| 摘要 |
PURPOSE: To accurately find the change with the lapse of time of the specified variable of a cathode and the work function after the long-hour operation by calculating the specified amount from a value of the front surface temperature measured by an optical thermometer, and reading values of current and voltage when the gradient of the voltage/current characteristics is equal to the specified amount. CONSTITUTION: The voltage Va (V) and the current Ia (mA) in the decelerating electric field state wherein an anode is electrically made negative in relation to a cathode is measured by using a diode bulb wherein an electron emitting-type cathode and an anode are parallely arranged, so as to form the voltage/current characteristics figure. A formula wherein the right of the formula to which Ia as a function of Va conventionally used as the relating formula of Va to Ia is multiplied by the current transmittance (u) is used. A value of e/(k.T) [C/J] is calculated from a value of T measured by an optical thermometer, the values of Ia and Va to be obtained when they are equal to the gradient of the characteristic figure of lm (Ia ) as a function of Va are adopted, and the accurate values of T, Ia , Va can be found. The accurate value ofβis found by using these values, and the change of the lapse of time ofβcan be accurately found.
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