A5049989679- Plasma Diagnostics and Applications
- Dust and Plasma Wave Phenomena
- Magnetic confinement fusion research
- Laser-induced spectroscopy and plasma
- Atomic and Molecular Physics
- High-pressure geophysics and materials
- Ionosphere and magnetosphere dynamics
- Plasma Applications and Diagnostics
- Electrohydrodynamics and Fluid Dynamics
- Solar and Space Plasma Dynamics
- Metal and Thin Film Mechanics
- Geomagnetism and Paleomagnetism Studies
- Particle accelerators and beam dynamics
- Vacuum and Plasma Arcs
- Theoretical and Computational Physics
- Material Dynamics and Properties
- Laser-Plasma Interactions and Diagnostics
- Semiconductor materials and devices
- Electrochemical Analysis and Applications
- Gas Dynamics and Kinetic Theory
- nanoparticles nucleation surface interactions
- Analytical Chemistry and Sensors
- Cold Atom Physics and Bose-Einstein Condensates
- Advanced Chemical Physics Studies
- Phase Equilibria and Thermodynamics
University of Michigan
2021-2025
Michigan United
2022-2023
University of California, San Diego
2023
Manufacturing Advocacy & Growth Network (United States)
2023
University of Iowa
2013-2022
Sandia National Laboratories
2014-2021
Los Alamos National Laboratory
2012-2020
Princeton Plasma Physics Laboratory
2015-2018
Princeton University
2018
Ohio Northern University
2017
Journal of Physics D: Applied published the first Plasma Roadmap in 2012 consisting individual perspectives 16 leading experts various sub-fields low temperature plasma science and technology. The 2017 is update a planned series periodic updates Roadmap. continuously growing interdisciplinary nature field its equally broad range applications are making it increasingly difficult to identify major challenges that encompass all many applications. This intellectual diversity ultimately strength...
Abstract The 2022 Roadmap is the next update in series of Plasma Roadmaps published by Journal Physics D with intent to identify important outstanding challenges field low-temperature plasma (LTP) physics and technology. format same as previous representing visions 41 leading experts 21 countries five continents various sub-fields LTP science In recognition evolution field, several new topics have been introduced or given more prominence. These emphasis highlight increased interests...
We report the results of second charged-particle transport coefficient code comparison workshop, which was held in Livermore, California on 24–27 July 2023. This workshop gathered theoretical, computational, and experimental scientists to assess state computational techniques for understanding coefficients relevant high-energy-density plasma science. Data electronic ionic coefficients, namely, direct current electrical conductivity, electron thermal ion shear viscosity, conductivity were...
Using a 1D particle-in-cell simulation with perpendicular electric, E0, and magnetic, B0, fields, modelling the azimuthal direction (i.e., E0 × B0 direction), we study cross-field electron transport in Hall effect thrusters (HETs). For low plasma densities, is found to be well described by classical electron-neutral collision theory, but at sufficiently high densities (representative of typical HETs), strong instability observed significantly enhance mobility, even absence collisions. This...
In Paper I [T. Lafleur et al., Phys. Plasmas 23, 053502 (2016)], we demonstrated (using particle-in-cell simulations) the definite correlation between an anomalously high cross-field electron transport in Hall effect thrusters (HETs), and presence of azimuthal electrostatic instabilities leading to enhanced scattering. Here, present a kinetic theory that predicts scattering rate provides mobility is good agreement with experiment. The large drift velocity HETs drives strong instability...
A plasma transport theory that spans weak to strong coupling is developed from a binary collision picture, but where the interaction potential taken be an effective includes correlation effects and screening self-consistently. This physically motivated approach provides practical model for evaluating coefficients across regimes. The shown compare well with classical molecular dynamics simulations of temperature relaxation in electron-ion plasmas as experiments self-diffusion one-component...
