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ZEISS
6 Operation | 6.6 Working with Variable Pressure
6.6.1 Changing to VP Mode
Info
If the VP system has not been used for several days, start with moderate pressure up to 30 Pa
for the first 10 minutes.
Afterwards the vacuum system is conditioned and the VP mode can be used with its full range.
Info
In VP mode, InLens SE detector and SE detector cannot be used. Instead, BSE detector or VPSE
detector are frequently used.
Prerequisite
ü
The microscope is operating in HV vacuum mode
1. In the Crossbeam SEM Control panel, select the Control tab.
2. In the
Variable Pressure
section, set the
VP Target
.
3. Click
VP
.
The following steps are executed automatically:
à
The acceleration voltage decreases to zero, the turbo isolation valve closes and the
roughing backing valve opens.
à
The pressure in the specimen chamber is increased until the selected value is reached.
à
Chamber = x Pa
message in the
Vacuum
tab displays the actual pressure in the speci-
men chamber.
à
Chamber Status = at VP
message is displayed when the target VP is reached.
à
The acceleration voltage is activated.
6.6.2 Returning to HV Mode
HV mode is the standard mode of a FESEM. It offers the possibility of analyzing and mapping con-
ducting specimens. In HV mode, the pressure in the specimen chamber is less than 10⁻⁶ mbar.
Info
A higher pressure can be set within a few seconds. Achieving a lower pressure may require
some more time, because the specimen chamber has to be evacuated by the pre-vacuum
pump.
Info
When switching from VP to HV mode, the column chamber valve closes automatically, as a rel-
atively poor vacuum is available in the specimen chamber when opening the TIV. Due to the
bypass between turbo pump and column area, this could damage the gun.
Prerequisite
ü
The microscope is operating in VP vacuum mode
1. In the Crossbeam SEM Control panel, select the Control tab.
2. In the
Variable Pressure
section, click
HV
.
The following steps are executed automatically:
à
The acceleration voltage decreases to zero and the column chamber valve closes.
à
The pre-vaccum pump pumps the specimen chamber to the lowest possible pressure.
à
The turbo isolation valve opens and the roughing backing valve connects the pre-vacuum
pump and the turbo pump.
Instruction Manual ZEISS Crossbeam 350 | en-US | Rev. 3 | 349500-8111-000
89