Development of Electron Gun of Carbon Nanotube Cathode

We have been developing a high brightness electron gun utilizing carbon nanotube (CNT) cathode since 2001. Recently we succeeded to achieve a realistic-size cold cathode which could stand comparison with current densities of oxide cathodes conventionally used in accelerators all over the world. The anode current was obtained to 0.48 A from the CNT-cathode of 2.6 mm diameter, which current density reduced from the anode current was about 9.1 A/cm²with 128 kV-DC acceleration voltage in pulse operations of 50 pps using about 8 ns pulses. The emission current was very stable in the long term period operation of about 3 weeks under about 10^-6Pa vacuum pressure.