An Innovative Proton Tracking System for Qualification of Particle Beam in Real-Time

This paper describes an innovative beam diagnostic and monitoring system composed of a position sensitive detector and a residual range detector (RRD), based on scintillating optical fibers and on an innovative read-out strategy and reconstruction algorithm. The distinguishing feature of these detectors is the possibility to work in imaging conditions (i.e., a particle at a time up to one million particles per second) and in therapy conditions up to one billion particles per second. The combined use of the two detectors allows the particle radiography of an object. In therapy conditions, in particular, the system measures the position, the profiles, the energy and the fluence of the beam. The position detector consists of two identical overlying and orthogonal planes each of which consists of two layers of prealigned and juxtaposed scintillating fibers. The 500 μm square section fibers are optically coupled to two silicon photomultiplier (SiPM) arrays using a channel reduction system patented by the Istituto Nazionale di Fisica Nucleare. The RRD consists of 60 parallel layers of the same fibers used in the position detector each of which is optically coupled to an SiPM array by wavelength shifting fibers. After being fully characterized at CATANA proton therapy center, the performance of the prototypes was tested at Trento Institute for Fundamental Physics and Applications, Italy, proton irradiation facility in June 2016.