A Versatile Digital Data Acquisition System for the 8π Gamma-Ray Spectrometer

Abstract

The $8\pi $ gamma-ray spectrometer is a highly-efficient and selective ball array of bismuth germanium oxide (BGO) detectors. In 2014, it was relocated from TRIUMF, Canada’s particle accelerator center, to the Simon Fraser University Nuclear Science Laboratory (SFU NSL), where it has been recommissioned with upgraded components for rare decay spectroscopy. In its current configuration, $8\pi $ has 12 BGO pentagon detectors and 60 BGO hexagon detectors arranged in an icosahedral symmetry. Together, they provide 132 readout channels and approximately 95% solid-angle coverage. A unique digital data acquisition system (DAQ) has been developed around the existing $8\pi $ BGO detectors for the study of rare decays. This system allows for the fine-tuning of logic and digitization parameters through a web interface, eliminating the need for physical reconfiguration and providing a level of flexibility not previously offered. This upgraded DAQ system includes three synchronized VF48 digitizers for waveform digitization, two XLM72S modules for online multiplicity filtering, and additional components for thresholding and pile-up handling functionality. Performance metrics such as energy resolution, timing resolution, and efficiency were measured, demonstrating the functionality of all $8\pi $ subsystems. The spectrometer is fully prepared for experiments demanding efficient and selective time-resolved gamma-ray spectroscopy. Designed with future expansion in mind, $8\pi $ can easily support additional detectors, making it well-suited for a wide range of future experiments.