Nuclear astrophysics measurements with DRAGON

The TRIUMF-ISAC facility: two decades of discovery with rare isotope beams

“…The breakdown of the shell model in this region known as the 'island of inversion' is now largely attributed to the monopole tensor interaction [88] that results in a lowering in the energy of the fp intruder states with respect to the standard sd orbitals, giving rise to deformed configurations. At ISAC, the β decay of 32 Na was studied with the 8π γ-ray spectrometer at a beam intensity of 2-3 ions per second. New transitions and levels were tentatively placed in the level scheme of Mg 32 from β-γ and γ-γ coincidences and previously unobserved transitions up to 5.4 MeV were observed but could not be placed in the decay scheme [89].…”

“…In general the γ ray intensities were in reasonable agreement with previous data. Recently this measurement has been repeated using GRIFFIN to obtain a factor of ∼200 more γ-γ coincidences, sufficient to determine the spin/parity of several excited states in 32 Mg from angular correlation measurements and also to establish a much more detailed decay scheme of 32 Na [90]. The spins and parities of excited states in -28 30 Mg have been studied following the β decay of polarized Na isotopes [91,92].…”

“…No direct feeding of the second excited + 2 level in 30 Mg was observed, suggesting it is a candidate for the γ-vibrational bandhead in 30 Mg. The first Penning trap measurements of the masses of -29 31 Na and -30 34 Mg allow a precise determination of the empirical shell gap for 32 Mg. The value of 1.10(3) MeV is the smallest closed-shell gap of any canonical magic-number nucleus [93].…”

“…The 3 He(α,γ) 7 Be reaction plays an important role in the production of 7 Be in the Sun and the direct measurement of this reaction is very important but also quite challenging. In preparation for an absolute cross-section measurement for this reaction at = E 2.8 MeV cm the DRAGON recoil mass separator [32,137,138] has demonstated a beam suppression of more than 10 14 [139]. A measurement at this energy can be used to extrapolate to solar energies with minimal model dependence.…”

“…The ISAC-I RFQ and DTL accelerators were optimized to provide highintensity, variable energy, < A 30 radioactive and stable beams in the range from 0.15-1.5A MeV required for nuclear astrophysics research. DRAGON, the TRIUMF Detector for Recoils And Gammas Of Nuclear reactions [32], is designed to measure radiative proton and alpha capture reaction rates of importance for astrophysics in inverse kinematics. The key features of DRAGON are: (1) a windowless gas target, surrounded by a high-efficiency array of BGO detectors, (2) high beam suppression achieved through a two stage electromagnetic separator that includes two magnetic and two electric dipoles, and (3) a focal plane end station equipped with a variety of detectors options including ionization chambers and double sided silicon strip detectors.…”