| 摘要 |
<p>A directly heated cathode comprises a metal tube 1 having a filling 2 of powdered metal which extends beyond the tube 1 and in which is embedded an electrical wire 3 which is coaxial and extensive with said outer tube 1 over part of its length. The electrical wire 3 is coated with insulating material 3a, normally alumina. The tube 1, said metal powder filling 2 and said wire 3 are sintered together.</p> |
