A diamond beam-tagging hodoscope for online range monitoring in hadrontherapy
Résumé
The efficiency of hadrontherapy could benefit from an online ion range monitoring. This work focuses on a CLaRyS collaboration development: a diamond-based hodoscope in the context of Prompt-Gamma range verification. It aims to provide temporal and spatial tagging of incoming ions. To perform bunch-by-bunch tagging with the best time resolution achievable, the hodoscope has to be very fast and radiation hard. Chemical Vapor Deposition (CVD) diamond detectors exhibit intrinsic properties that would satisfy these requirements. Single channel detectors made of single-crystal and polycrystalline diamonds together with Diamonds grown On Iridium (DOI) have been built. For the two last ones, 2 × 8 channels single diamond double-side stripped prototypes have also been tested. Diamond detectors were characterized with 68 MeV protons at ARRONAX-Nantes and with 8.5 keV X-rays micro-beam at the ESRF-Grenoble. In ARRONAX, a 59 ps RMS Time-of-Flight resolution was measured between a single-crystal diamond and a DOI sample. Using X-rays, a 103 ps RMS intrinsic timing resolution was achieved on a polycrystalline CVD stripped prototype. In addition to time measurements, the 68 MeV proton beam was used to evaluate the single proton detection efficiency on the polycrystalline CVD and DOI samples. Results were found to be 92% for the polycrystalline against 50 % for the DOI. The detection efficiency of the polycrystalline stripped sample was measured at ESRF. A 100% bunch detection efficiency was easily achieved at strip crossings but severe drops were observed in the inter-strip gaps highlighting a too wide (100 µm) gap (present prototype design). These results encourage the prototyping of a new demonstrator equipped with four stripped diamond sensors (single or polycrystalline) read by a dedicated fast readout integrated electronics developed at LPSC.