A Time-of-Flight based energy measurement system for the LIGHT medical accelerator

The LIGHT proton therapy facility is the first compact Linac that will deliver proton beams up to 230 MeV for cancer treatment. The proton beam is pulsed; pulses repetition rate can reach 200 Hz. LIGHT prototype is currently being commissioned by AVO/ADAM at CERN, while the first full installation is foreseen in 2019. Beam energy translates directly to range penetration in the body, so it is of the utmost importance to monitor it accurately especially for Linacs, since each beam pulse is directly transported to the patient. We present the implementation of a non-interceptive beam energy measurement system based on the Time-of-Flight technique. Unlike state of the art ToF systems this one has been designed to measure autonomously the mean energy of the beam with medical resolution (0.03 %) by processing as little as 1 mu s of data providing the result within 1 to 2 ms over an energy range from 5 to 230 MeV. The first results for beams up to 7.5 MeV are shown.