Calibration and use of a lithium‐drifted silicon detector for accurate analysis of X‐ray spectra

Abstract

Abstract A detailed study of the performance of a silicon detector system is reported, with emphasis on the feasibility of using such a system for accurate quantitative analysis of X‐ray spectra covering a wide range of photon energies (2.5‐50 ke V). Calibration of efficiency, with an accuracy of ± 0.1% over most of this range, is described. Second order effects in the detection system have been characterized quantitatively, including escape peaks, pulses due to Compton recoil electrons, pulses whose energies are reduced because of incomplete charge collection and sum pulses. This information has been used to devise programs that permit accurate correction of spectra as recorded in a multi‐channel analyzer. Corrections are made for the following factors in turn; sum pulses, the second order effects enumerated above and detector efficiency. An analysis of the formation and distribution of sum pulses that represent close coincidences not resolved and eliminated by the pulse pile‐up rejector is given in an Appendix. Methods are described for removing sum counts, including ‘mixed’ sum counts, from spectra. The removal of these counts reduces the overall count but results in essentially undistorted representations of spectra as they would be recorded in a system having infinitesimal dead‐time. Some recommendations are made for improving the design of silicon detectors for quantitative spectral analysis.