| 摘要 |
<p>PURPOSE:To further increase the luminance of an electron gun, which contains a monocrystal LaB6 cathode, by enabling a single beam to be obtained constantly even when the bias between the monocrystal LaB6 cathode and a Wehnelt electrode is made shallow. CONSTITUTION:A monocrystal LaB6 cathode 1 is set to have its given axial direction corresponding to the direction of electron discharge, and is formed by working the end of a square prism 2 into a circular cylinder having a small diameter. Here, the axial direction[100],[210]or[310]of the cathode 1 is adjusted to correspond to the direction of electron discharge. The extreme end of the cathode 1, that is to say, the end of a circular cylindrical part 3 is worked into a flat to say, the end of a circular cylindrical part 3 is worked into a flat surface, and is made to have an acute angle. In addition, a Wehnelt electrode, an anode and the like, which are not illustrated in the figure, are installed above the extreme end of the cathode 1. By thus constituting the cathode 1, any electron discharge doesn't develop from the other surface of the cathode 1 than the surface of the extreme end even when the Wehnelt bias is made shallow. As the result, a cross over image becomes almost constant irrespective of the Wehnelt bias.</p> |