Biased electrodes are common components of plasma sources and diagnostics. The plasma–electrode interaction is mediated by an intervening sheath structure that influences properties the electrons ions contacting electrode surface, as well bulk plasma. A rich variety structures have been observed, including ion sheaths, electron double layers, anode glow, fireballs. These represent complex self-organized responses depend not only on local influence electrode, but also global other boundaries...
Equilibrium states of anodic double layers that form near a positively biased disk-shaped electrode immersed in partially ionized plasma are studied experimentally using electrostatic probes. When the potential drop from to is less than critical value, Δϕc, an anode glow observed where layer within few millimeters surface. For larger biases spot forms centimeters and intervening region more luminous bulk plasma. A theoretical model developed which predicts Δϕc ∝ 1/P + C, P neutral pressure C...
A new mode of plasma confinement is demonstrated in which essentially all positive ions leave the to only one boundary while electrons are lost a different boundary. Sheaths near boundaries entirely responsible for this global nonambipolar flow. The bulk remains quasineutral and unperturbed even when one, physically small, location. necessary condition flow depends on ratio electron collection area ion area. temperature significantly higher than typical ambipolar due relative increase...
Electron sheaths are commonly found near Langmuir probes collecting the electron saturation current. The common assumption is that probe collects random flux of electrons incident on sheath, which tacitly implies there no presheath and collected due to a velocity space truncation distribution function (EVDF). This work provides dedicated theory sheaths, suggests they not so simple. Motivated by EVDFs observed in Particle-In-Cell (PIC) simulations, 1D model for sheath developed. In model,...
The shear viscosity coefficient of the one-component plasma is calculated with unprecedented accuracy using equilibrium molecular dynamics simulations and Green-Kubo relation. Numerical statistical uncertainties their mitigation for improving are analyzed. In weakly coupled regime, our results agree Landau-Spitzer prediction. moderately strongly regimes, found in good agreement recent obtained Yukawa nonequilibrium dynamics. A practical formula provided evaluating across coupling from regime...
A generalized Lenard-Balescu theory that accounts for instability-enhanced collective responses is used to calculate the collisional friction between ion species in plasma-boundary transition region (presheath). Ion-ion streaming instabilities are shown cause such a strong frictional force relative flow speed cannot significantly exceed critical threshold value ($\ensuremath{\Delta}{V}_{c}$) at which instability onset occurs. When combined with Bohm criterion, this condition uniquely...
The three-dimensional nature of plasmoid instabilities is studied using the reduced magnetohydrodynamic equations. For a Harris equilibrium with guide field, represented by $\vc{B}_o = B_{po} \tanh (x/λ) \hat{y} + B_{zo} \hat{z}$, spectrum modes are unstable at multiple resonant surfaces in current sheet, rather than just null surface polodial field $B_{yo} (x) (x/λ)$, which only 2D or absence field. Here $B_{po}$ asymptotic value poloidal $B_{zo}$ constant and $λ$ sheet width. Plasmoids on...
A model that uniquely determines the flow speed of each ion species at sheath edge two plasmas is developed. In this analysis, ion-ion two-stream instabilities can play an important role because they significantly enhance friction between species. Two-stream arise when difference in speeds exceeds a critical value: V1−V2≡ΔV≥ΔVc. The resultant instability-enhanced rapidly becomes so strong ΔV cannot exceed ΔVc. Using condition provided by ΔV=ΔVc and generalized Bohm criterion, determined as...
We present a theoretical model that allows fast and accurate evaluation of ionic transport properties realistic plasmas spanning from warm dense to hot dilute conditions, including mixtures. This is achieved by combining recent kinetic theory based on effective interaction potentials with for the equilibrium radial density distribution an average atom integral equations fluids. The should find broad use in applications where nonideal plasma conditions are traversed, inertial confinement...
