| 摘要 |
<p>PURPOSE:To decrease the load for a filament and extend its life by heating a cathode with an electron beam type heater without heating it with a filament type heater directly. CONSTITUTION:Electrons emitted from a heater cathode 1 by the potential applied across a cathode 6 and an electron beam type heater 50 heating the heater cathode 1 by the heat generated by a filament 2 form an electron beam 5, which is accelerated and hits the cathode 6 and heats it. The electron beam 5 is accelerated and focused by an electric field lens 4 formed by the cathode 1, a focusing electrode 3, and the cathode 6 and concentratively heats a point with a very small surface area. The cathode 6 can be kept at a high temperature even if it is so small that a filament type heater can not be incorporated, and an electron current with a fine diameter is obtained.</p> |
