Juan Casanova-Chafer, Pedro Atienzar, Carla Bittencourt
Theoretical studies have indicated that borophene is a promising two-dimensional material characterized by remarkable chemical, mechanical, and electrical properties. Nonetheless, its practical applications in areas such as catalysis and gas sensing are hindered by the limited density of reactive sites in its pristine form. To address this limitation, the present study explores the controlled fluorination of borophene nanoflakes as a strategy to modify their surface chemistry and enhance the availability of active sites. Furthermore, it is anticipated that surface fluorination will improve hydrophobicity, which is crucial for reducing humidity-related interference in sensing applications. In this study, we report the successful functionalization of borophene nanoflakes with fluorine using a plasma arc discharge technique for the first time. Borophene nanolayers were synthesized via a sonochemical-assisted exfoliation method, yielding nanosheets with an average lateral dimension of approximately 100 nm. The fluorinated samples were characterized using X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD), and high-resolution transmission electron microscopy (HRTEM). A systematic investigation of plasma exposure durations demonstrated that fluorine was effectively introduced as a dopant while maintaining the crystallinity of the borophene lattice.
Multiphysics analysis has become a common technique for nuclear reactor design validation, with neutronic-thermal analysis being the typical choice for understanding reactor dynamics. The concept of adding mechanical simulation such as thermal expansion to this coupling is still relatively new, however, and presents many computational challenges. While large reactors see relatively little neutronic impact from thermal expansion and may not warrant the challenge of undertaking this level of coupling, recent studies of microreactor geometries show that smaller reactors see larger impacts from thermal expansion. This work performs coupled neutronic-thermal-mechanical simulation of the Kilowatt Reactor Using Stirling TechnologY (KRUSTY) using OpenMC and Multiphysics Object-Oriented Simulation Environment in order to analyze the neutronic and thermal impact of including thermal expansion at steady state. The results show that while thermal expansion has a significant effect on global neutronic tallies, it has relatively minor impact on spatial heating rates or temperatures in the system. This remains true even when simulating a multiple heat pipe failure scenario to introduce thermal asymmetry.
Md Jahangir Alam, Abubakar Hamza Sadiq, Jaroslav Kristof
et al.
The blood–brain barrier (BBB) limits drug delivery to the brain, particularly for large or hydrophilic molecules. Brain microvascular endothelial cells (bEND.3), which form part of the BBB, play a critical role in regulating drug uptake. This study investigates the use of cold atmospheric microplasma (CAM) to enhance membrane permeability and facilitate drug delivery in bEND.3 cells. CAM generates reactive oxygen species (ROS) that modulate membrane properties. We exposed bEND.3 cells to CAM at varying voltages (3, 3.5, 4, and 4.5 kV) and measured drug uptake using the fluorescent drug FD-150, fluorescence intensity, ROS levels, membrane lipid order, and membrane potential. The results showed a significant increase in fluorescence intensity and drug concentration in the plasma-treated cells compared to controls. ROS production, measured by DCFH-DA staining, was higher in the plasma-treated cells, supporting the hypothesis that CAM enhances membrane permeability through ROS-induced changes. Membrane lipid order, assessed using the LipiORDER probe, shifted from the liquid-ordered (Lo) to liquid-disordered (Ld) phase, indicating increased membrane fluidity. Membrane depolarization was detected with DisBAC2(3) dye, showing increased fluorescence in the plasma-treated cells. Cell viability, assessed by trypan blue and LIVE/DEAD™ assays, revealed transient damage at higher voltages (≥4 kV), with recovery after 24 h. These results suggest that CAM enhances drug delivery in bEND.3 cells by modulating membrane properties via ROS production and changes in membrane potential. CAM offers a promising strategy for improving drug delivery to the brain, with potential applications in brain-targeted therapies.
Camilla Willim, Thales Silva, Luís Oliveira Silva
et al.
We present a novel mechanism in which plasma electrons and ions optically acquire angular momentum during local pump depletion of an azimuthally polarized laser, despite the laser carrying none. Using theoretical considerations and multi-dimensional particle-in-cell simulations, we find that this process is enabled by a strong frequency downshift at the gradually eroding laser pulse front. We further show that the angular momentum gained by the plasma electrons is compensated by the ions and by the combined electromagnetic fields of the laser and nonlinear plasma wave. By varying key laser parameters such as phase, frequency, and polarization, we demonstrate that the transverse momentum of high-energy electrons can be effectively controlled.
