AN IMPROVED SI(LI) DETECTOR RESPONSE FUNCTION

An improved Si(Li) detector response function model over the range from 5 to 60 keV has been developed. The values of the model parameters are obtained by least-squares fitting of the pulse-height spectra from a number of pure-element samples excited by Cd-109 or Am-241 sources. Simple functional forms of the separable parts of the detected X-ray pulse-height spectrum as functions of incident energy are summed to produce the generalized response function. Compared to previous work [Nucl. Instr. and Meth. A243 (1986) 121, ref. [1]] the following changes and improvements have been made: (1) the entire useful energy range of the Si(Li) detector from 5 to 60 keV is treated rather than the previous upper limit of about 20 keV, (2) a Compton-scattering continuum function from both the detector and the surrounding material has been added to account for the additional features observed with high-energy X-rays, (3) consideration of radiative Auger satellite X-ray lines has been found to account for the previously observed discrepancy in the model parameters for K-alpha and K-beta X-rays, (4) the resulting generalized detector response function has a much simpler and more consistent form than the previous one, ref. [1] and (5) the new model parameters expressed as functions of energy are more consistent with physical phenomena than before and are just fitted polynomials. Applications of the new Si(Li) detector response function are discussed.