Influence of Atom-Atom Collisions on the Population Densities of Excited Atomic Levels

1970 ◽  
Vol 25 (1) ◽  
pp. 145-147 ◽  
Author(s):  
H. W. Drawin
Keyword(s):  
Thermal Plasma ◽  
Neutral Particle ◽  
Particle Density ◽  
Coupled System ◽  
Rate Equations ◽  
Gas Temperature ◽  
Hydrogen Atoms ◽  
Population Densities ◽  
Non Thermal Plasma ◽  
Quantitative Spectroscopy

Abstract The number densities of excited hydrogen atoms in a non-thermal plasma have been calculated on the basis of a coupled system of rate equations (25 levels) in which one accounts for electron-atom and atom-atom collisions. The calculated population densities depend strongly on the neutral particle density na when ne/na≪1. When the electron temperature, Te, is different from the gas temperature, Tg , the number densities of the excited levels are determined by Tg rather than by Te. This is important in connection with the quantitative spectroscopy of plasmas.

Influence of Radiative Absorption on the Establishment of Local Thermodynamic Equilibrium

1969 ◽  
Vol 24 (10) ◽  
pp. 1492-1496 ◽  
Author(s):  
H. W. Drawin
Keyword(s):  
Steady State ◽  
Thermodynamic Equilibrium ◽  
Local Thermodynamic Equilibrium ◽  
Coupled System ◽  
Rate Equations ◽  
Population Densities ◽  
Hydrogen Plasmas ◽  
Radiative Rate ◽  
Radiative Absorption ◽  
State Plasma

Abstract By solving the coupled system of collisional-radiative rate equations for a homogeneous and steady-state plasma as a function of the radiative excitation rates one obtains the population densities of the ground and of the excited levels for any given degree of reabsorption. One finds that in hydrogen plasmas which are completely optically opaque towards all Lyman lines and partially optically opaque towards Hα the equilibrium populations will not be established for electron densities below 1X1016 cm-3.

Über das nichtthermische Gleichgewicht in einer Helium-Hohlikathodenentladung

1971 ◽  
Vol 26 (11) ◽  
pp. 1901-1908
Author(s):  
G. Schmid
Keyword(s):  
Electron Temperature ◽  
Hollow Cathode ◽  
Thermal Plasma ◽  
Detailed Examination ◽  
System Of Equations ◽  
Population Densities ◽  
Refined Method ◽  
Helium Line ◽  
Non Thermal Plasma

The non-thermal plasma in a helium hollow cathode discharge is analysed by means of experiments and theory. The population densities of excited levels are calculated by a system of equations, including the different processes which occur in the plasma. A detailed examination of the mechanism of exitation and deexcitation follows. From this, a refined method is developed for the determination of the electron temperature by the intensity of a helium line.

scholarly journals Plasma-Assisted Biomass Gasification in a Drop Tube Reactor at Atmospheric Pressure

2018 ◽  
Author(s):  
Yin Pang ◽  
Leo Bahr ◽  
Peter Fendt ◽  
Lars Zigan ◽  
Stefan Will ◽  
...  
Keyword(s):  
Reaction Kinetics ◽  
Thermal Plasma ◽  
Atmospheric Pressure ◽  
Drop Tube ◽  
Carbon Conversion ◽  
Gas Temperature ◽  
Gasification Process ◽  
Operation Conditions ◽  
Tube Reactor ◽  
Non Thermal Plasma

