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 applications such as 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 limit 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 with custom made circuits. The whole size of each detector is only about 5×5×6cm, and therefore, it can be carried by hand for investigation of nuclear materials in the field such as cargo or nuclear waste reservoirs. The intrinsic efficiency and angular resolution of the compact Compton camera was 1.1467×10^-4 and 17.1° for a 356 keV source and 2.9140 × 10⁵ and 12.8° for a 662 keV source.