| 摘要 |
PURPOSE:To prevent a charge-up, by making an arrow pattern deflecting electrode, which is the focusing electrode concurrently, at a negative potentials constantly in the operation. CONSTITUTION:The length x of an electrode G4 is selected to make its potential negative constantly even though the deflecting voltage is overlapped. At the 2/3 inch tube (tube bore phi=16mm), with a length l from the beams control opening LA to the mesh-form electrode G6 is l=42mm, for example, the length x is selected as x<=1/4l, for example. In such a way, since the potential of the electrode G4 is kept constantly negative during the operation, the returning electrons and the like cannot approach to the electrode, expelled by a Coulomb's power. Therefore, a charge-up can be prevented, and no focusing gap is produced owing to such a charge-up. |
