Modeling of photoplasma for creating EMF in slab cell one-sided irradiated by uniform radiation

Abstract

A modeling of the photoplasma in a slab cell filled with a sodium vapor and argon mixture one-sided irradiated by a uniform radiation flux was carried out. This study was performed for a spatially heterogeneous distribution of the resonance level density, unlike our previous works. An analytical form of this distribution for the slab available in the literature was used. The present investigation was performed at the sodium vapor pressure P_Na=0.005−0.3 torr and the ratio of argon and sodium pressures P_Ar/P_Na=10² for the spectral flux density F=5⋅10²−5.2⋅10⁴ Wm⁻²nm⁻¹. A set of plasma chemical reactions, radiation transfer and charge transport were considered. The spatial profiles of densities of the sodium atomic levels, atomic and diatomic ions, the electron density and temperature, and the electric potential in the volume of the cell were obtained from a self-consistent solution of the balance equations for densities of plasma components and the electron energy. It was established that spatial picture of the Na⁺ and Na₂⁺ ion density fractions depends significantly on the cell conditions. Parameters of wall sheaths were calculated used formulas from the literature. Used these data and the obtained spatial profiles of electric potential, the dependencies of electromotive force (the potential difference between the illuminated and dark walls of the cell) on the sodium pressure and incidental spectral flux density were obtained. The maximal EMF value was 1.5 V for the P_Na=0.05 torr and F=5.2⋅10⁴ Wm⁻²nm⁻¹. Obtained results can be used in the development of photo-electric converters.