Silicon photomultiplier choice for the scintillating fibre tracker in second generation proton computed tomography scanner

Scintillating fibers are capable of charged particle tracking with high position resolution, as demonstrated by the central fiber tracker of the D0 experiment. The charged particles will deposit less energy in the polystyrene scintillating fibers as opposed to a typical silicon tracker of the same thickness, while SiPM's are highly efficient at detecting photons created by the passage of the charged particle through the fibers. The current prototype of the Proton Computed Tomography (pCT) tracker uses groups of three 0.5 mm green polystyrene based scintillating fibers connected to a single SiPM, while first generation prototype tracker used Silicon strip detectors. The results of R&D for the Scintillating Fiber Tracker (SFT) as part of the pCT detector are outlined, and the premise for the selection of SiPM is discussed