Development of the Solenoid Spectrometer for Nuclear Astrophysics and Decays (SSNAPD)

The most common explosive astrophysical event is the Type 1 X-Ray Burst (XRB), in which low-Z fuel from a binary companion star incites periodic thermonuclear runaway on the surface of a neutron star. XRBs are a location of heavy element synthesis through the rp-process, and their light curves provide macroscopic information about the system’s neutron star.

Both ignition of the rp-Process and the shape of the observed light curve are heavily affected by key proton- and α-capture reactions involving Z=6-15, neutron-deficient nuclei. These reactions, such as ¹⁵O(α,γ)¹⁹Ne, are challenging to study directly, even at modern Radioactive Ion Beam facilities. Indirect methods measuring proton- and α-decay branching ratios of excited reaction products provide a feasible way of probing astrophysically-important resonances experimentally.

SSNAPD will be a charged-particle detector array developed to perform such particle-decay experiments at the TriSol facility at the University of Notre Dame. The SSNAPD array will be capable of measuring charged particle branching ratios as low as 10^-5, making it ideally suited for low cross-section reactions that govern XRB behavior. Development status, simulations, testing, and early experimental plans for SSNAPD will be discussed.