In this work, we investigate the generation of the ambipolar electric field in a gravitationally stratified, collisionless plasma atmosphere. In such environments, gravity tends to separate charged species. To prevent separation an electric field, classically described by the Pannekoek-Rosseland expression, is usually imposed externally. Here, we propose a self-consistent method to recover this field based on a multi-mode Fourier expansion of the electrostatic interaction. We show that, under suitable conditions, this approach naturally leads to the ambipolar electric field and restores charge neutrality. The method is tested in both isothermal and multi-temperature plasma configurations. This framework provides a foundation for future developments that may include collisions, ionization, and asymmetric boundary conditions to model more realistic stellar atmospheres.
We present an extended investigation of a recently introduced model of gravitationally confined, collisionless plasma (Barbieri et al. 2024a), which showed that rapid temperature fluctuations at the base of the plasma, occurring on timescales much shorter than the electron crossing time, can drive the system into a non-thermal state characterized by anti-correlated temperature and density profiles, commonly referred to as temperature inversion. To describe this phenomenon, a temporal coarse-graining formalism was developed (Barbieri et al. 2024b). In this work, we generalize that approach to cover regimes where the timescales of temperature fluctuations are comparable to or exceed the electron crossing time. We derive a set of kinetic equations that incorporate an additional term arising from the coarse-graining procedure, which was not present in the earlier formulation. Through numerical simulations, we analyze the plasma dynamics under these broader conditions, showing that the electric field influences the system when fluctuation timescales approach the electron crossing time. However, for timescales much larger than the proton crossing time, the electric field becomes negligible. The observed behaviours are interpreted within the framework of the extended temporal coarse-graining theory, and we identify the regimes and conditions in which temperature inversion persists.
This review explores the engineering and design aspects of plasma activated water (PAW) systems, focusing on their application in food safety and agriculture. This review aims to bridge the gap between research and practical application, paving the way for the development of robust and efficient PAW systems for enhancing food safety and agricultural productivity. By examining a variety of activation methods, including direct gas ionization, underwater discharges, and dynamic interactions of ionized gases with liquids, this work discusses the mechanical designs that facilitate these processes, highlighting their scalability and efficiency. The discussion is grounded in a comprehensive relevant scientific and patent literature, offering a critical overview of the systems’ design parameters that influence the generation of reactive oxygen and nitrogen species (RONS). The designs reported in literature have employed three major approaches, viz. direct underwater discharges, gas ionization followed by introduction of plasma into the liquid, creation of gas liquid mixtures and subsequent ionization. The laboratory systems have relied on natural convective diffusion of the RONS into water, while most of the patents advocate use of forced convective diffusion of RONS to increase transfer rates. Despite widespread laboratory-scale research in PAW, the transition to industrial-scale systems remains underexplored.
Shalaka A. Kamble, Sanket Jangale, Somnath Bhopale
et al.
Thermal plasma is one of the upcoming powerful tools used for materials processing. It covers a wide range of technological applications such as synthesis of various refractory ceramic materials, metals and alloys, deposition of coatings, high temperature processing of materials as well as disintegration of waste materials. Representative technologically important material systems viz rare earth hexaboride (e.g. GdB6) and carbonaceous materials are focus of the present manuscript. Both the material systems have been processed using DC thermal plasma route and characterized thoroughly for structural, morphological, surface properties using XRD, TEM, XPS respectively. Morphology of GdB6 has been tailored by varying plasma parameters during synthesis. Further, these GdB6 powder were investigated for electron emission performance using Field Electron Emission and maximum current density of 0.5 mA/cm2 was noted for the nanocrystalline GdB6 sample. Feasibility of thermal plasmas for production of nanocrystalline GdB6 and processing of a bio-waste to obtain technologically important carbonaceous materials has also been explored.
