Correlation Technique for High Sensitivity Detection of 239Pu

The Correlated Variation Method is a technique to improve detection sensitivity by examining the arriving count distribution. Counts coming from background are uncorrelated in time, and across detectors in multi-detector systems; counts arriving from signals correlate across detectors and during the time the source passes through the field of view. This method has demonstrated sub-Currie limit detection. In addition to these correlations, gamma sources with multiple energy peaks also show counts correlated in energy. At least conceptually background fluctuations at one energy should not influence background fluctuations at other energies; adding this additional correlation in the source detection algorithm should enable greater detection sensitivity while lowering the statistical false alarm rate. This addition to the Correlated Variation technique is being used to see if the method's effectiveness in detecting isotopes with multiple peaks, such as 60Co and 239Pu, can be increased. In this paper the results of the effort is shown, with predictions for system sensitivity to 239Pu shown.