| 摘要 |
PURPOSE:To make the measurement of the activity of the cathode possible by measuring a work function which is sensitive to the deterioration of the cathode and rarely depends upon cathode temps. CONSTITUTION:While the voltage of a cathode power source 6 is kept constant, the voltage of a heater power source 5 is dropped to maintain a cathode 2 at such a temp. about 700 deg.C which is in a temp. limiting range and at which cathode current of about 50% that in a standard working state can be drawn out. A switch 7 is turned off after this and the cathde is left standing (for about 5 minutes) until its temp. settles constantly. The heater power of this time is measured, and the value thereof is defined as Pf0. While the cathode current is recorded in a pen recorder 9, the switch 7 is turned on to apply an anode voltage Va1 instantaneously and the current of that time is defined as IK0. The voltage of the power source 5 is increased until the cathode current coincides with the IK0, and the heater power of that time is defined as Pf1. From this result, a work function is determined by W=e(Pf1-Pf0)/IK0-2kT. The deterioration is judged easily by this work function W. |
