Solar Probe Plus (SPP) will be the first spacecraft to fly into the low solar corona. SPP’s main science goal is to determine the structure and dynamics of the Sun’s coronal magnetic field, understand how the solar corona and wind are heated and accelerated, and determine what processes accelerate energetic particles. Understanding these fundamental phenomena has been a top-priority science goal for over five decades, dating back to the 1958 Simpson Committee Report. The scale and concept of such a mission has been revised at intervals since that time, yet the core has always been a close encounter with the Sun. The mission design and the technology and engineering developments enable SPP to meet its science objectives to: (1) Trace the flow of energy that heats and accelerates the solar corona and solar wind; (2) Determine the structure and dynamics of the plasma and magnetic fields at the sources of the solar wind; and (3) Explore mechanisms that accelerate and transport energetic particles. The SPP mission was confirmed in March 2014 and is under development as a part of NASA’s Living with a Star (LWS) Program. SPP is scheduled for launch in mid-2018, and will perform 24 orbits over a 7-year nominal mission duration. Seven Venus gravity assists gradually reduce SPP’s perihelion from 35 solar radii (RS$R_{S}$) for the first orbit to <10RS${<}10~R_{S}$ for the final three orbits. In this paper we present the science, mission concept and the baseline vehicle for SPP, and examine how the mission will address the key science questions
Sebastián Saldivia, Felipe A. Asenjo, Pablo S. Moya
In this work, we employ the set of ideal expanding magnetohydrodynamic (MHD) equations within the Expanding Box Model (EBM) framework to theoretically characterize the effects of radial solar wind expansion on its characteristic linear MHD waves. Through the analytical derivation of dispersion relations by a first-order expansion of the MHD-EBM equations, we explore the changes in wave propagation across a range of heliocentric distances on the linear magnetohydrodynamic modes: the Alfvén mode and the fast and slow magnetosonic modes, as obtained from the ideal MHD-EBM equations. Our findings reveal a spatial dependence in the derived dispersion relations that aligns with both the literature and the traditional ideal MHD case in the non-expanding limit, thereby helping to bridge the gap between theory and observation in solar wind dynamics. We observe a general decrease in wave frequencies as the plasma expands farther from the Sun. This decrease is reflected in the dispersion relations through the radial decrease of both the Alfvén and sound speeds, which decrease proportionally to $1/R$ and $1/R^{γ- 1}$, respectively, where $γ$ is the plasma polytropic index. The fast magnetosonic mode frequency and phase speed are significantly affected by the polytropic index value. We consider three models for the polytropic index evolution in the expanding solar wind: a constant (quasi-adiabatic) case, a radially decreasing profile in the outer heliosphere, and a model incorporating thermodynamic heating effects. Notably, we find that in the case of a decreasing polytropic index, the fast magnetosonic mode experiences an acceleration in the distant heliosphere, highlighting the significant influence of expansion on solar wind dynamics.
Neutral atoms recycled from wall interaction interact with confined plasma, thereby refueling it, most strongly in the region closest to the wall. This occurs near the X-point in diverted configurations, or else near the wall itself in limited configurations. A progression of analytic models are developed for neutral density in the vicinity of a planar or linear source in an ionizing domain. First-principles neutral transport simulations with DEGAS2 are used throughout to test the validity and limits of the model when using equivalent sources. The model is further generalized for strong plasma gradients or the inclusion of charge exchange. An important part of the problem of neutral fueling from recycling is thereby isolated and solved with a closed-form analytic model. A key finding is that charge exchange with the confined plasma can be significantly simplified with a reasonable sacrifice of accuracy by treating it as a loss. The several assumptions inherent to the model (and the simulations to which it is compared) can be adapted according to the particular behavior of neutrals in the divertor and the manner in which they cross the separatrix.
