Experimental investigation of ultraviolet laser induced plasma density and temperature evolution in air

Journal Article · Tue Jul 01 00:00:00 EDT 2008 · Journal of Applied Physics

DOI:https://doi.org/10.1063/1.2952540· OSTI ID:21137376

Thiyagarajan, Magesh; Scharer, John ^[1]

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1. Electrical and Computer Engineering Department, University of Wisconsin, Madison, Wisconsin 53706 (United States)

We present measurements and analysis of laser induced plasma neutral densities and temperatures in dry air by focusing 200 mJ, 10 MW high power, 193 nm ultraviolet ArF (argon fluoride) laser radiation to a 30 {mu}m radius spot size. We examine these properties that result from multiphoton and collisional cascade processes for pressures ranging from 40 Torr to 5 atm. A laser shadowgraphy diagnostic technique is used to obtain the plasma electron temperature just after the shock front and this is compared with optical emission spectroscopic measurements of nitrogen rotational and vibrational temperatures. Two-color laser interferometry is employed to measure time resolved spatial electron and neutral density decay in initial local thermodynamic equilibrium (LTE) and non-LTE conditions. The radiating species and thermodynamic characteristics of the plasma are analyzed by means of optical emission spectroscopy (OES) supported by SPECAIR, a special OES program for air constituent plasmas. Core plasma rotational and vibrational temperatures are obtained from the emission spectra from the N{sub 2}C-B(2+) transitions by matching the experimental spectrum results with the SPECAIR simulation results and the results are compared with the electron temperature just behind the shock wave. The plasma density decay measurements are compared with a simplified electron density decay model that illustrates the dominant three-and two-body recombination terms with good correlation.

• OSTI ID: 21137376
• Journal Information: Journal of Applied Physics, Vol. 104, Issue 1; Other Information: DOI: 10.1063/1.2952540; (c) 2008 American Institute of Physics; Country of input: International Atomic Energy Agency (IAEA); ISSN 0021-8979
• Country of Publication: United States
• Language: English

Related Subjects

71 CLASSICAL AND QUANTUM MECHANICS
GENERAL PHYSICS
AIR
ARGON FLUORIDES
DIAGNOSTIC TECHNIQUES
ELECTRON DENSITY
ELECTRON TEMPERATURE
EMISSION SPECTRA
EMISSION SPECTROSCOPY
EXCIMER LASERS
INTERFEROMETRY
LASER RADIATION
LTE
LUMINESCENCE
MULTI-PHOTON PROCESSES
PLASMA
PLASMA DENSITY
SHOCK WAVES
SIMULATION
THERMODYNAMIC PROPERTIES
TIME RESOLUTION
ULTRAVIOLET RADIATION