Abstract
Experiments are described in which the emission is measured from thin films of thorium deposited on different platinum-molybdenum phases of approximate composition Pt, Pt3Mo, Pt2Mo, Pt3Mo2 and Mo. The emission from all the platinum phases is considerably lower than that from pure molybdenum. The lowest emission was observed with the Pt3Mo phase. The emission from thorium deposited on to the Pt3Mo2 phase decays rapidly at temperatures of 1300° C and above, whereas that from similar deposits on molybdenum does not. The emission from thin films of thorium deposited on to titanium and tungsten has also been studied. The emission from a layer on titanium that had been thoroughly pre-cleaned was found to be much less than that from a similar layer on tungsten. The application of these results to the suppression of grid emission in the presence of thoriated tungsten cathodes in transmitting valves is discussed.
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