Determination of the solid angle of an Si(Li) detector

Abstract

Radial and longitudinal scanning of x-ray detectors with a 55 Fe source is a widely used method for determining their dimensions and position within the cryostat and thence deducing solid angle in an analytical arrangement. The scanning method is refined here to take account of various effects and issues hitherto ignored and therefore reducing its accuracy; these include finite source size, collimator 'channelling,' and uncertainty as to the correction for x-ray attenuation in the intervening air. With proper attention to these effects, it is possible to determine the window-crystal distance to an accuracy of about 0.2 mm; this translates into an accuracy of about 3% for solid angle when the source-detector distance is about 25 mm. However, uncertainty remains in calibrating an analytical system, owing to lack of knowledge of the actual construction of any internal collimator.

Atomic spectrometry update. X-ray fluorescence spectrometry

“…The Bremsstrahlung from the samples made the method unsuitable for energies less than 4 keV, which is unfortunately where a reliable and accurate response function becomes increasingly important. For truly standardless EDS and EDXRF spectrometry, the true solid angle of the detector is an important parameter and Hopman and Campbell 19 described a method for its determination to greater accuracy. The method, in which a point source was scanned across the detector, was refined to account for the oft-ignored effects of finite source-size, collimator ''channeling'' and X-ray attenuation by air.…”