Investigation of the local thermodynamic equilibrium of laser-induced aluminum plasma by Thomson scattering technique

In this work, the assumption of local thermodynamic equilibrium (LTE) for a laser-induced plasma in ambient air is examined experimentally using two different laser systems, namely an infrared short-pulse Ti:Sapphire laser and an ultraviolet long-pulse XeCl excimer laser. The LTE assumption is investigated by examining the plasma produced at a laser fluence of 10 J/cm2 from aluminum targets containing iron and magnesium impurities. The excitation temperature is deduced from Boltzmann diagrams built from a large number of spatially integrated neutral iron lines distributed from 3.21 to 6.56 eV. It is shown that at any time after the end of the laser pulse, the neutral excited states are in excellent Boltzmann equilibrium. Detailed investigation of Boltzmann equilibrium further validates previous temperature measurements using less accurate diagrams. However, observations of ion lines provide some evidence that the ionized species do not obey Saha equilibrium, thereby indicating departure from LTE. This could be explained by the fact that the plasma cannot be considered as stationary for these species.

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Thomson scattering diagnostics of thermal plasmas: Laser heating of electrons and the existence of local thermodynamic equilibrium

Physical Review E ◽

10.1103/physreve.69.016408 ◽

2004 ◽

Vol 69 (1) ◽

Cited By ~ 24

Author(s):

A. B. Murphy

Keyword(s):

Thermodynamic Equilibrium ◽

Laser Heating ◽

Local Thermodynamic Equilibrium ◽

Thomson Scattering ◽

Thermal Plasmas

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Investigation of thermodynamic equilibrium in laser-induced aluminum plasma using the Hα line profiles and Thomson scattering spectra

Applied Physics Letters ◽

10.1063/1.4926990 ◽

2015 ◽

Vol 107 (2) ◽

pp. 024102 ◽

Cited By ~ 6

Author(s):

M. Cvejić ◽

K. Dzierżęga ◽

T. Pięta

Keyword(s):

Thermodynamic Equilibrium ◽

Thomson Scattering ◽

Line Profiles ◽

Scattering Spectra ◽

Aluminum Plasma

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Blackbody Radiation, Boltzmann Statistics, Temperature, and Thermodynamic Equilibrium

10.1093/oso/9780199662104.003.0003 ◽

2017 ◽

Author(s):

Kelly Chance ◽

Randall V. Martin

Keyword(s):

Thermodynamic Equilibrium ◽

Local Thermodynamic Equilibrium ◽

Photophysical Properties ◽

Blackbody Radiation ◽

Boltzmann Constant ◽

Noise Sources ◽

Atmospheric Molecules ◽

Tightly Coupled ◽

Boltzmann Statistics ◽

Planck’S Law

Blackbody radiation, temperature, and thermodynamic equilibrium give a tightly coupled description of systems (atmospheres, volumes, surfaces) that obey Boltzmann statistics. They provide descriptions of systems when Boltzmann statistics apply, either approximately or nearly exactly. These apply most of the time in the Earth’s stratosphere and troposphere, and in other planetary atmospheres as long as the density is sufficient that collisions among atmospheric molecules, rather than photochemical and photophysical properties, determine the energy populations of the ensemble of molecules. Thermodynamic equilibrium and the approximation of local thermodynamic equilibrium are introduced. Boltzmann statistics, blackbody radiation, and Planck’s law are described. The chapter introduces the Rayleigh-Jeans limit, description of noise sources as temperatures, Kirchoff’s law, the Stefan-Boltzmann constant, and Wien’s law.

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