The magnetic plasma orbit control (MPOC) has been proposed for micro and nanosatellites in the sun-synchronous orbits (SSO) in the low earth orbit (LEO). This method utilizes the plasma drag force generated by the interaction between space plasma and the magnetic field surrounding magnetic torquers (MTQs). In this study, the effects of a finite satellite body on high-potential area generation are investigated by using a plasma flow simulation based on the fully kinetic model. The simulation results show that the predicted high-potential region shrinks due to the finite satellite body because the positive charges of stagnated ions in front of the satellite are absorbed into the satellite surface. In addition, simply applying a bias voltage at the front surface is ineffective in expanding the high-potential region. Specifically, applying a positive bias at the front surface resulted in the accumulation of electrons within the satellite enclosure, causing the floating potential of the satellite to drop according to the applied voltage.
A collaborative effort between Texas Tech University and the University of New Mexico is studying the ways to suppress or minimize outgassing from anode materials in the context of high-power microwave devices. Outgassing can lead to plasma formation with several deleterious effects such as anode-cathode gap closure with impedance collapse, pulse shortening, phase shifts, reductions in system efficiency, and degradation in the longevity and reliability of HPM systems. Here, a possible solution strategy based on quasi-isentropic compression (QIC) is probed with quantitative predictions based on molecular dynamics (MD) simulations. Using copper with hydrogen gaseous impurity as an example anode, our results show that a strong and short pressure ramp applied at one surface can lead to a herding of hydrogen atoms towards the opposite face as well as lead to an initial outgassing and neutral load reduction. Such gaseous impurity gathering could then be used for driving off the impurities by additional surface treatment and cleaning. Additionally, it is shown that upon compression, the surface becomes denser and resistant to subsequent diffusive uptake of hydrogen adsorbates, thus affecting a surface seal. Similar analysis could be applied to other gases (or gas mixtures) as well such as mitigating outgassing of oxygen, CO and CO2 in metals.
Plasma-based CO2 conversion is an emerging power-to-X technology, with the potential to recycle carbon emissions on Earth and produce fuel and life-support consumables in-situ for the human exploration of Mars. In this work, we present a zero-dimensional chemical kinetic modeling framework using ZDPlasKin to simulate nanosecond repetitively pulsed (NRP) discharges in pure CO2, enabling systematic exploration of reactor performance across pressure, temperature, and pulse repetition frequency (PRF) conditions relevant for integrated systems. A reduced chemical mechanism tailored for NRP discharges enabled long-timescale simulations (1–10 s) while still capturing key vibrational energy exchanges. The results of the simulations link the temporal dynamics between pulse and interpulse chemistry to the overall reactor performance. At atmospheric pressure, increasing the PRF reduces CO recombination between pulses and improves conversion without an energy efficiency penalty. Conversion reaches saturation when the overall rate of CO production during the pulse is equal to the rate of CO recombination between pulses. Higher temperatures, which may be required for membrane-based oxygen separation, increase recombination rates and result in lower saturation values of conversion compared to lower temperatures. Additionally, small changes in the maximum reduced electric field strength, influencing total energy coupling, have a strong influence on conversion and efficiency. At low pressures, recombination is negligible, and conversion scales linearly with frequency. These results inform strategies for co-optimizing plasma operating conditions, supporting the engineering and design of CO2 plasma reactors for both terrestrial and space-based applications.
Defect Engineering” is a term, which means the application of controlled defects in the ultrathin arrangement of 2D materials to improve its structure and various properties. Graphene a 2D single atom thick layer allotrope of carbon shows outstanding crystalline structure, various physicochemical properties, remarkable optoelectronic properties, a very good thermal conductivity, charge transport performance, optical transparency, electronic characteristics and extraordinary band gap structure is regarded as the building material for fifth generation electronic and optoelectronic devices. The highly ordered lattice of graphene displays extraordinary device performance, but during growth and processing development of structural defects decreases the performances of the material in the devices. However, these defects can be modified by applying several advanced techniques, so that to realize better performances for device applications. Hence, “Defect engineering of Graphene” actually means perfection of the structure as well as the properties of graphene in order to enhance the functions by using organized defects. In nanotechnology, it is growing towards the route of a perfect material with superior properties for better device performances. This review briefly describes the recently applied advanced techniques that are useful for defect engineering of graphene i.e. Electron beam irradiation, plasma, chemical treatment and doping. Key words: Graphene, functionality, bandgap, e-beam irradiation, plasma, chemical treatment, doping.
