On the Relation between the Secondary Electron Emission from Nickel and Tungsten and its Temperature

Abstract

The present research was worked out with three electrods value as shown in Fig. 1 and Fig. 2, which was exhausted to the pressnre of about 10^-5m.m. Hg., and its plate was heated with a separate battery. We used as its anode a nickel foil and a tungsten wire respectively in two different cases. This nickel foil was obtained by electroplating.
The temperature of the specimens was determined by the optical pyrometer for the nickel foil, and by Lungmuir's method⁽¹⁾ for the tungsten wire. The relation between the secondary electron emission and the Anode temperature was obtained at V_g=509.9 volts, and V_p=261.0 volts for nickel foil, and for tungsten wire V_g=500.1 volts constant corresponding to V_p=79.8, 90, 98, 110, 120.2, 130, 142.8, 148.8, 163.4, volts respectively.
This relation is shown in Fig. 6, Fig. 10, respectively. This figures show that the secondary electron emission for nickel increase gradually with temperature from room temperature to near 400°C and above this temperature decrease comparatively sharpe with its temperature, but at about 800°C this secondary electron emission again increase a little and immediately decrease. But with tungsten wire as the anode, the secondary electron emission was substantially constant up to the temperature at which the primary electron emission began to appear. The first abrupt change of the secondary electron emission with temperature for nickel foil at about 400°C correspond to A₂ transformation of nickel. But the second abrupt change correspond to A₂ transformation of iron. As we know only A₂ transformation for nickel, the first change may be due to the nature of a nickel but the second change due to the impurity of iron included in the nickel foil or some other unknown courses. We took also the (I_p-V_p) characteristic of tungsten wire at the room temerature, 850°K and 1350°K, but the critical potentials was not so clearly observed at 850°K and 1350°K as at room temperaturs. This disapperance of the critical potentials may be due to a greater energy of molecules at higher temperature.