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3.3. Principle of operation
The microscope uses a beam of electrons to generate an image or to analyse the specimen. The
focussed electron beam scans the specimen surface.
3.3.1. Vacuum system
For operation of the microscope, gun head (
2
), column and specimen chamber (
8
) have to be
evacuated. The vacuum is essential to operate the gun and to prevent collision of electrons with
gas molecules.
The Crossbeam 340 can be operated in two different modes:
•
High vacuum (HV) mode
•
Variable pressure (VP) mode
Mode
Characteristics
Pressure regions
HV
HV mode is the standard mode of a
FESEM. It offers the possibility of
analysing and mapping conducting
specimens.
In HV mode, the pressure in the speci-
men chamber is less than 10
-6
mbar.
VP
VP mode offers the possibility of
analysing and mapping non-conduct-
ing, strongly gassing or moist speci-
mens without any need for specimen
preparation.
In VP mode, the partial pressure in the
specimen chamber is between
•
10 - 133 Pa with In-lens SE
detector configuration
(i.e. 0.02 - 1.33 mbar)
•
10 - 60 Pa with In-lens Duo
detector configuration
10
-8
mbar
10
-6
mbar
0,01 - 1,33 mbar
10
-6
mbar
Summary of Contents for Crossbeam 340
Page 1: ...Crossbeam 340 Crossbeam workstation Instruction Manual ...
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Page 130: ...NPM çÑ NPQ fåëíêìÅíáçå j åì ä êçëëÄÉ ã PQM ÉåMOE loF NPK aÉÅä ê íáçå çÑ ÅçåÑçêãáíó ...
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