Experimental Investigation of High Temperature High Voltage Thermionic Diode for the Space Power Nuclear Reactor

摘要

It is well known that the rise of arc from the dense glow discharge is connected with the thermion and secondary processes on the cathode surface (Granovsky, 1971; Leob, 1953; Engel, 1935). First model of breakdown of the cathode layer is connected with the increase of the cathode temperature in consequence of the ion bombardment that leads to the grows its thermo-emissive current. Other model shows the main role of the secondary effects on the cathode surface - the increase of the secondary ion emission coefficient - γ_i with the grows of glow discharge voltage. But the author of this investigation work of breakdown in Cs vapor (a transmission the glow discharge into self-maintaining arc discharge) discovered the next peculiarity: the value of breakdown voltage is constant when the values of vapor temperature (its pressure p_(cs)) and cathode temperature T_k is constant too (U_b = constant with T_k = constant and p_(cs) = constant) and it is not a statistical value (Onufryev, Grishin, 1996) (that was observed in gas glow discharges other authors (Granovsky, 1971; Leob, 1953; Engel, 1935)). The investigations of thermion high voltage high temperature diode (its breakdown characteristics in closed state and voltage-current characteristics in disclosed state) showed that the value of the breakdown voltage is depended on the vapor pressure in inter-electrode gap (IEG) - p_(cs) and cathode temperature -T_k and is independent on IEG length - Δ_(ieg). On this base it was settled that the main role in transition of glow discharge to self-maintaining arc discharge plays an ion cathode layer but more exactly - the region of excited atoms -"Aston glow".