POP Nameplate
  • Volume/Page
  • Keyword
  • DOI
  • Citation
  • Advanced
   
 
 
 

Flickr Twitter iResearch App Facebook

Search Issue | RSS Feeds RSS
Previous Issue Next Issue

Mar 2013

Volume 20, Issue 3, Articles (03xxxx)

Issue Cover Spotlight Figure

Phys. Plasmas 20, 032106 (2013); http://dx.doi.org/10.1063/1.4794320 (10 pages)

M. Raghunathan and R. Ganesh
Enlarge Image | Read More
Return to All Sections
back to top
RSS Feeds
back to top Low-Temperature Plasmas, Plasma Applications, Plasma Sources, Sheaths

Ion impact distribution over plasma exposed nanocone arrays

S. Mehrabian, S. Xu, A. A. Qaemi, B. Shokri, and K. Ostrikov

Phys. Plasmas 20, 033501 (2013); http://dx.doi.org/10.1063/1.4794327 (8 pages) | Cited 1 time

Online Publication Date: 4 March 2013

Full Text: Read Online (HTML) | Download PDF

Show Abstract
The effect of an ordered array of nanocones on a conducting substrate immersed in the plasma on the transport of the plasma ions is investigated. The real conical shape of the cones is rigorously incorporated into the model. The movement of 105 CH3+ ions in the plasma sheath modified by the nanocone array is simulated. The ions are driven by the electric fields produced by the sheath and the nanostructures. The surface charge density and the total charge on the nanotips with different aspect ratios are computed. The ion transport simulation provides important characteristics of the displacement and velocity of the ions. The relative ion distribution along the lateral surfaces of the carbon nanotips is computed as well. It is shown that a rigorous account of the realistic nanostructure shape leads to very different distribution of the ion fluxes on the nanostructured surfaces compared to the previously reported works. The ion flux distribution is a critical factor in the nucleation process on the substrate and determines the nanostructure growth patterns.
Show PACS
52.40.Kh Plasma sheaths
52.65.Pp Monte Carlo methods
52.77.Dq Plasma-based ion implantation and deposition
81.16.Rf Micro- and nanoscale pattern formation
52.25.Fi Transport properties

Particle-in-cell/Monte Carlo collision simulation of the ionization process of surface-wave plasma discharges resonantly excited by surface plasmon polaritons

Zhaoquan Chen, Qiubo Ye, Guangqing Xia, Lingli Hong, Yelin Hu, Xiaoliang Zheng, Ping Li, Qiyan Zhou, Xiwei Hu, and Minghai Liu

Phys. Plasmas 20, 033502 (2013); http://dx.doi.org/10.1063/1.4794736 (11 pages)

Online Publication Date: 6 March 2013

Full Text: Read Online (HTML) | Download PDF

Show Abstract
Although surface-wave plasma (SWP) sources have many industrial applications, the ionization process for SWP discharges is not yet well understood. The resonant excitation of surface plasmon polaritons (SPPs) has recently been proposed to produce SWP efficiently, and this work presents a numerical study of the mechanism to produce SWP sources. Specifically, SWP resonantly excited by SPPs at low pressure (0.25 Torr) are modeled using a two-dimensional in the working space and three-dimensional in the velocity space particle-in-cell with the Monte Carlo collision method. Simulation results are sampled at different time steps, in which the detailed information about the distribution of electrons and electromagnetic fields is obtained. Results show that the mode conversion between surface waves of SPPs and electron plasma waves (EPWs) occurs efficiently at the location where the plasma density is higher than 3.57 × 1017 m−3. Due to the effect of the locally enhanced electric field of SPPs, the mode conversion between the surface waves of SPPs and EPWs is very strong, which plays a significant role in efficiently heating SWP to the overdense state.
Show PACS
52.65.Rr Particle-in-cell method
52.80.-s Electric discharges
02.60.Cb Numerical simulation; solution of equations
52.20.Fs Electron collisions
52.25.Fi Transport properties
52.50.Dg Plasma sources

Characteristics of plasma properties in an ablative pulsed plasma thruster

Tony Schönherr, Frank Nees, Yoshihiro Arakawa, Kimiya Komurasaki, and Georg Herdrich

Phys. Plasmas 20, 033503 (2013); http://dx.doi.org/10.1063/1.4794198 (8 pages)

Online Publication Date: 12 March 2013

Full Text: Read Online (HTML) | Download PDF

Show Abstract
Pulsed plasma thrusters are electric space propulsion devices which create a highly transient plasma bulk in a short-time arc discharge that is expelled to create thrust. The transitional character and the dependency on the discharge properties are yet to be elucidated. In this study, optical emission spectroscopy and Mach-Zehnder interferometry are applied to investigate the plasma properties in variation of time, space, and discharge energy. Electron temperature, electron density, and Knudsen numbers are derived for the plasma bulk and discussed. Temperatures were found to be in the order of 1.7 to 3.1 eV, whereas electron densities showed maximum values of more than 1017 cm−3. Both values showed strong dependency on the discharge voltage and were typically higher closer to the electrodes. Capacitance and time showed less influence. Knudsen numbers were derived to be in the order of 10−3−10−2, thus, indicating a continuum flow behavior in the main plasma bulk.
Show PACS
52.75.Di Ion and plasma propulsion
52.80.Mg Arcs; sparks; lightning; atmospheric electricity
52.25.Kn Thermodynamics of plasmas
52.70.Kz Optical (ultraviolet, visible, infrared) measurements

