Abstract
This paper shows the thermionic effects caused by alminium and magnesium on the commercial tungsten filaments. The electron mission from the surface of the filaments was increased considerably by the impacts of alminium ions or magnesium ions. The nature of such filaments was studied carefully by measuring the rate of activation, the thermionic emission and the secondary electron emission from the surface of the filaments.
The filament which have never b en heated to a very high temperature during the various treatments have the extraordinary high value in the rate of activation, and the relations between the voltage and the secondary electron current from the surface are quite abnormal as are shown in Fig. 6 and Fig. 7. It is proposed here that the alminium oxide and the magnesium oxide may exist on the surface in special state with the atoms of rare metals. This state is named here "A-state".
Another state can be obtained by heating the filaments at the very high temperature. In this state, the condition of the surface is similar to those of the thoriated tungsten filaments. the manners of the secondary electron emis-sion in this state are shown in Fig. 8 and the curve III in Fig. 10. This state is named here "B-state".
The spectrum analysis of the commercial filaments which were employed in this study showed the existance of Th, Zr and the trace of Ce.
Fig. 5 B shows the rough sketch of the principal part of the apparatus for measuring the aecondary electron emission. In Fig. 5 B, α, b and c denole the filament under the test, the source of the primary electrons and the grid which absorves the secondary electrons (Vg=500 volts) correspondingly Fig. 9 shows the result obtained in the case of the special pure tungsten filament.
No distinct difference was recognized in the secondary electron emission curves which were obtained from the activated filament and the deactivated one.
