Large area polycrystalline diamond detectors for online hadron therapy beam tagging applications

The French national collaboration CLaRyS aims at the on-line monitoring of hadron therapy by means of imaging nuclear reaction products that are related to the ion range. For this purpose, the MoniDiam project is dedicated to the development of a large area detector with a high detection efficiency for the primary carbon or proton beams, giving time and position measurements at count rates greater than 100 MHz. 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 are studied starting with plasma etch thinning and contact metallization done at the LPSC laboratory. Their applicability as particle detector is being investigated using a and β radioactive sources, 95 MeV/u carbon ion beams and short-bunched 8.5 keV photons from the European Synchrotron Radiation Facility (ESRF). This last facility offers unique capability of highly focused beams, the X-ray energy deposition is continuous along the irradiated detector volume. It permits us to mimic the interaction of single ion beams. The possible application of diamonds as a position sensitive detector will be discussed from these radiation tests results. Finally, we focused on the diamond time response and energy resolution measurements. The reported study prefigures dedicated microelectronics developments.