Improved measurements of (α,p) reactions with a new ANASEN design*

Several (α,p) reactions on proton-rich nuclei are among the most important nuclear reactions occurring during Type I X-ray bursts. However, large uncertainties remain in these reaction rates due to the lack of direct measurements. The Array for Nuclear Astrophysics and Structure with Exotic Nuclei (ANASEN) is a gas target and charged particle detector designed for studying (α,p) reactions. We have developed a new approach, replacing the proportional counter with a hexagonal barrel of thin (~80 μm) silicon detectors to improve the tracking resolution, though at a cost of overall efficiency. The new setup was used in stable beam tests at the Fox Laboratory at Florida State University, and in both stable and radioactive beam measurements at TRIUMF-ISAC. Results from a measurement of the ¹⁸F(α,p)²¹Ne excitation function at TRIUMF-ISAC, which may impact asymptotic giant branch nucleosynthesis and helium burning on accreting white dwarfs, will be presented. Plans for future measurements at TRIUMF-ISAC and FRIB will be discussed.