Transition from ballistic to thermalized transport of the metal sputtered species in DC magnetron

2021 ◽  
Author(s):  
Adrien Revel ◽  
Abderzak El Farsy ◽  
Ludovic de Poucques ◽  
Jacques Robert ◽  
Tiberiu M. Minea
Keyword(s):  
Initial Conditions ◽  
Metal Transport ◽  
Initial Distribution ◽  
Distribution Functions ◽  
Tunable Diode Laser ◽  
Magnetron Discharge ◽  
Velocity Distribution Functions ◽  
Numerical Parametric Study ◽  
Gauss Distribution

Abstract Tunable Diode Laser Induced Fluorescence (TD-LIF) technique has been optimized to accurately measure the titanium (Ti) sputtered Atoms Velocity Distribution Functions (AVDF) in a magnetron discharge operating in Direct Current (DC) mode. The high spatial and spectral resolution achieved unveils some features of the transport of the metal sputtered atoms and their thermalization. The two groups of thermalized and energetic atoms have been very well separated compared to previous works. Hence, the fitting of the energetic atoms group shows dumping from modified Thompson to Gauss distribution when the product pressure-distance from the target increases. In parallel, sputtered metal transport from the target has been simulated using the Monte Carlo collision (MCC) approach. The direct comparison between numerical and experimental results led to an improved cross section for Titanium - Argon momentum transfer, based on the \textit{ab initio} formulae of the interaction potential derived from noble gases interaction. The numerical parametric study of the angular distribution and cut-off energy for the initial distribution of sputtered atoms steered to a precise characterization of the initial conditions, allowed by the accuracy of experimental data. A very good overall agreement is obtained for measured and calculated AVDFs. The confrontation between measured and modeling results emphasized the major role played by the argon ions not only in the sputtering process but also in the neutral metal transport, by the gas rarefaction near the target. The microscopic description provided by the MCC model clearly reveals different transport regimes: ballistic, diffusive, and back-scattering and brings new insights on the thermalization of sputtered species in the intermediate pressure range.

On the multifractality of plasma turbulence in the solar wind

2019 ◽  
Vol 15 (S354) ◽  
pp. 371-374
Author(s):  
Sebastián Echeverría ◽  
Pablo S. Moya ◽  
Denisse Pastén
Keyword(s):  
Solar Wind ◽  
Velocity Distribution ◽  
Distribution Functions ◽  
Fluctuation Analysis ◽  
Magnetic Fluctuations ◽  
Multifractal Detrended Fluctuation Analysis ◽  
Particle In Cell ◽  
Velocity Distribution Functions ◽  
Detrended Fluctuation

AbstractIn this work we have analyzed turbulent plasma in the kinetic scale by the characterization of magnetic fluctuations time series. Considering numerical Particle-In-Cell (PIC) simulations we apply a method known as MultiFractal Detrended Fluctuation Analysis (MFDFA) to study the fluctuations of solar-wind-like plasmas in thermodynamic equilibrium (represented by Maxwellian velocity distribution functions), and out of equilibrium plasma represented by Tsallis velocity distribution functions, characterized by the kappa (κ) parameter, to stablish relations between the fractality of magnetic fluctuation and the kappa parameter.

scholarly journals Catalog of fine-structured electron velocity distribution functions – Part 1: Antiparallel magnetic-field reconnection (Geospace Environmental Modeling case)

2017 ◽  
Vol 35 (5) ◽  
pp. 1051-1067 ◽  
Author(s):  
Philippe-A. Bourdin
Keyword(s):  
Fine Structure ◽  
Velocity Distribution ◽  
Initial Conditions ◽  
Sampling Site ◽  
Initial Perturbation ◽  
Environmental Modeling ◽  
Distribution Functions ◽  
Electron Velocity ◽  
Diffusion Region ◽  
Velocity Distribution Functions

Abstract. To understand the essential physics needed to reproduce magnetic reconnection events in 2.5-D particle-in-cell (PIC) simulations, we revisit the Geospace Environmental Modeling (GEM) setup. We set up a 2-D Harris current sheet (that also specifies the initial conditions) to evolve the reconnection of antiparallel magnetic fields. In contrast to the GEM setup, we use a much smaller initial perturbation to trigger the reconnection and evolve it more self-consistently. From PIC simulation data with high-quality particle statistics, we study a symmetric reconnection site, including separatrix layers, as well as the inflow and the outflow regions. The velocity distribution functions (VDFs) of electrons have a fine structure and vary strongly depending on their location within the reconnection setup. The goal is to start cataloging multidimensional fine-structured electron velocity distributions showing different reconnection processes in the Earth's magnetotail under various conditions. This will enable a direct comparison with observations from, e.g., the NASA Magnetospheric MultiScale (MMS) mission, to identify reconnection-related events. We find regions with strong non-gyrotropy also near the separatrix layer and provide a refined criterion to identify an electron diffusion region in the magnetotail. The good statistical significance of this work for relatively small analysis areas reveals the gradual changes within the fine structure of electron VDFs depending on their sampling site.

