Quantitative analysis of Fe ion interactions with the negative pressure phase of ultrasound pulses in water

Abstract We investigated heavy-ion irradiation and ultrasound interactions in water by simultaneously applying a 500 MeV n −1 Fe-ion beam and pulsed ultrasound. Bright, point-like echoes were repeatedly observed near the Bragg peak, suggesting that radiation-induced microscopic voids serve as nuclei for cavitation during the ultrasound pulse’s negative-pressure phase. To interpret this phenomenon, we developed a probabilistic model based on the spatial overlap between the ion stopping distribution and the ultrasound field’s negative-pressure region. The model qualitatively reproduces the depth distribution and the number of observed bright spots, supporting the hypothesis of radiation-induced cavitation. These results indicate that high linear energy transfer irradiation-induced nanoscale void formation can substantially lower the effective cavitation threshold. This study provides a new perspective on coupled radiation–acoustic phenomena and offers a potential pathway for acoustic visualization of radiation-induced structural changes in liquids.