In EMs (electron microscopes), the X-ray signals are detected with EDS detectors placed close to the specimens inside the objective lens of the microscopes.
Figure 3992 shows the position of the EDS detector in a TEM system in combination with a stray aperture. The stray aperture is used to protect the specimen from the impingement of x-rays because it can strongly absorb the signals from stray radiation and thus, improves the accuracy of the measurements.
Figure 3992. Schematic illustration of stray aperture for accurate EDS measurements in TEM system.
X-rays cannot be deflected into an appropriate detector so that their collection is always inefficient (usually < 1%) and thus signal intensity is a problem from a thin specimen.