Abstract:
Background In near-field pulsed neutron measurements (at distances of less than 1 m), large-sized plastic scintillators (ϕ100 mm × 100 mm) exhibit neutron sensitivity deviation due to geometric discrepancies between calibration and measurement, and the inverse-square law has limited applicability under close-proximity conditions, hindering accurate metrology.
Purpose To address this deviation, reduce systematic errors from traditional single-point calibration, and extend the neutron sensitivity calibration range, this study proposes a dual-extrapolation dynamic calibration method combining experimental extrapolation with Monte Carlo (MC) simulation.
Methods An MC model was established to quantify the distance’s effect on sensitivity, and a scattering background extrapolation method was developed via near-field experiments for close-proximity sensitivity measurement.
Results MC results show that the source-to-detector distance of less than 80 cm significantly impacts sensitivity, with an 8.44% correction factor at 20 cm; experiments validated the simulation accuracy.
Conclusions This method effectively mitigates sensitivity deviation, clarifies the inverse-square law’s limitations under close proximity, extends the calibration scope, and provides a new technical approach for precise neutron metrology in harsh environments such as pulsed reactor transient diagnostics and fusion devices.
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