Secondary neutron ambient dose equivalent measurement of the wobbling system of a proton beam radiotherapy facility

We assessed the H*(10)/D values of the wobbling system of the first proton beam radiotherapy facility in Taiwan. The H*(10)/D values increased as the wobbling size increased, and these values decreased with increasing distance between the measurement position and isocenter. The H*(10)/D values of the wobbling nozzle proton beam system were higher than those of the uniform scanning system because of the interaction between proton beams and the internal components of the nozzle. The discrepancies in H*(10)/D values between facilities depend on the design of a proton beam line and the operational setup of the irradiated condition. Our experiment can serve as a reference for comparing secondary neutron radiation in wobbling system of the proton beam system.