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3.4.1
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(2) Setting electron optical system parameters on DETAIL
The DETAIL menu provides a consolidated view of all parameters related to the electron
optical system, including Vacc, Filament Current, Gun Bias, Probe Current, WORKING
DISTANCE, automated functions (AFS and ABC), and DeGauss.
Fig. 3.4-2 DETAIL Window
The following methods can be used to set parameters:
(a) Setting a Gun Bias
The emission current can be adjusted by varying the bias voltage for the electron gun.
The bias voltage can be changed from 0 to 100 by pressing the slider. The higher the
value, the lower the emission current. To increase the emission current, set the gun bias
low. Conversely, for a low emission current, set the gun bias to high. For a standard
imaging environment, set a maximum emission current of 130 µA. Hitachi recommends
the use of the Auto Gun Bias function as described below for most operating conditions.
(b) Setting an Auto Gun Bias
The Auto Gun Bias function corrects any change in emission current when the
accelerating voltage is changed so that imaging can be done at a fixed emission current
of approximately 100 µA. Normally, this function should be used with the checkmark on.