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3 Product and Functional Description | 3.2 Main Components
ZEISS
3.2 Main Components
3.2.1 Vacuum System
Purpose
For operation of the microscope, the gun head, the column, and the specimen chamber have to
be evacuated. The vacuum is essential to operate the gun and to prevent collisions of electrons
with gas molecules.
1
2
3
4
5
8
9
10
6
7
Fig. 10: Schematics of the vacuum system
1
Gun with filament
2
Gun head
3
Multihole aperture
4
Column chamber valve
5
Turbo pump
6
Sigma 300 and Sigma 500 have one ion
getter pump, Sigma 300 VP and Sigma
500 VP have two ion getter pumps, as
shown here
7
Specimen chamber
8
9
Vent valve
10
System Vacuum
The pre-vacuum pump
10
and the turbo pump
5
evacuate the specimen chamber
7
.
The vacuum in the specimen chamber is measured by a Penning gauge
8
. The detected vac-
uum values are displayed as
System vacuum
in the SmartSEM user interface. As long as the de-
tected pressure in the specimen chamber is not ready for operation, the column chamber valve
4
is closed in order to separate the specimen chamber from the column.
Gun Vacuum
In the gun head, an ultra high vacuum is maintained by ion getter pumps
6
. The vacuum in
the gun head is displayed as
Gun vacuum
in the SmartSEM software. It should be below
1 × 10⁻⁸ mbar.
Venting
The specimen is located in the evacuated specimen chamber. To open the specimen chamber for
specimen exchange, you have to break the vacuum in a controlled manner. This is done by the
Vent
command via the SmartSEM user interface or by pressing the
Exchange
push button on the
optional control panel.
30
Instruction Manual ZEISS SIGMA series | en-US | Rev. 7 | 352102-9344-006