Speaker
Description
Neutrons are a major source of secondary radiations in particle accelerators, posing significant challenges in radiation protection for research, medical, and industrial facilities. Key concerns include radiation dose exposure (impacting workers and patients) and neutron activation, which affects accelerator components and surrounding materials. Regardless of application, minimizing these risks and improving operational efficiency depends on enhanced characterization of neutron fields during accelerator use. However, achieving regular spatio-temporal monitoring of neutron production remains challenging, as current reference methods—such as activation foils, Bonner spheres, and solid nuclear track detectors—are costly in both economic and human terms, limiting the quantity and quality of available neutron data essential for a better risk management.
To address these limitations, the IPHC-DeSIs team is developing an innovative CMOS-based counter for real-time neutron monitoring. The AlphaBeast CMOS sensor, leveraging XFAB 0.35 µm technology, is a fully integrated device with high photon transparency and optimized for low power consumption. Neutrons are detected from their conversion into protons (fast neutrons, PE converter) and alpha particles (thermal neutrons, 10B converter). Internal thresholds are used to separate the two populations, providing real-time insights into thermal and fast neutron fluxes. Accurate measurements in complex radiation environments requires a comprehensive assessment of the CMOS sensor's response to various particles, including photons, electrons, protons, and alpha particles. To this end, we present a thorough experimental characterization of the AlphaBeast sensor, performed across multiple test beam facilities. Complementary Geant4/GATE Monte Carlo simulations further define the sensor's efficiency and refine the precision of selection criteria for thermal (alpha) and fast (proton) neutron separation. Additionally, we examine various background sources—such as direct neutron interactions within the silicon substrate—and apply necessary correction factors to enhance data accuracy. AlphaBeast’s measurements of fast and thermal neutrons have been validated across diverse facilities, including research cyclotrons, medical (LINAC) and industrial (rhodotrons) accelerators, with results benchmarked against Monte Carlo calculations and CR-39 reference detectors.
The AlphaBeast sensor is a foundational component of an upcoming real-time neutron mapping system dedicated to improving radiation safety in particle accelerators and associated applications. This system envisions a network of connected, autonomous CMOS sensors strategically positioned throughout irradiation facilities, enabling continuous, real-time monitoring of neutron production. It will be instrumental in the on-going Simβ-AD project (BPI-ANDRA), a methodology initiative focused on calculating cyclotron activation to support safe dismantling procedures. By enabling on-line monitoring of secondary neutron production, AlphaBeast sensors offer critical, experimentally verified data to reinforce the reliability of neutron activation models during accelerator operations. This breakthrough promises a significant advancement in radiation safety protocols, offering an affordable, scalable, and highly accurate real-time neutron monitoring solution adaptable across various high-radiation applications.
