Directionality in the GammaTracker Handheld Radioisotope Identifier

Several computationally simple methods are presented for determining the direction to one or more radiation sources using the GammaTracker handheld radioisotope identifier. GammaTracker will display a heading indicating the direction to one or more sources; no gamma-ray images will be shown to the user. The details of each directionality method are presented and performance is compared using radiation transport simulations of gamma-ray point sources at varying activity levels on a natural background. All methods achieved sufficiently high pointing accuracy and precision in the tested scenarios, which included background-to-source ratios up to 10:1. The prospects for implementation in the GammaTracker firmware architecture are discussed.