VHEE facilities in Europe with the potential for FLASH dose irradiation: Conspectus and dose rate parameterisation

• Analysis of VHEE facilities in Europe and capability for radiobiological research. • Facility dose rates calculated based on Monte Carlo simulations. • CLEAR, CLARA and SAFEST beam dose rates exceed the FLASH radiotherapy threshold. • Functional dependence of dose rates on transverse beam size, energy, source-to-surface distance. Very High Energy Electrons (VHEE) are gaining significant interest in combination with FLASH radiotherapy as a potential cancer treatment with potential reduction in side effects. This study reviews European VHEE facilities, their FLASH capabilities and applications to radiobiological research, with study objectives: 1. Determining FLASH capabilities through Monte Carlo beam modelling and fitting to analytical functions. 2. Assessing VHEE facility infrastructure suitability for radiobiological research. Parameter variation studies were performed to determine dose dependency on beam dimension and source-to-surface distance (SSD). The dose rate was calculated from surface dose, linearly scaled based on the beamline. Empirical dose rate functions were developed, with an average discrepancy < 3 % between simulation and fit data. Dose rates were compared to the FLASH threshold of 40 Gy/s. Further parameter and infrastructure considerations provided an overview of each facility’s radiobiological experiment capabilities, providing researchers with a useful resource in designing and planning of future VHEE-FLASH experiments.