| 摘要 |
<p>PURPOSE:To shorten time for rise operation without inviting deterioration in mechanical strength, life and electric insulating performance between a coiled core and a cathode by making a diameter of two linear cores extended in the same direction from both ends of the coiled core larger than a diameter of the coiled core. CONSTITUTION:A diameter of two linear cores 12 is made larger than that of a coiled core 11 and when voltage is applied to a heater 1 to start conduction, temperature of the coiled core 11 having small thermal capacity rises firstly and next, temperature of the linear cores 12 having large thermal capacity rises. As to resistance value, which increases together with rising temperature like this, an increasing degree resistance value of the linear cores 12 is smaller than resistance value of the coiled core 11 so that, for some time immediately after starting conductivity, an overcurrent flows through the coiled core 11 so as to accelerated heat of this coiled core 11. As a result, heating and temperature rise of a base metal 22 is rapid for quickening emission of an electron beam. And, when the linear cores 12 having large thermal capacity reach prescribed temperature, an operation current reduces to be stabilized. Accordingly, time for rise operation can be shortened.</p> |
