Applications of carbon film cold cathodes in vacuum electron devices

Carbon film cathodes have been shown to be very robust and stable in over 5,000 hours of testing in continuous operation at 0.2A/sqcm and capable of at least 2.OA/cm2 in pulsed operation. The primary evaluation vehicle is a metal ceramic diode that is constructed and processed with methods that are standard in the high vacuum tube industry. Some of the information presented was developed from X-ray and vacuum gauge tubes designed specifically to utilize carbon film emitters. Additional analytical measurements have been made to establish the work function, emittance, noise and stability at pressure levels above 10/sup -4/ Torr.