GUN对中

工程师这么说的：新灯丝以灯丝像为主，旧灯丝以亮度为主。

但按照TECNAI本身提供的对中程序是以亮度为准的.

The following alignment procedures exist:
Gun

Gun tilt :
Purpose: The gun tilt makes sure that the electron beam from the gun comes down parallel to the optical axis, so that no electrons from the beam are lost before they can be used for imaging, etc.
Importance: ESSENTIAL for having sufficient beam intensity.
Method: Obtain maximum intensity.

Gun tilt pivot point

Gun shift:
Purpose: Shift the electron beam sideways so that it comes down along the optical axis.
Importance: ESSENTIAL for minimizing movements between different spot sizes and for having the beam correctly along the optical axis for all spot sizes.
Method: Minimize spot displacement when spot size (that is focal length of C1 lens) is changed.

Spot-size dependent gun shift

一般新灯丝对中好了也就是最亮的状态吧。

如果你使用的是FEG，你看不到灯丝像。gun-tilt以最亮为标准，照明束的对称由gun-shift来完成。注意，这是一个反复的过程，你需要再gun-tilt和gun-shift之间反复几次。