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3 Product and Functional Description | 3.2 Main Components
ZEISS
VP mode characteristics
Pressure regions
VP mode (optional) offers the possibility of an-
alyzing and mapping non-conducting, strongly
gassing or moist specimens without any need
for specimen preparation. In VP mode, the par-
tial pressure in the specimen chamber is be-
tween 10 - 60 Pa (i.e. 0.1 - 0.6 mbar).
Operating
Principle
The pre-vacuum pump
16
and the turbo pump
9
evacuate the specimen chamber
6
.
The roughing backing valve (RBV)
15
opens the connection between pre-vacuum pump and
turbo pump. The turbo isolation valve (TIV)
8
is open. The pressure in the specimen chamber
is measured by a Penning gauge
13
.
The detected pressure values are displayed as System vacuum in the SmartSEM user interface. As
long as the detected pressure in the specimen chamber is not ready for operation, the column
chamber valve is closed in order to separate the specimen chamber from the column.
System Vacuum in VP Mode
The pre-vacuum pump
16
directly evacuates the specimen chamber
6
. The roughing back-
ing valve (RBV)
15
opens the connection between pre-vacuum pump and specimen chamber.
The Turbo isolation valve (TIV)
8
is closed so that the turbo pump
9
is separated from the
specimen chamber. The turbo pump evacuates the lower part of the column via bypass
5
. The
needle valve
11
supplies nitrogen to the specimen chamber. The required variable pressure (VP)
can be set via the Control tab in the Crossbeam SEM control panel. The pressure in the specimen
chamber is measured by the Pirani gauge
12
.
The detected pressure values are displayed as
Chamber = x Pa
in the SmartSEM user interface
(see Crossbeam SEM Control panel > Vacuum tab or Vacuum menu > VP Controls...). As long as
the detected 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.
For switching between HV mode and VP mode see
and
.
28
Instruction Manual ZEISS Crossbeam 350 | en-US | Rev. 3 | 349500-8111-000