The large electron drift (relative to the ions) in azimuthal direction of Hall-effect thrusters is well known excite a strong instability. In recent paper (Lafleur et al 2016 Phys. Plasmas 23 053503) we demonstrated that this instability leads an enhanced electron–ion friction force increases cross-field mobility levels similar those seen experimentally. Here extend work by considering detail onset criteria for formation (both xenon, and other propellants interest), identify number important...
A method for extending traditional plasma transport theories into the strong coupling regime is presented. Like theories, this based on a binary scattering approximation, but where physics associated with many body correlations included through use of an effective interaction potential. The latter simply related to pair-distribution function. Modeling effects in manner can extend theory orders magnitude stronger coupling. Theoretical predictions are tested against molecular dynamics...
Equilibrium molecular dynamics simulations are used to calculate the thermal conductivity of one component plasma (OCP) via Green-Kubo formalism over a broad range Coulomb coupling strength, $0.1\le\Gamma\le180$. These address previous discrepancies between computations using equilibrium versus nonequilibrium methods. Analysis heat flux autocorrelation functions show that very long ($6\times10^5\omega_p^{-1}$) time series needed reduce noise level allow $\lesssim2\%$ accuracy. The new...
In this paper, we present ideas that were part of the miniconference on crossover between High Energy Density Plasmas (HEDP) and Ultracold Neutral (UNPs) at 60th Annual Meeting American Physical Society Division Plasma Physics, November 2018. We give an overview UNP experiments with emphasis measurements time-evolving ion density velocity distributions, electron-ion thermalization rate, plasma self-assembly—all just inside strongly coupled regime. also theoretical computational models...
Angularly resolved X-ray scattering measurements from fs-laser heated hydrogen have been used to determine the equilibration of electron and ion temperatures in warm dense matter regime. The relaxation rapidly cryogenic is visualized using 5.5 keV pulses Linac Coherent Light (LCLS) source a 1 Hz repetition rate pump-probe setting. We demonstrate that electron-ion energy transfer faster than quasi-classical Landau-Spitzer models use ad hoc cutoffs Coulomb logarithm.
The Particle-in-Cell (PIC) method, a cornerstone in plasma modeling, is widely employed for its ability to simulate kinetic phenomena device-scale domains. Part of what makes this possible that computational macroparticles represent many physical particles. It converges under certain constraints, including grid spacing resolves the Debye length and time step small enough respect Courant–Friedrichs–Lewy condition frequency stability limit. Here, we introduce new constraint necessary avoid...
A kinetic theory of the Bohm criterion is developed that based on positive-exponent velocity moments plasma equation. This result contrasted with conventional a v^{-1} moment Vlasov The salient difference between two results low particles dominate in theory, but are essentially unimportant new theory. It shown derivation flawed. Low can cause unphysical divergences These divergent contributions avoided this approach. theories compared using example distribution functions from previous...
As the size of a positively biased electrode increases, nature interface formed between and host plasma undergoes transition from an electron-rich structure (electron sheath) to intermediate containing both ion electron rich regions (double layer) ultimately forms electron-depleted (ion sheath). In this study, measurements are performed further test how electron-collecting impacts discharge is immersed in. This accomplished using segmented disk in which individual segments individually...
The generalized Bohm criterion is revisited in the context of incorporating kinetic effects electron and ion distribution functions into theory.The underlying assumptions results two different approaches are compared: conventional 'kinetic criterion' a fluid-moment hierarchy approach.The former based on asymptotic limit an infinitely thin sheath (λ D /l = 0), whereas latter perturbative expansion that compared to plasma 1).Here λ Debye length, which characterizes length scale, l measure or...
The intrinsic bulk viscosity of the one-component plasma (OCP) is computed and analyzed using equilibrium molecular dynamics simulations Green-Kubo formalism. It found that exhibits a maximum at Γ≈1, corresponding to condition average kinetic energy particles equals potential interparticle spacing. weakly coupled strongly limits are used construct model captures full range coupling strengths simulated: Γ≈10^{-2}-10^{2}. Simulations also run Yukawa (YOCP) in order understand impact electron...