation of high densities of electrons and neutrals is described. The abundance of low energy free electrons produces intense electric fields that reduce the Coulomb barrier in nuclear fusion. Meanwhile, high-density rotating neutrals provide high centrifugal forces to achieve the extreme pressure gradients of electrons and consequent negative electric fields to reduce the ion repulsive Coulombic fields. These high-density neutrals also provide better stability and higher reaction rates. Ion–neutral coupling is responsible for the control of neutral dynamics. Since high-frequency excitations favor the generation of free electrons, pulsed operations are recommended to achieve fusion with higher gains.

Jianwei Wang

Understanding how environmental variables influence the dissolution rate of nuclear waste materials in aqueous systems is crucial for developing durable nuclear waste forms. In experiments to estimate dissolution rates, the amount of aqueous solution reacting with the material surface is often used as a convenient variable to control the solution saturation state, which then controls the dissolution rate. An exponential function between the dissolution rate and the solution volume-to-surface area ratio was derived, based on an empirical relation of a power function between the Gibbs free energy of dissolution and the volume-to-surface ratio. The relationship was employed to model the dissolution rates of several oxide minerals. The results suggest that the relationship is robust in numerically describing the dissolution rates as a function of the volume-to-surface ratio. Applying the relationship to the dissolution datasets of a nuclear glass and a ceramic nuclear waste form demonstrates its applicability to nuclear materials, providing important insights into the saturation state of the experimental conditions and the chemical durability of these materials. The proposed empirical relationship provides a convenient tool to help design dissolution experiments and offers important insights into the dissolution behavior of materials.

Soheil Khoshbinfar

The magnetized target fusion (MTF) concept is considered an economic way to harness fusion energy that resides between two ICF and MCF pathways. Here, we have proposed a new DT fuel initial density profile that improves final fusion yield in cylindrical targets in MTF. We have employed the Deira-4 MHD code to investigate the performance of these configurations. The potential advantage of an initial density gradient over a common uniform profile assumption in inertial fusion energy is its higher energy gain at the cost of lower input driver energy. It was shown that its energy gain is higher by a factor of two and reduction in driver input energy by a factor of three for a fixed DT fuel mass regime, mDT∼2.2 mg. The radial density profile of DT fuel also promises to make larger targets that work at a sub-MJ regime which resolves our concern about the Rayleigh-Taylor instability growth rate during the implosion phase. It has also been shown that the best results with a seed axial magnetic field ∼10 T would be achieved for a power-law density profile, ρ∝rn, with an exponent n=3. Moreover, the optimal target geometry attains for initial aspect ratio of ∼15 and ignition threshold reduced from <ρR>DT,th=0.56 g/cm2 in uniform density of DT fuel to the power law density profile of ρ∝r3 to <ρR>DT,th =0.21 g/cm2.

M. Bengtson, A. Barrie, M. Benna

The Modular Spectrometer for Atmosphere and Ionosphere Characterization (MoSAIC) is a quadrupole mass spectrometer (QMS), which will fly on NASA's Geospace Dynamics Constellation (GDC) mission in low Earth orbit, providing measurements of neutral and ionized gas density, temperature, composition, and wind/drift. MoSAIC includes a Baffle Scanning Mechanism (BSM), which periodically sweeps in front of the QMS aperture, enabling determination of the ion temperature and cross-track velocity. Accurate knowledge of the plasma wake formed by the BSM is critical for accurate determination of these quantities. We conduct particle-in-cell simulations modeling the interactions between the baffle and plasma across the full range of ion densities, temperatures, and flow speeds GDC is expected to encounter. We discuss the wake physics and present an empirical model, which can be implemented in the MoSAIC data analysis process to determine the relevant ion quantities.

Beata Stańczyk, M. Wiśniewski

The outstanding properties and chemistry of cold atmospheric plasma (CAP) are not sufficiently understood due to their relatively complex systems and transient properties. In this paper, we tried to present a detailed review of the applications of CAP in modern medicine, highlighting the biochemistry of this phenomenon. Due to its unique characteristics, CAP has emerged as a promising tool in various medical applications. CAP, as a partially—or fully ionized—gas-retaining state of quasi-neutrality, contains many particles, such as electrons, charged atoms, and molecules displaying collective behaviour caused by Coulomb interactions. CAP can be generated at atmospheric pressure, making it suitable for medical settings. Cold plasma’s anti-microbial properties create an alternative method to antibiotics when treating infections. It also enhances cell proliferation, migration, and differentiation, leading to accelerated tissue regeneration. CAP can also be a powerful tool in anti-tumour therapies, stem cell proliferation, dental applications, and disease treatment, e.g., neurology. It is our belief that this article contributes to the deeper understanding of cold plasma therapy and its potential in medicine. The objective of this study is to demonstrate the potential of this relatively novel approach as a promising treatment modality. By covering a range of various biomedical fields, we hope to provide a comprehensive overview of CAP applications for multiple medical conditions. In order to gain further insight into the subject, we attempted to gather crucial research and evidence from various studies, hopefully creating a compelling argument in favour of CAP therapy. Our aim is to highlight the innovative aspects of CAP therapy where traditional methods may have limitations. Through this article, we intend to provide a convenient reference source for readers engaged in the examination of CAP’s potential in medicine.

