The DAQ system for the Nab Experiment at ORNL

Decay correlations in free neutron beta decay are a probe of the Cabbibo-Kobayashi-Maskawa matrix in the standard model and also new physics. The Nab experiment will measure the electron-neutrino correlation term, a, as well as the Fierz interference term, b, from detecting the beta decay electrons and protons in coincidence using two Si detectors with 127 pixels each at both ends of the Nab spectrometer. The DAQ system for this experiment has 32 ADC modules, each with 8 channels at a 14 bit sampling rate of 250 MS/s. We took advantage of the fully user-programmable FPGA on each module to implement a low-threshold trigger with high efficiency for 30 keV protons that allows us to record the waveforms necessary to reconstruct decay events. This system is capable of reading out a peak signal rate of ~2 GB/s. In this talk, I will give an overview of the current Nab DAQ system as well as detail future plans for improvement.