Detection of X-Rays with a Si Li Detector

The width F is indicated as electronic noise in Fig. 12.41. Of the three types of X-ray detectors mentioned—scintillation, proportional, and semiconductor counters—the Si(Li) detector has the best energy resolution for X-rays. This fact is demonstrated in Fig. 12.42, which shows the same energy peak obtained with the three different detectors. Notice that only the Si(Li) detector can resolve and lines, an ability absolutely necessary for the study of fluorescent X-rays for most elements above oxygen. The manganese fluorescence spectrum obtained with a Si(Li) detector is shown in Fig. 12.43 

1 = Photon energy(eV) w = (average energy to create hole-electron pair at LN temperature) 

The dependence of Si(Li) detector efficiency on the X-ray energy is shown in Fig. 12.44. For E 3 keV, the efficiency drops because of absorption of the incident X-rays by the beryllium detector window. For 15 keV, the efficiency falls off because of the decrease of the total linear attenuation coefficient of X-rays in silicon (Fig. 12.45). 

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