Examining the Linearity of Silicon Detectors in the Nab Experiment*

When neutrons are outside of a nucleus, they undergo β decay; they decay into a proton, an electron, and an antineutrino. The Nab experiment seeks to precisely determine the electron-neutrino correlation parameter through unpolarized neutron β decay. The Nab experimental methods are highly sensitive to the energies of electrons produced during β decay, which are measured with silicon detectors. It is commonly expected that silicon detectors are linear. However, we must test this assumption to a high level of precision. To accomplish this, we conducted linearity studies with a precision pulser in three stages to (1) characterize pulser output, (2) investigate methods for splitting the pulse, and (3) search for nonlinearity in the detection system. We created Python programs to organize and analyze the data. We found maximum residuals of 0.068% in the detection system, which exceeds the Nab precision goal of 0.01%, indicating that further study is required.