Measuring the ¹⁵O(α, γ)¹⁹Ne reaction rate in Type I X-ray bursts using the GADGET II TPC

A neutron star can accrete H/He-rich material from a low-mass stellar companion (e.g., a main sequence star or a red giant). This can lead to thermonuclear runaway, which manifests as a Type I X-ray burst in a space-based telescope. Sensitivity studies have shown that the ¹⁵O(α, γ)¹⁹Ne reaction is one of the most important reaction rate uncertainties affecting the modeling of the resulting light curve. This reaction is expected to be dominated by the 4.03 MeV resonance in ¹⁹Ne. This state has a well known lifetime, so only a finite value for the alpha-particle branching ratio is needed to determine the reaction rate. Previous measurements have shown that this state is populated in the decay sequence of ²⁰Mg. ²⁰Mg(βpα)¹⁵O events through the key ¹⁵O(α, γ)¹⁹Ne resonance yield a characteristic signature: the emission of a proton and alpha particle. To identify these coincidence events we have upgraded the GADGET Proton Detector into a time projection chamber to form the GADGET II detection system. GADGET II has been constructed, and is in the final testing phase before FRIB PAC approved experiment 21072. Additionally, machine learning will be leveraged in analysis by fine-tuning a pre-trained convolutional neural network to identify the proton-alpha events of interest.