Secondary Electron Emission from Molybdenum

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Abstract
The secondary electron emission from a very clean molybdenum plate in a simple three-electrode tube has been studied. The number of primary electrons striking the plate was calculated by means of the positive ion calibration method previously reported. The number of secondary electrons per primary reaches a maximum value of 1.15 at 600 volts and then decreases to 1.00 at 2000 volts. One definite discontinuity in the secondary emission curve occurs at 13.5 volts; the others are very small and are not reproducible. The emission increases about 3 percent within a few minutes after heating if the gas pressure is very low and then remains quite constant for a long period of time. The emission decreases with time when there is more gas present. The secondary emission appears to increase by about 4 percent when the temperature of the target increases from the normal operating temperature to 1600°K.