Article
Physics, Fluids & Plasmas
Federica Causa, Gabriele Gervasini, Andrea Uccello, Gustavo Granucci, Daria Ricci, Natale Rispoli
Summary: The proposed method utilizes the perimeter sheath expansion method to effectively obtain plasma parameters in low-density, low-temperature plasmas which are easily perturbed by Langmuir probes. By modifying the perimeter sheath expansion method, the approach allows for proper assessment of plasma potential values.
PLASMA SOURCES SCIENCE & TECHNOLOGY
(2021)
Article
Physics, Fluids & Plasmas
Pengfei Zhang, Xin Liu, Mengjiao Lin, Jia Zhang
Summary: This research introduces a high-energy pulsed plasma jet that can generate highly dynamic and steep plasma gradients. By modulating the dynamics of the plasma sheath electron density, the high-speed vehicle can achieve stealth. The characteristics of the plasma were extensively diagnosed through various measurements and observations. The analysis of high-energy pulsed plasma jets provides a framework for future research on stealth technology in high-speed vehicles.
PHYSICS OF PLASMAS
(2022)
Article
Multidisciplinary Sciences
Archie F. A. Bott, Petros Tzeferacos, Laura Chen, Charlotte A. J. Palmer, Alexandra Rigby, Anthony R. Bell, Robert Bingham, Andrew Birkel, Carlo Graziani, Dustin H. Froula, Joseph Katz, Michel Koenig, Matthew W. Kunz, Chikang Li, Jena Meinecke, Francesco Miniati, Richard Petrasso, Hye-Sook Park, Bruce A. Remington, Brian Reville, J. Steven Ross, Dongsu Ryu, Dmitri Ryutov, Fredrick H. Seguin, Thomas G. White, Alexander A. Schekochihin, Donald Q. Lamb, Gianluca Gregori
Summary: Understanding magnetic field generation and amplification in turbulent plasma is crucial for explaining observations of magnetic fields in the universe. This study validates a theoretical framework for the origin and sustainment of these fields, and reports an experiment on laboratory plasma dynamo with Pm & 1. By characterizing plasma evolution and measuring various properties, it is shown that plasma turbulence from strong shear can generate fields more efficiently than previously thought, potentially explaining large-scale fields in astrophysical systems.
PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA
(2021)
Article
Astronomy & Astrophysics
Naveen Jingade, Nishant K. Singh
Summary: In this study, we investigate the impact of temporal fluctuations in kinetic helicity on the generation of large-scale magnetic fields in the presence of a background linear shear flow. Our findings show that growing solutions can be obtained when the correlation time of helicity is greater than the correlation time of velocity. Interestingly, under certain conditions, the axisymmetric modes exhibit non-monotonic behavior in relation to shear rate.
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
(2021)
Article
Astronomy & Astrophysics
K. A. Mizerski
Summary: Non-stationarity in plasma turbulence can induce a strong electromotive force (EMF) and enhance the dynamo effect in large-scale hydromagnetic systems.
ASTRONOMY & ASTROPHYSICS
(2022)
Article
Multidisciplinary Sciences
Muni Zhou, Vladimir Zhdankin, Matthew W. Kunz, Nuno F. Loureiro, Dmitri A. Uzdensky
Summary: In this study, we investigate the generation of seed magnetic fields through the Weibel instability in an initially unmagnetized plasma driven by a large-scale shear force. We develop an analytical model and confirm its predictions through particle simulations. This work has important implications for magnetogenesis in dilute astrophysical systems.
PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA
(2022)
Article
Chemistry, Physical
Fang Zhao, Yevgeny Raitses, Xiaofang Yang, Andi Tan, Christopher G. Tully
Summary: Chemical functionalization of two-dimensional materials, such as graphene, is an effective method for tailoring their properties, with potential applications in energy, catalysis, and electronics. A promising plasma-based method has been developed to provide high hydrogen coverage on graphene, demonstrating higher coverage than previous results and showing potential for diverse applications. The use of radial electric and axial magnetic fields in low-pressure discharge generates a fine-tunable low-temperature hydrogen-rich plasma with enhanced hydrogen density, paving the way for further research and technological advancements in this field.
