Fast silicon detectors as proton therapy beam monitors

Low Gain Avalanche Detectors (LGADs) are fast silicon sensors with potential for high-resolution proton beam monitoring. In this work, we investigated their response in a 60 MeV proton beam from an AIC-144 cyclotron. Several features of the pulse structure of the cyclotron were observed for the first time. The detector and acquisition system tested was shown to provide accurate flux measurements up to an instantaneous dose rate of about 7.5 Gy/s. Above this, there is an efficiency loss due to multiple protons crossing the detector, which could be addressed through a redesign of the sensors and electronics. LGADs therefore offer a viable alternative for proton therapy beam diagnostics.