S-Parameter and Langmuir Probe Measurements in RF Plasma with Novel Capacitive Electrode Configuration

ALISSA (A Laboratory Investigation in Signal Scattering and Attenuation) is a modular plasma device designed to study the modification of electromagnetic wave transmission through plasmas. This is a long-standing research issue related to the atmospheric re-entry blackout problem identified during the earliest development of the space program. Current research is focused on analyzing signal attenuation during transmission through plasma layers and mitigation techniques for such losses. ALISSA features a novel electrode design which generates a capacitively coupled RF plasma for which initial measurements have shown electron density values as high as 10¹⁶ m^-3. We seek to fully characterize the plasma generated in ALISSA using both probe and signal measurements to develop a robust understanding of the operational parameters of ALISSA. Electron density measurements are taken using Langmuir probe analysis and using scattering matrix analysis with a vector network analyzer (VNA). Electron temperature measurements are taken using Langmuir probe analysis. This presentation provides a comprehensive description of the plasma temperature and density in ALISSA as a function of input RF power and gas flow.