Proton-Induced Thermoacoustic Process as Linear-Time-Invariant System

This article presents a cross-domain model that defines and sets the acoustic signal generation process due to the fast dose deposition induced by a proton beam penetrating an energy absorber. The proposed model reduces the complex iono-acoustic energy transformation process to a simple impulse-response of a linear-time-invariant (LTI) system and is validated by comparing LTI output simulation results (in both time and frequency domain) with experimental acoustic signals emitted by a physical proton beam at 20 MeV and 70-120-ns pulse time width. Thanks to the intrinsic simplicity of the system, it is possible to predict and estimate the effective acoustic power at the sensor and the resultant beam range measurement precision. More importantly, the information coming from LTI simulations provides well-defined methodologies that allow to increase acoustic signal amplitude from +3 up to +9 dB and to improve the measurement precision of the beam range localization (up to +/ - 0.3 mm versus +/ - 0.6 mm state of the art for 200-MeV energy and 75-mGy total dose).