Ultra-high dose rate (UHDR) radiation of electron or proton beam has been shown to spare normal tissues surrounding the tumors while killing tumor cells effectively which is called the FLASH effect (FE). However, the internal mechanisms of FE has not yet been fully revealed, and the optimal parameter range for its use remains unknown.

This study aims to design an UHDR cell irradiation experimental platform that provides a stable, appropriate and wide range of adjustable dose and average dose rates for exploring the FE dependence on total dose.

Based on a 7 MeV medical proton linear injector, a single scattering nozzle was designed and optimized using the Monte Carlo code FLUKA. A 40-μm-thick tantalum foil, acting as both a vacuum window and a scatterer, was comprised in the nozzle with a source-to-surface distance of 26 cm. Finally, a single pulsed shoot-through UHDR cell penetration irradiation experiment was conducted by simulation using optimized parameters for this platform.

The simulation results demonstrate that the experimental platform can provide a 2 cm diameter irradiation field with a dose homogeneity of 4.9%. By adjusting the beam intensities (0.1~1 mA) and pulse widths (20~200 μs) of proton beam pulses, the dose and corresponding average dose rate of this platform can be adjusted within the range of 6~667 Gy and 3.3×10⁵~3.3×10⁶ Gy·s^-1, respectively. Results of simulated UHDR cell irradiation experiment show that the monolayer cells can be irradiated using a single pulsed shoot-through mode with a dose rate of 3.3×10⁵ Gy·s^-1 and doses ranging from 7~40 Gy.

This platform enables UHDR experiments to explore the FE dependence on total dose, providing further experimental data for clarifying the FE mechanisms.