Radioluminescence properties of rare earth doped LiF-MgF₂ compounds for fiber optic dosimetry

This work investigates the radioluminescence (RL) properties of LiF-MgF₂ compounds doped with rare earth (RE) ions (Eu, Ce, Lu, Tm) for their potential use in fiber optic dosimetry (FOD). Polycrystalline powders were synthesized via a two-step thermal treatment and tested under beta and clinical LINAC X-ray irradiation. Among all compositions, the Eu-doped sample at 0.4mol% (LiF-MgF₂:Eu) showed the highest RL yield, excellent repeatability, and no significant signal afterglow, making it the most promising candidate. The RL spectrum of LiF-MgF₂:Eu revealed broad emission bands attributed to intrinsic defects and Eu-related transitions. An FOD probe was constructed using this material and evaluated under clinical 6 MV LINAC irradiation. Time-resolved measurements confirmed the feasibility of the time-delayed readout method to suppress the Cherenkov stem effect. Percentage depth dose (PDD) curves obtained with the FOD probe showed good agreement with those measured using a reference ionization chamber and Monte Carlo simulations. These findings suggest that LiF-MgF₂:Eu is a suitable, tissue-equivalent scintillator for real-time dosimetry in LINAC radiotherapy.