Hasil untuk "Plasma engineering. Applied plasma dynamics"

Abdulla-Al- Mamun, Samsun Nahar Ananna, Chunhui Lu

Sujit Handibag, R. M. Wayal, Sandeep Malik

This research investigates the modified Benjamin-Bona-Mahony (mBBM) equation, a crucial model within nonlinear wave dynamics, which effectively characterizes long-wave propagation in dispersive media. By applying the Kumar-Malik method, the study obtains novel exact solutions to the mBBM equation, represented through diverse mathematical forms, including Jacobi elliptic, hyperbolic, trigonometric, and exponential functions. The flexibility of this approach facilitates the construction of various traveling wave solutions, including periodic, singular periodic, bright, dark, kink, anti-kink, and singular waveforms. The graphical visualization of these solutions in multiple dimensions elucidates their propagation behavior and stability, thereby reinforcing the reliability of the proposed methodology. This investigation enhances the knowledge of mathematical techniques for solving nonlinear differential equations and demonstrates their applicability to other nonlinear wave models across various scientific fields. Additionally, the findings not only provide deeper insights into the dynamics of the mBBM equation but also offer new opportunities for studying nonlinear phenomena in diverse physical systems, such as hydromagnetic waves in cold plasma, coastal engineering, nonlinear optics, fluid dynamics, plasma physics, and optical illusions. This work highlights the Kumar-Malik method as a powerful analytical tool, significantly contributing to exploring and comprehending complex wave phenomena within mathematical physics and the applied sciences.

Jamshad Ahmad, Khalid Masood, Fatima Ayub et al.

The Zakharov–Kuznetsov–Benjamin–Bona–Mahony equation (ZKBBME) is a crucial mathematical model used in fractional quantum mechanics, optical fiber signal processing, ion-acoustic waves in plasma, water waves driven by gravity, turbulent flow, fluid flow waves, and for describing many other real-world phenomena. This article employs the modified exp-function method and exp\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$(-\Phi (\psi ))$$\end{document}-expansion method, along with a truncated M-fractional wave transformation, to investigate new rational, trigonometric, hyperbolic, and exponential function solutions. Assigning specific parameter values generates diverse wave shapes most significantly, a new combined wave type called the compacton-kink and a class of peakon waves, which has not yet been documented in previous research of this model. 2-dimensional, 3-dimensional, contour, density, and polar plots illustrate the physical properties of soliton solutions, demonstrating the method’s suitability for analyzing a range of nonlinear fractional models with truncated M-fractional derivative (TMFD). Furthermore, utilizing the Galilean transformation to transform the equation into a planar dynamical system, bifurcation theory is applied to investigate its bifurcation and equilibrium points. The findings show that the TMFD framework captures intricate nonlinear wave dynamics and considerably enriches the ZKBBME solution space. These results advance our knowledge of wave structures in engineering and applied physics models controlled by fractional-order nonlinear partial differential equations (FNLPDEs).

D. A. Kaltsas, J. W. Burby, P. J. Morrison et al.

We present a method for imposing quasineutrality and, more generally, charge density conservation in the Vlasov-Poisson (VP) and Vlasov-Ampère (VA) systems, which describe electrostatic plasma dynamics, by applying the Dirac theory of constraints. Leveraging the Hamiltonian field formulations of the VP and VA models, we construct generalized Dirac brackets using the Dirac algorithm. The resulting constrained systems enforce charge density conservation, and consequently quasineutrality, given that the initial charge density is zero, through new advection terms in the Vlasov equations involving generalized-force terms, while the electric field is eliminated from the constrained Vlasov dynamics. To verify charge density conservation we conduct one-dimensional numerical experiments using a semi-Lagrangian method, demonstrating that the enforcement of the quasineutrality constraint significantly modifies the dynamics. This approach enables us to identify the forces required to enforce quasineutrality, offering a systematic way to assess the validity of the quasineutral approximation across different kinetic scales.

