The HOPE mass spectrometer of the Radiation Belt Storm Probes (RBSP) mission (renamed the Van Allen Probes) is designed to measure the in situ plasma ion and electron fluxes over 4π sr at each RBSP spacecraft within the terrestrial radiation belts. The scientific goal is to understand the underlying physical processes that govern the radiation belt structure and dynamics. Spectral measurements for both ions and electrons are acquired over 1 eV to 50 keV in 36 log-spaced steps at an energy resolution ΔEFWHM/E≈15 %. The dominant ion species (H+, He+, and O+) of the magnetosphere are identified using foil-based time-of-flight (TOF) mass spectrometry with channel electron multiplier (CEM) detectors. Angular measurements are derived using five polar pixels coplanar with the spacecraft spin axis, and up to 16 azimuthal bins are acquired for each polar pixel over time as the spacecraft spins. Ion and electron measurements are acquired on alternate spacecraft spins. HOPE incorporates several new methods to minimize and monitor the background induced by penetrating particles in the harsh environment of the radiation belts. The absolute efficiencies of detection are continuously monitored, enabling precise, quantitative measurements of electron and ion fluxes and ion species abundances throughout the mission. We describe the engineering approaches for plasma measurements in the radiation belts and present summaries of HOPE measurement strategy and performance.
Intricate, self-organized plasma structures observed above the surface of a liquid anode of atmospheric DC glow discharge were found to give rise to coherent, organized surface deformation and mechanical wave formation at the plasma–liquid interface. This new phenomenon indicates that the liquid is closely coupled to the plasma by the anode sheath’s electrohydrodynamic (EHD) force. A scientific question then arises: Do surface perturbations, coupled with the nonuniform surface charge distribution, enhance the electric field and induce self-organization? Using the reflective background-oriented schlieren technique, the liquid surface profile under the plasma pattern was measured for the first time. The results show that surface distortions are driven by the repulsive Coulomb force of nonuniform net-negative surface charge acted by the anode sheath field. The impacts of various operating parameters on the patterns and surface waves were examined, revealing the significance of gas heating and liquid charge relaxation time in the pattern formation mechanism. Time-resolved dynamics of a pulsed DC discharge indicated that the surface deformation only appeared after the establishment of plasma patterns. Statistically, the surface wave under the plasma has high wave numbers (8000–16000 m−1) and small amplitudes ( <10 µm), generally found in the capillary wave regime. Yet the motion of surface deformations is in tandem with the plasma pattern and exhibits a nondispersive nature of constant phase velocity (0.1–0.4 m s−1), suggesting the dominant role of EHD force over the surface tension in the observed surface wave. These results indicate that the deformed liquid surface is driven by the EHD force of the plasma sheath. Although they share a similar geometry, the deformation and wave dynamics of the liquid surface do not stimulate a plasma pattern. Importantly, the complex EHD coupling in the plasma–liquid system raises awareness and new challenges for plasma control engineering, and the quantitative characteristics of the nondispersive surface wave are informative for advancing relevant theory and modeling.
Efficiency of recombination is of crucial importance for the existence of ultracold plasmas (UCP), particularly, the ones formed in magneto-optical traps. Unfortunately, an equilibrium thermodynamic treatment of the ionization-recombination processes is inappropriate for the evolving UCP clouds, while a straightforward kinetic simulation encounters a problem of huge difference in spatial and temporal scales for free and bound motion of the electrons. As a result, only the 'virtual' electron-ion pairs are usually reproduced in such modeling, and it is necessary to employ some heuristic criteria to identify them with recombined atoms. The aim of this paper is to present the first successful ab initio simulation of a non-equilibrium recombination in the evolving UCP plasmas. We employ a special algorithm, which is based on using the 'scalable' reference frame, co-moving with an expanding substance. Then, the recombination events are identified by a series of sharp equidistant peaks in the kinetic and/or potential energies, which are caused by captured electrons passing near the pericenters of their orbits; and this is confirmed by a detailed inspection of their trajectories. Thereby, we are able to trace the real, rather than 'virtual', electron-ion pairs; and the total efficiency of their formation was found to be about 20%, which is in agreement with laboratory measurements.
