Planar Miniaturized Fast Neutron Detector spectroscopy evaluation

A planar neutron spectrometer, the Miniaturized Fast Neutron Detector, has been conceptualized. The device consists of a plastic converter layer followed by several stacked layers of thin-silicon diode detectors. Incident neutrons interact in the plastic converter layer to produce recoil ions which subsequently deposit energy in the diode detectors that follow. The device can be used to reconstruct incident neutron energy spectra with no prior knowledge of the spectrum via the SPUNIT unfolding algorithm. In this work, a Miniaturized Fast Neutron Detector with 20 stacked diode detectors is considered. Particle transport simulations were conducted to generate absorbed dose response functions for each of the 20 diode detectors and to compute the absorbed dose in each layer due to incident ²⁵²Cf, AmBe, and AmB neutron energy spectra as a function of integral neutron fluence. The results of this work demonstrate that the MFND is capable of unfolding three different, increasingly complex neutron energy spectra via the SPUNIT unfolding method with no a priori information. Additionally, the “effectiveness” of the MFND as a spectrometer is quantified as a function of integral neutron fluence. Spectrometer effectiveness metrics are useful for determining the minimum integral neutron fluence required to obtain acceptable resulting unfolded energy spectra, absorbed dose values, and risk-related quantities.