Radiochromic responses of Gafchromic EBT3 film under neutron exposure

Abstract

The response of Gafchromic^TM EBT3 films to moderated and fast neutron fields was systematically investigated to assess their potential for neutron detection. The reliability of the EBT3 films in high-resolution neutron dosimeters makes them suitable for applications in neutron-based radiotherapy, where accurate neutron fluence mapping is critical for treatment planning and verification. The film responses were quantified by flatbed scanning using color channel analysis and UV–Vis absorption spectroscopy for the determination of optical properties such as band gaps and Urbach energy. Both moderated and fast neutrons induced a measurable change in optical density, demonstrating the intrinsic neutron sensitivity of the film through internal conversion mechanisms (proton recoils and ${}^6\text{Li}\left(n{,}^3\text{H}\right)\alpha$ reaction). Flatbed scanning analysis demonstrated a useful dynamic range in the Red, Green, and weighted Gray channels that was highly correlated with neutron fluence. The moderated neutron setup exhibited a significantly higher response and faster transition to saturation compared to the fast neutron setup. This elevated sensitivity is attributed to the coincident dose contribution from associated prompt and delayed gamma radiation inherent in the moderated field, highlighting a challenge for neutron-only dosimetry. Results showed that Urbach energy is a highly sensitive parameter, superior to that from standard optical density and band gap measurements, for characterizing the structural effects of neutron irradiation, offering an adjunct technique to complement traditional fluence estimation.