Stability and Radiation Hardness of Plastic Scintillation Detectors for Ultra-High Dose Rate Electron Beam Dosimetry
Abstract
Purpose
Accurate dose measurement in ultra-high dose rate (UHDR) electron beams is essential for clinical quality assurance. Plastic scintillation detectors (PSDs) are promising candidates for UHDR dosimetry but must demonstrate radiation hardness and calibration stability to avoid cumbersome daily dose recalibration. This study evaluates the stability and radiation hardness of PSD prototypes to identify configurations suitable for routine UHDR dose measurements.
Methods
Three PSD scintillators from Medscint, Canada, were evaluated over two weeks using 6MV photon beams delivered by a VersaHD linac. Detector stability was assessed through daily irradiations of 10Gy. Radiation-induced damage was quantified by comparing dose response in conventional electron beams following repeated UHDR irradiations of 500Gy, up to a total dose of 3kGy. Three scintillator types (Scint01, BCF10, BCF60) and two optical fibers (plastic and silica) were investigated.
Results
Over two weeks of daily 10Gy irradiations, response variability was lowest for Scint01 (1.72%), compared with BCF10 (6.20%) and BCF60 (6.72--7.35%). Scint01 demonstrated repeatability within clinical tolerances, whereas other scintillators exhibited a systematic drift that resolved after prolonged rest (two weeks), indicating a reversible dose-history effect. For high-dose deliveries of 500Gy, radiation-induced light transmission loss depended on scintillator and fiber type. BCF60 coupled to plastic fiber showed the highest radiation hardness, with approximately 1% loss at 3kGy, while Scint01 with silica fiber exhibited moderate degradation (approximately 5%). BCF10 with plastic fiber showed substantial degradation (approximately 74%). Stability measurements indicated minimal dependence on fiber type for Scint01.
Conclusion
This study provides systematic evidence of PSD performance under clinically relevant conventionnal and UHDR irradiations. Among tested configurations, Scint01 demonstrated superior calibration stability and acceptable radiation-induced degradation when coupled to a silica fiber, providing the best balance between stability and radiation hardness. This configuration is suitable for routine UHDR dose measurement and supports the clinical implementation of PSD-based UHDR dosimetry.