Real-time monitoring of the Bragg peak location of carbon ions is urgently required for the quality control of hadron therapy. In this study, we design an annular detector to monitor the Bragg peak location of carbon ions with Geant4 simulation. This 360° surrounding structure has a high detection efficiency for the small-dose situation. The detector consists of a multilayered collimator system and an NaI scintillator for prompt gamma counting. The multilayered collimator includes a lead layer to prevent unwanted gammas and the paraffin and bo...
