The ⁴⁰Ca(α,γ)⁴⁴Ti reaction is thought to be the main production method for the short-lived radionuclide, ⁴⁴Ti (t_1/2 = 58.9 ± 0.3 yr). Production in the α-rich freeze-out zone of a core-collapse supernova makes ⁴⁴Ti an important nuclide in the understanding of nucleosynthesis in explosive stellar environments.

A new measurement of the ⁴⁰Ca(α,γ) ⁴⁴Ti reaction has been performed through two different experimental approaches. During this work, a new accelerator mass spectrometry (AMS) facility was developed and commissioned at the University of Notre Dame, primarily for the measurement of reaction cross-sections of astrophysical interest. Using this facility, a series of ⁴⁴Ti activation measurements were performed with a ⁴⁰Ca beam incident on a ⁴He gas target. The four discrete energy ranges over which the activations occurred all lie within the temperature range relevant for α-rich freeze-out. Further to this, an excitation curve was measured over the energy range E _α = 4600 - 3000 keV, using α-particles incident on a ⁴⁰Ca target. The good agreement between these two results resulted in the successful commissioning of the AMS facility.

The new reaction rates derived in this work results in an increased expected yield of ⁴⁴Ti in proposed supernova environments (for example Cassiopeia A) by ∼ 40 %, when compared to 1D supernova models using reaction rates based on previous prompt γ-ray studies .