Abdolkazem Ansarinejad - Istituto Nazionale di Fisica Nucleare (INFN), via Giuria ۱, ۱۰۱۲۵ Torino, Italy Dipartimento di Fisica Sperimentale, Universita’ di Torino, via Giuria ۱, ۱۰۱۲۵ Torino, Italy Presently at the Nuclear Science Research School, Nuclear Science
Marco Donetti - Fondazione CNAO, strada Campeggi, ۲۷۱۰۰ Pavia, Italy
Maria Adelaide Garella - Fondazione CNAO, strada Campeggi, ۲۷۱۰۰ Pavia, Italy
Simona Giordanengo - Fondazione CNAO, strada Campeggi, ۲۷۱۰۰ Pavia, Italy

Introduction Hadron-therapy is an effective technique used to treat tumors that are located between or nearby vital organs. The Italian National Center of Oncological Hadron-therapy (CNAO) has been realized as the first facility in Italy to treat very difficult tumors with protons and Carbon ions. The on-line monitor system for CNAO has been developed by the Department of Physics of the University of Torino and Italian National Institute of Nuclear Physics (INFN). The monitoring system performs the on-line checking of the beam intensity, dimension, and beam position. Materials and Methods The monitor system is based on parallel plate ionization chambers and is composed of five ionization chambers with the anodes fully integrated or segmented in pixels or strips that are placed in two boxes. A series of measurements were performed that involve the background current and the detectors have been characterized by means of a series of preliminary testes in order to verify reproducibility and uniformity of the chambers using an X-ray source. Results The measured background currents for StripX, StripY and Pixel chambers are five orders of magnitude smaller than the nominal treatment current. The reproducibility error of chambers is less than 1%. The analysis of the uniformity showed that the monitor devices have a spread in gain that varies, but only about 2%. Conclusion The reproducibility and the uniformity values are considered as a good result, taking into account that the X-ray energy range is several orders of magnitude smaller than the particle energies used at CNAO.

Active Beam Delivery System, Hadron Therapy, Ionization Chamber, On-Line Detectors