Evaluation of the detection capability of the recoil electron tracks of 511 keV gamma rays with an advanced Compton camera using an SOI pixel sensor

In the fields of astrophysics and nuclear medicine diagnostics, the use of a 511-keV line gamma rays probe is indispensable. Compton-imaging techniques are suitable for measuring 511-keV line gamma rays because of the high probability of Compton scattering at this energy level. However, a reconstructed image obtained by a traditional Compton camera has false spots because this camera reconstructs an image with smeared rings. On the other hand, an advanced Compton camera can enhance the angular resolution and reduce the background by detecting recoil electron tracks. We focus on a silicon-on-insulator (SOI) pixel sensor with 30 m cells because of its small pixel pitch and high-energy resolution. In this study, we developed a prototype of an advanced Compton camera using an SOI sensor and evaluated its performance for detecting the recoil electron tracks of 511-keV gamma rays.