A 100 ps TOF detection system for on-line range-monitoring in hadrontherapy

International audienceOnline Range monitoring is crucial to increase the precision of treatment delivery in hadrontherapy. This workdescribes the development of a TOF-resolved (time-of-flight) Prompt Gamma (PG) imaging system with 100 ps timeresolution. The system consists of a diamond-based beam hodoscope for single proton tagging, operated in timecoincidence with one or more gamma detectors placed downstream of the patient. The TOF between the protontrigger in the hodoscope and the PG trigger provides an indirect measurement of the proton range in the patient witha precision strictly related to the system time resolution.We already developed a single channel version of this detector based either on BaF2 or LaBr3 scintillators of largevolume (~38 cm3). The detector was tested using 68 MeV protons impinging on a heterogeneous PMMA target withan air insert of variable size. From the PG TOF spectra we were able to detect the position and width of the air insert:with this approach a 3 mm shift can be detected at 2s within a single irradiation spot (~108 protons). For the BaF2 weobtained a coincidence time resolution of 102 ps σ.We are conceiving a multi-channel version of our system consisting of ~30 pixel detectors of reduced sizesurrounding the target region. Knowing the PG hit position and time of arrival it is possible to reconstruct analyticallythe longitudinal PG vertex on an event-by-event basis. The center of gravity of the hit detectors provides the vertexcoordinates in the transverse plane. We are currently studying the expected performances of this detector throughMonte Carlo simulation. At the same time, we are testing different technologies for the pixel detector (standardscintillators or Cherenkov radiators coupled to Silicon PM).We will present the experimental performances in terms of range shift sensitivity of our single channel detector, aswell as the expected performances of the 3D system as obtained from Monte Carlo simulations