A silicon pixel detector system as an imaging tool for proton beam characterization

High energy protons represent a very promising alternative in the tumor irradiation, as respect the photon and electron beams. In Italy, the first and at present the only proton-therapy facility, CATANA (Centro di AdroTerapia e Applicazioni Nucleari Avanzate), was built in Catania, at the Istituto Nazionale di Fisica Nucleare-Laboratori Nazionali del Sud (INFN-LNS). Here a 62 MeV proton beam, produced by a Superconducting Cyclotron (SC), is used for the treatment of shallow tumors like those of the ocular region. A beam monitoring system, based on ion chambers for dose monitoring and on silicon diodes scanning the beam cross section for the beam quality control. Moreover, gaf-chromic films are used to measure the geometric features of the beams. Even though these systems are stable and reliable, nevertheless they are time consuming and, in the gas-chromic film case, they require an off-line analysis. In this paper we present a feasibility study for using a silicon pixel detector as device for proton beams imaging and characterization. We present the performance of such a device exposed to the CATANA proton beam in terms of dose, dose rate and exposure time response.