This paper presents a review of studies on photoplasma in sodium-containing gas mixtures, along with the development of a self-consistent model of resonant photoplasma in sodium vapor. The model is designed for conditions where radiation fluxes are far from saturating the resonance transition and incorporates plasma-chemical reactions, radiation transfer within the Biberman-Holstein approximation, and charge transport via ambipolar diffusion.
The study highlights the necessity of generating non-homogeneous plasma with spatial gradients in electron density and temperature to achieve photo-electromotive force (photo-EMF) in gas cells. Two mechanisms for creating such heterogeneity are analyzed:
1. A one-sided irradiated slab, where spatial gradients are induced by asymmetric illumination.
2. A two-chamber cell, in which the first chamber containing quasi-homogeneous photoplasma acts as the active region, while the second chamber serves as a ballast to establish spatial gradients of electron density and temperature.
The generation of photo-EMF in Na–Ar gas cells under these scenarios is examined in detail. The study provides calculated values for electron densities, atomic and diatomic ion densities, electron temperatures, and other plasma parameters, both within the plasma volume and in the near-wall sheath regions where quasi-neutrality is broken. Additionally, data on the thickness of wall sheaths and their associated electric potential drops are presented.
An analysis of the dependence of photo-EMF on key factors – such as gas component pressures, radiation flux density, and cell dimensions—is conducted. The findings of this study are highly relevant to the design of gas-containing photovoltaic converters and the development of novel energy sources that leverage concentrated solar energy.