This paper explores a recently proposed scalable z-pinch-based space propulsion engine in greater detail. This concept involves a “modified plasma focus with a tapered anode that transports current from a pulsed power source to a consumable portion of the anode in the form of a hypodermic needle tube continuously extruded along the axis of the device”. This tube is filled with a gas at a high pressure and also optionally with an axial magnetic field. The current enters the metal tube through its contact with the anode and returns to the cathode via the plasma sliding over its outer wall. The resulting rapid electrical explosion of the metal tube partially transfers current to a snowplough shock in the fill gas. Both the metal plasma and the fill gas form axisymmetric converging shells. Their interaction forms a hot and dense plasma of the fill gas surrounded by the metal plasma. Its ejection along the axis provides the impulse needed for propulsion. In a nonnuclear version, the fill gas could be xenon or hydrogen. Its unique energy density scaling could potentially lead to a neutron-deficient nuclear fusion drive based on the proton-boron avalanche fusion reaction by lining the tube with solid decaborane. In order to explore the inherent potential of this idea as a scalable space propulsion engine, this paper discusses its theoretical foundations and outlines the first iteration of a conceptual engineering design study for a proof-of-concept experiment based on the UNU-ICTP Plasma Focus facility at the Nanyang Technological University, Singapore.
We report on the first implementation of a miniature laser-driven shock tube (LDST) of 5 × 5 mm cross section and 50-mm length for generating and studying strong shock waves (SW) and hypersonic gas flows with M > 10. Operation of the LDST is based on the acceleration of a thin CH-film by ablative plasma pressure produced when the film is irradiated by high-energy UV pulse of the GARPUN KrF laser (100 J & 100-ns). The film serves as a piston that pushes a SW in the gas filling the LDST. An optical system based on a multi-element prism raster provides focusing of KrF laser beam into 7 × 7 mm square spot with 100 J/cm2 energy fluence (1 GW/cm2 intensity) with inhomogeneity ∼3 % across the LDST aperture. It is expected that the LDST with KrF laser driver can be an effective tool for studying hydrodynamic phenomena, such as hydrodynamic instabilities and transition to a turbulence, hypersonic gas flow around bodies, reflection and cumulation of strong SW.
Ultra-intense laser-plasma wakefield accelerator possess several superior properties compared with the traditional radio-frequency accelerators. These characteristics include femtosecond duration, micro-source size, and ultra-dense beam density, result in highly advantageous for various important applications. In this paper, we reviewed the generation of ultra-intense and high charge electron beam based on laser-plasma acceleration and its nuclear applications in Shanghai Jiao Tong University, including the production of 10 s nC charge beams, the generation of ultra-high flux neutron source on the order of 1019 n/cm2/s, and the excitation of nuclear isomers with the peak efficiency on the order of 1015 particle/s. This laser driving ultra-dense electron source, in conjunction with the plasma environment, presents immense potential in addressing critical problems in astrophysics, and facilitating various nuclear applications. Based on above progress in nuclear astrophysics, a new research plateform about laboratory astrophysics with a 2.5 PW laser will be constructed in TDLI institute.
Edgar C. Buck, Dallas D. Reilly, Luke E. Sweet
et al.
The degradation of the internal structure of plutonium (IV) oxalate during calcination was investigated with Transmission Electron Microscopy (TEM), electron diffraction, Electron Energy-Loss Spectroscopy (EELS), and 4D Scanning TEM (STEM). TEM lift-outs were prepared from samples that had been calcined at 300°C, 450°C, 650°C and 950°C. The resulting phase at all calcination temperatures was identified as PuO2 with electron diffraction. The grain size range was obtained with high-resolution TEM. In addition, 4D STEM images were analyzed to provide grain size distributions. In the 300°C calcined sample, the grains were <10 nm in diameter, at 650°C, the grains ranged from 10 to 20 nm, and by 950°C, the grains were 95–175 nm across. Using the Kolmogorov-Smirnov (K-S) two sample test, it was shown that morphological measurements obtained from 4D-STEM provided statistically significant distributions to distinguish samples at the different calcination conditions. Using STEM-EELS, carbon was shown to be present in the low temperature calcined samples associated with oxalate but had formed carbon (possibly graphite) deposits in the 950°C calcined sample. This work highlights the new methods of STEM-EELS and 4D-STEM for studying the internal structure of special nuclear materials (SNM).
