Amorphous Silicon Detectors for Proton Beam Monitoring in FLASH Radiotherapy

Ultra-high dose rate radiation therapy (FLASH) based on proton irradiation isof major interest for cancer treatments but creates new challenges for dosemonitoring. Amorphous hydrogenated silicon is known to be one of the mostradiation-hard semiconductors. In this study, detectors based on this materialare investigated at proton dose rates similar to or exceeding those requiredfor FLASH therapy. Tested detectors comprise two different types of contacts,two different thicknesses deposited either on glass or on polyimide substrates.All detectors exhibit excellent linear behaviour as a function of dose rate upto a value of 20 kGy/s. Linearity is achieved independently of the depletioncondition of the device and remarkably in passive (unbiased) conditions. Thedegradation of the performance as a function of the dose rate and its recoveryare also discussed.