Pulse Pileup Recovery for Energy Dispersive Spectroscopy

Quantitative energy dispersive spectroscopy (EDS) x-ray microanalysis provides important information regarding the distribution of elements within a biological sample. The low elemental concentrations in biological specimens require dwell times of several seconds livetime to obtain spectra with significant statistical information, especially for quantitative EDS imaging. Deadtime caused by the rejection of pulse pileup counts is a major limiting factor of x-ray collection during the acquisition of x-ray spectra. The dwell time can be reduced by 25% or more (depending upon beam current conditions) by recovering rejected pulse pileup counts. This significant reduction in deadtime would increase efficiency (both in cost and time) for the collection of quantitative x- ray data and images from biological samples; such improved instrumentation is not currently available. In Phase I, the real-time recovery of pulse pileup counts will be examined using current analog/digital electronics and a digital signal processor to establish the most effective (cost and performance) method. The Phase II goals will be the low cost realization of a new form of pulse pileup-free microanalyzer based on the Phase I results and its application to quantitative x-ray imaging and data acquisition of biological samples.