Temperatures In Oxygen Atmosphere Research Articles

Some Factors Affecting the Decay of Secondary Electron Emission of Silver-Magnesium Alloys

The secondary emission yield is observed to decay very rapidly under electron bombardment especially during the exhaust process using oil diffusion pump. In this paper, factors affecting the decay, a method of remedy to make the decayed yield to recover, and effects of various gases and vapors on the yield are discussed. A major cause of the secondary yield decay is attributed to the deposition of amorphous carbon, which is produced on the dynode surface through the decomposition of hydrocarbon or carbon-containing gases by the electron beam. Heating the contaminated dynode at high temperatures in oxygen atmosphere for some period results in a recovery of the yield. Keeping the dynode at high temperatures during electron bombardment is effective in bringing about a marked decrease in the decay. From the data on the temperature dependence of the decay, the heat of adsorption of a gas which is considered to be the source of contamination, is calculated to be about 1.6 kcal/mole. N 2 , CO and CO 2 do not exert any harmful effects upon activated dynodes, while H 2 exerts somewhat harmful effects, and, particularly, electric discharge in H 2 should be avoided. The most unfavorable gas is the grease vapor. The process of contamination is briefly discussed.