| 摘要 |
<p>PURPOSE:To uniformalize the current density of an aperture image, control the spreading by means of the space charge effect of an electron beam, and obtain ample brightness by specifying the half vertical angle of a cathode chip whose tip is machined into a cone or a pyramid. CONSTITUTION:The tip of a cathode chip 101 is machined into a cone or a pyramid and thermoelectrons are taken out from the tip. This cathode chip 101 consists of the materials, for example, LaBb, ZrC, TiC, TaC or those in which impurities are mixed, whose work function is W and whose relationship of temperature Te which renders the vapor pressure of 1X10<-5>Torr is W/Te <=1.5X10<-3>. The half vertical angle of the cone or the pyramid on the tip of the cathode chip 101 is set to 60 deg.- 85 deg..</p> |
