Quasi-optimum γ and X spectroscopy based on real-time digital techniques

Abstract

An adaptive, self-calibrated instrument for γ- and X-ray digital spectroscopy is proposed and demonstrated. Most of the typical processing features (pole-zero cancellation, baseline restoration, and shaping) are digitally implemented and optimized. Initialization is performed through a software procedure, which makes the system particularly flexible and allows periodical adaptivity. It is shown that spectroscopy performances are achieved even while using low-cost, low-frequency (5 Ms/s), and relatively low-resolution (12-bit) AD converters. The ADC differential nonlinearity (DNL), for example, is improved of two orders of magnitude, as estimated over the Compton shoulder of a 60 Co spectrum, owing to an equivalent built-in sliding-scale effect. Using the system with an high-purity germanium (HPGe) detector a resolution of 1.9 keV FWHM (1.6‰) is obtained on the 1.17 MeV spectral line of a 60 Co source. An Integral Nonlinearity (INL) of 0.3‰ is measured in the range from 0.2 to 2 MeV from the spectral lines delivered by an 152 Eu source in such range.