The exceptional charge transport properties of single-walled carbon nanotubes (SWCNTs) enable numerous ultrafast optoelectronic applications. Modifying SWCNTs by introducing defects significantly impacts the performance of nanotube-based devices, making defect characterization crucial. This research tracked these effects in oxygen plasma-treated SWCNT thin films. Sub-picosecond electric fields of varying strengths and additional photoexcitation were used to assess how defects influence charge carrier transport. Changes in effective conductivity within the terahertz (THz) range were found to be strongly dependent on impurity levels. The plasmon resonance shift to higher THz frequencies aligns with the defect-induced reduction in conductivity and slowed carrier migration within the network. An increase in THz field strength resulted in diminished conductivity due to intraband absorption bleaching. To address the emergence of hot charge carriers, a modified Drude model, which considers non-equilibrium charge carrier distribution via fielddependent scattering rates, was applied. The dominant charge-impurity scattering rate in plasma-treated samples corresponded with an increase in defects. Additionally, the impact of defects on charge carrier dynamics on a picosecond timescale was examined. The modeled plasma-treated SWCNTs wire-grid polarizer for the THz range reveals the potential for multi-level engineering of THz devices to customize properties through controlled defect populations.
Henrik van Impel, David Steuer, Robin Labenski
et al.
Atmospheric pressure dielectric barrier discharges (DBDs), such as the micro cavity plasma array (MCPA), have emerged as promising technologies for the conversion of volatile gases. These conversion processes’ effectiveness can be enhanced by integrating catalytically active surfaces. To deepen the understanding of the plasma-catalyst interaction, it is crucial to study the transport dynamics of charged species to the catalytic surface, which, due to collisions with neutrals, also directly affects the transport of reactive species to the catalyst. Thereby the transport of the charged species is in particular influenced by the electric field perpendicular to the catalytic surface. However, experimental data on the component-wise electric field strength within SDBDs are rare. To address this issue, we performed polarized optical emission spectroscopy on the shifting and splitting of the allowed 492.19 nm (1D →1P0) and forbidden 492.06 nm (1F0 →1P0) helium line pair. This diagnostic approach requires a non-radially symmetric geometry, which leads to an adapted reactor design of the MCPA allowing the side-on observation of the discharge. The discharge operates in pure helium at atmospheric pressure, utilizing a triangular excitation voltage with a frequency of 15 kHz and an amplitude of 600 V. We performed phase-resolved measurements of the electric field components with a temporal resolution of 1 µs. Our results revealed an electric field strength of approximately 22 kV cm−1 for the component perpendicular to the dielectric surface, while the component parallel to the dielectric surface is about 5 kV cm−1 larger during the decreasing potential phase of the applied voltage.
A new Smoothed Particle Magnetohydrodynamics (SPMHD) code that combines smoothed particle hydrodynamics (SPH) and finite element method (FEM) has been developed to accurately simulate the motion of fluids and electromagnetic fields. This hybrid approach allows for a more comprehensive simulation of magnetohydrodynamic phenomena, especially at plasma/vacuum interface, by separately treating the fluid motion (by SPH module) and the electromagnetic field dynamics (by FEM module). The SPH module of the code excels in handling fluid dynamics, including large deformations, fluid instabilities, fluid-solid boundary interactions, shock capturing, and plasma properties. Its robust formulation enables accurate modeling of complex fluid behaviors and interactions. On the other hand, the FEM module of the SPMHD code is capable of handling complex geometry, ensuring magnetic field conservation by solving the equations for magnetic vector potential and electric scalar potential, and globally solving the current density in electrodes and moving plasma. The coupling between SPH and FEM in the SPMHD code is achieved through an operator splitting method. This capability enables the accurate representation of electromagnetic phenomena and their interactions with the fluid, enabling real-time coupling of magneticelectric-thermal-fluid fields. To validate the capabilities of the SPMHD code, we present benchmark tests and compare the results with analytical solutions and other numerical codes. The blow-by instability simulations demonstrate the accuracy and efficiency of the hybrid SPH-FEM approach in capturing the complex interplay between fluid dynamics and magnetic field behavior. The SPMHD code is designed for three-dimensional simulations, exhibits high MPI parallelism, robustness and reliability throughout the simulation process. All the features of the SPMHD code make it suitable for a wide range of applications in plasma physics, astrophysics, and engineering.