P. Davidson

Monika Niwas, Sachin Kumar

Erik Schroedter, M. Bonitz

Correlated classical and quantum many‐particle systems out of equilibrium are of high interest in many fields, including dense plasmas, correlated solids, and ultracold atoms. Accurate theoretical description of these systems is challenging both, conceptionally and with respect to computational resources. While for classical systems, in principle, exact simulations are possible via molecular dynamics, this is not the case for quantum systems. Alternatively, one can use many‐particle approaches such as hydrodynamics, kinetic theory, or nonequilibrium Green functions (NEGF). However, NEGF exhibit a very unfavorable cubic scaling of the CPU time with the number of time steps. An alternative is the G1–G2 scheme [N. Schlünzen et al., Phys. Rev. Lett. 124, 076601 (2020)] which allows for NEGF simulations with time linear scaling, however, at the cost of large memory consumption. The reason is the need to store the two‐particle correlation function. This problem can be overcome for a number of approximations by reformulating the kinetic equations in terms of fluctuations – an approach that was developed, for classical systems, by Yu.L. Klimontovich [JETP 33, 982 (1957)]. Here, we present an overview of his ideas and extend them to quantum systems. In particular, we demonstrate that this quantum fluctuations approach can reproduce the nonequilibrium GW approximation [E. Schroedter et al., Cond. Matt. Phys. 25, 23401 (2022)] promising high accuracy at low computational cost which arises from an effective semiclassical stochastic sampling procedure. We also demonstrate how to extend the approach to the two‐time exchange‐correlation functions and the density response properties. [E. Schroedter et al., Phys. Rev. B 108, 205109 (2023)]. The results are equivalent to the Bethe–Salpeter equation for the two‐time exchange‐correlation function when the generalized Kadanoff‐Baym ansatz with Hartree‐Fock propagators is applied [E. Schroedter and M. Bonitz, phys. stat. sol. (b) 2024, 2300564].

Chao Chen, Wenzhi Zhai, Qiang Wang et al.

For the realization of magnetic confinement fusion, the negative hydrogen ions produced by an radio frequency (RF) ICP (inductively coupled plasma) source are employed for neutralization process of the neutral beam injection system. A 3D fluid model tailored for the RF ICP source has been developed to explore the negative hydrogen ion distribution. The negative hydrogen ion source consists of the cylindrical driver containing Faraday shield (FS) and the expansion chamber equipped with permanent magnets. The study is focused on the influences of FS, pressure (0.5–2.0 Pa) and permanent magnet remanence (0–1.03 T) on the negative hydrogen ions distribution. When the FS is applied in the driver, the negative hydrogen ion density is low owing to the high electron temperature. The maximum density of the negative hydrogen ions rises monotonically and shifts to the driver with the increased gas pressure. The distribution of negative hydrogen ions is dominated by transport processes at low pressures, while the collision processes become significant at high pressures. The density of negative hydrogen ions near the plasm grid increases with the transverse magnetic filter (TMF) strength as a result of the decreased temperature of electrons. The asymmetry in the density of negative hydrogen ion is enhanced with the increased TMF strength. Our current model offers valuable insights into the behavior of negative hydrogen ions within RF ICP source, thereby advancing our comprehension of this critical component in fusion engineering.

C. Ashe, S. I. Muldrew

Spherical tokamaks (STs) exhibit significant promise as the foundation for compact fusion power plants, offering reduced aspect ratios and enhanced plasma performance that can potentially lower capital costs compared to conventional tokamak designs. The key to achieving an optimal design lies in understanding the sensitivity of the fusion power plant to plasma energy confinement times. However, due to the intricate nature of transport physics and the scarcity of data on highly radiative plasmas required for power plants, extrapolating performance from existing machines introduces substantial uncertainties. In this study, we employed the world-leading fusion power plant systems code, PROCESS, to explore the effects of different energy confinement time scalings on scoping and determining the design of a 1-GWe net electric ST power plant. By comparing various commonly used scalings, we highlight the design impact of employing ST scalings versus those typically applied to conventional aspect ratios, considering both size and performance aspects. Our findings demonstrate that when allowed to freely optimize the choice of confinement scaling has negligible impact on the optimally found design point and is instead driven highly by engineering constraints. In a highly constrained scenario, the conventional IPB98(y,2) scaling consistently shows conservative values across a range of ST plasma performance scenarios. We recommend its utilization for future large design space exploration studies as a low-risk choice due to its intermediary performance between the broad scope of ST scalings and also as a proxy for addressing complex transport considerations in configuring initial ST concept designs.

Sachin Kumar, N. Mann

Markus Battarbee, Konstantinos Papadakis, Urs Ganse et al.

Vlasiator is a space plasma simulation code which models near-Earth ion-kinetic dynamics in three spatial and three velocity dimensions. It is highly parallelized, modeling the Vlasov equation directly through the distribution function, discretized on a Cartesian grid, instead of the more common particle-in-cell approach. Modeling near-Earth space, plasma properties span several orders of magnitude in temperature, density, and magnetic field strength. In order to fit the required six-dimensional grids in memory, Vlasiator utilizes a sparse block-based velocity mesh, where chunks of velocity space are added or deleted based on the advection requirements of the Vlasov solver. In addition, the spatial mesh is adaptively refined through cell-based octree refinement. In this paper, we describe the design choices of porting Vlasiator to heterogeneous CPU/GPU architectures. We detail the memory management, algorithmic changes, and kernel construction as well as our unified codebase approach, resulting in portability to both NVIDIA and AMD hardware (CUDA and HIP languages, respectively). In particular, we showcase a highly parallel block adjustment approach allowing efficient re-ordering of a sparse velocity mesh. We detail pitfalls we have overcome and lay out a plan for optimization to facilitate future exascale simulations using multi-node GPU supercomputing.

