The schematic in Figure 3811a illustrates the components of an entire EDS system.
Figure 3811a. Schematic illustration of the components of an entire EDS system.
Overall, each absorbed X-ray photon generates a charge cloud that is composed of a number of electron-and-hole pairs, and the charge carriers are moved due to high voltage and are collected in the detector. The charge-sensitive preamplifier (PA) converts the charge pairs into a voltage pulse. The pulse is amplified and shaped in a spectroscopic amplifier (SPA). In this SPA process, one needs to optimize some constants such as gain, shaping time, pole zero, and base-line. The maximum of the intensified pulse is detected or stretched by peak-detector or peak-stretcher (PS). Finally, each pulse is individually measured with an analog-digital converter (ADC).
The main functions of the LN2 device in EDS systems in EMs are to reduce thermal e-h pair, prevent the Li atoms from diffusing, reduce noise in the FET (Field Effect Transistor) preamplifier, and optimize the energy-resolution. Figure 3811b shows the schematic illustration of an EDS detector with a FET preamplifier.
Figure 3811b. Schematic illustration of EDS detector.