There is a complex dynamic coupling process between lightning arc and carbon fiber reinforced polymer (CFRP) structure with the fastener during lightning attachment. Based on Magneto Hydro Dynamics (MHD) theory, this paper conducts an in-depth analysis of the time-accurate response of attached arc under the influence of lightning current, exploring the factors affecting the nonlinear interaction mechanism between CFRP structure with the fastener and electrical arc. The research focuses on the presence of fasteners, the size of the discharge gap, and the effects of different discharge current waveforms on the interaction mechanism between the arc and the CFRP structure. By establishing physical models of discharge under various conditions, this paper simulates the evolution of the electrical arc during current injection. It comprehensively analyzes how changes in the structure’s current conduction path, surface temperature distribution, and the arc plasma’s spatiotemporal thermal conduction characteristics affect the interaction between the lightning channel and the composite material. Additionally, the state variable setting method is applied to track the expansion behavior of high-temperature region on the surface of CFRP structure and evaluate the dynamic evolution of the interaction between the arc and the structure. The results showed that the fastener play a crucial role in the process of current conduction, where the differences in material properties between the fasteners and CFRP result in a preferential path for current conduction along the depth of the fastener assembly which significantly affects the coupling between the lightning channel and the CFRP structure. Variation in the discharge gap length results in a hysteresis phenomenon in arc attachment behavior. The interaction relationship between changes in the surface state of CFRP and arc evolution is particularly evident. This work presents a method for studying coupled behavior between lightning arc and CFRP structure with fastener under various discharge conditions.
Here attention is focused on the (1+1)-dimensional Sawada–Kotera (SK) model that is prominent in mathematical physics and engineering to analyze plasmas and coherent systems for communication. Our techniques offer fresh perspectives on the model’s attributes and structure, deepening our comprehension of the underlying dynamics. First, the SK model is reduced to ordinary differential equations by constructing the Lie symmetries and using the associated transformation. Graphs are used to build and display invariant solutions. This strategy has caused the revelation of novel constant solutions that have not been found in the previous works. We offer new understandings of nature and changes observed during the SK derivation by taking advantage of the Lie symmetries powerful tools. Next, the fluctuating layout of proposed framework is examined from several perspectives such as sensitivity and bifurcation analysis. We examined the bifurcation analysis of planar dynamical system by using bifurcation theory. We also include an external periodic perturbation term that breaks regular patterns in the perturbed dynamical system. Graphical structures are provided to display the invariant solutions. The sensitivity of the SK model is determined to be strong after sensitivity analysis under different initial conditions. These results are fascinating, fresh, and conceptually useful for understanding the suggested framework. In mathematics and the applied sciences, forecasting and learning about new technologies are greatly aided by the dynamic aspect of system processing.
The effluent of coking wastewater comprises hundreds of refractory organics and is characterized by high toxicity and non-biodegradation. Electrochemical advanced oxidation processes (EAOPs) have been widely applied in the field of water purification. In this study, a Ti4O7 reactive electrochemical membrane (REM) was prepared using the plasma spraying method for the electro-oxidation of coking wastewater. The composition and surface morphology of the Ti4O7 REM were characterized via X-ray diffraction (XRD) and scanning electron microscopy (SEM), respectively. The computational fluid dynamics (CFD) simulation was used to compare the mass transfer performance of the Ti4O7 REM in traditional batch (TB) mode and flow-through (FT) mode. In the FT mode, the effects of current density and anode–cathode distance on the treatment efficiency were investigated, and the electrocatalytic performance of the anode on coking wastewater was analyzed. The results showed that the COD removal efficiency reached 76.2% with an energy consumption of 110.5 kWh kg−1 COD under the optimal condition. In addition, cathodic polarization provides an effective technique for maintaining the long-term activity of the Ti4O7 REM. The three-dimensional fluorescence results and UV-vis spectrum showed that the aromatic compounds could be effectively degraded using the Ti4O7 REM. The Ti4O7 REM demonstrated excellent performance of electrochemical oxidation and satisfactory stability, which had a strong potential for application in the field of practical wastewater and engineering practices that respond to the concept of sustainable development.
