Advanced Experimental Equipment for Proton-Rich Nucleosynthesis

Abstract

Constraining the properties of the proton- and alpha-capture reactions that occur in novae and X-ray bursts is necessary to accurately model these explosive events. Unfortunately, most of these reactions are very difficult to measure experimentally due to low cross sections and availability of sufficiently intense radioactive beams. While direct measurements help us to understand the rates, indirect measurements provide an opportunity to gain insight into these reactions by studying resonance properties in the compound nucleus. Gammasphere ORRUBA: Dual Detectors for Experimental Structure Studies (GODDESS) is a device that allows for such measurements. Recent studies of the 19F(3He,t)19Ne and 40Ca(3He,α)39Ca reactions have been performed to reduce the uncertainties in the 18F(p,α)15O and 38K(p,γ)39Ca reactions, which are important in novae and X-ray bursts. To further constrain the nucleosynthesis in these explosive events, radioactive beam experiments are also necessary, but can be more difficult to perform. Traditional solid targets often have increased background from unwanted reactions on contaminants, or the other components of the target material, and suffer from worsened energy resolution due to energy loss straggling in the target body. Advanced targetry, such as supersonic gas jets, solves some of these target-related issues. The Jet Experiments in Nuclear Structure and Astrophysics (JENSA) target at the Facility for Rare Isotope Beams (FRIB) has seen recent success in providing experiments with a localized and dense helium gas target. A next-generation gas jet called The SOLenoid and Supersonic Target in Structure Experiments (SOLSTISE), currently under development at Oak Ridge National Laboratory, aims to further broaden our measurement capabilities by optimizing the experimental resolution of the solenoidal spectrometer SOLARIS. The recent GODDESS results will be discussed, as well as the current simulations and design status of SOLSTISE. Download Abstract