FEI Quanta FEG 250, User'S Operation Manual

Page: 164 / 228

System Options: Optional Detectors
9-16
ESEM & GASEOUS ANALYTICAL DETECTOR
This detector has both GAD and GSED functionality. The GAD diode
is combined with the needle shaped gaseous SE detector, which
could be used at pressures above 200 Pa.
FIGURE 9-10 ESEM & GAD DETECTOR
QUAD BACKSCATTERED ELECTRONS
DETECTOR (QUAD BSED)
These are four-segment low voltage silicon diode. Either diode has an
active area of approximately 100 mm
2
and is positioned directly
above the sample to obtain maximum detector efficiency.
FIGURE 9-11 QUAD BSED DIODE UNITS
It can be used down to a high voltage about 1 kV and works best at a
slow scan conditions. It can be used in parallel with the LFD, which
allows simultaneous use of SE, BSE and X-ray detectors in a gaseous
environment. It is designated for a HiVac and LoVac imaging.
Installing / Removing the Diode
Follow the Installing / Removing instructions for the standard BSED
(see Chapter 5).
Detector home position
While the Quad BSED detector is not used, it could be placed into a
holder which is mounted on the upper edge of the pole piece, saving it
from a mechanical damage and pollutions.
Caution!
The diode is sensitive to a mechanical damage so the active area
(shiny diode) should never be touched.