Experimental verification of the Boltzmann relation in confined plasmas: Comparison of noble and molecule gases

Hyo-Chang Lee, Hye-Ju Hwang, Young-Cheol Kim, June Young Kim, Dong-Hwan Kim, and Chin-Wook Chung

Phys. Plasmas 20, 033504 (2013); http://dx.doi.org/10.1063/1.4794344 (8 pages) | Cited 1 time

Online Publication Date: 12 March 2013

Full Text: Read Online (HTML) | Download PDF

Show Abstract
Experimental verification of the Boltzmann relation is performed in argon and oxygen gas inductively coupled plasmas from the measurements of both the spatial electron currents (as a fluid approach) and the electron energy probability functions (EEPFs, as a kinetic approach). At a low gas pressure of 10 mTorr, the measured electron currents are spatially uniform, and the EEPFs in the total electron energy scale are identical, which indicate that the Boltzmann relation is valid at both the argon and oxygen gases. As the gas pressure increases to 30–40 mTorr, however, the Boltzmann relation is broken in the oxygen gas discharge, while the Boltzmann relation is still valid in the argon gas discharge. This different variation in the oxygen gas discharge is mainly due to the presence of various inelastic collisions in the entire electron energy region, which causes the transition of the electron kinetics from a non-local to a local regime.
Show PACS
52.25.Fi Transport properties
52.25.Kn Thermodynamics of plasmas
52.80.-s Electric discharges
52.20.Fs Electron collisions
52.25.-b Plasma properties
52.25.Dg Plasma kinetic equations

Particle simulation of collision dynamics for ion beam injection into a rarefied gas

Paul N. Giuliano and Iain D. Boyd

Phys. Plasmas 20, 033505 (2013); http://dx.doi.org/10.1063/1.4794954 (20 pages) | Cited 1 time

Online Publication Date: 15 March 2013

Full Text: Read Online (HTML) | Download PDF

Show Abstract
This study details a comparison of ion beam simulations with experimental data from a simplified plasma test cell in order to study and validate numerical models and environments representative of electric propulsion devices and their plumes. The simulations employ a combination of the direct simulation Monte Carlo and particle-in-cell methods representing xenon ions and atoms as macroparticles. An anisotropic collision model is implemented for momentum exchange and charge exchange interactions between atoms and ions in order to validate the post-collision scattering behaviors of dominant collision mechanisms. Cases are simulated in which the environment is either collisionless or non-electrostatic in order to prove that the collision models are the dominant source of low- and high-angle particle scattering and current collection within this environment. Additionally, isotropic cases are run in order to show the importance of anisotropy in these collision models. An analysis of beam divergence leads to better characterization of the ion beam, a parameter that requires careful analysis. Finally, suggestions based on numerical results are made to help guide the experimental design in order to better characterize the ion environment.
Show PACS
52.40.Mj Particle beam interactions in plasmas
52.65.Pp Monte Carlo methods
52.65.Rr Particle-in-cell method
52.25.Fi Transport properties
52.20.Hv Atomic, molecular, ion, and heavy-particle collisions

Sheath formation criterion in magnetized electronegative plasmas with thermal ions

M. M. Hatami and B. Shokri

Phys. Plasmas 20, 033506 (2013); http://dx.doi.org/10.1063/1.4795297 (6 pages)

Online Publication Date: 18 March 2013

Full Text: Read Online (HTML) | Download PDF

Show Abstract
Taking into account the effect of collisions and positive ion temperatures, the sheath formation criterion is investigated in a weakly magnetized electronegative plasma consisting of electrons, negative and positive ions by using the hydrodynamics equations. It is assumed that the electron and negative ion density distributions are the Boltzmann distribution with two different temperatures. Also, it is assumed that the velocity of positive ions at the sheath edge is not normal to the wall (oblique entrance). Our results show that a sheath region will be formed when the initial velocity of positive ions or the ion Mach number M lies in a specific interval with particular upper and lower limits. Also, it is shown that the presence of the magnetic field affects both of these limits. Moreover, as an practical application, the density distribution of charged particles in the sheath region is studied for an allowable value of M, and it is seen that monotonically reduction of the positive ion density distribution leading to the sheath formation occurs only when M lies between two above mentioned limits.
Show PACS
52.40.Kh Plasma sheaths
52.20.Hv Atomic, molecular, ion, and heavy-particle collisions
52.25.Xz Magnetized plasmas

