On the non-thermal contribution to the generation of sound waves due to rapid and localized energy input with laser pulses and particle bunches

• Applicant: Professor Dr. Jörg Schreiber
• Subject Area: Statistical Physics, Nonlinear Dynamics, Complex Systems, Soft and Fluid Matter, Biological Physics ; Medical Physics, Biomedical Technology ; Optics, Quantum Optics and Physics of Atoms, Molecules and Plasmas ; Physical Chemistry of Molecules, Liquids and Interfaces, Biophysical Chemistry
• Term: since 2021
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 491853809

Laser pulses and proton bunches can generate ultrasonic wave-packets in water. According to current understanding, those are excited due to local heat input. The localized heating leads to an expansion and a pressure pulse with positive polarity at over 4 ° C, under 4° C the polarity is negative. This was indeed shown in experiments with non-ionizing laser pulses. But when using protons, the polarity changes at significantly higher temperatures at around 4.5 ° C. Therefore, there must be a yet unexplained, non-thermal contribution to the pressure pulse that is to be examined here for the first time. We will use laser pulses as well as proton pulses for ionizing excitation and measure the ultrasound pulses with transducers and by time-resolved and spatially resolved interferometry at different temperatures in order to find the underlying cause of this contribution. In addition to the interesting physics, understanding this phenomenon has potentially far-reaching consequences on the understanding of the origin of radiation damage in living and non-living matter.

• DFG Programme: Research Grants