Место издания:SARATOVSKIY ISTOCHNICK Saratov, Russia
Первая страница:79
Последняя страница:80
Аннотация:Laser-induced breakdown spectrometry (LIBS) is an actively developing technique for rapid elemental analysis. The emission of laser-induced plasma resulting from interaction of a high-power pulsed laser radiation with a sample is used for both quantitative and qualitative analysis. The optical excitation and registration of plasma radiation allows a high-performance remote elemental analysis of any substance, including those in aggressive environments. Since the analysis of unknown remote objects is the key advantage of the technique the use of standard samples is not appropriate solution. In this regard, the development of robust variants of LIBS analysis without CRMs is highly desirable.
In this work, we considered the possibility of the use of multi-parametric (plasma parameters and plasma elemental composition) optimization for spectra approximation. We used the NLopt library of nonlinear optimization algorithms to obtain a solution. In this work we have considered only derivativefree optimization algorithms, since in our implementation of the model the synthetic spectrum cannot be represented in analytical form as a function of plasma parameters, and it is not possible to provide adequate initial values for the most varied parameters. To verify the suitability of the suggested algorithm, we approximated the specially generated synthetic spectra of steel (range 190–470 nm) and aluminum alloy (range 250–480 nm) at 𝑁𝑒 = 1016,7𝑐𝑚−3 and 𝑇 = 0,8𝑒𝑉. Since pronounced self-reversed lines are present in the spectrum of the aluminum alloy, a two-zone model was also tested to thoroughly describe both the hot core and the cold periphery of plasma. Slight variation of each parameter (T-0.005 eV; logarithm of electron density - 0.005; radius of the plasma zone - 0.1 mm; the value of element concentration - 1%) served as stopping criterion for successfully completed optimization. Convergence of the multi-parametric optimization has been shown in the case of synthetic spectra, which allows the use of the algorithms for studying plasma and determination of its composition.