Article
Materials Science, Characterization & Testing
Jiacai Li, Zhicheng Si, Kai Shang, Yang Feng, Shihang Wang, Shengtao Li
Summary: The crosslinking reaction behaviors of peroxide-induced low-density polyethylene (PLDPE) were fully characterized and analyzed by combining kinetic and thermodynamic analysis. The results show complex order and autocatalysis reactions, with the autocatalysis reaction considered as the driving force of the whole crosslinking reaction. Diffusion has a significant effect on the autocatalysis reaction, while the effect on the order reaction can be ignored. A new kinetic model incorporating the diffusion factor effectively describes the diffusion-limited crosslinking reaction behaviors of PLDPE.
Article
Astronomy & Astrophysics
F. Pucci, M. Viviani, F. Valentini, G. Lapenta, W. H. Matthaeus, S. Servidio
Summary: We demonstrate an efficient mechanism for generating magnetic fields in turbulent, collisionless plasmas through fully kinetic, particle-in-cell simulations. The complex motion is initiated via a Taylor-Green vortex, and the plasma locally develops strong electron temperature anisotropy, due to the strain tensor of the turbulent flow. Subsequently, in a domino effect, the anisotropy triggers a Weibel instability which leads to magnetization.
ASTROPHYSICAL JOURNAL LETTERS
(2021)
Article
Computer Science, Interdisciplinary Applications
Emily Bourne, Yann Munschy, Virginie Grandgirard, Michel Mehrenberger, Philippe Ghendrih
Summary: Numerical methods based on non-uniform splines of varying degrees are used to simulate the plasma sheath in this study. A new well-conditioned method and the construction of a simulation grid from non-uniform knots are proposed to improve precision and reduce memory requirements. The non-uniform simulations using GPU parallelization achieve a 5.5 times speedup compared to uniform simulations.
JOURNAL OF COMPUTATIONAL PHYSICS
(2023)
Article
Physics, Multidisciplinary
Alif Din
Summary: This study extends the basic kinetic theory of an electron emitting inverse sheath to floating and current carrying electrode/wall scenarios, exploring the potential profile and kinetic energy flux. By considering velocity distribution functions and solving the Poisson's equation numerically, the relationship between emitted-electron and ion temperatures is investigated, leading to a valid inverse sheath solution for specific temperature ranges. The numerical solutions show a decrease in total or kinetic flux received by the electrode/wall surface with increasing emitted-electron temperature, approaching zero for equal values of emitted-electron and plasma-electron temperatures.
Article
Mathematics
Olga Sheremetyeva
Summary: The article investigates a large-scale model of an a?-dynamo in the low-mode approximation. The intensity of the a-effect is regulated by a process with hereditarity properties. The stability of the MHD-system solution is studied based on the control parameters and the parameters of the alternating kernel. The results are represented on the phase plane, and the change in pattern depending on the damping coefficient, damping frequency, and waiting time is compared with previous studies.
Article
Astronomy & Astrophysics
Cristian Vega, Vadim Roytershteyn, Gian Luca Delzanno, Stanislav Boldyrev
Summary: This study investigates three-dimensional kinetic-scale turbulence numerically under strongly magnetized conditions. The simulations show that the turbulent cascade in these regimes can reach scales smaller than the electron inertial scale, leading to the formation of electron-scale current sheets. Statistical analysis reveals that the thickness of these current sheets is on the order of the electron inertial length or below, while their half-length falls between the electron and ion inertial length. The pressure-strain interaction, used as a measure of energy dissipation, exhibits high intermittency, with the majority of the total energy exchange occurring in current structures occupying about 20% of the total volume. Some of the current sheets associated with the largest pressure-strain interaction are found to be connected to Alfvenic electron jets and magnetic configurations typical of reconnection.
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
(2023)
Article
Geosciences, Multidisciplinary
S. Sharan, B. Langlais, H. Amit, E. Thebault, M. Pinceloup, O. Verhoeven
Summary: Unique information about the dynamo process acting at Jupiter is obtained through modeling and interpreting its magnetic field. By analyzing the fluxgate magnetometer measurements from the Juno mission, a magnetic field model is derived that accurately describes both the main field and the secular variation up to high spherical harmonic degrees. The analysis reveals similarities between Jupiter's magnetic field and Earth's, suggesting dominance of advection and presence of zonal and non-zonal deep fluid motions.
GEOPHYSICAL RESEARCH LETTERS
(2022)
Article
Energy & Fuels
Jie Xue, Zhifan Wang, Xiaojun Zhou, Fan Wang
Summary: This study investigates the use of DFAs to calculate reasonable kinetic data for reactions of large fuels, which can be used for the construction of low-temperature combustion mechanisms.
