Positive SNM Gamma Detection Achieved Through Synthetic Enhancement of Sodium Iodide Detector Spectra

We have developed a new algorithm, ASEDRA, to post-process scintillator detector spectra to render photopeaks with high accuracy. ASEDRA, or ldquoAdvanced Synthetically Enhanced Detector Resolution Algorithm,rdquo is currently applied to NaI(Tl) detectors, which are robust, but suffer from poor energy resolution. ASEDRA rapidly post-processes a NaI(Tl) detector spectrum over a few seconds on a standard laptop without prior knowledge of sources or spectrum features. ASEDRA incorporates a novel denoising algorithm based on an adaptive Chi-square methodology called ACHIP, or ldquoAdaptive Chi-quare Processed denoising.rdquo Application of ACHIP is necessary to remove stochastic noise, yet preserve fine detail, and can be used as an independent tool for general noise reduction. Following noise removal, ASEDRA sequentially employs an adaptive detector response algorithm using detector Monte Carlo data to remove the spectrum attributed to specific gammas. Tests conducted using a 2rdquo times 2rdquo NaI(Tl) detector, along with a HPGe detector demonstrate the accuracy of ASEDRA for both photopeak identification and relative yield. In this paper, we present successful results for both WGPu and natural uranium Special Nuclear Materials (SNM) sources, comparing key photopeak energies and intensities to known values. Moreover, the denoising and synthetic resolution enhancement algorithms can be adapted to any detector. ACHIP and ASEDRA are covered under a Provisional Patent, Registration Number #60/971,770, 9/12/2007.