On the response function of solid‐state detectors, based on energetic electron transport processes

Abstract

In studies of the response function of state-of-the-art Si(Li) and HPGe detectors to low-energy (2-20 keV) mono-energetic x-rays, various characteristic features have been observed. To trace their origin we have studied the effect of the signal processing electronics on the evolution of the electronic signal, and measured the spectral shape of energetic electrons originating from the surfaces of Si and Ge crystals and front contact materials, using a high-energy range electrostatic electron spectrometer. From the measured electron spectra leaving the surfaces of the detector and front contact materials, and from the details of electron transport processes, the origin of the distinct features is identified and an approximate analytical form for the representation of the detector response function has been derived. It gives an excellent description of the response function and may replace the frequently applied Hypermet function. On the basis of this study, an explanation is given of the origin of the exponential tail and other various discrete structures on the low-energy side of the primary peak. The difference in low-energy side tailing between Si and HPGe detectors is explored. A detailed analysis of the so-called dead layer concept is given. Characteristic structures, 'kinks', are predicted in the spectra measured by solid-state detectors.

Quality Assurance Challenges in X-ray Emission Based Analyses, the Advantage of Digital Signal Processing

“…Furthermore, if the line shape and the low energy tailing are close to those described in Ref. 19 which is expected from the basic physical operation of the detector, then we have a second measure. However, these measures would only relate to the events that the noise filtering and signal recognition algorithms or circuitry deemed to be acceptable.…”

“…This capability was demonstrated in Ref. 19. We have found that many processors produce ghost peaks.…”

“…Our message differs from all previous investigators, as we declare that the signal processor DOES modify the spectra as confirmed by experiments. We recommend the reader look at the spectra presented in the literature [19][20][21][22][24][25][26] to see the large variations.…”

“…19 Comparative spectra are presented. 20,21 The majority of spectra in the literature are similar to the upper curve, with poorer resolution, an exponential tail and a flat plateau towards lower energies.…”

Bremsstrahlung of the free electrons arising in an irradiated specimen

“…As longwave primary radiation is absorbed by the window of an x-ray tube, the background in this spectral region can be caused either by the bremsstrahlung of photoelectrons, Auger electrons, and Compton electrons arising in the irradiated material [1,2] or by the instrumental factors related to incomplete charge collection in detecting short-wave x radiation [3,4].…”