A Magnetically Filtered Atomic Oxygen Plasma Source for Low-Earth-Orbit Simulation

A magnetically filtered oxygen plasma source has been developed and characterized for the purpose of simulating the low-Earth-orbit environment. The source uses a magnetic ring cusp geometry coupled with a transverse magnetic filter to produce a plasma stream consisting of streaming atomic oxygen ions with energy, density, and ion species composition corresponding to orbital conditions at altitudes ranging from 275 to 550 km. Plasma properties downstream of the source are dependent on the operational settings for source flow rate and discharge current. The properties are examined as a function of these operating parameters to optimize the production of O+ ions with energy and density relevant for low-Earth-orbit satellite drag applications. At each source operational setting presented in this work, the ion energy distributions are measured 0.55 m downstream of the source using a retarding potential analyzer, and the streaming ions were shown to have most probable energies ranging from 2.8 to 7 eV or 5800 to 9500 m . s(-1). In addition, a Wein filter (E x B) and a residual gas analyzer are used to measure the ion species percent composition as a function of the operational conditions. Source flow rate and discharge current settings are presented that allow for the composition of atomic oxygen ions to be adjusted from 63 to 90% of the total plasma ion population.