Application specific electrode-integrated nanotube cathodes (ASINCs) for miniature analytical instruments for space exploration

Abstract

JPL has developed high performance cold cathodes using arrays of carbon nanotube bundles that routinely produce > 15 A/cm2 at applied fields of 5 to 8 V/μm without any beam focusing. They have exhibited robust operation in poor vacuums of 10-6 to 10-4 Torr- a typically achievable range inside hermetically sealed microcavities. A new double-SOI process to monolithically integrate gate and additional beam tailoring electrodes has been developed. These electrodes are designed according to application requirements making carbon nanotube field emission sources application specific (Application Specific electrode-Integrated Nanotube Cathodes or ASINCs). ASINCs, vacuum packaged using COTS parts and a reflow bonding process, when tested after 6-month shelf life have shown little emission degradation. Lifetime of ASINCs is found to be affected by two effects- a gradual decay of emission due to anode sputtering, and dislodging of CNT bundles at high fields (> 10 V/μm). Using ASINCs miniature X-ray tubes and mass ionizers have been developed for future XRD/XRF and miniature mass spectrometer instruments for lander missions to Venus, Mars, Titan, and other planetary bodies.