| 摘要 |
PURPOSE:To prevent generation of false signal from reflected beams, by forming an electron gun with an electrode facing the target formed in a cone being smaller as approaching the target, in order to avoid return beams to hit the electrode plate of the electron gun. CONSTITUTION:At the electrode plate 8 of an electron gun is arranged a conical electrode 80 which is connected with the electrode 8 electrically. A deflecting electrode 5 is applied with 300V d-c voltage while, the electrode 80 with 105V voltage, for example. This potential difference makes a static deflection electric field between the electrode 5 and electrode 80, so that return beams 10 from the target will flow outside the electrode 80 to the tube wall 1 side, passing through a space between the electrode 8 and the tube wall 1. Therefore, no return beam reflection occurs, generating no reflected beam to the target. |