Rusko T. Ruskov, Robert Bingham, Luis O. Silva et al.

There is renewed interest in direct-drive inertial confinement fusion, following the milestone December 2022 3.15 MJ ignition result on the National Ignition Facility. A key obstacle is the control of the two plasmon decay instability. Here, recent advances in inhomogeneous turbulence theory are applied to the broadband parametric instability problem for the first time. A novel dispersion relation is derived for the two plasmon decay in a uniform plasma valid under broad-bandwidth laser fields with arbitrary power spectra. The effects of temporal incoherence on the instability are then studied. In the limit of large bandwidth, the well-known scaling relations for the growth rate are recovered, but it is shown that the result is more sensitive to the spectral shape of the laser pulse rather than to its coherence time. The range of wavenumbers of the excited plasma waves is shown to be substantially broadened, suggesting that the absolute instability is favoured in regions further away from the quarter critical density. The intermediate bandwidth regime is explored numerically -- the growth rate is reduced to half its monochromatic value for laser intensities of $10^{15} \, \text{W}/\text{cm}^{2}$ and relatively modest bandwidths of $5 \, \text{THz}$. The instability-quenching properties of a spectrum of discrete lines spread over some bandwidth have also been studied. The reduction in the growth rate is found to be somewhat lower compared to the continuous case but is still significant, despite the fact that, formally, the coherence time of such a laser pulse is infinite.

The International Conference on Frontiers in Pure and Applied Physics (ICFPAP-2024), held from 29 February to 2 March 2024, was organized by the Department of Physics, University of Science and Technology Meghalaya (USTM) in collaboration with the Physics Academy of North-East (PANE). This conference served as a vital platform for researchers and scientists to exchange ideas, with tracks covering a broad spectrum from fundamental physics to advanced concepts. Aimed at bridging science and engineering, the conference aligned with the Indian government’s focus on outcome-based research to drive indigenous technology and innovation. It also provided young researchers a unique opportunity to learn from peers, enhancing their knowledge and career growth. The conference brought together around 250 researchers from diverse countries, including Bangladesh, Brazil, Turkey, Japan, Germany, the USA, Spain, Poland, the UK, Israel, Taiwan, and India. Featuring two plenary speakers and fourteen keynote speakers, ICFPAP-2024 presented a dynamic program with fifteen sessions spread across five parallel tracks, alongside two poster segments. With 120 oral and 90 poster presentations, the conference attracted both active presenters and attendees keen to learn from leading scientists. Held in a hybrid format, it offered flexibility with 20 online presentations upon request, while emphasizing in-person collaboration and engagement. The conference received 68 paper submissions, of which 63 were forwarded for review, with 76 reviewers ensuring the highest standards of scholarship to meet journal requirements, further elevating the quality and impact of the research shared. This book stands as a testament to the dedication of researchers bringing forward the latest advances in both theoretical and experimental physics from around the world. Covering a wide range of disciplines, it delves into areas such as condensed matter physics, material science, high energy and particle physics, atomic, molecular, and laser physics, as well as general relativity, astrophysics, and cosmology. It also explores plasma physics, nonlinear dynamics, nuclear and radiation physics, alongside instrumentation and communication technology. The book further extends into meteorology, atmospheric physics, and interdisciplinary sciences, showcasing the breadth of modern research aimed at deepening our understanding and pushing the boundaries of science. On behalf of the conference organizers, we extend our heartfelt gratitude to all Guest Editors and Reviewers for their dedication and significant efforts, which greatly enriched the quality and success of this conference. We also wish to thank the authors and speakers for their invaluable contributions, which brought depth and relevance to the discussions. Our special thanks go to the USTM community and its outstanding facilities, which played a vital role in ensuring the smooth execution of the event. We are equally grateful to the members of PANE for their collaborative spirit, which enriched the conference experience. With such dedicated support, we are confident that future ICFPAP conferences will continue to reach new heights. Finally, we express our sincere appreciation to the editors and staff of Journal of Physics: Conference Series for their gracious assistance in publishing these proceedings. List of Committee Members are available in this Pdf.

Kevin Ollegott, P. Wirth, Christian Oberste‐Beulmann et al.

