OPTO-EDU A63.7069, Instruction Manual

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1.2. Structure Feature and Operating Principle
1.2.1. General Structure
The interaction of between a certain energy electron beam and sample, will produce various
physical signals. The SE detector collects and amplifies secondary electronic signal, then transmit
the signal to electrics console, converts to digital signal. Finally, the computer receives the signal
and form an image. The main structure of A63.7069 are electron optics column, chamber,
automatic vacuum system, electronics and display console, etc.
1.2.2. Electron Optics Column
A63.7069 electron optics column can produce and focus electron beam to form a fine spot on
specimen. The electron optics column consists of electron gun, electromagnetic beam alignment
system, dual condenser lenses, column isolation valve (V1), objective lens, scanning coil assembly,
stigmator and electron detector. The system has one set of electromagnetic shielding column
outside the optical path, which can eliminate the electromagnetic interference from the
environment.
1.2.2.1. Electron Gun
❖
Electron gun is a high brightness electron source, which is a self-biased triple structure. The
filament tip, wehnelt cap hole center and anode hole center are coaxial for the result of
highest brightness. The distance between anode and wehnelt cap is adjustable for high or
low accelerating voltage. Three screws above electron gun are used to adjust the position of
electron gun in order to realize filament alignment (mechanical alignment).
1.2.2.2. Electromagnetic Beam Alignment System
❖
In daily work, the mechanical alignment can not ensure strict alignment of electron beam,
so electromagnetic beam alignment system is also adopted to ensure coincidence of electron
beam and the optical axes. The control of electromagnetic beam alignment system can be
adjusted by software. (Refer to Section 3.4.12. Control Panel of Basic Function for Beam
Alignment.)
1.2.2.3. Dual Condenser Lenses
❖
Electron optics column includes two same condenser lenses. The pole pieces of the two
condenser lenses are installed on the two ends of one cylinder and share one coil. For the
reasons of convenient cleaning and vacuum sealing, a metal liner is set in the middle of
condenser lens. When working normally, inside the liner is vacuum state, outside the liner is