Accurate efficiency determination of a Si(Li) detector in the Si-K and Au-M absorption edge energy region

Abstract

The particle-induced X-ray emission (PIXE) method with use of thin evaporated and ion-implanted targets and 1H and 4He ion impact, combined with the standard X-ray source technique, is applied to determine the efficiency of a Si(Li) detector in the photon energy range 1.5–150 keV. An existing database for the efficiency determination by PIXE method is discussed in detail. Special care has been devoted to the reliable reproduction of the Si-K and Au-M absorption edge structure which strongly affect the low-energy part (1.5–4 keV) of the efficiency curve. For this purpose, it has been found necessary to measure the thickness of the detector Au contact by the fluorescence method, to fit then uniquely the thickness of a uniform Si dead-layer. It has been also demonstrated that the observed efficiency increases in the intermediate photon energy region (6–20 keV) can be well described assuming the existence of an additional peripheral Si dead-layer. An extended Si(Li) detector model including this effect is proposed. The procedure developed for the efficiency determination is applied to monitor the Si(Li) detector parameters over a year. During which the increase of an ice build-up layer with time was observed.