Cascade Arc Studies of Hydrogen/Nitrogen Plasmas in Nonequilibrium

Abstract

A cascade arc facility was developed to study the characteristics of nonequilibrium plasma propellants for electric propulsion applications. The cascade arc was operated with 50 A hydrogen arcs at absolute pressures of 1.34 × 10 4 and 4.14 × 10 4 Pa. Spatially resolved spectral emission data were collected using a two-dimensional optical multichannel analyzer (OMA), and radial distributions of H α line widths of the Abel inverted emission line profiles were obtained. The measured H α line widths were compared to values predicted by nonequilibrium cascade arc simulations using the UTSI Cascade Arc Plasma Simulation (CAPS) code and dynamic ion Stark broadening/electron number density correlations. Agreement was sensitive to the finite-rate kinetic model used for hydrogen. When used in CAPS, University of Illinois kinetics model gave the best agreement with the hydrogen cascade arc measurements. The experimental electric field and radially resolved H α line widths accurately predicted measured values at both pressures within experimental uncertainty. H α line widths for simulated ammonia and hydrazine were also obtained at pressures of 1.34 × 10 4 , 4.14 x 10 4 , and 6.89 × 10 4 Pa. These mixture data can be used for future evaluations of kinetic models for hydrogen/nitrogen mixtures.