Development of a geometric uncertainty model describing the accuracy of position-sensitive, coincidence neutron detection

A diameter of uncertainty (Du) was derived from a geometric uncertainty model describing the error that would be introduced into position-sensitive, coincidence neutron detection measurements by charged-particle transport phenomena and experimental setup. The transport of α and Li ions, produced by the 10B(n,α) 7Li reaction, through free-standing boro-phosphosilicate glass (BPSG) films was modeled using the Monte Carlo code SRIM, and the results of these simulations were used as input to determine Du for position-sensitive, coincidence techniques. The results of these calculations showed that Du is dependent on encoder separation, the angle of charged particle emission, and film thickness. For certain emission scenarios, the magnitude of Du is larger than the physical size of the neutron converting media that were being modeled. Spheres of uncertainty were developed that describe the difference in flight path times among the bounding-case emission scenarios that were considered in this work. It was shown the overlapping spheres represent emission angles and particle flight path lengths that would be difficult to resolve in terms of particle time-of-flight measurements. However, based on the timing resolution of current nuclear instrumentation, emission events that yield large Du can be discriminated by logical arguments during spectral deconvolution.