Computer simulation of RF induction-heated argon plasma discharges at atmospheric pressure for spectrochemical analysis-I. preliminary investigations (original) (raw)
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Entrainment of ambient air into a spectrochemical inductively coupled argon plasma
Spectrochimica Acta Part B: Atomic Spectroscopy, 2003
A spectrochemical inductively coupled argon plasma (ICP) is normally operated in the open air. Therefore, it is suggested in the literature that entrainment of air molecules into such an ICP may cause loss of electrons, especially so at the plasma's edge. The present study discusses the significance of this effect. The density and temperature of electrons and nitrogen molecules around the edge of the plasma were measured by Thomson and rotational Raman scattering. A region where both electrons and nitrogen were present in detectable amounts (10 and 10 m , 19 24 y3 respectively) could not be observed. Above the torch inner wall the nitrogen concentration drops rapidly towards the plasma. Measurements suggest that the nitrogen concentration at 1 mm from the plasma is only a few percent, and in the active zones of the plasma (far) below 0.1%. This is not enough to affect the plasma significantly. Moreover, electron loss due to diffusion of nitrogen into the plasma is calculated to be much slower than the loss observed in earlier studies. Hence, air entrainment is unlikely to play a significant role in the ICP. A possible alternative is the formation and destruction of molecular rare gas ions. ᮊ
Plasma Formed in Argon, Acid Nitric and Water Used in Industrial ICP Torches
Plasma Science and Technology, 2012
Inductively coupled plasmas (ICPs) are used in spectrochemical analyses. The introduction of the sample by means of an aerosol are widely used. The introduction and the total evaporation of the aerosol is required in order to obtain a good repeatability and reproducibility of analyses. To check whether the vaporization of the aerosol droplets inside the plasma is completed, a solution could be used to compare the experimental results of the emission spectral lines with theoretical results. An accurate calculation code to obtain monatomic spectral lines intensities is therefore required, which is the purpose of the present paper. The mixtures of argon, water and nitric acid are widely used in spectrochemical analyses with ICPs. With these mixtures, we calculate the composition, thermodynamic functions and monatomic spectral lines intensities of the plasma at thermodynamic equilibrium and at atmospheric pressure. To obtain a self sufficient paper and also to allow other researchers to compare their results, all required data and a robust accurate algorithm, which is simple and easy to compute, are given.
Spectrochimica Acta Part B: Atomic Spectroscopy, 2007
An optical emission spectroscopy method for determination of electron temperature, electron density and gas temperature is developed and applied for diagnostics of inductively-driven argon discharges in a cylindrical geometry. The discharges are maintained at frequency 27 MHz, applied power varied in the limits P = (90 -160) W and gas pressure in the range p = (1.1 -117.3) Pa. The method combines measurements of emission spectral line intensities and profile broadenings with a collisional-radiative model of argon plasma at low pressure. The model is employed for investigation of the plasma kinetics governing the population densities of 3p 5 4s and 3p 5 4p argon configuration levels, treated separately. In the numerical calculations the electron density and electron temperature are varied whereas the values of the third plasma parameterthe gas temperatureare involved as obtained data from the experiments. Comparison of the experimental results of the line-intensity ratios with those calculated by the model yields the values of the electron density and temperature. The dependence of the electron temperature, electron density and gas temperature on the discharge conditions is obtained and discussed in the study.
Inductively coupled plasmas (ICPs) are used in spectrochemical analyses. The introduction of the sample by means of an aerosol are widely used. The introduction and the total evaporation of the aerosol is required in order to obtain a good repeatability and reproducibility of analyses. To check whether the vaporization of the aerosol droplets inside the plasma is completed, a solution could be used to compare the experimental results of the emission spectral lines with theoretical results. An accurate calculation code to obtain monatomic spectral lines intensities is therefore required, which is the purpose of the present paper. The mixtures of argon, water and nitric acid are widely used in spectrochemical analyses with ICPs. With these mixtures, we calculate the composition, thermodynamic functions and monatomic spectral lines intensities of the plasma at thermodynamic equilibrium and at atmospheric pressure. To obtain a self sufficient paper and also to allow other researchers to compare their results, all required data and a robust accurate algorithm, which is simple and easy to compute, are given.
Applied Spectroscopy, 1987
An inductively coupled plasma spectrometer was modified for gaseous sample introduction. The system uses a gas proportioner utilizing rotameters to achieve sample gas concentrations and mixing with the sample argon gas. Modifications of instruments were performed to enhance stability and compatability of gaseous sample introduction. Instrument performance was characterized for optimization of spectral signals produced from plasma gases. Spectral analyses of gaseous samples including CF4, SF6, 02, N2, air, and mixtures of CF4-O~ and CF4-O2/Nz were performed. Identification of plasma gas and plasma-induced byproducts, both atomic and molecular, were determined.
