Calibration and Characterization of the UNCB and Nab Detectors

The UCNB and Nab experiments are designed to produce precision measurements of the free neutron decay angular correlations $B$, $a$, and $b$. Measurements of $B$ and $a$ require a coincident detection of the proton and electron produced in neutron decay, while for $b$, which manifests as a subtle shift in the electron energy spectrum, energy resolution better than $3$ keV is desired and excellent fidelity for energy reconstruction is required, including characterization of non-linearity to the $10^{-4}$ level. To this end, a thick segmented silicon detector with a $100$ nm dead layer and a $100$ cm active area has been extensively characterized at LANL. The thin dead layer allows protons accelerated to $30$ keV to deposit energy above threshold in the active volume of the detector, and the paired amplifer chain, developed at LANL, has a risetime of approximately $40$ ns. Comparison of simulation to experiment reveals a detector resolution better than $\sigma = 2.5$ keV. A complete characterization of the detector will be presented.