| 摘要 |
PURPOSE:To lower arc discharge voltage in order to leng then the life of a thermal electron emission element by dividing a plasma chamber wall in a plural number, and further, putting the plasma wall chamber located farthest from an electrode group in the floating potential. CONSTITUTION:A plasma chamber 1 is a space surrounded by a floor board 2, outer walls 3-5 and an electrode group 6 and inside thereof, a thermal electron emission element 7 made of a heat-resisting metal filament such as W is arranged, further a part of the floor board 2 is provided with a gas leading-in port 8 through which desired gas is sent into the plasma chamber. Each electrode is fixed by supporting members 9-12 while each supporting member is electrically insulated by insulating materials 13-16. Further, a static rod 17 for fixing said supporting plates and insulating materials each other is also prepared while the insulating materials 19 for separating the outer walls 3-5 of the plasma chamber are inserted between the outer walls. Thereby, plasma can be generated in a low arc discharge voltage thus enabling the life of a thermal electron emission element to be extended. |