Hao Shang, W. Ning, Saikang Shen et al.

P. Viegas, Elmar Slikboer, Z. Bonaventura et al.

Plasma jets are sources of repetitive and stable ionization waves, meant for applications where they interact with surfaces of different characteristics. As such, plasma jets provide an ideal testbed for the study of transient reproducible streamer discharge dynamics, particularly in inhomogeneous gaseous mixtures, and of plasma–surface interactions. This topical review addresses the physics of plasma jets and their interactions with surfaces through a pedagogical approach. The state-of-the-art of numerical models and diagnostic techniques to describe helium jets is presented, along with the benchmarking of different experimental measurements in literature and recent efforts for direct comparisons between simulations and measurements. This exposure is focussed on the most fundamental physical quantities determining discharge dynamics, such as the electric field, the mean electron energy and the electron number density, as well as the charging of targets. The physics of plasma jets is described for jet systems of increasing complexity, showing the effect of the different components (tube, electrodes, gas mixing in the plume, target) of the jet system on discharge dynamics. Focussing on coaxial helium kHz plasma jets powered by rectangular pulses of applied voltage, physical phenomena imposed by different targets on the discharge, such as discharge acceleration, surface spreading, the return stroke and the charge relaxation event, are explained and reviewed. Finally, open questions and perspectives for the physics of plasma jets and interactions with surfaces are outlined.

M. Korth, R. Manasherob, S. Mrutyunjaya et al.

Modern plasma medicine is a field of medical research combining plasma physics, life sciences, and clinical medicine. It aims to achieve direct application of physical plasma on or in the human body for therapeutic purposes. In medical contexts, the term plasma denotes the liquid component of blood, while in the physical sciences, it refers to ionized gas-also known as the fourth state of matter alongside solid, liquid, and gas. The biological effects of plasma are based on various mechanisms, involving synergistic actions of reactive species such as ionized argon gas molecules and ultraviolet light. Cold-atmospheric plasma (CAP), a specific subtype of plasma, maintain temperatures below 104°F/40°C at the application point, allowing plasma treatment on living tissue at tissue tolerable temperatures. The invention of CAP generating devices has expanded the possibilities for clinical application of plasma in medicine, with growing evidence supporting its efficacy in bacterial load reduction and potential biofilm eradication through debridement. Its antimicrobial effect, coupled with minimal adverse effects on healthy cells, positions it as a promising alternative or additional therapy option. This review provides an overview of current clinical applications of plasma medicine and explores potential roles for plasma application in orthopaedic surgery.

Audrey Lamson McCombs, Madeline Anne Stricklin, Katherine Goode et al.

Over the past decade, a variety of innovative methodologies have been developed to better characterize the relationships between processing conditions and the physical, morphological, and chemical features of special nuclear material (SNM). Different processing conditions generate SNM products with different features, which are known as “signatures” because they are indicative of the processing conditions used to produce the material. These signatures can potentially allow a forensic analyst to determine which processes were used to produce the SNM and make inferences about where the material originated. This article investigates a statistical technique for relating processing conditions to the morphological features of PuO2 particles. We develop a Bayesian implementation of seemingly unrelated regression (SUR) to inverse-predict unknown PuO2 processing conditions from known PuO2 features. Model results from simulated data demonstrate the usefulness of the technique. Applied to empirical data from a bench-scale experiment specifically designed with inverse prediction in mind, our model successfully predicts nitric acid concentration, while results for Pu concentration and precipitation temperature were equivalent to a simple mean model. Our technique compliments other recent methodologies developed for forensic analysis of nuclear material and can be generalized across the field of chemometrics for application to other materials.

Sergey Sadakov, Fabio Villone, Daniel Iglesias et al.

