  We describe a detection system designed for precise measurements of angular
correlations in neutron $\beta$ decay. The system is based on thick, large
area, highly segmented silicon detectors developed in collaboration with Micron
Semiconductor, Ltd. The prototype system meets specifications for $\beta$
electron detection with energy thresholds below 10 keV, energy resolution of
$\sim$3 keV FWHM, and rise time of $\sim$50 ns with 19 of the 127 detector
pixels instrumented. Using ultracold neutrons at the Los Alamos Neutron Science
Center, we have demonstrated the coincident detection of $\beta$ particles and
recoil protons from neutron $\beta$ decay. The fully instrumented detection
system will be implemented in the UCNB and Nab experiments, to determine the
neutron $\beta$ decay parameters $B$, $a$, and $b$.
