Highly Efficient Micro Cathode

Potential applications of the micro cathode are abundant, though the likely first and highest NASA interest will be for very high frequency TWT microwave generators. As the frequencies of these sources increase, the size (diameter) of the electron feed beams needs to decrease. NASA could also have interest for this low power, micro cathode for scientific sensor such as probes for measuring electric fields in earth orbit is by measuring the ExB electron drift. This requires small beam spot and as spacecraft shrink in size and power, the exceptional low power of the proposed cathode will be needed. Another potential application for the proposed cathode is for use as a neutralizer and plasma initiation electron source for our micro RF ion engines. Developing a thermionic cathode that emits on the order of 1mA for 100mWatt input would eliminate on critical hurdle for efficient micro ion engine utilization for space propulsion. We currently have a field emission cathode that can emit this current, but has difficulty starting the plasma. The proposed cathode should be able to be overdriven for a fraction of a second to deliver multiple mA of current. The cathode can be scaled larger for the larger ion engines if needed.

Non-NASA applications mirror the NASA applications plus there is significant interest in developing the necessary equipment to enable the use of the extremely high frequency (EHF) band for military and commercial applications. For the armed services, realization of millimeter wave amplifiers enables Gigabit rate point-to-point satellite communications, as well as access to currently unused spectrum. Furthermore, millimeter wave radio communications enable reduced antenna size and increased signal directionality, increasing effective signal gain to the target. Commercial applications for EHF amplifiers tend to focus on atmospheric science, in particular monitoring upper atmospheric temperatures. More »