Dead time correction in the DP5 digital pulse processor

Abstract

All X-ray and gamma-ray spectroscopy systems exhibit pulse pile-up and dead time losses arising in the signal processing electronics. To accurately determine the true incoming count rate and spectrum, one must determine and correct for these losses. Many correction methods were developed using analog shaping amplifiers and multichannel analyzers, providing the concepts and terms traditionally used to describe these losses and correction factors. Digital pulse processors have a much higher throughput due to fundamental differences in their deadtime and pile-up characteristics. They also permit improved variations of the traditional correction methods. This paper will highlight key distinctions between analog and digital approaches, the implementation used in Amptek’s DP5 digital pulse processor, and show measured results. The DP5 was designed to support Amptek’s silicon drift diodes, operating at input count rates up to 10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">6</sup> s <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">−1</sup> at a peaking time of 0.6 μs with an accurate determination of input spectrum and count rate. Several different deadtime correction algorithms and pile-up rejection algorithms were tested for the DP5 and their measured performance will be presented.