Determination of the Maximum Temperature at the Center of an Optically Thick Laser-Induced Plasma Using Self-Reversed Spectral Lines

Abstract

A method of temperature measurement based on the model developed by Bartels of an optically thick inhomogeneous plasma was applied to a laser plasma induced on a target containing barium. The method involves the intensity ratio measurement of two self-reversed Ba(II) lines. The temperature thus determined corresponds to the maximum temperature in the plasma center. The plasma temperature was measured for delay times between 0.5 micros and 10 micros in two spectrometer operating modes: the scanning mode and the dual-wavelength mode, the latter resulting in better precision. A detailed analysis of experimental errors was performed. The error strongly depended on the wavelength separation of the lines used. The most accurate results were obtained for the largest line separation. Using one line in the UV and the other in the visible region, the relative error was 2-6% for temperatures between 8000 K and 20 000 K. The distribution of the plasma temperature along the plasma height was measured in the same delay time range. The temperature was found to be uniform along the plasma vertical axis, thus confirming the plasma cylindrical symmetry.

CSigma graphs: A new approach for plasma characterization in laser-induced breakdown spectroscopy

“…The model predicts spatial and temporal distributions of atom, ion and electron number densities, evolution of an atomic line profile and optical thickness and the resulting absolute intensity of plasma emission in the vicinity of a strong non-resonance atomic transition. The same group reported a method of temperature measurement based on an optically thick inhomogeneous laser-induced plasma [16]. The method provides maximum temperature in the plasma center from the intensity ratio of two self-reversed lines.…”

Investigation on the effect of nonlinear processes on similarity law in high-pressure argon discharges

“…All comparisons were made based on results from simulations at steady-state. As is shown in Table I, both electron and ion densities are proportional to k 2 , which indicates that the relations of the electron and ion densities in random two similar gaps will be k 2 ðmÞ Á n e; i ðmÞ ¼ k 2 ðjÞ Á n e; i ðjÞ; (5) where m, j 2 {1,2,3,4,5} (m 6 ¼ j) are gap numbers, and k(m) and k(j) are scale-up factors for the m-th and the j-th gap, respectively. The normalized electron density from Eq.…”

“…Combining the Eqs. (1), (5), and (10), the production rate relation between the j-th and the m-th gap turns out to be dn dt…”

“…High-pressure discharges are receiving considerable attention because of their wide industrial applications, such as plasma display panels (PDPs), ion sources, spectroscopy, micro-chips, and so on. [1][2][3][4][5] These discharges have been investigated by many authors through experimental diagnostics, analytical methods, and numerical simulations in the past decades. [6][7][8][9] Due to the sharply reduced discharge scales, the diagnostics of microscope parameters in high-pressure discharges are usually much more difficult than those in low-pressure discharges, since the commonly used techniques, such as plasma probes, can hardly be implemented.…”

Semiempirical model for analysis of inhomogeneous optically thick laser-induced plasmas

“…This model was further extended to an atmospheric plasma expansion where a shock wave formation was considered [32]. In addition, a two-line method for determination of the maximum temperature in the plasma center along the line of sight assuming a parabolic temperature distribution was successfully applied based in that framework [33]. These works are aimed at spectroscopic applications and provide a simple theoretical framework to match observed spectral features to plasma parameters.…”