A Configurable Epithermal Neutron Multiplicity Counter

The Epithermal Neutron Multiplicity Counter (ENMC) is a rapid, nondestructive assay device that measures impure plutonium. The ENMC, like all neutron multiplicity counters built to date, has one principal drawback: its measurement well is restricted to a single configuration. Such a restriction has been necessary to maintain a static geometry for the counter, so that the detector parameters—and thus its calibration—are well known. Using modern Monte Carlo techniques, it is now possible to allow for more flexibility in the detector geometry and to calculate parameters after-the-fact, so long as the detector’s configuration is well documented. In this paper, we will describe the design and manufacture of a new “mini” ENMC with the necessary flexibility to measure oddly shaped items or objects whose geometry is not well known at the time of deployment.