Development of a range counter with SiPM readout for proton CT

We report on the development of a range counter to be used in a new head scanner developed for proton Computed Tomography (pCT) in support of proton therapy treatment planning. The scanner consists of two silicon telescopes which track the proton before and after the phantom/patient, and an energy detector which measures the residual energy or range of the proton to reconstruct the Water Equivalent Path Length (WEPL) in the phantom. The optimization of the range counter is based on a simulation using GEANT4 and tests of hardware prototypes both in proton beams, beta source, and cosmic rays in the laboratory. Using 3.75 mm thick polystyrene tiles with a silicon photomultiplier (SiPM) attached directly to the 40 cm long scintillator, excellent efficiency and very low thermo-electric noise were observed in the 200 MeV proton beam.