This paper describes a new practical numerical model for the calculation of lateral electromagnetic (EM) loads in tokamaks during asymmetric vertical displacement events (AVDEs). The model combines key features of two recently reported trial models while avoiding their drawbacks. Their common basic feature is the superposition of two patterns of halo current: one perfectly symmetric and another perfectly anti-symmetric. This model combines the following features that have not been combined before (a) a helically distorted halo layer wrapping around core plasma, and (b) halo-to-wall interception belts slipping along plasma-facing walls. This combination almost doubles the lateral net forces. An AVDE creates significant lateral net moments. Being relatively modest at VDEs, the lateral moments become a dominant component of EM loads at AVDEs. The model carefully tracks the balance of net EM loads (zero total for the tokamak), as a necessary condition for the consequent numerical simulation of the tokamak’s dynamic response. This balance is needed as well for the development of tokamak monitoring algorithms and simulators. In order to decouple from the current uncertainties in the interpretation and simulation of AVDE physics, the model does not simulate AVDE evolution but uses it as an input assumption based on the existing interpretation and simulation of AVDE physics. This means the model is to be used in a manner of parametric study, at widely varied input assumptions on AVDE evolution and severity. Parametric results will fill a library of ready-for-use waveforms of asymmetric EM loads (distributed and total) at tokamak structures and coils, so that the physics community may point to specific variants for subsequent engineering analysis. This article presents the first practical contribution to this AVDE library.

Philippa K. Browning, Mykola Gordovskyy, Luiz A.C.A. Schiavo et al.

We show how some different fundamental plasma processes - the ideal kink instability, magnetic reconnection and magnetohydrodynamic oscillations - can be causally linked. This is shown through reviewing a series of models of energy release in twisted magnetic flux ropes in the solar corona, representing confined solar flares. 3D magnetohydrodynamic simulations demonstrate that fragmented current sheets develop during the nonlinear phase of the ideal kink instability, leading to multiple magnetic reconnections and the release of stored magnetic energy. By coupling these simulations with a test particle code, we can predict the development of populations of non-thermal electrons and ions, as observed in solar flares, and produce synthetic observables for comparison with observations. We also show that magnetic oscillations arise in the reconnecting loop, although there is no oscillatory external driver, and these lead to pulsations in the microwave emission similar to observed flare quasi-periodic pulsations. Oscillations and propagating waves also arise from reconnection when two twisted flux ropes merge, which is modelled utilising 2D magnetohydrodynamic simulations.

Kenji Ishikawa, Kazunori Koga, Noriyasu Ohno

Plasma-driven science is defined as the artificial control of physical plasma-driven phenomena based on complex interactions between nonequilibrium open systems. Recently, peculiar phenomena related to physical plasma have been discovered in plasma boundary regions, either naturally or artificially. Because laboratory plasma can be produced under nominal conditions around atmospheric pressure and room temperature, phenomena related to the interaction of plasma with liquid solutions and living organisms at the plasma boundaries are emerging. Currently, the relationships between these complex interactions should be solved using science-based data-driven approaches; these approaches require a reliable and comprehensive database of dynamic changes in the chemical networks of elementary reactions. Consequently, the elucidation of the mechanisms governing plasma-driven phenomena and the discovery of the latent actions behind these plasma-driven phenomena will be realized through plasma-driven science.

Connor Moreno, Aaron Bader, Aaron Bader et al.

The three-dimensional variation inherent to stellarator geometries and fusion sources motivates three-dimensional modeling to obtain accurate results from computational modeling in support of design and analysis of first wall, blanket, and shield (FWBS) systems. Manually constructing stellarator fusion power plant geometries in computer-aided design (CAD) and defining the corresponding fusion source can be cumbersome and challenging. The open-source parametric modeling toolset ParaStell has been developed to automate construction of such geometries in low-fidelity. Low-fidelity modeling is useful during the conceptual phase of engineering design as a means of rapidly exploring the design space of a given device. The modeling capability of ParaStell includes in-vessel components and magnets, for any given stellarator configuration, using a parametric definition and plasma equilibrium data. Furthermore, the toolset automates the generation of detailed, tetrahedral neutron source definitions and DAGMC geometries for use in neutronics modeling. ParaStell assists rapid design iteration, parametric study, and design optimization of stellarator fusion cores. As a demonstration of the design iteration capability, the effect of the three-dimensional parameter space on tritium breeding and magnet shielding is investigated, using the WISTELL-D configuration as a design basis. Blanket and shield thicknesses are varied in three dimensions, using the space available between the plasma edge and magnet coils as a constraint. The corresponding effects on tritium breeding ratio and magnet heating are tallied using the open-source Monte Carlo particle transport code OpenMC. The inclusion of additional and higher-fidelity modeling capabilities is planned for ParaStell’s future, as well as its implementation in machine-driven optimization.