| 摘要 |
<p>PROBLEM TO BE SOLVED: To form an electric field necessary and sufficient to introduce a secondary signal to a detecting element side without giving a strong electric field to a sample by arranging a control electrode between a rear step accelerating cylinder and the sample, and giving the positive voltage to the control electrode in relation to the negative voltage given to a protecting electrode and a holder. SOLUTION: A control electrode 28 is added between a protecting electrode 27 and an objective lens 17, and a control voltage power source 36 is applied to the control electrode 28. When the same voltage with a retarding voltage power source 13 is applied to the control voltage power source 36, voltage of the control electrode 28 becomes the grounding voltage, and the nearly same electric field with an electric field in the condition that the control electrode 28 is eliminated is applied to a surface of a sample 12. When the control voltage power source 36 is set zero, a surface of the sample 12 becomes zero. Namely, electric field of the sample surface can be freely controlled by adjusting the control voltage power source 36. When the control voltage power source 36 is fixed, a constant electric field can be applied to the sample surface, but it is desirable that an operator can freely adjust the control voltage power source 36 as a variable power source in response to the kind of the sample 12.</p> |