Article
Physics, Multidisciplinary
Yuzhi Li, Bhuvana Srinivasan, Yanzeng Zhang, Xian-Zhu Tang
Summary: This study investigates the constraint of the Bohm criterion on the plasma exit flow speed. The analysis demonstrates that the Bohm speed is explicitly dependent on local plasma heat flux, temperature isotropization, and thermal force. Comparison with kinetic simulations confirms the accuracy of the Bohm speed over the plasma-sheath transition region where quasineutrality is weakly perturbed and the Bohm criterion applies.
PHYSICAL REVIEW LETTERS
(2022)
Article
Physics, Fluids & Plasmas
Nathan A. Garland, Hyun-Kyung Chung, Mark C. Zammit, Christopher J. McDevitt, James Colgan, Christopher J. Fontes, Xian-Zhu Tang
Summary: This study investigates the phenomenon of minority relativistic electron populations in complex plasmas, particularly in tokamak plasma discharges with runaway electrons. The research finds that the relativistic enhancement of electron impact inelastic cross sections has significant effects on ion charge state distributions, radiation, and spectral characteristics.
PHYSICS OF PLASMAS
(2022)
Article
Computer Science, Interdisciplinary Applications
Qi Tang, Luis Chacon, Tzanio Kolev, John N. Shadid, Xian-Zhu Tang
Summary: This paper presents a high-order stabilized finite-element algorithm based on the MFEM finite element library for solving the reduced visco-resistive MHD equations. The use of physics-based preconditioning strategy and adaptive mesh refinement scheme is also discussed. Experimental results demonstrate the accuracy, efficiency, and scalability of the implicit scheme in the presence of large scale disparity.
JOURNAL OF COMPUTATIONAL PHYSICS
(2022)
Article
Physics, Fluids & Plasmas
Min-Gu Yoo, W. X. Wang, E. Startsev, C. H. Ma, S. Ethier, J. Chen, X. Z. Tang
Summary: By analyzing the 3D magnetic topology of the connection length and effective magnetic mirror ratio, this study provides a comprehensive understanding of electron and ion dynamics related to the magnetic topology. The connection length and effective magnetic mirror ratio determine the motion and mixing of electrons and ions in the magnetic field, leading to a reduction in plasma temperature.
PHYSICS OF PLASMAS
(2022)
Article
Physics, Fluids & Plasmas
Ryan M. Park, Willem Kupets, Mark C. Zammit, James Colgan, Christopher J. Fontes, Brett S. Scheiner, Eddy Timmermans, Xian-Zhu Tang, Liam H. Scarlett, Dmitry Fursa, Igor Bray, Nathan A. Garland
Summary: Accurate modeling techniques are crucial for understanding the interplay between microscopic and macroscopic processes in laboratory and industrial plasma applications. This study proposes a systematic method to approximate non-trivial angular scattering behavior, which can be implemented in particle-in-cell (PIC) and/or MC plasma simulation codes. The proposed angular distribution function is validated through benchmark scattering data and shows good agreement with other calculations and measurements.
PLASMA SOURCES SCIENCE & TECHNOLOGY
(2022)
Article
Physics, Fluids & Plasmas
Christopher J. McDevitt, Xian-Zhu Tang, Christopher J. Fontes, Prashant Sharma, Hyun-Kyung Chung
Summary: In a post-thermal-quench plasma, the power balance between collisional or Ohmic heating and plasma radiative cooling determines the plasma temperature, ion charge state distribution, parallel electric field, and electron density. These factors also set the threshold electric field for runaway avalanche growth, which is important for avoiding and minimizing runaways in fusion-grade tokamak plasmas during rapid termination.
Article
Physics, Fluids & Plasmas
Yuzhi Li, Bhuvana Srinivasan, Yanzeng Zhang, Xian-Zhu Tang
Summary: In this study, an expression for the Bohm speed in the presheath-sheath transition region is derived from a set of anisotropic plasma transport equations. The accuracy of this expression is validated by comparing it with kinetic simulation results.
