GADGET II TPC for decay spectroscopy studies at FRIB*

The calorimetric Proton Detector of the GAseous Detector with GErmanium Tagging (GADGET) system has been upgraded to operate as a Time Projection Chamber (TPC) to detect low-energy, β-delayed single- and multi-particle emission of interest to astrophysics. The upgrade, known as GADGET II, uses micro pattern gaseous amplifier detector technology and is surrounded by an array of high-purity germanium detectors for efficient high-resolution detection of γ-rays. A new high-granularity MICROMEGAS (MM) board with 1024 pads and high density Generic Electronics for TPCs data acquisition system have been installed. This TPC is among the first generation of resistive MM detectors in low-energy nuclear physics and has been tested using a ²²⁸Th alpha source and cosmic-ray muons. In addition, decay events in the TPC have been simulated by adapting the ATTPCROOTv2 data analysis framework. A novel method of using 2D convolutional neural networks for event classification with GADGET II is also introduced.  In November 2022, GADGET II was successfully used for in-beam measurements to investigate the nuclear physics of Type I X-ray bursts.