FEI Quanta FEG 250, User'S Operation Manual, Page: 176 / 228

System Options: Cooling Stage / Waterless Cooling Stage
9-28
The Humidity tab
The Humidity tab is displayed only when the CS is connected to the
feed-through plate connector.
This application controls humidity of wet samples during ESEM
microscope operations with the FEI Cooling Stage installed. It is
possible to do so manually by the sample temperature and specimen
chamber water vapour pressure control. User can set a desired
sample humidity directly via the
Humidity tab.
Note:
A humidity value can also be displayed in the databar.
To start the work and control the humidity follow the steps:
1. Vent the chamber. Install the GSED, if it is not.
2. Insert a wet sample and add water drops when needed.
3. Close the door and pump down the chamber to the ESEM / LoVac
mode.
4. Set the Column module / Pressure (usually 400 Pa).
5. Click the Cooling button.
6. Set the Temperature tab / Target temperature (usually 2 - 5 °C)
and click the Go To button
7. Set Humidity tab / Target humidity (usually 90 - 100%) and click
the Go To button.
Any pressure change causes a target temperature change and vice
versa to keep a desired humidity constant.
Three phase diagram shows a pressure (vertical axis) against actual
temperature (horizontal axis). If the
Go To button either at
Temperature or at Humidity tab is active (which is represented by its
yellow color), moving red line appears in the graph to depict actual
pressure / temperature values.
If the system is at the stable condition, changing target humidity
causes a pressure change.
153 - Cooling Stage Calibration
For precise humidity control this alignment procedure must be
performed.
By obtaining condensation on a sample surface and correction of the
theoretical 100% relative humidity value to the actual conditions, a
temperature difference between thermistor readout and real sample
surface temperature can be minimized (assuming pressure readout is
precise).