FEI Quanta FEG 250, User'S Operation Manual

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System Options: Heating Stage 1000 °C / Heating Stage 1500 °C
9-46
Outgassing Samples
Some types of samples may contain compounds which evaporates
under high temperatures. This does not affect the pressure in the
chamber. However, if large quantities of compounds are given off,
they may condense and get on the aperture inside of the GSED
assembly (PLA), and then astigmatism could result. If this happens,
the detector must be cleaned.
Using HS with BSED
If the 1000 °C heating stage is being operated with the BSED (which
should only be installed for temperatures up to 400 °C), the working
distance should be kept greater than 9 mm.
Using the HS with EDX Detectors
There are a number of variables to be taken into account then
selecting operating temperatures for EDX detectors. Some of these
include window materials, window thickness, window support
structure and the closeness of the window.
Above 400 °C the sample begins to radiate infrared light, and this
blinds the EDX detector, preventing further analysis. For this reason,
do not perform elemental analysis above 400 °C. It is also advisable
to retract the EDX detector fully when temperatures above 400 °C are
to be attempted.
Caution!
Be very careful when determining operating temperatures. To avoid
damaging a detector, always consult the EDX manufacturer for
guidelines and operating limits.
Once cooled, swing the heat shield out of the way of the stage. (the
optical image may be helpful to see into the chamber.) Raise the
stage to a working distance of 12 mm (the GSED is 8 mm), then
collect X-rays as usual.
Inclined Crystal EDX Detectors
The detector comes in at a take-off angle (TOA) of 35°, and the
sample is not tilted. This illustration is shown with the high
temperature GSED installed.
FIGURE 9-39 INCLINED CRYSTAL EDX DETECTOR
CONFIGURATION
Positioning the High Temperature GSED
The high temperature GSED must be installed so that the collection
ring does not interfere with the angle of the EDX detector. This can be