This investigation discusses the (2+1)-dimensional complex modified Korteweg–de Vries (cmKdV) system. The cmKdV system describes the nontrivial dynamics of water particles from the surface to the bottom of a water layer, providing a more comprehensive understanding of wave behavior. The cmKdV system finds applications in various fields of physics and engineering, including fluid dynamics, nonlinear optics, plasma physics, and condensed matter physics. Understanding the behavior predicted by the cmKdV system can lead to insights into the underlying physical processes in these systems and potentially inform the design of novel technologies. A new version of the generalized exponential rational function method (nGERFM) is utilized to discover diverse soliton solutions. This method uncovers analytical solutions, including exponential function, singular periodic wave, combo trigonometric, shock wave, singular soliton, and hyperbolic solutions in mixed form. Moreover, the planar dynamical system of the concerned equation is created, all probable phase portraits are given, and sensitive inspection is applied to check the sensitivity of the considered equation. Furthermore, after adding a perturbed term, chaotic and quasi-periodic behaviors have been observed for different values of parameters, and multistability is reported at the end. To gain a deeper understanding of the dynamic behavior of the solutions, analytical results are supplemented with numerical simulations. These obtained outcomes provide a foundation for further investigation, making the solutions useful, manageable, and trustworthy for the future development of intricate nonlinear issues. This study’s methodology is reliable, strong, effective, and applicable to various nonlinear partial differential equations (NLPDEs). As far as we know, this type of research has never been conducted to such an extent for this equation before. The Maple software application is used to verify the correctness of all obtained solutions.
Abstract During the operation of nuclear fusion reactors, plasma-facing components lining the reactor vessel are continually bombarded by plasma species. The penetration and subsequent trapping of these bombarding plasma ions has implications for component damage as well as in-vessel inventory. Accurately predicting the expected ion penetration depth profiles at a range of plasma ion and surface temperatures typical of fusion reactor operating conditions will inform the scrape-off layer design to limit particle radiation damage and tritium trapping in order to prolong the lifetime of the plasma-facing components and satisfy the DT fuel cycle requirements. By defining a statistical distribution for ion penetration depth and describing the evolution of its parameters across the fusion parameter space of interest, the expected ion deposition depth profiles can be calculated for any subset of ion and surface temperature ranges as needed. Molecular dynamics simulations were used to study the bombardment of beryllium lattices with surface temperatures of up to 1100 K by 5 eV–150 eV deuterium and tritium ions, and the resulting ion penetration depths were investigated. The distributions of two penetration depth quantities, considered from the perspectives of lattice damage and hydrogen retention are defined and their distribution parameter dependence on surface and ion temperature is identified. The expected positive correlation between penetration depth and ion temperature is observed, where the non-linear relationship between these quantities indicates the expected form of the velocity dependence of nuclear stopping power at low bombardment energies. Isotope effects on the distributions are also investigated, with results suggesting that heavier ions have comparably lower mobility within the sample and will generally accumulate closer to the surface. A short study on ion deposition rates is also performed; a non-linear increase of deposition rate with increasing bombarding ion energy has been observed, and evidence of a weak positive surface temperature correlation has been noted.
Sneha Latha Kommuguri, Smrutishree Pratihary, Thangjam Rishikanta Singh
et al.
Unlike junctions in solid-state devices, a plasma-metal junction (pm-junction) is a junction of classical and quantum electrons. The plasma electrons are Maxwellain in nature, while metal electrons obey the Fermi-Dirac distribution. In this experiment, the current-voltage characteristics of solid-state devices that form homo or hetero-junction are compared to the pm-junction. Observation shows that the turn-on voltage for pn-junction is 0.5V and decreases to 0.24V for metal-semiconductor junction. However, the pm-junction's turn-on voltage was lowered to a negative value of -7.0V. The devices with negative turn-on voltage are suitable for high-frequency operations. Further, observations show that the current-voltage characteristics of the pm-junction depend on the metal's work function, and the turn-on voltage remains unchanged. This result validates the applicability of the energy-band model for the pm-junction. We present a perspective metal-oxide-plasma (MOP), a gaseous electronic device, as an alternative to metal-oxide-semiconductor (MOS), based on the new understanding developed.
