Science
First direct measurement of the 23Mg(p,γ)24Al reaction
The lowest-energy resonance in the 23Mg(p,γ)24Al reaction, which is dominant at classical nova temperatures, has been measured directly for the first time using the DRAGON recoil spectrometer. The experiment used a radioactive 23Mg beam (mixed within a significantly stronger 23Na beam) of peak intensity 5×107 s-1, at the ISAC facility at TRIUMF. We extract values of ER=485.7-1.8+1.3keV and ωγ=38-15+21 meV from our data (all values in the center-of-mass frame unless otherwise stated). In addition, the experiment prompted a recalculation of the Q value for this reaction based on a revision of the 24Al mass. The effect on the uncertainties in the quantities of ejected 22Na and 26Al from oxygen-neon classical novae is discussed.
Journal: Physical Review C
Radioactive Beams
(January 2006 - Canadian Chemical News article)
Journal: Canadian Chemical News 58(1) 16 (2006)
Production of intense radioactive beams at ISAC using low-energy protons
Journal: # low-energy protons Can. J. Phys. 84 325 (2006)
Measurement of the 40Ca(α,γ) 44Ti reaction relevant for supernova nucleosynthesis
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.
Journal: Phys. Rev. C 76 035801 (2007).
40Ca(α,γ) 44Ti and the production of 44Ti in supernovae
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.
Journal: J. Phys. G: Nucl. Part. Phys. 35 014034 (2008)
