Nuclear Astrophysics at ISAC with DRAGON

NovaeSupernovaeX-Ray Bursts

In his Nobel Prize acceptance speech in 1984, Prof. Willie Fowler of the California Institute of Technology, and the father of nuclear astrophysics said, "Direct measurements on short-lived radioactive nuclei and the excited states of all nuclei are impossible at the present
time. In this connection the production of radioactive ion beams holds great promise for the future"[Fow84]. It has taken a number of years to reach this point but this future promise is now here. The new ISAC facility combined with the DRAGON and TUDA experimental facilities will help realize this future.

Author: See Paper Document

Measurement of the 40Ca(α,γ) 44Ti reaction relevant for supernova nucleosynthesis

AlphaCalcium 40GammaPeer ReviewedScienceSupernovaeTitanium 44

The short-lived nuclide 44 Ti is an important nuclide for the understanding of explosive nucle-osynthesis. The main production reaction, 40 Ca(α, γ)44 Ti, has been studied in inverse kinematics with the recoil mass spectrometer DRAGON located at the TRIUMF-ISAC facility in Vancouver, Canada. The temperature range relevant for α-rich freeze-out during a core-collapse supernova has been covered entirely with a 40 Ca beam of 0.60 to 1.15 MeV/nucleon. All relevant quantities for the calculation of the astrophysical reaction rate have been measured directly. Due to many previously undiscovered resonances, the reaction rate derived from the energy dependent 44 Ti yield is higher than the one based on previous prompt γ-ray studies commonly used in supernova models. The presented new rate results in an increased 44 Ti production in supernovae.

Author: See Paper Document
Journal: Phys. Rev. C 76 035801 (2007).

40Ca(α,γ) 44Ti and the production of 44Ti in supernovae

AlphaCalcium 40GammaPeer ReviewedScienceSupernovaeTitanium 44

The nuclide 44 Ti is predicted to be produced in significant quantities in core-collapse supernovae, and indeed it has been observed in the supernova remnant Cassiopeia-A by space-based γ-ray telescopes. The main production of 44 Ti takes place in the α-rich freeze-out phase deep inside the supernova. The key reactions governing the 44 Ti abundance have been identified in an earlier sensitivity study. Using the recoil mass spectrometer DRAGON at the TRIUMF-ISAC facility in Vancouver, Canada, we measured the main production reaction 40 Ca(α,γ)44 Ti, resulting in an increased reaction rate compared to the rate derived from previous prompt γ-ray studies, which is commonly used in supernova models. The uncertainty of the 44 Ti production is now dominated by the rate of reactions with short-lived nuclides around 44 Ti, namely 45 V(p,γ)46 Cr, 44 Ti(α,p)47 V and 44 Ti(α,γ)48 Cr. The sensitivity of these reactions on the 44 Ti production has been revisited.

Author: See Paper Document
Journal: J. Phys. G: Nucl. Part. Phys. 35 014034 (2008)