Fig. 1. Dose distribution in a 2-cm-diameter × 700-μm-long water phantom irradiated by a single proton beam pulse (7 MeV, 6.5 mA, 50 μs) passing through a 10-μm-thick titanium vacuum window

Fig. 2. Structural schematic of the UHDR cell irradiation experiment

Fig. 3. Variation of multiple scattering angles with energy loss for 7 MeV protons in various materials

Fig. 4. Flowchart for determining the optimal set of nozzle parameters based on FLUKA

Fig. 5. Monte Carlo model of the UHDR cell irradiation experimental platform

Fig. 6. Homogeneity of longitudinal dose in water versus residual range in water with different nozzles

Fig. 7. Beam spot sizes and residual ranges in water corresponding to different nozzles (a) Nozzles with varying materials and thicknesses of metal foils and SSDs, (b) Nozzles with different thicknesses of tantalum foil and SSDs

Fig. 8. Simulation results for UHDR cell irradiation experiments using a single proton beam pulse (7 MeV, 0.1 mA, 50 μs) on this experimental platform(a) Overall distribution of proton fluence in the experimental platform, (b) Energy spectrum distribution of the proton pulse directed into the water surface, (c) Depth-dose curve in the 150-μm-long × 2-cm-diameter water phantom of the proton pulse, (d) Dose distribution in the irradiation field of the experimental platform

Fig. 9. The pulse dose rate as a function of beam intensity for this experimental platform (a), and the experimental plan for irradiating monolayer cells at various average doses with constant dose rates (b)