Development of a Compton imager based on bars of scintillator

We have developed a compact Compton gamma-ray imager with a large field of view and a low channel-count that is capable of quickly localizing gamma-ray sources in the few hundred keV - several MeV range. The two detector planes (scatter and absorber) employ bars of NaI(Tl) read out by photomultiplier tubes (PMTs) located at each end. The long-range imaging performance has been tested from 392 keV to 1274 keV. An angular resolution measure of 2.72±0.06° and an efficiency of (1.79±0.04)×10−3 at 662 keV is obtained. A 137Cs (662 keV) source equivalent to a 10 mCi source 40 m away can be located in 60 s with an uncertainty of about a degree. No significant degradation in imaging performance is observed for source angles up to 40° off axis.