Development of a Proton Tomography scanner

iMPACT, innovative Medical Proton Achromatic Calorimeter and Tracker, is a University of Padova and INFN research project, funded by the European Research Council. The project aims to design, develop and prototype a fast and accurate proton Computed Tomography (pCT) Scanner, with the ultimate goal of demonstrating the technology necessary to realize a clinically viable pCT system. The overall development, current state, and projected performances of the scanner will be illustrated and discussed. Monte Carlo simulation, a selection of data collected with cosmic rays, and tests with a proton beam will be reviewed as well to quantitatively assess the performance of the apparatus. Preliminary studies on proton track reconstruction, based on a Maximum Likelihood path formalism, will be also presented, together with a supporting object shape identification algorithm. The iMPACT scanner is essentially made by a multi-layer silicon pixels sensors tracker stage using the ALPIDE sensors, and a scintillators-based range calorimeter. There will be an in-depth review of the innovative, highly segmented structure of the calorimeter, based on multiple, orthogonal scintillating elements, and of its read-out architecture, which exploits massive FPGAs parallelism and distributed memory to achieve the triggering and data collection performance necessary to cope with the extremely high event-rate requested by pCT applications. On the tracker side, an overview of the ALPIDE sensor, developed within the ALICE Collaboration for its Inner Tracking System (ITS), and currently adopted for the prototyping phase of the iMPACT tracker, will be illustrated as well, together with the general tracker layout and operations. In parallel, in order improve upon the techniques and methods used in particle physics for tracking purposes, specific studies have been performed to optimize the ALICE ITS alignment, which results will be also presented. Finally, a brief mention will be given to the INFN project ARCADIA, focused on the development of innovative Monolithic Active Pixel Sensors characterized by fully depleted substrate to improve the charge collection efficiency and timing characteristics over a wide range of operational and environmental conditions. The iMPACT project in fact plans to employ the ARCADIA technology to build a pixel detector more suited for the pCT application respect to the ALPIDE sensor.