22 dB Signal-to-Noise Ratio Real-Time Proton Sound Detector for Experimental Beam Range Verification

This paper presents the design and experimental characterization of a Proton Sound Detector (ProSD), a device that physically captures and senses the weak acoustic signal emitted by the fast energy deposition at the end of the same proton beam range. The measured acoustic signal Time-of-Flight provides a very accurate (13 μm accuracy) measure of the proton beam penetration depth in water, improving the proton range verification accuracy w.r.t. previous works in pre-clinical scenarios. This suggests interesting possibilities for high-accuracy and real-time beam monitoring and calibration in hadron-therapy for cancer treatment. The detector has been fully characterized and tested with a physical 20 MeV proton beam in a water energy absorber. The ProSD and the water tank have been mounted in front of the exit layer of a 20 MeV 120 ns pulse time-width proton beam. A clear sinusoidal-like acoustic signal of 5 Pa and 2.3 MHz frequency has been detected at 12 dB SNR with 0.8 Gy single shot dose. After averaging 10 beam shots the achieved Signal-to-Noise-Ratio is 22 dB allowing a ±7.5 μm precision vs. previously reported ±45μm ionoacoustic precision.