Chan-Won Park, Benedek Horváth, Aranka Derzsi
et al.
Plasma simulations are powerful tools for understanding fundamental plasma science phenomena and for process optimization in applications. To ensure their quantitative accuracy, they must be validated against experiments. In this work, such an experimental validation is performed for a 1d3v particle-in-cell simulation complemented with the Monte Carlo treatment of collision processes of a capacitively coupled radio frequency plasma driven at 13.56 MHz and operated in neon gas. In a geometrically symmetric reactor the electron density in the discharge center and the spatio-temporal distribution of the electron impact excitation rate from the ground into the Ne 2p$_1$ state are measured by a microwave cutoff probe and phase resolved optical emission spectroscopy, respectively. The measurements are conducted for electrode gaps between 50 mm and 90 mm, neutral gas pressures between 20 mTorr and 50 mTorr, and peak-to-peak values of the driving voltage waveform between 250 V and 650 V. Simulations are performed under identical discharge conditions. In the simulations, various combinations of surface coefficients characterising the interactions of electrons and heavy particles with the anodized aluminium electrode surfaces are adopted. We find, that the simulations using a constant effective heavy particle induced secondary electron emission coefficient of 0.3 and a realistic electron-surface interaction model (which considers energy-dependent and material specific elastic and inelastic electron reflection, as well as the emission of true secondary electrons from the surface) yield results which are in good quantitative agreement with the experimental data.
Nonlinear Schrödinger-type equations are important models that have emerged from a wide variety of fields, such as fluids, nonlinear optics, the theory of deep-water waves, plasma physics, and so on. In this work, we obtain different soliton solutions to coupled nonlinear Schrödinger-type (CNLST) equations by applying three integration tools known as the G′G2 -expansion function method, the modified direct algebraic method (MDAM), and the generalized Kudryashov method. The soliton and other solutions obtained by these methods can be categorized as single (dark, singular), complex, and combined soliton solutions, as well as hyperbolic, plane wave, and trigonometric solutions with arbitrary parameters. The spectrum of the solitons is enumerated along with their existence criteria. Moreover, 2D, 3D, and contour profiles of the reported results are also plotted by choosing suitable values of the parameters involved, which makes it easier for researchers to comprehend the physical phenomena of the governing equation. The solutions acquired demonstrate that the proposed techniques are efficient, valuable, and straightforward when constructing new solutions for various types of nonlinear partial differential equation that have important applications in applied sciences and engineering. All the reported solutions are verified by substitution back into the original equation through the software package Mathematica.
Shintaro Sato, Kodai Mitsuhashi, Tomoki Enokido
et al.
A relationship between electric potential distribution on a dielectric surface and electrohydrodynamic (EHD) force generation is experimentally investigated to improve the performance of dielectric-barrier-discharge (DBD) plasma actuators. Direct current (DC) biased repetitive pulses are applied to the DBD plasma actuator, which has two or three electrodes. Although the additional downstream exposed electrode has little effect on the electrical and optical characteristics of the DBD plasma actuator, the electric potential distribution strongly depends on the presence of the additional exposed electrode. Moreover, the saturation time of the surface charge is hundreds of milliseconds when the pulse repetition frequency is 5 kHz , showing a large difference in the time scale of surface DBD. We also demonstrated a significant improvement in the generation of ionic wind by adding an additional downstream exposed electrode owing to the prevention of the electric field screening. A concept that separates the ionization process and the acceleration process works properly for improving the performance of the DBD plasma actuators, but at the same time, the dynamics of the surface charge should be controlled so that a strong electric field is generated rather than the electric field being screened by surface charge.
