| 摘要 |
PURPOSE:To accurately guide an ion beam to a sample by providing a detection electrode just in front of the sample. CONSTITUTION:For example, a detection electrode 15 is provided at the upper that of an object pole piece 18. The detection electrode 15 is provided with a permeation hole 14 of several mm.phi that allows passing of an electron beam almost at the center and a hole for passing through an ion beam is provided obliquely at a position far from the central part. The detection electrode 15 is insulated by an insulating spacer 25 and a current detection terminal is taken out at the outside under vacuum from the detection electrode through hermetic seal 17 via a lead wire 16. When the beam does not pass through an ion beam permeation hole 13, ion current flows. Conversely, when the beam fully passes through the center, the ion is not bombarded on the detection electrode 15 and current does not flow. The axial shift of the ion beam can be known by always measuring current while irradiation is continuing. |
