Thermo-acoustic sound generation in the interaction of pulsed proton and laser beams with a water target

Abstract

The generation of hydrodynamic radiation in interactions of pulsed proton and laser beams with matter is explored. The beams were directed into a water target and the resulting acoustic signals were recorded with pressure sensitive sensors. Measurements were performed with varying pulse energies, sensor positions, beam diameters and temperatures. The obtained data are matched by simulation results based on the thermo-acoustic model with uncertainties at a level of 10%. The results imply that the primary mechanism for sound generation by the energy deposition of particles propagating in water is the local heating of the medium. The heating results in a fast expansion or contraction and a pressure pulse of bipolar shape is emitted into the surrounding medium. An interesting, widely discussed application of this effect could be the detection of ultra-high energetic cosmic neutrinos in future large-scale acoustic neutrino detectors. For this application a validation of the sound generation mechanism to high accuracy, as achieved with the experiments discussed in this article, is of high importance.

Listening to pulses of radiation: design of a submersible thermoacoustic sensor

“…The next pulse of remarkable amplitude comes from the surface, and it is the result of a significant energy deposition near the air/water interface where the transfer of the photons’ moment to the liquid medium generates a pressure pulse. This signal was also detected in other studies 32 , 46 .…”

“…About after the impact of the laser beam on the free surface of the liquid, we can observe a bipolar pulse (BiP)—a compression pulse followed by a rarefaction pulse. This characteristic pulse is predicted by several studies 2 – 4 , 45 , 46 as originated from the thermoelastic interaction process.…”

“…We observe a strong linear dependency between the signal amplitude and the total deposited energy ( ), verified trough the coefficient of determination . Although this result shows a promising trend, since the thermoacoustic model preaches a linear relationship between the two quantities 46 , 47 , further experiments should be conducted to investigate the complete sensor response.…”

Acoustic detection of high energy neutrinos in sea water: status and prospects

“…The resulting energy deposition of the hadronic cascade within a cylindrical volume of a few centimetres in radius and several metres in length leads to a local heating of the medium, see e.g. [2] and references therein.…”

Application of three-dimensional graphene in sound generation via thermoacoustics

“…Utilization of pulses of a programmed EM wave source, a temperature gradient can be induced with increasing and decreasing thermal energy transference. This agitation of the surrounding medium in a cyclical longitudinal motion hence results in the generation of acoustic waves [65][66][67][68][69][70].…”