| 摘要 |
PURPOSE:To emit sufficient thermoelectrons even if the filament temperature is low when a magnetron is driven by the low voltage by arranging a tubular impregnated type cathode surrounding the filament by the specific method. CONSTITUTION:An electron emitting face 16 impregnated with barium oxide into porous tungsten is soldered to the outer periphery of a molybdenum tube 15 with an inner diameter of 5mm end an outer diameter of 6mm, for example, to form an impregnated type cathode 14. The upper and lower ends of a spiral filament 10 are soldered to end shields 12, 11 respectively. One of the end shields, e.g., the shield 12, has a recess covered with an insulating film 13 made of zirconium oxide with a thickness of 0.05mm, one end of the cathode 14 is coupled with it, and the other end is soldered to the shield 11. When the cathode with this structure is used, a large quantity of thermoelectrons can be emitted when a magnetron is driven by the low voltage.
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