scholarly journals On Both Spatial And Velocity Distribution Of Sputtered Particles In Magnetron Discharge

2012 ◽  
Vol 56 (1) ◽  
pp. 43-57
Author(s):  
C. Vitelaru ◽  
V. Pohoata ◽  
V. Tiron ◽  
C. Costin ◽  
G. Popa
Keyword(s):  
Velocity Distribution ◽  
Diode Laser ◽  
Pulse Mode ◽  
Distribution Functions ◽  
Tunable Diode Laser ◽  
Space Distribution ◽  
Mean Velocity ◽  
Magnetron Discharge ◽  
Peak Voltage ◽  
Time Space

AbstractThe kinetics of the sputtered atoms from the metallic target as well as the time-space distribution of the argon metastable atoms have been investigated for DC and high power pulse magnetron discharge by means of Tunable Diode – Laser Absorption Spectroscopy (TD-LAS) and Tunable Diode – Laser Induced Fluorescence (TD-LIF). The discharge was operated in argon (5-30 mTorr) with two different targets, tungsten and aluminum, for pulses of 1 to 20 μs, at frequencies of 0.2 to 1 kHz. Peak current intensity of ~100 A has been attained at cathode peak voltage of ~1 kV. The mean velocity distribution functions and particle fluxes of the sputtered metal atoms, in parallel and perpendicular direction to the target, have been obtained and compared for DC and pulse mode.

Large-Debye-distance effects in a homogeneous plasma

1989 ◽  
Vol 41 (3) ◽  
pp. 493-516 ◽  
Author(s):  
Jan Scheffel ◽  
Bo Lehnert
Keyword(s):  
Normal Mode ◽  
Numerical Solutions ◽  
Normal Mode Analysis ◽  
Distribution Functions ◽  
Mode Analysis ◽  
Larmor Radius ◽  
Order Unity ◽  
Phase Velocities ◽  
Standard Normal ◽  
Velocity Distribution Functions

The classical phenomenon of electron plasma oscillations has been investigated from new aspects. The applicability of standard normal-mode analysis of plasma perturbations has been judged from comparisons with exact numerical solutions to the linearized initial-value problem. We consider both Maxwellian and non-Maxwellian velocity distributions. Emphasis is on perturbations for which αλD is of order unity, where α is the wavenumber and λD the Debye distance. The corresponding large-Debye-distance (LDD) damping is found to substantially dominate over Landau damping. This limits the applicability of normal-mode analysis of non-Maxwellian distributions. The physics of LDD damping and its close connection to large-Larmor-radius (LLR) damping is discussed. A major discovery concerns perturbations of plasmas with non-Maxwellian, bump-in-tail, velocity distribution functions f0(ω). For sufficiently large αλD (of order unity) the plasma responds by damping perturbations that are initially unstable in the Landau sense, i.e. with phase velocities initially in the interval where df0/dw > 0. It is found that the plasma responds through shifting the phase velocity above the upper velocity limit of this interval. This is shown to be due to a resonance with the drifting electrons of the bump, and explains the Penrose criterion.

Computational Characterization of Passive Fluid Mixing in Microfluidics

Volume 3 ◽  
2004 ◽  
Author(s):  
Erik D. Svensson
Keyword(s):  
Stokes Equations ◽  
Initial Conditions ◽  
Three Dimensional ◽  
Fluid Mixing ◽  
Navier Stokes ◽  
Navier Stokes Equations ◽  
Fluid Systems ◽  
Sensitive Dependence ◽  
Microfluidic Mixers

In this work we computationally characterize fluid mixing in a number of passive microfluidic mixers. Generally, in order to systematically study and characterize mixing in realistic fluid systems we (1) compute the fluid flow in the systems by solving the stationary three-dimensional Navier-Stokes equations or Stokes equations with a finite element method, and (2) compute various measures indicating the degree of mixing based on concepts from dynamical systems theory, i.e., the sensitive dependence on initial conditions and mixing variance.

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