Maricarmen A. Winkler, Víctor Muñoz, Felipe A. Asenjo
Nonlinear effects in the propagation of perturbations in a dusty electron-ion plasma are studied, considering fully relativistic wave motion. A multifluid model is considered for the particles, from which a KdV equation can be derived. In general, two different soliton solutions are found depending on the kind of dispersion of the KdV equation. We study when the dispersion coefficient of this equation is positive. In this case, two kinds of behavior are possible, one associated with a slow wave mode, another with a fast wave mode. It is shown that, depending on the value of the system parameters, compressive and/or rarefactive solitons, or no soliton at all, can be found and that relativistic effects for ions are much more relevant than for electrons. It is also found that relativistic effects can strongly decrease the soliton amplitude for the slow mode, whereas for the fast mode they can lead to compressive-rarefactive soliton transitions and vice versa, depending on the dust charge density in both modes.
Many applications of Neural Networks (NN) to plasma science have appeared in the last years. The author describes here some of the early applications of NNs to plasma science at the beginning of the 90 s, when multi-layer, feed-forward-back-propagation (FFBP) architectures found several applications in this field: they were used to solve inversion problems, to create complete sets of input data, to replace time-consuming modules in models and to predict the outcome of real processes. From a partially personal perspective the author reviews the details of plasma problems to which NNs were successfully applied, and those of the related architectures. It turns out that some solutions, which are perceived today as marking the difference between the previous and contemporary NNs application practices, were in common use >30 years ago when they were deemed fruitful. This can help create deeper historical insight into a field that is getting much attention today.
Norbert Maes, Sergey Churakov, Sergey Churakov
et al.
After isolation of radioactive waste in deep geological formations, radionuclides can enter the biosphere via slow migration through engineered barriers and host rocks. The amount of radionuclides that migrate into the biosphere depends on the distance from a repository, dominant transport mechanism (diffusion vs. advection), and interaction of dissolved radionuclides with minerals present in the host rock and engineered barrier systems. Within the framework of the European Union’s Horizon 2020 EURAD project (https://www.ejp-eurad.eu/), a series of state-of-the-art reports, which form the basis of a series of papers, have been drafted. This state-of-the-art paper aims to provide non-specialists with a comprehensive overview of the current understanding of the processes contributing to the radionuclide retention and migration in clay and crystalline host rocks, in a European context. For each process, a brief theoretical background is provided, together with current methodologies used to study these processes as well as references for key data. Owing to innovative research on retention and migration and the extensive knowledge obtained over decades (in the European context), process understanding and insights are continuously improving, prompting the adaptation and refinement of conceptual descriptions regarding safety assessments. Nevertheless, there remains important research questions to be investigated in the future.
Emil R. Ingelsten, Madox C. McGrae-Menge, E. Paulo Alves
et al.
Progress in understanding multi-scale collisionless plasma phenomena requires employing tools which balance computational efficiency and physics fidelity. Collisionless fluid models are able to resolve spatio-temporal scales that are unfeasible with fully kinetic models. However, constructing such models requires truncating the infinite hierarchy of moment equations and supplying an appropriate closure to approximate the unresolved physics. Data-driven methods have recently begun to see increased application to this end, enabling a systematic approach to constructing closures. Here, we utilise sparse regression to search for heat flux closures for one-dimensional electrostatic plasma phenomena. We examine OSIRIS particle-in-cell simulation data of Landau-damped Langmuir waves and two-stream instabilities. Sparse regression consistently identifies six terms as physically relevant, together regularly accounting for more than 95% of the variation in the heat flux. We further quantify the relative importance of these terms under various circumstances and examine their dependence on parameters such as thermal speed and growth/damping rate. The results are discussed in the context of previously known collisionless closures and linear collisionless theory.
Processes associated with plasma self-organization in tokamaks are presented in the possible logical sequence. The resulting picture of physical processes in self-organized plasmas is predicted based on the nonrequiibrium thermodynamic approach, which uses the Smoluchowski-type equation for the energy balance. The self-organization of magnetized plasma leads to the formation of the universal MHD structure, where the normalized pressure profiles are similar. Finally, experimental confirmation of the proposed physical picture in magnetic fusion facilities is given.
We propose a polytropic-like index that depends on the concentration and number of degrees of freedom of a gas of charged particles following a nonextensive distribution. An equation of state of the gas is obtained and a dispersion relation describing Langmuir waves is derived. Comparison of the acquired dispersion relation with a previous one, recently deduced in the realm of the Kappa distribution, provides an adiabatic map of suprathermal onto nonextensive parameters. In the isothermal limit, the map recovers a well-known relation between those quantities. The results presented here may be useful for investigating the physics of coupled and weakly interacting systems in the nonextensive framework.