Dielectric barrier discharges are an emerging technology for the plasma-catalytic removal of volatile organic compounds and other gas purification challenges such as the removal of O2 traces from H2. Packed-bed reactors are mainly used for these applications, but surface dielectric barrier discharges (SDBDs) typically printed on thin dielectric plates are promising alternatives for the treatment of large volumetric flow rates due to their low flow resistance causing a low pressure drop. Especially for SDBDs the flow conditions are crucial, because the active plasma filled volume covering the mentioned plates with a typical thickness of 0.1 mm is small in comparison to the overall reactor volume with a typical distance of some tens of millimeters to the reactor wall. In this study, the flow conditions of a twin-SDBD were investigated by Schlieren imaging applied in converting O2 traces in H2 containing gas mixtures to H2O and compared to fluid dynamics simulations. Schlieren imaging was used to visualize local gradients of the refractive index inside the SDBD reaction chamber, while gas composition, dissipated power, or flow rate were varied. Without a plasma discharge, laminar flow dominates, resulting in a conversion below 10% over a Pt-coated electrode configuration in the reaction of O2 traces with H2. With the plasma discharge, full conversion was achieved for the same reaction without catalyst, although the plasma is also confined to the surface of the electrode configuration. Schlieren structures covering the complete cross section of the reaction chamber were observed, showing that strong radial mass transport is induced by the plasma. The shape and extent of the Schlieren structures is ascribed to a superimposition of gas flow, thermal expansion from the plasma volume, thermal buoyancy as well as an electrohydrodynamic force between the electrodes and the grounded reactor walls. Fluid dynamics simulations show vortex formation above and below the electrode, created by the electrohydrodynamic force further implying extensive mass transport by the plasma, which is visualized in addition by carbonaceous deposits on the reactor lid. This emerging deposition pattern during toluene decomposition closely corresponds to the electrode geometry. It is proposed that the reaction proceeds only in the active plasma volume and that reactive species transported to the bulk gas phase only have a minor contribution. Thus, the degree of conversion of the SDBD reactor is not only determined by the chemical reactivity in the plasma volume, but also by its plasma-induced mass transport resulting in efficient gas mixing. These findings reveal new possibilities to improve SDBD reactors for gas purification applications based on their favorable flow conditions.

H. Ismael, H. Bulut, M. Osman

I. S. Chernoshtanov

J. F. Caneses Marin, C. L. Lau, R. H. Goulding et al.

The principal objective of this work is to report on the power coupled to a tungsten target in the Proto-MPEX device during oblique injection of a microwave beam (< 70 kW at 28 GHz) into a high-power (~100 kW at 13.56 MHz) over-dense (n_e>1E10^19 m^(-3)) deuterium helicon plasma column. The experimental setup, electron heating system, electron heating scheme, and IR thermographic diagnostic for quantifying the power transport is described in detail. It is demonstrated that the power transported to the target can be effectively controlled by adjusting the magnetic field profile. Using this method, heat fluxes up to 22 MWm-2 and power transport efficiencies in the range of 17-20% have been achieved using 70 kW of microwave power. It is observed that most of the heat flux is confined to a narrow region at the plasma periphery. Ray-tracing calculations are presented which indicate that the power is coupled to the plasma electrons via an O-X-B mode conversion process. Calculations indicate that the microwave power is absorbed in a single pass at the plasma periphery via collisions and in the over-dense region via 2nd harmonic cyclotron resonance of the electron Bernstein wave. The impact of these results is discussed in the context of MPEX.

V. Tiron, Ioana-Laura Velicu

The physical vapor deposition techniques are nowadays widely used at industrial scale to produce thin films and surface coatings. Despite their proven utilities and benefits, these techniques still need to be improved in order to build other exigent and innovative coating systems, able to satisfy the market demand and to meet modern society’s needs. In this context, the bipolar high power impulse magnetron sputtering (BP-HiPIMS) technology is gaining ground and popularity due to its extraordinary ability to control the energy of the incoming ion flux to the growing film, enabling an energy-enhanced deposition process thanks to the existence of a dynamic double layer (DL) structure which develops in the after-glow plasma. In this work, the HiPIMS discharge was operated in bipolar mode, in which the negative pulses are followed by positive pulses whose amplitude, duration and delay can be independently controlled. The temporal and spatial evolutions of the plasma potential in BP-HiPIMS discharge were investigated using an emissive probe. Energy-resolved mass spectrometry was used to study the influence of the pulsing configuration (positive/negative pulse duration) on the energy distribution and flux of the ionic species bombarding the substrate. It was found that the ion energy distributions and ion flux were mainly determined by the specific time-and-space evolution of the plasma potential throughout the cycle of the voltage pulses applied to the target and the spatial distribution of the ions at the onset of the positive pulse. The ion propagation dynamics is strongly related to the potential drop across the DL structure whose characteristic features are mainly influenced by the amplitude and duration of the positive pulse. Short negative HiPIMS pulses followed by short and highly positive reverse pulses are favorable for an efficient acceleration mechanism of the metal ions in the potential drop of the DL.

T. Silva, M. Grofulović, L. Terraz et al.