| 摘要 |
PURPOSE:To improve the positional accuracy of an annular filament by making a hot cathode by unifying together the annular filament, a few arms for supporting the annular filament and a rim for connecting the arms. CONSTITUTION:A hot cathode 7 is formed by unifying an annular filament 8 formed by electrodepositing sodium oxide on a member made of tungsten or similar element, three radially-extending arms 9 for supporting the filament 8 and an annular rim 10 which connect the arms 9. After that, the thus formed hot cathode 7, an anode 5 having a semispherical molybdenum wire net and a lead- out electrode 6 having a trumpet-like opening are attached to an insulating ceramic plate 11, thereby making an electron-impact-type ion source for a mass spectrometer, etc. Therefore the sensitivity variation of the ion source can be reduced by increasing the positional accuracy of the filament 7. Additionally it is possible to replace the filament 7 without directly touching it. |
