Large Area Polycrystalline Diamond Detectors for Online Hadron Therapy Beam Tagging Applications

International audienceThe MoniDiam project of the LPSC laboratory is part of the French national collaboration CLaRyS for the on-line monitoring of hadron therapy. It relies on the imaging of nuclear reaction products that is related to the ion range. The goal here is to provide large area detectors with a high detection efficiency for carbon or proton beams giving time and position measurement at count rates greater than 100 MHz (beam tagging hodoscope). High radiation hardness and intrinsic electronic properties make diamonds reliable and very fast detectors with a good signal to noise ratio. Commercial Chemical Vapor Deposited (CVD) diamonds were studied starting with plasma etch thinning and contact metallization done at the LPSC laboratory. Their applicability as particle detector was investigated using α and β radioactive sources, 95 MeV/u carbon beams and short-bunched 8.5 keV photons from the European Synchrotron Radiation Facility (ESRF). This facility offers unique capability of highly focused beams. The energy deposition is uniform in the irradiated detector volume. It permits us to mimic the interaction of single ion beams. A time resolution ranging from 20 ps up to 40 ps and an energy resolution ranging from 7 % up to 10% were measured. It permitted us to conclude that polycrystalline CVD diamond detectors are good candidates for our beam tagging hodoscope development. The final detector will consist in a ~15×15 cm2 mosaic arrangement of stripped diamond sensors read by a dedicated integrated fast read-out electronics (~1800 channels)