Small Business Innovation Research/Small Business Tech Transfer
Iodine Hollow Cathode
Project Description
Plasma Controls, LLC will develop an iodine-compatible hollow cathode for use in Hall-effect thrusters. Materials in current state-of-the-art electron emitters, and many of the materials used in mounting hardware, are not compatible in a high-temperature iodine environment. This includes cathodes that use inserts made from porous tungsten impregnated with ceramics containing barium oxide, which can be susceptible to rapid decomposition of the ceramic by iodine, and lanthanum hexaboride-based inserts, which are subject to rapid surface decomposition by iodine. The work function of both types of inserts increases in the presence of iodine, and the temperature of the cathode increases, which further exacerbates the decomposition processes. We will use a materials science based approach to evaluate the chemical interactions between iodine and a range of potential materials at elevated temperature. We will construct and experimentally test candidate cathodes in relevant iodine environments to identify robust, safe-to-handle, chemically-stable material systems. In Phase II work, we will (1) perform long duration wear tests to demonstrate adequately long lifetime capability and (2) integrate the cathodes into iodine storage, feed, and thruster systems through industry and government partnerships.
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Anticipated Benefits
NASA aims to mature and demonstrate iodine electric propulsion technologies. Of particular interest are iodine 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.
A fully iodine compatible hollow cathode and thruster system is of great interest to commercial spaceflight satellite and cube-sat missions as a size, weight, and power and economic and enabler of smaller propulsion systems. In addition, 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. More »
A fully iodine compatible hollow cathode and thruster system is of great interest to commercial spaceflight satellite and cube-sat missions as a size, weight, and power and economic and enabler of smaller propulsion systems. In addition, 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. More »
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Primary U.S. Work Locations and Key Partners
| Organizations Performing Work | Role | Type | Location |
|---|---|---|---|
| Plasma Controls, LLC | Lead Organization | Industry | Fort Collins, Colorado |
Glenn Research Center
(GRC)
|
Supporting Organization | NASA Center | Cleveland, Ohio |
Primary U.S. Work Locations
-
Colorado
-
Ohio
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