Compared to conventional allothermal gasification of solid fuels (e.g. biomass, charcoal, lignite etc.), plasma-assisted gasification offers an efficient method to apply energy into the gasification process to increase the flexibility of operation conditions and to increase the reaction kinetics. In particular, non-thermal plasmas (NTP) are promising, in which thermal equilibrium is not reached and electrons have substantially higher mean energy than gas molecules. Thus it is generally assumed that in NTP the supplied energy is utilized more efficiently for generating free radicals initiating gasification reactions than thermal plasma processes. In order to investigate this hypothesis, we compared purely thermal to non-thermal plasma assisted gasification of biomass in steam in a drop tube reactor at atmospheric pressure. The NTP was provided by means of gliding arcs between two electrodes aligned in the inlet steam flow. Electric power of about 1 kW was supplied using a high voltage generator operating at frequencies between 70 and 150 kHz and voltage amplitudes up to 10 kV. A laser-assisted optical method (Raman spectroscopy) was applied for measuring the gas temperature both in the conventionally heated steam and flow-down of the visible plasma filaments of the gliding arcs. Reaction yields and rates were evaluated using these measured gas temperatures. The first experimental results have shown that the non-thermal plasma not only promotes the carbon conversion of the fuel particles, but also accelerates the reaction kinetics. The carbon conversion is increased by nearly 10% using wood powder as the fuel. With charcoal powder more than 3% are converted into syngas.

scholarly journals The Propagation of Compressional Alfven Waves in Nonuniform Plasmas

1974 ◽  
Vol 27 (2) ◽  
pp. 181 ◽  
Author(s):  
R Morrow ◽  
MH Brennan
Keyword(s):  
Neutral Particle ◽  
Cyclotron Frequency ◽  
Particle Density ◽  
Alfven Waves ◽  
Alfvén Waves ◽  
Theoretical Treatment ◽  
Hydrogen Atoms ◽  
Ion Density ◽  
Total Particle ◽  
Plasma Nonuniformity

A theoretical treatment is presented for the propagation of Alfven waves in a plasma. It includes the effects of resistivity, ion-neutral collisions, the ion cyclotron frequency and radial nonuniformities in ion density, neutral particle density and temperature. The theory is applied to plasmas with conducting and nonconducting walls and the results are compared with those of experiments conducted in the afterglow of a shock-produced plasma. Nonuniformity in the ion density is found to have a marked effect on the dispersion relation and wave field profiles, while non uniformities in the total particle density and temperature are less important. Excellent agreement is obtained between theory and experiment and this allows unambiguous and accurate determinations to be made of the average total particle density, which is found to be - 50 % of the initial filling density, and of the cross section for momentum transfer between protons and hydrogen atoms.

Use of non-thermal plasma in lignocellulosic materials: A smart alternative

2021 ◽  
Vol 109 ◽  
pp. 365-373
Author(s):  
Gabriela N. Pereira ◽  
Karina Cesca ◽  
Anelise Leal Vieira Cubas ◽  
Débora de Oliveira
Keyword(s):  
Thermal Plasma ◽  
Lignocellulosic Materials ◽  
Non Thermal Plasma

Non-thermal pulsed plasma activated water: environmentally friendly way for efficient surface modification of semiconductor nanoparticles

2021 ◽  
Author(s):  
Pavel Galář ◽  
Josef Khun ◽  
Anna Fučíková ◽  
Kateřina Dohnalová ◽  
Tomáš Popelář ◽  
...  
Keyword(s):  
Surface Modification ◽  
Free Surface ◽  
Thermal Plasma ◽  
Environmentally Friendly ◽  
Semiconductor Nanoparticles ◽  
Reactive Species ◽  
Pulsed Plasma ◽  
Non Thermal Plasma ◽  
Plasma Activated Water

Non-thermal plasma activated water can be used for cheap, easy and chemicals-free surface modification of nanoparticles, with all the reactive species originating solely in air and water.

scholarly journals Non-thermal plasma-assisted hydrogenolysis of polyethylene to light hydrocarbons

2021 ◽  
Vol 150 ◽  
pp. 106274
Author(s):  
Libo Yao ◽  
Jaelynne King ◽  
Dezhen Wu ◽  
Steven S.C. Chuang ◽  
Zhenmeng Peng
Keyword(s):  
Thermal Plasma ◽  
Light Hydrocarbons ◽  
Non Thermal Plasma
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