[en] The study of the nuclear physics properties which govern energy generation and nucleosynthesis in the astrophysical phenomena we observe in the universe is crucial to understanding how these objects behave and how the chemical history of the universe evolved to its present state. The low cross sections and short nuclear lifetimes involved in many of these reactions make their experimental determination challenging, requiring developments in beams and instrumentation. A selection of developments in nuclear astrophysics instrumentation is discussed, using as examples projects involving the nuclear astrophysics group at Oak Ridge National Laboratory. These developments will be key to the instrumentation necessary to fully exploit nuclear astrophysics opportunities at the Facility for Rare Isotope Beams which is currently under construction

[en] To make measurements with the intense (but often contaminated) radioactive beams available today, one often needs to identify the reaction products to determine the events of interest. The low energies required for many astrophysics measurements make impossible the use of traditional energy loss techniques, and additional constraints are required. We demonstrate a simple technique to measure the risetimes of silicon strip-detector signals and show partial discrimination can be obtained even at energies below 1 MeV/u.

[en] Neutron transfer (d,p) reactions have been measured with rare isotope beams of ¹³²Sn, ¹³⁰Sn and ¹³⁴Te accelerated to ∼4.5 MeV/u interacting with CD₂ targets. Reaction protons were detected in an early implementation of the ORRUBA array of position-sensitive silicon strip detectors. Neutron excitations in the 2f_7/2, 3p_3/2, 3p_1/2 and 2f_5/2 orbitals were populated.

[en] Background: Current nuclear structure models indicate that the shell structure near the valley of stability, with well-established shell closures at N=50, for example, changes in very neutron-rich nuclei far from stability. Single-particle properties of nuclei away from stability can be probed in single-neutron (d,p) transfer reactions with beams of rare isotopes. The interpretation of these data requires reaction theories with various effective interactions. Often, approximations made to the final bound-state potential introduce a large uncertainty in the extracted single-particle properties, in particular the spectroscopic factor. Purpose: Mitigate this uncertainty using a combined measurement method to constrain the shape of the bound-state potential and to reliably extract the spectroscopic factor. Methods: The ²H(⁸⁶Kr,p)⁸⁷Kr reaction was measured at 33 MeV/u at the National Superconducting Cyclotron Laboratory (NSCL) as a test of the combined method. The reaction protons were detected with the Oak Ridge Rutgers University Barrel Array (ORRUBA) of position sensitive silicon strip detectors, the first implementation of ORRUBA coupled to the S800 spectrograph with fast beams at NSCL. Results: These measurements at 33 MeV/u are combined with previous studies of the ⁸⁶Kr(d,p) reaction at 5.5 MeV/u to demonstrate a successful case of the combined method to constrain the shape of the single-particle potential and deduce asymptotic normalization coefficients and spectroscopic factors. In particular, the single-particle asymptotic normalization coefficient for the ground state of ⁸⁷Kr was constrained to b_d5/2=6.46${}_{\text{–<!-- ??? -->}0.57}^{+1.12}$ fm^–1/2, and therefore the deduced spectroscopic factor is S=0.44${}_{\text{–<!-- ??? -->}0.13}^{+0.09}$ with uncertainties dominated by experimental statistics. Conclusions: By combining measurements at two very different beam energies, single-particle asymptotic normalization coefficients, at least for low angular momentum transfers, can be constrained. Thus, spectroscopic factors can be deduced with uncertainties dominated by experimental uncertainties, rather than limited knowledge of bound-state potential parameters.

[en] A new program to measure (d,p) reactions on rare isotopes of fission fragments has been established at Oak Ridge National Laboratory. Initial measurements on N=50 isotones and prospects for Z=50 experiments are reported

[en] GODDESS is a coupling of the charged-particle detection system ORRUBA to the gamma-ray detector array Gammasphere. This coupling has been developed in order to facilitate the high-resolution measurement of direct reactions in normal and inverse kinematics with stable and radioactive beams. GODDESS has been commissioned using a beam of ¹³⁴Xe at 10 MeV/A, in a campaign of stable beam measurements. The measurement demonstrates the capabilities of GODDESS under radioactive beam conditions, and provides the first data on the single-neutron states in ¹³⁵Xe, including previously unobserved states based on the orbitals above the N=82 shell closure.

[en] The 7Li(7Li, 11B*)t, 12C(7Li, 10B*)9Be and 7Li(7Li, 12B*)d reactions have been studied at 58 MeV in order to determine the relative strengths of the H + Be and α + Li decay of 10,11,12B. A study of the relative yields for the decay of a number of excited states in 10,11,12B*, obtained following the coincident detection of the H + Be and α + Li decay fragments, indicates that the α-decay channel dominates in all cases

[en] Neutron-capture reactions on neutron-rich nuclei are important to understand r-process nucleosynthesis, as well as applied needs such as stewardship science and nuclear energy. Because of the short half-lives of these species, it is not possible to measure these reactions directly with neutron beams on unstable targets. The (d,p gamma) reaction with radioactive ion beams has been proposed as a surrogate reaction for (n,γ). Experiments to develop (d,p gamma) techniques with radioactive ion beams and to demonstrate the efficacy of the (d,p gamma) reaction as a surrogate for (n,γ) are discussed

[en] We have developed a new experimental setup based at the GANIL/SPIRAL facility in Caen, France to measure one-nucleon transfer reactions in inverse kinematics in order to study the evolution of the single particle structure of exotic nuclei. The setup couples together three state-of-the-art detection systems: the TIARA Si array, the large-acceptance magnetic spectrometer VAMOS and the high-efficiency segmented Ge γ-ray array EXOGAM. In a first experiment, the 24Ne(d,p)25Ne reaction has been studied to probe the N=16 shell closure. Details of the setup, data analysis and preliminary results are presented

[en] The g factor of the 2₁⁺ state in ₅₂¹³²Te, E(2₁⁺) = 0.9739 MeV, r = 2.6 ps, was measured by the transient field technique applied to a radioactive beam. The development of an experimental approach necessary for work in radioactive beam environments is described. The result g = 0.28(15) agrees with the previous measurement by the recoil-in-vacuum technique, but here the sign of the g factor is measured as well