Analytical Chemistry, 2009
We have investigated the plasma processes in an atmospheric pressure glow discharge (APGD) in He used for analytical spectrometry by means of fluid and Monte Carlo (MC) simulations. Typical results include the potential and electric field distributions in the plasma, the density profiles of the various plasma species throughout the discharge, the mean electron energy, as well as the rates of the various collision processes in the plasma, and the relative importance of the different production and loss rates for the various species. The similarities and differences with low-pressure glow discharges are discussed. The main differences are a very small cathode dark space region and a large positive column as well as the dominant role of molecular ions. Some characteristic features of the APGD, such as the occurrence of the different spatial zones in the discharge, are illustrated, with links to experimental observations. Glow discharges (GDs) at reduced pressure (typically 50-500 Pa) are widely used for the analysis of (mainly solid) materials. 1,2 In recent years, however, there is increased interest for the analysis of liquids and gaseous samples. For these applications, GDs operating at atmospheric pressure (so-called APGDs) appear to be particularly useful. Various groups have proposed different plasma designs, and several review papers have been published on these APGDs and microplasmas, not only for analytical applications (e.g., refs 3-6) but also for materials processing, environmental, and biomedical applications. 7,8 The miniaturized direct current (dc) GDs (e.g., refs 9-13) are based on similarity
Review of Scientific Instruments, 1994
A "reference cell" for generating radio-frequency (rf) glow discharges in gases at a frequency of 13.56 MHz is described. The reference cell provides an experimental platform for comparing plasma measurements carried out in a common reactor geometry by different experimental groups, thereby enhancing the transfer of knowledge and insight gained in rf discharge studies. The results of performing ostensibly identical measurements on six of these cells in five different laboratories are analyzed and discussed. Measurements were made of plasma voltage and current characteristics for discharges in pure argon at specified values of applied voltages, gas pressures, and gas flow rates. Data are presented on relevant electrical quantities derived from Fourier analysis of the voltage and current wave forms. Amplitudes, phase shifts, self-bias voltages, and power dissipation were measured. Each of the cells was characterized in terms of its measured internal reactive components. Comparing results from different cells provides an indication of the degree of precision needed to define the electrical configuration and operating parameters in order to achieve identical performance at various laboratories. The results show, for example, that the external circuit, including the reactive components of the rf power source, can significantly influence the discharge. Results obtained in reference cells with identical rf power sources demonstrate that considerable progress has been made in developing a phenomenological understanding of the conditions needed to obtain reproducible discharge conditions in independent reference cells.
Spectroscopic Investigation of Argon DC Glow Discharge in Plasma Medium
Journal of Naval Sciences and Engineering
In this study, UV-VIS-NIR (Ultraviolet Visible Near-Infrared) spectra emitted from Argon Glow discharge plasma in a low vacuum were recorded with a high-resolution Czerny-Turner type spectrometer. Argon plasma was produced at a pressure of 5mTorr and with a voltage of 584 V. Argon plasma was produced between two parallel stainless steel plates anode and cathode with a diameter of 15 cm, a thickness of 0.8 cm, and a distance of 13 cm between them. The radiative and collisional processes of the Argon plasma medium were modeled by the PrismSPECT atomic physics software (Software). The distributions of ion densities were calculated using the Saha-Boltzmann equation. The intensity of the excited energy levels of Ar(I) and Ar (II) ions were calculated in the electron temperature range of (0.4-3.5eV) and the mass density of (10-4-10-1gr/cm3). The UV-Visible-NIR spectra were simulated and compared with experimental spectra. The ratios of the intensities of the ArII/ArI (1s22s22p63s23p44f1/1...
International Journal of Modern Physics B, 2003
Spectroscopic and Langmuir probe measurements are presented to characterize the argon glow discharge plasma generated by a cost-effective 50 Hz AC power source. Optical emission spectra (400-700 nm) are recorded for different gas flow rates and filling pressures at constant power level. The plasma parameters (electron temperature and density) are deduced from the relative intensities of Ar-I and Ar-II lines. The variation in the intensity ratio of the selected emission lines, electron temperature and density is studied as a function of gas flow rate and filling pressure. Slight increase in the intensity ratio I 2 (426.62 nm)/I 1 (404.44 nm) of the emission lines is observed whereas the electron temperature and density are found to decrease with increase in gas flow rate and filling pressure.