| 摘要 |
<p>The directly heated grating cathode is designed as a hollow metal cylinder eg. made of tungsten, with two rings (1,2) at both ends, between which is a working surface of intersecting spiral filaments. The filaments have a width which increases from both ends towards the middle. This cathode is best prepared by electro- erosion spark machining, using a tool electrode to produce one vertical line of meshes and half of the lines on both side of it. The tool is shifted after each cycle through twice the pitch. Such a cathode has a large effective emission surface. The electro- erosion spark method produces cathodes with a high accuracy.</p> |
