A digital system for ‘‘optimum’’ resolution in x-ray spectroscopy

Abstract

This paper describes an experimental setup for spectroscopy measurements based on the digital processing of samples obtained by digitizing the signal pulse as it appears at the output of a proper conditioning circuit. The system shares with conventional pulse-height analysis systems the connection to the detector and the preamplifier, but differs from them as it uses an antialiasing filter and a digitizer instead of a shaper and a multichannel analyzer. The implemented algorithm maximizes the signal-to-noise ratio in the estimate of the amplitude of the signal pulse and represents the digital counterpart of the optimum analog processor stated by the theory of the optimum filtering. The system is able to synthesize the best possible filter through the on line measurement of the noises actually present in the experiment, thus leading to the best resolution and allowing a total flexibility in adapting to changeable noise conditions. The performance of the digital system in terms of resolution is investigated and its count rate capability is mentioned. In particular, an improvement in energy resolution of more than 10% has been experimentally achieved with respect to conventional systems based on analog circuitry. All the components of the system are described and, as an example of application, the energy spectrum of 241Am is acquired and reported.