High-fidelity unfolding of 252Cf neutron spectra in EJ-301 scintillators via calibrated response matrices and Monte Carlo simulations

Accurate reconstruction of neutron spectra is essential for fissile material identification and nuclear safeguard applications. However, most existing studies only reconstructed neutron spectrum above 1-2 MeV, leaving the detector response in low energy region poorly constrained. This study introduces a unified experimental-simulation framework for high-fidelity spectrum unfolding in EJ-301 liquid scintillators. Detailed Geant4 Monte Carlo simulations were performed to model energy deposition and light-output processes for both gamma rays and neutrons, generating ideal response functions. To reproduce real detector behavior, energy-resolution parameters were experimentally calibrated using Compton-edge measurements from ¹³⁷Cs and ²²Na sources for 1-inch and 2-inch detectors. Validated by accurate reconstruction of ²²Na gamma spectra, the calibrated response matrices were then applied in iterative unfolding algorithms(GRAVEL and MLEM) to reconstruct the neutron spectrum of a ²⁵²Cf source. The proposed approach achieves a lower energy threshold of 0.35 MeV and maintains an average deviation below 4.28%, with the best agreement of 1.42% from ISO 8529-1 reference data. The 2-inch detector demonstrated higher efficiency and resolution. This experimentally validated framework bridges the gap between ideal simulations and practical detector performance, providing a robust pathway for precise neutron spectroscopy and quantitative nuclear safeguards verification.