Radiative emission analysis of an expanding hydrogen arc plasma—II. Plume region diagnostics through radial emission

Abstract

An experimental investigation of the plasma plume of a 1 kW class radiatively-cooled hydrogen arcjet thruster is presented. The line-of-sight emission of the Balmer-alpha line is measured at several radial positions using a high resolution monochromator and photon counting detection. The line-of-sight spectra are deconvolved radially into Voigt profiles, from which radial distributions of translational temperature and electron number density are determined. Absolute intensity calibration is also performed providing radial distributions of atomic hydrogen m = 3 excited state number density. Electron temperature profiles are calculated using a non-equilibrium collisional-radiative model. The hydrogen translation temperature displays good agreement with previous measurements. The electron number density profiles are consistent with Langmuir probe measurements made downstream of the exit plane. The results of the model indicate that the plasma at the nozzle exit plane is strongly recombining.