| 摘要 |
<p>PURPOSE:To prevent dielectric breakdown of a grid electrode by containing AlMo3 and Al2O3 free from Al3Mo as components of a blackened heat absorptive film regarding an impregnated cathode structural body in which the blackened heat absorptive film is formed in the inner wall face on the heater side for heating a sleeve. CONSTITUTION:One end of a cylindrical sleeve 5 is closed and the sleeve 5 having a hole in the center is made of Mo. A blackened heat absorptive film 5A is formed in the whole area of the inner wall face of the sleeve 5. As the components of the film 5A, AlMo3 and Al2O3 free from Al3Mo are produced. The sleeve 5 is provided with a heater for heating which is inserted into the inside of the sleeve from the open part in the other end. Consequently, the sleeve 5 can be heated to, for example, 900-1000 deg.C by the heat radiated from the heater for heating through the heat absorptive film 5A. The closed end side of the sleeve 5 is fixed by a cup made of Mo through a supporting wire 4. As a result, the grid electrode is prevented from dielectric breakdown.</p> |
