Compton imaging in a high energetic photon field

Through the well defined range of charged particles in matter, cancer irradiation by means of ions can be very tumor conformal. However, external range verification is needed to fully exploit the advantages of ion beam therapy. Nuclear interactions between the projectiles and targets result in excited nuclei which emit photons in the MeV energy range during deexcitation. With a Compton camera, it should be possible to image the origin of these photons which is correlated to the beam position. A prototype Compton camera comprising CdZnTe layers and scintillation detectors has been developed and tested with radioactive point sources. In this work, the performance of the camera is tested at a tandetron beam line in a clean radiation field of 4.44 MeV photons. It was shown that Compton imaging at this energy is feasible.