A METHOD OF CALCULATING EVAPORATION RATE FOR THERMIONIC CATHODES

An improved method using crystal oscillator for measuring the evaporation rate of ca-thodes is proposed, in which the distance between the crystal (substrate) and the cathode (source) is smaller than usually maintained. Thus more evaporation products from the cathode can be received by the crystal, and consequently the method can be used for measuring lower evaporation rate. Formulae for calculating the evaporation rate are derived, and the precision of the these is given. In this paper a method to prevent the resonant frequency change caused by the change of temperature is also given. The experimental result shows that one Hertz resonant frequency shift can be detected while the oscillation frequency is 5 MHz.