| 摘要 |
<p>PROBLEM TO BE SOLVED: To reduce the occurrence rate of malfunctions, such as contamination of a grid due to evaporation of an electron emission agent 33, quick exhaustion of the electron emission agent 33, and changes in the dimensions of a cathode sleeve 31 caused as side effects of head of a heater 38 necessary for generating thermoelectrons, to a fractional number by reducing a temperature difference between electron emission agent 33 temperature and a heater 38 temperature, from 140 deg.C of a conventional cathode structure 30 up to 120 deg.C, since it is better the lower the heater 38 temperature is, as long as the electron emission agent 33 is can be maintained at a predetermined temperature. SOLUTION: In the cathode structure 10, a contact area of a cathode sleeve 11 and a cathode support 12 is reduced to a minimum level necessary for fixing, and heat transferred from a heater 18 to the cathode support 12 is reduced. Using this, a heater 18 temperature can be reduced, while maintaining the temperature of an electron emission agent 13 at a conventional level.</p> |
