Temperature and density measurements in an iodine RF-CCP plasma with emission and absorption spectroscopy
Résumé
Iodine is a promising alternative to the expensive Xenon as propellant for electric propulsion devices. Aiming for dedicated optical diagnostics for ion thrusters fueled by iodine, a closed iodine cell (25cm x 3cm quartz cylinder, with a tube for temperature control) is connected to a 13.56 MHz RF generator. The resulting capacitively-coupled plasma is studied by emission and absorption spectroscopy. Absorption spectroscopy is used to measure saturation intensities, temperatures, and densities. Two lasers are used: a Ti-Sa cw laser to study transitions within excited states and a laser diode to study the fundamental one. The resulting I temperature and density are to be compared to global models. The experiment is to be reproduced in an ICP plasmas: at same but better controlled pressure; and at lower pressure with cavity ring-down spectroscopy.