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The p-nuclei are the few stable nuclei heavier than iron on the neutron-deficient side of the valley of stability that cannot be produced through astrophysical neutron-capture reactions. The limited experimental data on reactions through which the p-nuclei might be produced leaves the origin of their production largely unknown. This work presents the first cross section measurements of the $^{76}$Se(α,γ)$^{80}$Kr reaction. The rate of the time reversed reaction, $^{80}$Kr(γ,α)$^{76}$Se, is one of the most uncertain of possible reactions which can occur at the $^{80}$Kr branching point on the γ-process photo-disintegration pathway. The reaction flow through $^{80}$Kr will directly affect the final abundance of the p-nuclide $^{78}$Kr. Experimental cross sections at two astrophysically relevant energies are reported and compared to cross sections calculated using Hauser-Feshbach codes talys, non-smoker, and smaragd. The success of these first (α,γ) cross section measurements performed in inverse kinematics in the energy region of the γ-process opens the door for future studies of reactions on radioactive γ-process nuclides.

During the slow neutron capture process in massive stars, reactions on light elements can both produce and absorb neutrons thereby influencing the final heavy element abundances. At low metallicities, the high neutron capture rate of $^{16}$O can inhibit s-process nucleosynthesis unless the neutrons are recycled via the $^{17}$O(α,n)$^{20}$Ne reaction. The efficiency of this neutron recycling is determined by competition between the $^{17}$O(α,n)$^{20}$Ne and $^{17}$O(α,γ)$^{21}$Ne reactions. While some experimental data are available on the former reaction, no data exist for the radiative capture channel at the relevant astrophysical energies.The $^{17}$O(α,γ)$^{21}$Ne reaction has been studied directly using the DRAGON recoil separator at the TRIUMF Laboratory. The reaction cross section has been determined at energies between 0.6 and 1.6 MeV Ecm, reaching into the Gamow window for core helium burning for the first time. Resonance strengths for resonances at 0.63, 0.721, 0.81 and 1.122 MeV Ecm have been extracted. The experimentally based reaction rate calculated represents a lower limit, but suggests that significant s-process nucleosynthesis occurs in low metallicity massive stars.

During the slow neutron capture process in massive stars, reactions on light elements can both produce and absorb neutrons thereby influencing the final heavy element abundances. At low metallicities, the high neutron capture rate of 16O can inhibit s-process nucleosynthesis unless the neutrons are recycled via the ¹⁷O(α,n)²⁰Ne reaction. The efficiency of this neutron recycling is determined by competition between the ¹⁷O(α,n)²⁰Ne and ¹⁷O(α,γ)²¹Ne reactions. While some experimental data are available on the former reaction, no data exist for the radiative capture channel at the relevant astrophysical energies. The ¹⁷O(α,n)²⁰Ne reaction has been studied directly using the DRAGON recoil separator at the TRIUMF Laboratory. The reaction cross section has been determined at energies between 0.6 and 1.6 MeV , reaching into the Gamow window for core helium burning for the first time. Resonance strengths for resonances at 0.63, 0.721, 0.81 and 1.122 MeV have been extracted. The experimentally based reaction rate calculated represents a lower limit, but suggests that significant s-process nucleosynthesis occurs in low metallicity massive stars.

The first measurement of the one-neutron transfer reaction 11 Li(p,d) 10 Li performed using the IRIS facility at TRIUMF with a 5.7A MeV 11 Li beam interacting with a solid H 2 target is reported. The 10 Li residue was populated strongly as a resonance peak with energy Er=0.62±0.04 MeV having a total width Γ=0.33±0.07 MeV . The angular distribution of this resonance is characterized by neutron occupying the 1p1/2 orbital. A DWBA analysis yields a spectroscopic factor of 0.67±0.12 for p1/2 removal strength from the ground state of 11 Li to the region of the peak.

Preliminary studies in preparation for an absolute cross-section measurement of the radiative capture reaction 3He(α,γ)7Be with the DRAGON recoil separator have demonstrated beam suppression >1014 at the 90% confidence level. A measurement of this cross section by observation of 7Be recoils at the focal plane of the separator should be virtually background free. & 2012 Elsevier B.V.