Nowadays, thermionic plasma devices based on Cs-Ba filling are promising for cosmic and earth-based nuclear power industry. The results of the research into plasma's electro kinetic parameters of Knudsen high-current diode and triode switching devices are presented in this talk: It has been established, that current modulation in both devices is formed as result of plasma structure generation in the electrode gap without applying any external forces. Such structures develop due to electron instabilities in plasma. Unique regimes for effective grid discharge quenching were attained: the increase in the modulated power is accompanied by the decrease in the power consumption for controlling the current in the triode switching devices. Unprecedented energy parameters were obtained: stable frequency modulation in the range from 1 to10 kHz, an anode potential of 50 V, the electric power density of 5 kW/cm2and the efficiency more than 95%. The experiments on the Cs-Ba Knudsen diode demonstrate the feasibility of creating a full current modulation at an ignition voltage of 5...6 V and a discharge current density of 10 A/cm2. At a gap of 0.2...2 mm, a stable current and voltage modulation of 5...20 kHz frequency exists in a Cs-pressure range from 1 . 5 .10-3 to 3 . 5 .10-3 Torr .