Design of a semiconductor-based proton spectrometer for laser-driven sources applications

Laser-driven proton sources are attracting increasing interest because of their promising uses in several fields, from basic science to materials analysis. Applications require quantitative and accurate measurements of the laser-driven particle spectra. However, the peculiar features of these sources pose several challenges to their in-depth characterization. In this work, we present the design of a spectrometer based on silicon photodiodes, focusing on TW-class laser proton sources and their foreseen applications. The device comprises a dipole magnet to deflect the ions along different trajectories according to their energies. The magnet can also be removed to avoid beam deflection and make the particles available for applications. We exploit a finely shaped differential filter to cut the contribution of unwanted heavy ions and a photodiode array for proton detection. These elements are described and experimentally characterized, allowing the development of an analytical description useful to size the instrument. We perform Monte Carlo simulations to validate the model and calibrate the system. The retrieved data are used to simulate the detection of protons in a typical laser-driven particle acceleration experiment. The spectrum reconstructed by Monte Carlo simulations wellmatches the distribution provided as source, demonstrating the founding principles of the spectrometer. Lastly, a first test in a real laser environment at Centro de Láseres Pulsados (1 PW VEGA-3 laser) is also presented, showing the full response of the device and its potential as a laser-driven proton beam monitor in application-oriented scenarios.