High average power field emitter cathode and testbed for X/Ku-band cold cathode TWT

A new field emitter geometry that utilizes a dielectric shield between the emitter tip and gate has been optimized to eliminate flashover in the cathode emitter cavities and improve cathode reliability. A high average power testbed has been designed and fabricated to test these cathodes at currents and current densities required for TWT operation in the X/Ku-Band frequency regime. Experimental tests in the water-cooled testbed demonstrated a record 100 hours of CW operation at 100 mA. A 200 mA X/KuBand TWT was designed to integrate these cathodes and to provide RF gain and power across the entire 6 - 18 GHz frequency band. Preliminary results taken at a cathode current of 50 mA show excellent focus of the emittance-dominated electron beam. RF results at 50 mA demonstrated positive gain over the entire frequency band with a maximum of 13.5 dB gain and 10 W output power at 10 GHz and low duty. Cathode testing as well as TWT design and preliminary operation will be described.