| 摘要 |
<p>Normal operation such as observation or etching can be carried out parallel with measurement of flow impedance without changing the emission current. Before the device is operated, the relationship between the emission current variation ΔIe and the suppression voltage variation ΔVsup in a state where the extraction voltage Vext is fixed is stored as a function ΔIe=f(ΔVsup) in a storage unit (113). When the flow impedance is measured, the suppression voltage variation ΔVsup of when the extraction voltage Vext is varied by ΔVext in a state where the emitter current Ie is fixed. By using the voltage variations ΔVext and ΔVsup and the function retrieved from the storage unit, the flow impedance ΔVext/ΔIe is calculated.</p> |