Generation of high-voltage pulses with subnanosecond front rise times in open discharge

P. A. Bokhan, P. P. Gugin, M. A. Lavrukhin, and Dm. E. Zakrevsky

Phys. Plasmas 20, 033507 (2013); http://dx.doi.org/10.1063/1.4794858 (6 pages)

Online Publication Date: 19 March 2013

Full Text: Read Online (HTML) | Download PDF

Show Abstract
The investigation results for plasma switching devices of high-voltage pulses with pulse rise times less than 1 ns are presented. The approach is based on using conditions suitable for bringing a gas discharge chamber in a state with high conductivity due to generation of an electron beam owing to photoelectron emission from the device cathode. It is shown that in co-axial geometry pulses, switching time 0.45 ns on an active load RL = 50 Ω at voltage U = 20 kV can be achieved. It is shown with the method of doubled impulses that such a device can regenerate the acceptable electric strength during 10 μs. It is indicated of the principle possibility of working in the pulse-periodical regime to the repetition rate of 100 kHz.
Show PACS
52.80.-s Electric discharges
52.25.Mq Dielectric properties
52.75.Kq Plasma switches (e.g., spark gaps)

A numerical model of non-equilibrium thermal plasmas. I. Transport properties

Xiao-Ning Zhang, He-Ping Li, Anthony B. Murphy, and Wei-Dong Xia

Phys. Plasmas 20, 033508 (2013); http://dx.doi.org/10.1063/1.4794969 (11 pages) | Cited 1 time

Online Publication Date: 27 March 2013

Full Text: Read Online (HTML) | Download PDF

Show Abstract
A self-consistent and complete numerical model for investigating the fundamental processes in a non-equilibrium thermal plasma system consists of the governing equations and the corresponding physical properties of the plasmas. In this paper, a new kinetic theory of the transport properties of two-temperature (2-T) plasmas, based on the solution of the Boltzmann equation using a modified Chapman–Enskog method, is presented. This work is motivated by the large discrepancies between the theories for the calculation of the transport properties of 2-T plasmas proposed by different authors in previous publications. In the present paper, the coupling between electrons and heavy species is taken into account, but reasonable simplifications are adopted, based on the physical fact that me/mh ≪ 1, where me and mh are, respectively, the masses of electrons and heavy species. A new set of formulas for the transport coefficients of 2-T plasmas is obtained. The new theory has important physical and practical advantages over previous approaches. In particular, the diffusion coefficients are complete and satisfy the mass conversation law due to the consideration of the coupling between electrons and heavy species. Moreover, this essential requirement is satisfied without increasing the complexity of the transport coefficient formulas. Expressions for the 2-T combined diffusion coefficients are obtained. The expressions for the transport coefficients can be reduced to the corresponding well-established expressions for plasmas in local thermodynamic equilibrium for the case in which the electron and heavy-species temperatures are equal.
Show PACS
52.25.Fi Transport properties
52.25.Dg Plasma kinetic equations
52.20.Fs Electron collisions
52.20.Hv Atomic, molecular, ion, and heavy-particle collisions
02.60.-x Numerical approximation and analysis
52.25.Kn Thermodynamics of plasmas

A numerical model of non-equilibrium thermal plasmas. II. Governing equations

He-Ping Li, Xiao-Ning Zhang, and Wei-Dong Xia

Phys. Plasmas 20, 033509 (2013); http://dx.doi.org/10.1063/1.4794970 (11 pages)

Online Publication Date: 27 March 2013

Full Text: Read Online (HTML) | Download PDF

Show Abstract
Governing equations and the corresponding physical properties of the plasmas are both prerequisites for studying the fundamental processes in a non-equilibrium thermal plasma system numerically. In this paper, a kinetic derivation of the governing equations used for describing the complicated thermo-electro-magneto-hydrodynamic-chemical coupling effects in non-equilibrium thermal plasmas is presented. This derivation, which is achieved using the Chapman-Enskog method, is completely consistent with the theory of the transport properties reported in the previous paper by the same authors. It is shown, based on this self-consistent theory, that the definitions of the specific heat at constant pressure and the reactive thermal conductivity of two-temperature plasmas are not necessary. The governing equations can be reduced to their counterparts under local thermodynamic equilibrium (LTE) and local chemical equilibrium (LCE) conditions. The general method for the determination of the boundary conditions of the solved variables is also discussed briefly. The two papers establish a self-consistent physical-mathematical model that describes the complicated physical and chemical processes in a thermal plasma system for the cases both in LTE or LCE conditions and under non-equilibrium conditions.
Show PACS
52.25.Fi Transport properties
02.60.-x Numerical approximation and analysis
52.25.Kn Thermodynamics of plasmas
Return to All Sections
Close

Google Calendar

ADVERTISEMENT

Go to AIP Home   © AIP Publishing LLC
close