Proton Bragg curve and energy reconstruction using an online scintillator stack detector

Real-time measurement and characterization of laser-driven proton beams have become crucial with the advent of high-repetition-rate laser acceleration. Common passive diagnostics such as radiochromic film (RCF) are not suitable for real-time operation due to time-consuming post-processing; therefore, a novel approach is needed. Various scintillator-based detectors have recently gained interest as real-time substitutes to RCF-thanks to their fast response for a wide range of dose deposition rates. This work introduces a compact, scalable, and cost-effective scintillator-based device for proton beam measurements in real-time suitable for the laser-plasma environment. An advanced signal processing technique was implemented based on detailed Monte Carlo simulations, enabling an accurate unfolding of the proton energy and the depth-dose deposition curve. The quenching effect was accounted for based on Birks' law with the help of the Monte Carlo simulations. The detector was tested in a proof-of-principle experiment at a conventional cyclotron accelerating protons up to 35 MeV of energy. The signal comparison with a standard RCF stack was also performed during the test of the device, showing an excellent agreement between the two diagnostics. Such devices would be suitable for both conventional and laser-driven proton beam characterization.