| 摘要 |
PURPOSE:To remove a contaminant without disassembling a device and changing the vacuum state by supplying heating current to a coil-shaped body which is formed by enclosing a charge current beam channel. CONSTITUTION:When the outside frame (for example, lens yoke) of a coil-shaped heating element 6 is polluted and charge is charged, the electric field is shielded by the coil-shaped heating element 6. Consequently, it does not expand to an electron beam channel and has no effect on the electron beam. On the other hand, when part of the coil-shaped heating element 6 is polluted, the accumulated contaminant is evaporated and removed by switching a switch 7 into (a), connecting the coil- shaped heating element 6 to a power supply 8, and heating the coil-shaped heating element 6 at 1,500 deg.C or more. |
