A real-time, large area, high space resolution particle radiography system

In this paper we describe a new detection system for the high resolution measurement of the residual range of charged particles, designed and developed with the aim of achieving real-time data acquisition and large detection areas. A prototype of the residual range detector, with a sensitive area of about 4 x 4 cm(2), consisting of a stack of sixty ribbons of scintillating fibers (Sci-Fi) has been designed and tested. Each layer is read-out by two wavelength shifter (WLS) fibers and a position sensitive photomultiplier (PSPM). The Bragg peak shape is calculated real-time by the time over a suitable threshold for each channel. The results of the measurements taken using the prototype and a 62 MeV proton beam and a comparison with the GEANT4 simulations of the detector are presented. The main concepts on which the prototype is based have been used to demonstrate the technique patented by the INFN. The next step will be to design and validate the final detector which will have 30 x 30 cm(2) FOV and cover the 250 MeV proton range with about 150 micron range resolution. These performances are suitable for almost all medical imaging applications.