Testing of Carbon Nanotube Field Emission Cathodes

*† ‡ § ** †† , Busek has been developing field emission cathodes using our proprietary, arc-grown, carbon multi-wall nanotubes. A cathode is slated for use in the upcoming SMART-2 mission, part of NASA’s Space Technology 7 (ST-7) New Millennium program. These field emission cathodes typically produce between 2 µA and 2 mA of current at voltages between 100 and 600 volts. As part of our qualifying program, we have subjected the cathodes to long duration life tests and vibration testing designed to simulate launch loads. We have accumulated >13,000 hours of operation on a cathode operating at 100 µA and ~ 6,000 hours for a cathode operating at 1 mA. While there is a gradual increase in voltage over time, the cathodes operated reliably, including periods of on-off operation. Characterization of voltage-current behavior before and after vibration testing indicated little or no degradation in performance due to 3-axis random vibrational loads. In addition, the cathodes have been operated under 10 -4 torr of molecular oxygen pressure with some drop-off in current but no