Yield calibration stability of a Si(Li) X‐ray detector system in a PIXE experimental setup over a period of 3 years in the 0.9–9.5 keV photon energy range

Abstract

AbstractRelative experimental detector yields and yield ratios measured on mono‐ and bi‐element standard samples from 1984 to 1987 are presented. Above 3 keV photon energy the yields show good long‐term reproducibility. For example, the spread of 38 single yield measurements on the Au Lα x‐ray line is 1.5%. No temporary changes are observed. In contrast, the measured yields in the photon energy range from 3 keV down to 0.9 keV show distinct temporary changes. At the beginning and end of the measurement period the detector was routinely warmed and re‐pumped in order to ensure a good vacuum in the detector housing. At these times the yields show jumps, which increase with decreasing photon energy up to 20% for Na K x‐rays with 1.041 keV photon energy. Between the detector regenerations the yields show a decreasing tendency with time. This behaviour is attributed to the photon absorption in a varying ice layer on the liquid nitrogen‐cooled Si(Li) detector crystal. After the first regeneration the ice layer thickness was reduced by 0.7 μm. Between the regenerations the ice layer growth rate is estimated to be 0.004 μm per month corresponding to a 0.15 μm ice layer after 35 months. The second regeneration reduced the ice layer by a further 0.22 μm.