Pierre Everaere | Searcharxiv

arXiv2025

Observation of narrow-band $\gamma$ radiation from a boron-doped diamond superlattice with an 855 MeV electron beam

We report the first observation of narrow band 1.3 MeV $\gamma$ radiation from a crystalline diamond micro-undulator. A diamond superlattice was grown with a periodical varying boron doping profile. Four sinusoidally deformed (110) periods resulted with a period length of 5.0 $\mu$m and an amplitude of 0.098 nm. A channeling experiment was performed with the 855 MeV electron beam of the Mainz Microtron MAMI accelerator facility. A clear peak was detected with a large sodium iodide scintillation detector close to the expected photon energy of 1.28 MeV. Key characteristics of the peak, including photon energy, width and intensity, were reproduced fairly well by Monte-Carlo simulation calculations. Based on the latter, optimized boron doping profiles were designed for a hypothetical 3 GeV electron beam, enabling preparation of a highly directional $\gamma$-ray beam with a photon energy of 14.5 MeV. The predicted spectral bandwidth is 13\%, however, with a high energy continuum tail. The on-target photon flux at a beam current of 100 $\mu$A would be about $10^{12}$/s.

physics.ins-det↗

arXiv2021

Performance of CVD diamond detectors for single ion beam-tagging applications in hadrontherapy monitoring

In the context of online ion range verification in particle therapy, the CLaRyS collaboration is developing Prompt-Gamma (PG) detection systems. The originality in the CLaRyS approach is to use a beam-tagging hodoscope in coincidence with the gamma detectors to provide both temporal and spatial information of the incoming ions. The ion range sensitivity of such PG detection systems could be improved by detecting single ions with a 100 ps ($\sigma$) time resolution, through a quality assurance procedure at low beam intensity at the beginning of the treatment session. This work presents the investigations led to assess the performance of Chemical Vapor Deposition (CVD) diamond detectors to fulfill these requirements. A $^{90}$Sr beta source, 68 MeV protons, 95 MeV/u carbon ions and a synchrotron X-ray pulsed beam were used to measure the time resolution, single ion detection efficiency and proton counting capability of various CVD diamond samples. An offline technique, based on double-sided readout with fast current preamplifiers and used to improve the signal-to-noise ratio, is also presented. The different tests highlighted Time-Of-Flight resolutions ranging from 13 ps ($\sigma$) to 250 ps ($\sigma$), depending on the experimental conditions. The single 68 MeV proton detection efficiency of various large area polycrystalline (pCVD) samples was measured to be $>$96% using coincidence measurements with a single-crystal reference detector. Single-crystal CVD (sCVD) diamond proved to be able to count a discrete number of simultaneous protons while it was not achievable with a polycrystalline sample. Considering the results of the present study, two diamond hodoscope demonstrators are under development: one based on sCVD, and one of larger size based on pCVD. They will be used for the purpose of single ion as well as ion bunches detection, either at reduced or clinical beam intensities.

physics.ins-det↗