PHYSICS OF PLASMAS
(2022)
Article
Physics, Multidisciplinary
Yanzeng Zhang, Jun LI, Xian-zhu Tang
Summary: A localized energy or particle sink introduced into a nearly collisionless plasma can trigger a plasma thermal collapse, known as a thermal quench. We demonstrate that electron thermal conduction in such a plasma follows the convective energy transport scaling due to ambipolar transport, resulting in a robust cooling flow and the formation of four propagating fronts along the magnetic field line. The slowest front is a shock front responsible for deep cooling.
Article
Physics, Fluids & Plasmas
Jun Li, Yanzeng Zhang, Xian-Zhu Tang
Summary: In disruptions of tokamak, when the magnetic connection length is comparable to or shorter than the plasma mean-free-path, parallel transport can dominate energy loss. During the thermal quench of the core plasma, there are four distinct phases with different temperature ranges and durations. The main temperature drop occurs in a nearly collisionless state, with the parallel electron temperature decreasing as T-e |∝ t(-2) and a cooling time proportional to the ion sound wave transit time over the length of the open magnetic field line. These unexpected physics scalings result from the effective suppression of parallel electron thermal conduction in a bounded, quasineutral, and collisionless plasma, which is different from what is known about electron thermal conduction in a nearly collisionless and quasineural plasma.
Article
Physics, Fluids & Plasmas
Ben Zhu, Xue-qiao Xu, Xian-Zhu Tang
Summary: The edge plasma turbulence and transport dynamics, as well as the divertor power loads during the thermal-quench phase of tokamak disruptions, are numerically investigated. Interesting features, such as surging of divertor heat load and broadening of heat-flux width on the outer-divertor target plate, are observed in the simulation, in qualitative agreement with experimental observations.
Article
Physics, Fluids & Plasmas
Yanzeng Zhang, Yuzhi Li, Bhuvana Srinivasan, Xian-Zhu Tang
Summary: This article studies the temperature anisotropy in plasmas, finding that the electron temperature in the sheath is lower in the flow direction and higher with spikes in the transverse direction, due to the negative gradient of the transverse heat flux in the sheath.
PHYSICS OF PLASMAS
(2023)
Article
Physics, Fluids & Plasmas
Yanzeng Zhang, Xian-Zhu Tang
Summary: For plasma velocity space instabilities driven by non-Maxwellian particle distributions, weak collisions can damp the instabilities significantly beyond the collisional rate. This is because collisions have a dual effect of relaxing the plasma distribution towards a Maxwellian and suppressing the linearly perturbed distribution function. The dominance of the former effect occurs when the non-Maxwellian distribution is driven by collisionless transport on a timescale much shorter than that of collisions, and the growth rate of the ideal instability is highly dependent on the distribution function. The strong collisional damping effect of plasma velocity space instabilities is demonstrated using the example of whistler instability driven by electrostatically trapped electrons, which is confirmed through first-principles kinetic simulations.
PHYSICS OF PLASMAS
(2023)
Article
Physics, Fluids & Plasmas
Yuzhi Li, Bhuvana Srinivasan, Yanzeng Zhang, Xian-Zhu Tang
Summary: The high recycling regime of a divertor is characterized by high plasma particle fluxes and low temperature at the target, where a strong hydrogen recirculation loop exists. Atomic processes in the high recycling regime, such as ion-neutral friction and radiation, can affect the plasma momentum and energy transport in the sheath transition region. The study investigates the plasma-sheath transition near a high recycling wall and demonstrates the accuracy of the Bohm speed model in predicting ion exit flow speed in the transition region.
PHYSICS OF PLASMAS
(2023)
Article
Computer Science, Artificial Intelligence
Nathan A. Garland, Romit Maulik, Qi Tang, Xian-Zhu Tang, Prasanna Balaprakash
Summary: Effective modeling of plasma transport in magnetically confined fusion devices requires accurate understanding of ion composition and radiative power losses. Artificial neural network (ANN) surrogates can be used for rapid evaluation, but training an accurate ANN relies on a large and representative dataset, which can be time-consuming to generate.
MACHINE LEARNING-SCIENCE AND TECHNOLOGY
(2022)
Article
Mathematics, Applied
Shuang Liu, Qi Tang, Xian-zhu Tang
Summary: This study introduces a parallel cut-cell algorithm to solve the free-boundary problem of the Grad--Shafranov equation, which reformulates the problem in an irregular bounded domain and utilizes various methods to optimize the solution process, resulting in good parallel scaling.
SIAM JOURNAL ON SCIENTIFIC COMPUTING
(2021)
