An estimation of the signal‐to‐background ratio, limited by radiation and electron transport in EDXRF

Abstract

A mathematical model for an energy-dispersive X-ray spectrometer is proposed, which is based on the analysis of the radiation transport in a sample and in a detector, and an electron transport in the detector. The results obtained by using this model are compared with experimental data. The influence of parameters of sources of the primary X-rays, and the thickness and material of the detector on the signal-to-background ratios, was estimated. These ratios limited by electron and photon transport were compared. It is shown that the signal-to-background ratio can vary by several orders of magnitude at changing conditions of recording, and there are conditions when the use of Si or Ge detector is preferable.

An estimation of EDXRF spectrometer properties, based on a two‐layer composite Si‐Ge detector

“…A photon coming to the X-ray detector with energy E det may be fully absorbed and transformed into a flux of electrons than produce an impulse of current with charge Q det = C*E det (C is a proportionality factor, see also. [19] ) This current is registered by the electronics as the impulse corresponding to E det . At the same time, the photon may be incoherently scattered by the detector material, or it may escape with energy E det_out , or photons may be absorbed by atoms of the detector upon escape of fluorescent photons from the detector.…”

“…Probabilities of p ph and p comp detection in photo escape peaks and in the Compton escape plateau (correspondingly) are significant at the background formation (Figure 4). According to, [19] variations of the detector thickness mainly affect detection probabilities in full absorption peak p eff and in the Compton escape plateau p comp . Probabilities of detection in the electron loss tail are practically independent of the detector's thickness.…”

“…The model used for simulation of detector radiation spectra includes single radiation/sample interactions: fluorescence, coherent and incoherent scattering, bremsstrahlung of photo-, Auger and Compton electrons produced in a sample. [19] Besides, the model includes a geometrical factor, [17] which is required for definition of scattering angles at small distances between the source, the sample, and the detector. The spectrum registered by the detector is calculated as convolution of spectra incident into the detector and the detector response function.…”

“…According to, [18,19] in case of applying X-ray tubes (with voltage up to 50 kV) for excitation of fluorescence, the signal and the background are slightly dependent on the detector because the background is mainly formed by detection of X-ray tube bremsstrahlung, scattered by the sample. Figure 5 shows the calculated signal and the background in case of irradiation of a copper sample by a radioactive source 109 Cd and detection radiation with single-layer Si, Ge, and composite Si-Ge detectors.…”

“…[1][2][3][4][5][6] An important parameter related to signal-to-background ratio is the response function of a detector; results of its studies are described in. [7][8][9][10][11][12][13][14][15][16] In our publications, [17][18][19] calculation of the response function is done by the Monte Carlo method, taking into account the lowenergy Compton escape plateau. It is shown that signals and backgrounds can be calculated in EDXRF by considering energy transport processes in a sample and in a detector.…”