A compact Compton camera using scintillators for the investigation of nuclear materials

Through its ability to reconstruct high energy (up to several MeV) radiation distributions without using thick mechanical collimation, the Compton camera has been used in many studies like astrophysics, industrial survey, homeland security and medical purposes. Whereas the performance of mechanical collimation decreases with radiation energy, the Compton camera is effective for detecting higher energy radiation. Even though scintillation detectors show high efficiencies, high timing resolution and usability without a cooling device, the bulky size of conventional photomultiplier tubes limits the scope of their applications to gamma-ray imaging. In order to overcome the limitation we constructed a Compton camera, which combined sodium doped cesium iodide (CsI(Na)) scintillators with position sensitive photomultiplier tubes (PSPMTs), which had multiple anodes connected to custom made circuits. The whole size of each detector is only about 5 cm×5 cm×6 cm, and therefore, it can be carried in hand for investigation of nuclear materials at seaports, airports or nuclear power plants. The intrinsic imaging efficiency and angular resolution of the compact Compton camera were 1.7293×10−4 and 17.1° for a 356 keV source and 4.5254×10−5 and 12.8° for a 662 keV source.