Charge identification of nuclear fragments with the FOOT Time-Of-Flight system

FOOT (FragmentatiOn Of Target) is an applied nuclear physics experiment conceived to conduct high-precision cross section measurements of nuclear fragmentation processes relevant for particle therapy and radiation protection in space. These measurements are important to estimate the physical and biological effects of nuclear fragments, which are produced when energetic particle beams penetrate human tissue.A component of the FOOT experiment is the Delta E-TOF system. It is designed to measure energy loss and timeof-flight of nuclear fragments produced in particle collisions in thin targets in order to extract their charge and velocity. The Delta E-TOF system is composed of a start counter, providing the start time for the time-of-flight, and a 40 x 40 cm(2) wall of thin plastic scintillator bars, providing the arrival time and energy loss of the fragments passing through the detector. Particle charge discrimination can be achieved by correlating the energy loss in the scintillator bars with the measured time-of-flight.Recently, we have built a full-size Delta E-TOF detector. In this work, we describe the energy and time-of-flight calibration procedure and assess the performance of this system. We use data acquired during beam tests at CNAO with proton and C-12 beams and at GSI with O-16 beams in the energy range relevant for particle therapy, i.e., from 60 to 400 MeV/u. For heavy fragments (C and O), we obtain energy and time resolutions ranging from 4.0 to 5.2% and from 54 to 76 ps, respectively. The procedure is also applied to a fragmentation measurement of a 400 MeV/u O-16 beam on a 5 mm carbon target, showing that the system is able to discriminate the charges of impinging fragments.