Géraldine Faure

Determination of rotational and vibrational temperatures in a discharge with liquid non-metallic electrodes in air at atmospheric pressure

Rotational and vibrational temperatures are measured by optical emission spectroscopy in a discharge with liquid non-metallic electrodes (DLNME) in air at atmospheric pressure. We used the transition of the second positive system of to determine the two parameters of this discharge. In this paper we describe first the experimental set-up and then the method of determination of rotational and vibrational temperatures by comparison with calculated spectra. We present the results obtained along the discharges axis.

Modelling radiation spectrum of a discharge with two liquid non-metallic (tap-water) electrodes in air at atmospheric pressure

The emission spectra of a column of a direct-current discharge in open air which is performed between two tap-water electrodes (two tap-water flows) are studied in the 240–450 nm spectral range. A comparison of the values of spectral emissivities is made between experimental spectra and the calculated spectra. The emission spectrum calculation is made for four molecules, N2 ,O 2, NO and OH that are present in air plasma. The first part of this paper focuses on building the spectra calculation; the required data are detailed. In the second part, rotational, vibrational and excitational temperatures are determined with the Boltzmann distribution assumed on the quantum states. For that purpose, a comparison of the modelled spectra and the experimental spectra is made in the different parts of the discharge column. (Some figures in this article are in colour only in the electronic version)

Experimental investigations of emission spectrum of a discharge with two liquid non-metallic (tap-water) electrodes in air at atmospheric pressure

Experimental investigations of the emission spectrum in the wavelength range 240 nm < λ< 850 nm of a discharge burning in open air between two flows of tap water (a discharge with two liquid electrodes) with direct current supply are carried out. The axial and radial distributions of spectral characteristics at different currents i and discharge lengths L (i = 40-80 mA; L = 4-8 mm) are investigated. From spectral distributions of plasma emissivity, the obtained results show that the discharge radiates mainly in the ultraviolet region of the spectrum. The main contribution to the radiation power is made by N2, OH and NO molecules. The near-electrode regions radiate most intensively. A comparison of the previously published results of the investigations of such a discharge with the present results allows us to give qualitative explanations of the regularities in the axial distributions of spectral characteristics and their dependences on current and discharge length. An estimation of the dose of irradiation of the electrode liquid (tap water) by discharge radiation, having bactericidal effect (λ < 310 nm) is made. The estimation shows that when water flows through the electrode attachment, the dose received by it is, by an order of magnitude, comparable to the dose which is necessary for sterilization.

Partition Functions for Diatomic Molecules in Plasmas out of Thermal Equilibrium

Two calculation methods on the partition functions for diatomic molecules in plasmas out of thermal equilibrium are reported. A Boltzmann distribution for the electronic, vibrational and rotational quantum levels is assumed in the two calculation methods. The results obtained by two methods are displayed for four sorts of diatomic molecules, O2, N2, OH and NO, that are present in humid air plasmas. The calculation method of density for the electronically excited states is developed. Finally, a method to calculate the partition functions for simulating the non-normalized diatomic spectra is discussed.

Measurement of Rotational Temperature by Simulated Molecular Spectra

Abstract The measurement of temperature of heavy particles in a thermal plasma is based on the comparison of experimental rotational spectrum obtained by optical emission Spectroscopy and synthetic spectra calculated for different temperatures. The calculation principle of the synthetic spectra is detailed as well as the temperature accuracy obtained. This method is used to measure the temperature of an Ar-CO2 mixture plasma produced in a wall stabilized arc with molecular spectra of C2 (Swan system) and CN (violet system).

INLUENCE OF THE ELECTRIC FIELD AND MAGNETIC FIELD ON DEBYE LENGTH, LONDON LENGTH AND KELVIN LENGTH

Deeply linked with ElectroMagnetic Compatibility (EMC) issues, plasma generation is often in non-thermal equilibrium. For instance, in several applications such as discharge with liquid non-metallic electrodes, radio frequency (RF) plasmas, circuit breakers, arc tracking, the electrons reach a temperature higher than the ions and neutral temperature. The interaction between charged particles plays a key role. In such plasma, the influence of the Debye length can lead to an overestimation of about a factor of ten in the determination of electrical conductivity for higher temperature due to the electrostatic potential shielding. The same remark can be made to the magnetic shielding leading to an overestimation of the skin effect. The non-ideality definition of the plasma has been well established at thermal equilibrium. In this paper, we would like to establish the limit of the validity of the Debye length, and the London length in plasmas at and out of thermal equilibrium. The Kelvin length (skin effect) is also study in plasma for frequency of 13.56 MHz and 60 MHz. We applied the calculation in an argon plasma.

A simple generator of a stationary flow of non-equilibrium atmospheric-pressure plasma

A simple design of a plasma discharge set up, providing a stationary flow of non-equilibrium atmospheric-pressure plasma is proposed. The non-equilibrium state of plasma is maintained by using a cathode with a weakly conducting liquid like tap water. The anode is formed with a cooled metal ring-shaped inserted in a dielectric barrel. This assembly is fixed at ~ 1 cm above the water surface. The velocity of the air flow through the anode hole may be changed from 0 m/s up to ~ 10 m/s. The studied discharge in the open air gap between the tap water surface and the anode ring is powered by direct current I ~ 0.1 A. The voltage on the air gap is ≥ 1 kV. Measurements of current-voltage characteristics at different flow velocities were carried out. Spectra of radiation of the discharge column and the torch above the anode were measured. The measurement results were compared with the results of radiation spectra modeling for non-equilibrium plasma of humid air. The comparison made possible to determine the characteristics of plasma. The characteristics of the plasma depending on the speed of the airflow and the current are studied.