de Fpj Frank Groote

On the electron temperatures and densities in plasmas produced by the “torche à injection axiale”

Abstract The electron temperature and the electron density of plasmas created by the “Torche a Injection Axiale” (TIA) are determined using Thomson scattering. In the plasma with helium as the main gas, temperatures of around 25 000 K and densities of between 0.64 and 5.1 × 1020m−3 are found. In an argon plasma the electron temperature is lower and the electron density is higher: 17 000 K and around 1021 m−3 respectively. From these results it can be established that the ionisation rates of both plasmas are much larger than the recombination rates, which means that the plasmas are far from Saha equilibrium. However, deviations from a Maxwell electron energy distribution function, as reported for the “Microwave Plasma Torch” (MPT), are not found in the TIA. The excitation and ionisation power of the TIA appears to be stronger than that of the MPT.

Thomson scattering experiments on a 100 MHz inductively coupled plasma calibrated by Raman scattering

A new calibration method to obtain the electron density from Thomson scattering on an inductively coupled plasma is discussed. Raman scattering of nitrogen is used for recovering the Rayleigh scattering signal. This has the advantage that no corrections are necessary for stray light, like with other calibration methods, using the direct measured Rayleigh scattering signal on a well‐known gas. It is shown that electron densities and electron temperatures can be measured with an accuracy of about 15% in density and of about 150 K in temperature.

Comparison of active and passive spectroscopic methods to investigate atmospheric inductively coupled plasmas

A comparison of Thomson and Rayleigh scattering, diode laser absorption and line emission measurements is performed on a 100 MHz atmospheric argon-flowing inductively coupled plasma. The parameters, which are measured in two or more ways, are the electron density, the electron temperature and the heavy particle temperature. The optimized diagnostics show the same behavior for the electron density and temperature. Nevertheless, the Thomson scattering diagnostic is the best at retrieving the radial profile. The heavy particle temperature, as measured by using both Rayleigh scattering and diode laser absorption, is identical within the estimated errors. The technique of measuring the temperature during power interruption, with both Thomson scattering and emission spectroscopy, shows that the electron and heavy particle temperatures are not equal during the period of power interruption.

Atomic emission spectroscopy for the on-line monitoring of incineration processes

A diagnostic measurement system based on atomic emission spectroscopy has been developed for the purpose of on-line monitoring of hazardous elements in industrial combustion gases. The aim was to construct a setup with a high durability for rough and variable experimental conditions, e.g. a strongly fluctuating gas composition, a high gas temperature and the presence of fly ash and corrosive effluents. Since the setup is primarily intended for the analysis of combustion gases with extremely high concentrations of pollutants, not much effort has been made to achieve low detection limits. It was found that an inductively coupled argon plasma was too sensitive to molecular gas introduction. Therefore, a microwave induced plasma torch, compromising both the demands of a high durability and an effective evaporation and excitation of the analyte was used as excitation source. The analysis system has been installed at an industrial hazardous waste incinerator and successfully tested on combustion gases present above the incineration process. Abundant elements as zinc, lead and sodium could be easily monitored.

Air entrainment in an inductively coupled plasma measured by Raman and Rayleigh scattering

A new technique to study the entrainment of air into the inductively coupled argon plasma is presented. The combination of vibrational Raman scattering and Rayleigh scattering enables measuring absolute particle densities of air and argon. The measurements show the entrainment of air into the plasma. At an axial position of 2 mm above the end of the quartz torch it is found that at 90% of the plasma radius 55% of the particles originate from air and by exponential extrapolation towards 70% of the radius about 1% entrainment of air is predicted to be present. Furthermore, a comparison with a cold argon flow shows that due to the higher viscosity the entrainment in the plasma is lower than in the cold argon flow.

Air entrainment in an inductively coupled plasma measured with Raman and Rayleigh scattering

Summary form only given, as follows. The inductively coupled plasma is well known from its spectrochemical application. The argon plasma operates at atmospheric pressure and flows out into the open air. The observation zone is usually taken in the plasma part above the end of the quartz torch where the argon plasma is surrounded by air so that it might be expected that this plasma part will be influenced by air entrainment. To study this we combined two techniques namely vibrational Raman scattering and Rayleigh scattering. In this way it was possible to measure absolute densities of air and argon. At an axial position of 2 mm above the end of the quartz torch and at 90% of the plasma radius it is found that 55% of the particles originate from air. By exponential extrapolation towards 70% of the radius it is predicted that about 1% of the particles originates from air entrainment. The same diagnostical techniques were effectuated on a cold argon flow (no plasma). By comparing the results it is found that the entrainment in the cold argon flow is larger than in the plasma case. So apparently the high temperature (and thus high viscosity) avoids the air entrainment.Summary form only given, as follows. The inductively coupled plasma is well known from its spectrochemical application. The argon plasma operates at atmospheric pressure and flows out into the open air. The observation zone is usually taken in the plasma part above the end of the quartz torch where the argon plasma is surrounded by air so that it might be expected that this plasma part will be influenced by air entrainment. To study this we combined two techniques namely vibrational Raman scattering and Rayleigh scattering. In this way it was possible to measure absolute densities of air and argon. At an axial position of 2 mm above the end of the quartz torch and at 90% of the plasma radius it is found that 55% of the particles originate from air. By exponential extrapolation towards 70% of the radius it is predicted that about 1% of the particles originates from air entrainment. The same diagnostical techniques were effectuated on a cold argon flow (no plasma). By comparing the results it is found that the entrainment in the cold argon flow is larger than in the plasma case. So apparently the high temperature (and thus high viscosity) avoids the air entrainment.