Experimental evaluation of Cs-Ba thermionic switch/inverter - 'Tacitron'

Preliminary test results demonstrated the potential of the Cs-Ba tacitron as a switch/inverter. Operation parameters measured include switching frequency up to 5 kHz, hold-off voltage up to 170 V, current densities in excess of 15 A/sq cm, switch power density of 1 kW/sq cm, voltage drop as low as 1.5 V, for a switching efficiency in excess of 99 percent, turn-on voltage of 10 V to 30 V, and turn-off voltage of -15 V to -30 V. Experimental results show that the maximum voltage drop in the triode sections of the tacitron can be as low as 1.25 V, at a Cs vapor pressure of about 0.01 torr, a Ba vapor pressure of about 6 x 10 exp -4 torr, and an emitter temperature of 1569 K, for a switch efficiency greater than 99 percent. At lower emitter temperatures and/or lower Cs vapor pressures the largest voltage drop measured is about 7 V. Also, the voltage drop decreases significantly as the discharge current is decreased. Results show that switching frequencies of 12 kHz to 20 kHz may be attainable.