  We explore the use of microstructured semiconductor neutron detectors (MSNDs)
to map the ratio between thermal neutrons and higher energy neutrons. The
system consists of alternating layers of modular neutron detectors (MNDs), each
comprising arrays of twenty-four MSNDs, and high-density polyethylene
moderators (HDPE) with gadolinium shielding to filter between thermal neutrons
and higher energy neutrons. We experimentally measured the performance of three
different configurations and demonstrated that the sensor system prototypes
detect and differentiate thermal and epithermal neutrons. We discuss future
planetary exploration applications of this compact, semiconductor-based
low-energy neutron detection system.
