Acoustic Analog Signal Processing for 20–200 MeV Proton Sound Detectors

Proton sound detectors rely on sensing the weak thermoacoustic signals emitted by the fast energy deposition at the end of the beam penetration path through the energy absorber. The energy of the ions/protons is first converted into heat, and then, into pressure by a thermodynamic process. The pressure signal propagates through the energy absorber, and it is read by an acoustic sensor, which, in turn, converts the pressure wave into an analog electrical voltage. Such an analog signal is digitalized by the analog front-end. Its digital representation is used for the measurement of the beam depth. This emerging technique attracts attention in both physics experiments and medical applications (hadron therapy). This article investigates the signal-to-noise-ratio performance in proton sound detectors exploring all critical steps that lead to both reduction of the power of the electrical signal and noise power increasing. Nonetheless, this article proposes specific technical solutions to mitigate such signal-to-noise-ratio degradations with particular attention to higher energy (i.e., 200 MeV) proton beams, which are crucial for medical applications, and where the maximum achievable signal-to-noise ratio can be 50/60 dB lower than 20 MeV acoustic pulses.