M. Ivković

A program for the evaluation of electron number density from experimental hydrogen balmer beta line profiles

Abstract A program for the determination of plasma electron number density, 1020≤(Ne)≤1023 m−3, from the comparison of experimental and theoretical hydrogen Balmer beta (Hβ) line profiles is described in detail. Three theoretical data sets (one set is calculated within the framework of this paper) are included with the program and may be selected as a users choice. Apart from Ne determination from the comparison of the whole experimental and theoretical profiles, this program offers a fast estimation of Ne from the halfwidth of the experimental line shape. If necessary, certain parts of the experimental profile may be neglected in the procedure of comparison with theory. This possibility enables the use of noisy line shape recordings for Ne determination. The Hβ asymmetry study may be carried out by generating the difference between experimental and best-fitted theoretical line profiles.

Parametric study of an atmospheric pressure microwave-induced plasma of the mini MIP torch } I. Two-dimensional spatially resolved electron-number density measurements

Abstract The results of spatial distribution measurements of the electron-number density, N e , in an atmospheric pressure microwave-induced plasma in argon are presented. Electron-number density is determined from the width of the hydrogen H β 486.13-nm line. The influence of the microwave input power in the range 80–150 W on the spatial distribution of N e is first determined. For the selected input power of 100 W, the influence of molecular hydrogen in wet and desolvated nebulizer and support gas, and the corresponding changes in the electron density distributions are studied. The influence of potassium as a low ionization-potential element on the spatial distribution of N e is also studied, with the result that a considerable lowering of the electron number density is detected.

Optical emission spectroscopy for simultaneous measurement of plasma electron density and temperature in a low-pressure microwave induced plasma

The simple optical emission spectroscopy technique for diagnostics of low pressure microwave induced plasma (MIP) in hydrogen or in MIP seeded with hydrogen is described and tested. This technique uses the Boltzmann plot of relative line intensities along Balmer spectral series in conjunction with the criterion for partial local thermodynamic equilibrium for low electron density (Ne) plasma diagnostics. The proposed technique is tested in a low pressure MIP discharge for simultaneous determination of electron density Ne (1017–1018 m−3) and temperature Te.

Parametric study of an atmospheric pressure microwave-induced plasma of the mini MIP torch — II. Two-dimensional spatially resolved excitation temperature measurements

Abstract Two-dimensional mapping of the excitation temperatures have been carried out in the microwave-induced plasma torch with tangential argon flow. It is detected that the presence of wet aerosols in a nebulizer gas increases axial excitation temperature while desolvation acts in the opposite direction. The influence of low hydrogen concentration in the support gas and potassium in the nebulizer gas on the temperature distribution is studied in detail. The comparison of excitation temperature and electron number density distributions clearly indicates non-equilibrium plasma conditions.

Plasma diagnostics using the He I 447.1 nm line at high and low densities

The broadening of the He I 447.1 nm line and its forbidden components in plasmas is studied using computer simulation techniques and the results are compared with our and other experiments. In these calculations wide ranges of electron densities and temperatures are considered. Experimental measurements are performed with a high electron density pulsed discharge and with a low electron density microwave torch at atmospheric pressure. Both calculations and experimental measurements are extended from previous works towards low electron densities in order to study the accuracy of plasma diagnostics using this line in ranges of interest in different practical applications. The calculation results are compared with experimental profiles registered in plasmas diagnosed using independent techniques. The obtained agreement justifies the use of these line parameters for plasma diagnostics. The influence of self-absorption on line parameters is also analysed. It is shown that the separation between the peaks of the allowed and forbidden components exhibits a clear dependence upon plasma electron density free of self-absorption influence. This allows the peak separation to be used as a good parameter for plasma diagnostics. From the simulation results, a simple fitting formula is applied that permits obtaining the electron number density plasma diagnostics in the range 5 × 1022–7 × 1023 m−3. At lower densities the fitting of simulated to experimental full profiles is a reliable method for Ne determination.

Spatial and Temporal Characteristics of Laser Ablation Combined With Fast Pulse Discharge

Fast pulse discharge initiated by the laser ablation of target material was used to enhance the analytical capabilities of single pulse laser-induced breakdown spectroscopy. Fast imaging of such combined pulse plasma is presented. The recorded images show that the enhancement of the optical emission can be attributed to additional ablation of targets, besides prolonged duration and greater volume of plasma. Spatially resolved spectra show that limiting the recording volume improves signal to background ratio and enhances the analytical possibilities of such plasma.

Separation between Allowed and Forbidden Component of the He I 447 nm Line in High Electron Density Plasma

Stark broadened He I 447.1 nm line is measured and the dependence of the separation between its allowed and forbidden components upon electron density is analyzed. Experimental results are compared with computer simulation results and with former experimental results.

Transitions between Glow and Arc Modes and Its Influences to the Performance of a Hollow-Cathode Discharge CO2 Laser

Hollow cathode discharge is used for excitation of a CO2 laser. With the aluminum alloy cathode a maximum laser output power of 4.1 W is obtained. This laser output power is related to the formation of aluminum oxide at the cathode surface. These oxide layers induce the transitions between the glow and arc modes of the discharge and formation of microarcs at the cathode surface. This was found beneficial for the laser operation. The results of the time resolved study of the laser parameters are also reported.