In nuclear fusion (ITER and the future DEMO), those components that face the plasma are exposed to high temperature and irradiation which, in the long term, modifies their thermal and mechanical properties and tritium retention. Tungsten is a candidate material and is the subject of many studies of microstructure evolution under various irradiation and temperature conditions. One milestone is the characterization of its defect properties. We here readdress the diffusion of nanocavities on broad ranges of size and temperature and compare it with dissociation, a competing process during nanocavity growth. First, at the atomic scale, we used molecular dynamics to explore the variety of elementary events involved in the nanocavity diffusion. Second, an experimental study of ion-irradiated samples, annealed at different temperatures up to 1,773 K, revealed the creation and growth of nanocavities on transmission electron microscopy images. Third, we performed multi-objective optimization of the nanocavity diffusion input of our object kinetic Monte Carlo model to reproduce the experimental results. Finally, we applied a sensitivity analysis of the main inputs of our model developed for these particular conditions—the source term which combines two cascade databases and the impurities whose interaction with the defects is characterised with a supplemented database of density functional theory calculations. Three domains of nanocavity size were observed. The first is the small vacancy clusters, for which atomistic calculations are possible and dissociation is negligible. The second is the small nanocavities, for which we provide new diffusion data and where a competition with the dissociation can take place. The third domain is the large nanocavities, for which, in any case, the dissociation prevents their existence above 1,500 K in the absence of a stabilizing interface.
This feature article presents insights concerning the correlation of plasma‐enhanced chemical vapor deposition and plasma‐enhanced atomic layer deposition thin film structures with their barrier or membrane properties. While in principle similar precursor gases and processes can be applied, the adjustment of deposition parameters for different polymer substrates can lead to either an effective diffusion barrier or selective permeabilities. In both cases, the understanding of the film growth and the analysis of the pore size distribution and the pore surface chemistry is of utmost importance for the understanding of the related transport properties of small molecules. In this regard, the article presents both concepts of thin film engineering and analytical as well as theoretical approaches leading to a comprehensive description of the state of the art in this field. Perspectives of future relevant research in this area, exploiting the presented correlation of film structure and molecular transport properties, are presented.
Jeong-Young Ji, Eric D. Held, J. Andrew Spencer
et al.
A general method of solving the drift kinetic equation is developed for an axisymmetric magnetic field. Expanding a distribution function in general moments a set of ordinary differential equations are obtained. Successively expanding the moments and magnetic-field involved quantities in Fourier series, a set of linear algebraic equations is obtained. The set of full (Maxwellian and non-Maxwellian) moment equations is solved to express the density, temperature, and flow velocity perturbations in terms of radial gradients of equilibrium pressure and temperature. Closure relations that connect parallel heat flux density and viscosity to the radial gradients and parallel gradients of temperature and flow velocity, are also obtained by solving the non-Maxwellian moment equations. The closure relations combined with the linearized fluid equations reproduce the same solution obtained directly from the full moment equations. The method can be generalized to derive closures and transport for an electron-ion plasma and a multi-ion plasma in a general magnetic field.
Herein, polyaniline functionalized magnetic nanoparticles (MNPs) were prepared and investigated as the adsorbents for the separation and enrichment of inorganic selenium and tellurium species. The prepared Fe3O4@SiO2@polyaniline (PANI) MNPs presents selective adsorption performance for SeIV and TeIV, along with fast adsorption and desorption dynamics. Based on it, a method combining magnetic solid phase extraction (MSPE) with inductively coupled plasma mass spectrometry (ICP-MS) was developed for the simultaneous speciation of inorganic Se and Te in environmental waters. The adsorption mechanism was investigated preliminarily. Various parameters affecting Fe3O4@SiO2@PANI MSPE of SeIV and TeIV were investigated. Under the optimized conditions, the limits of detection (3σ) for SeIV and TeIV were found to be 5.3 and 1.2 pg mL-1, with the relative standard deviations (cSe(IV) = 100 pg mL-1, cTe(IV) = 10 pg mL-1, n = 7) of 3.8 and 8.0%, respectively. The enrichment factor of the proposed method is 100-fold. The proposed method was successfully applied to the speciation of inorganic Se and Te in environmental water samples. The developed MSPE-ICP-MS method possesses the advantages of low cost, high enrichment factor, rapid operation and can simultaneously analyze inorganic Se and Te species in real-world samples.
The kinetic theory of $\mathrm{sech}^2 x$-type electron holes is studied. The potential of the electron holes is solved in the weak amplitude limit by the pseudo-potential method. We investigate the existence condition of the $\mathrm{sech}^2 x$ electron holes. It indicates that the derivatives of trapped and untrapped distributions at the separatrix play significant roles in determining the potential profile. The theory is then applied to the Kappa-distributed plasmas. The amplitude and width of the $\mathrm{sech}^2 x$ electron holes are analyzed. Finally, the theoretical results are verified by numerical calculations.