Design and Characterization of an Atomic Rubidium Jet Source for Particle Beam Space Propulsion

Advanced propulsion systems based on light and particle beams have long been studied as an alternative to reaction engines for ultra high velocity missions to the outer solar system and interstellar space. Recently, a new concept for a combined light and particle beam has been proposed which exploits a self-guiding phenomena based on waveguide action and optical forces. In this work, we describe the design and evaluation of high flux, low temperature atomic rubidium jet sources for laboratory investigations of light guiding in rarefied flows. Analytical modeling of two jet sources are presented: an effusive source and a supersonic jet source. These flow-fields are then evaluated based on their ability to affect light propagation, as quantified by the V-number commonly used in the study of waveguides. In addition, detailed designs and design considerations are discussed for each type of source, including thermal management inside the chamber and operational factors associated with handling and cleaning hazardous alkali vapors. The model results indicate that both sources produce sufficient mass flow to enable the observation of strong light-guiding effects, corresponding to a V-number greater than unity, with the supersonic source providing a 1 - 2 order of magnitude enhancement compared to the effusive source. However, the effusive source provides practical advantages to implementation in future experiments, including less stringent thermal management constraints and safer handling of materials and cleaning procedures.