First demonstration of a Compton gamma imager based on silicon photomultipliers

We are developing a rugged and person-transportable Compton gamma imager for use in security investigations of radioactive materials, and for radiological incident remediation. The imager is composed of layers of scintillator with light collection for the forward layers provided by silicon photomultipliers and for the rear layer by photomultiplier tubes. As a first step, we have developed a 1/5th-scale demonstration unit of the final imager. We present the imaging performance of this demonstration unit for 137Cs at angles of up to 30° off-axis. Results are also presented for 113Sn and 22Na. This represents the first demonstration of the use of silicon photomultipliers as an embedded component for light collection in a Compton gamma imager.