A modified ECR plasma cathode operating on CO₂ in the presence of a Penning gas

Electron cyclotron resonance (ECR) plasma cathodes have the ability to operate on reactive molecular propellants, which can enable multi-mode operation by combining electric propulsion with chemical rockets systems using the same propellant. In this work, an ECR plasma cathode is operated on the molecular gas CO₂. Previous testing with CO₂ alone had discharge losses near 200 W/A, well above the target performance goal of under 100 W/A. This work investigates the addition of neon as a “Penning gas” to improve ionization efficiency via Penning Ionization. Here, the Penning gas essentially stores energy from electron excitation events in the form of excited neutrals, which have an enhanced reaction cross-section for ionization with CO₂, as compared to that of standard electron-impact ionization events. ECR sources are capable of generating high energy electrons needed for the Penning effect. This experimental effort will employ a parametric study to identify operating conditions that maximize both device efficiency and quantity of extractable electrons, with a key parameter being the fraction of Penning gas required to make such an approach practical.