Figure 1

Experimental setup of the ionoacoustic CA study. (a) Schematic of the experimental setup in the case of irradiation with the ripple filter. The proton beam enters the water tank through a \({50}\,{\upmu \hbox {m}}\)-thick polyimide foil and stops inside the CA phantom. The ionoacoustic (IA) pressure waves are measured by a CMUT single-element on the proton beam axis. (b) Laterally integrated 2D dose map of the 22 MeV proton beam in water, with a range of 4.92 mm (corresponding to 80 % of dose fall-off). (c) Simulated ionoacoustic emission resulting from the mono-energetic 22 MeV proton beam for a single proton pulse of 200 ns in water in time (black) and frequency-___domain (orange). (d) Laterally integrated 2D dose map of the spread-out 22  MeV proton beam in water, with a range of 3.04 mm (corresponding to 90 % of dose fall-off). (e) Simulated ionoacoustic emission resulting for the spread-out proton beam from a single proton pulse of 200 ns in water in time (black) and frequency-___domain (orange). The dose maps, obtained from Fluka2021.1beta, are the averaged values over 6 randomly sampled pencil beams.