The energy flux of a nanosecond pulsed cold atmospheric pressure (CAP) plasma jet in contact with a substrate surface was measured to improve the understanding of the correlation between energy flux, flow dynamics and applied electrical power. The flow pattern properties of the CAP jet were imaged using Rayleigh scattering showing a transition from laminar to turbulent flow at Reynolds number of 700, significantly smaller than the conventional critical Reynolds number of 2040. The energy flux to the surface was determined using a passive thermal probe as a substrate dummy. As expected, the energy flux decreases with increasing distance to the nozzle. Measurements of the floating potential of the probe revealed a strong positive charging (up to 165 V) attributed to ion flux originating mainly from Penning ionization by helium metastables. Negative biasing of the probe doubled the energy flux and showed a significantly increased ion contribution up to a nozzle distance of 6 mm to the surface. For positive biasing an increased contribution of electrons and negative ions was only found at 3 mm distance. The relevance of particle transport to the surface is shown by switching from laminar to turbulent flow resulting in a decreased energy flux. Furthermore, a linear correlation of energy flux and input power was found.
Human mesenchymal stem cells can differentiate into various cell types and are useful for applications in regenerative medicine. Previous studies indicated that dental pulp exfoliated from deciduous teeth is a valuable alternative for dental tissue engineering because it contains stem cells with a relatively high proliferation rate. For clinical application, it is necessary to rapidly obtain a sufficient number of cells in vitro and maintain their undifferentiated state; however, the abundance of stem cells in the dental pulp tissue is limited. Non-thermal atmospheric pressure plasma (NTAPP) has been applied in regenerative medicine because it activates cell proliferation. Here, we examined the effects of NTAPP to activate the proliferation of human deciduous dental pulp fibroblast-like cells (hDDPFs) in vitro. Compared with untreated cells, NTAPP increased cell proliferation by 1.3-fold, significantly upregulated well-known pluripotent genes for stemness (e.g., Oct4, Sox2, and Nanog), and activated the expression of stem cell-specific surface markers (e.g., CD105). Overall, NTAPP activated the proliferation of various mesodermal-derived human adult stem cells while maintaining their pluripotency and stemness. In conclusion, NTAPP is a potential tool to expand the population of various adult stem cells in vitro for medical applications.
Capacitively coupled plasmas (CCPs) are widely used for material processing, for example, for the manufacturing of semiconductors textile and modified surface. The ever-increasing requirements that companies face with respect to the quality, efficiency, and environmental friendliness of their manufacturing processes demand continuous progress. One simple and significant path to gain insight is the global model. Global models, which are, in engineering, called the lumped element model, allow for a complete and transparent mathematical analysis. Therefore, this work will study three models, the example of the exact model, and its verification using the step model to find the analytical relation between the sheath charge and the overall voltage drop across it. This formula is the missing factor in the global model that establishes the aim of the research. In addition, an effective lumped element model was studied, which allows describing the sheath dynamics in simple, though nonlinear engineering terms, such as resistance, capacitance, and inductance. The study achieves more detailed dynamics, such as the time-varying charge, voltage distribution, charge–voltage distribution $V_{\text {sh}}(Q)$ that controls the nonlinear sheath dynamics, current distributions, and the equation of the sheath distance for dc and ac sheaths. The results obtained at low computational complexity provide satisfactory calculations for nonlinear dynamics of collision sheath behavior.
China fusion engineering test reactor is a new tokamak device, which is one design option under the consideration of the China National Integration Design Group employs superconducting magnets. The main target of this project is to build a self-sufficient fusion engineering tokamak reactor with its fusion power 50–200 MW. Toroidal field coils, center solenoid coils, and poloidal field (PF) coils, whose rated current range from 52.9 to 90 kA, produce the magnetic field for plasma generation and confinement. The core of quench protection unit is to divert the coil current into discharge resistor by using commutation technology, which should be determined by the rated current and voltage requirement of magnets. Different kinds of technologies for quench protection unit (QPU) are considered, and an advanced commutation technology composed of a mechanical bypass switch, vacuum circuit breaker (VCB), and LC commutation circuit based on artificial current zero technology has been worked out to meet the current and voltage requirement (10 kV/100 kA). To provide a faster and more reliable removal of the energy stored in those superconducting coils, this paper analyzes in detail the feasibility of a commutation scheme based on artificial current zero technology by analyzing and simulating each stage of the commutation process at such large rated current and voltage conditions. Both analysis and simulation results verified that the operating reliability of QPU can be guaranteed by this 100 kA dc commutation scheme.