Thermochemical equilibria of residual gases in vacuum devices: Part 2: The oxide cathode, the anode and the residual gas

Abstract

Two principal equations are derived which in the average may apply for four chemically active gases in well-functioning radio valves. The equations are obtained by making use of a chemical model. The chemical model is a diode in which a barium oxide cathode and a deposit of evaporation products on the anode are present together with low pressures of hydrogen, carbon monoxide, water vapour and carbon dioxide. In the diode the preparation of the electron emitter and that of the deposit are thought to take place on the pump with the co-operation of gas. The preparation of both the emitter and the deposit are finished on the pump. To maintain the chemical connection between emitter, gas and deposit regard should be paid to a relation between the temperatures of the cathode and the anode during pumping, screening and life. The two principal equations mentioned before are valid during manufacturing and the whole life cycle if in the diode local chemical equilibria occur between the substances of fixed composition and the gases. Then, the bulk compositions of the layers do not change and a good functioning of the valve throughout life is guaranteed. The assumptions made for the model are affirmed by experiments with well-functioning pentodes. The chemical model is adaptable to conditions which apply in other vacuum devices. Also, adaptation to conditions that occur in open vacuum systems is feasible.