This project aimed at developing a robotic pencil beam scanning (PBS) system for preclinical proton FLASH on a fixed beamline. Initial work using a Python-controlled robotic arm to move a mouse phantom through a proton beam revealed issues with the aluminum collimator: excessive radiation leakage and an ill-defined aperture. A new brass collimator with a 5mm x 5mm aperture was designed and constructed using electric discharge machining (EDM) to minimize leakage and create a precise aperture. Gafchromic EBT-3 films were irradiated with 230 MeV protons at a FLASH dose rate of 120 Gy/s using both collimators to compare leakage. TOPAS Geant4 Monte Carlo and MatRad simulations were used to validate experimental data. Results showed the brass collimator significantly reduced radiation leakage. Future studies will use this collimator to advance robotic FLASH PBS towards live small animal studies.
