A gated alpha-particle time-of-flight spectrometer for laser-driven proton-boron fusion reactions

A gated scintillator-based α-particle time-of-flight (αTOF) spectrometer is developed for real-time diagnosis of nuclear reaction products in harsh laser-plasma experiments. The system employs fast-response EJ-204 plastic scintillator coupled with a gated microchannel plate photomultiplier tube and uses gating technique to suppress intense prompt x/γ-ray and relativistic electron radiation backgrounds. Calibration experiments are performed using 100-250 keV protons and 100-300 keV α-particle beams from a 320 kV high-voltage platform. The measured response efficiency increases linearly with particle energy and agrees well with theoretical calculations based on the ionization quenching model. The spectrometer is validated in laser-driven proton-boron fusion experiments at the XG-III laser facility, where a distinct α-particle peak at 3.65 MeV from the dominant 11B(p, α1)8Be* reaction channel is clearly resolved. The results demonstrate that the αTOF spectrometer enables real-time, shot-to-shot acquisition of energy spectra and yield measurements of α particles in high-radiation harsh environments. This work provides a robust online diagnostic tool for laser-driven nuclear reaction studies, with future improvements aimed at extending MeV energy calibration and developing multiplexed detection systems for quantitative yield measurements.