NASA aims to mature and demonstrate iodine electric propulsion technologies. Of particular interest are hollow cathodes with lifetimes greater than 10,000 hours. Hollow cathodes are used in electric propulsion devices, including Hall effect and ion thrusters, to sustain discharge plasmas and neutralize ion beams, and in plasma contacting devices to neutralize spacecraft charge. Ultra-long-life, high-power, and wide-operating-current-range cathodes are needed for the Science Mission Directorate's ambitious deep space missions; and low-power, high-efficiency cathodes for secondary payload cube-sat missions.
Hollow cathode electron sources are commonly used as components of ion and plasma sources in ground-based, materials processing applications. This includes ion etching of surfaces, ion-assisted film deposition, ion implantation, and chemical vapor deposition; processes which can present similarly challenging chemical environments to that of iodine. Robust and long life hollow cathodes developed through this work are anticipated to be highly commercially attractive as they would reduce maintenance expenses and process downtime. However, their attractiveness grows exponentially if they could be used in applications that were previously off limits due to the presence of highly reactive gases and plasmas. Hollow cathode technologies are also advantageous as electron sources in high current, electron-beam melting applications and in gas/liquid/solid material analysis equipment.