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Carbon and oxygen burning reactions, in particular, $^{12}$C+$^{12}$C fusion, are important for the understanding and interpretation of the late phases of stellar evolution as well as the ignition and nucleosynthesis in cataclysmic binary systems such as type Ia supernovae and x-ray superbursts. A new measurement of this reaction has been performed at the University of Notre Dame using particle-$\gamma$ coincidence techniques with SAND (a silicon detector array) at the high-intensity 5U Pelletron accelerator. New results for $^{12}$C+$^{12}$C fusion at low energies relevant to nuclear astrophysics are reported. They show strong disagreement with a recent measurement using the indirect Trojan Horse method. The impact on the carbon burning process under astrophysical scenarios will be discussed., Comment: accepted for publication in Phys. Rev. Lett

The Silicon Array for Branching Ratio Experiments (SABRE) has been developed for use to study reactions of interest to nuclear structure and astrophysics . The array has been incorporated into the Super Enge Split-Pole Spectrograph (SE-SPS) experimental setup at Florida State University’s John D. Fox accelerator laboratory to detect charged-particle decays in coincidence with reaction products detected by the SE-SPS focal plane detector. Its construction and electronics processing are discussed, as well as the commissioning data used to validate its performance.

The performance of the maximum likelihood expectation maximization method for unfolding neutron energy spectra using deuterated liquid scintillator is evaluated for future utilization with rare isotope beams. High-resolution neutron energy spectra as well as the detector response matrix were measured at the Edwards Accelerator Laboratory at Ohio University. Maximum-likelihood expectation maximization (MLEM) unfolded neutron spectra are compared with spectra from neutron time-of-flight. The effects of the MLEM stopping criteria and spectrum statistics are also investigated.

Background: The $^{17}\mathrm{F}(p,\ensuremath{\gamma})^{18}\mathrm{Ne}$ reaction is part of the astrophysical ``hot CNO'' cycles that are important in astrophysical environments like novas. Its thermal reaction rate is low owing to the relatively high energy of the resonances and therefore is dominated by direct, nonresonant capture in stellar environments at temperatures below 0.4 GK.Purpose: An experimental method is established to extract the proton strength to bound and unbound states in experiments with radioactive ion beams and to determine the parameters of direct and resonant capture in the $^{17}\mathrm{F}(p,\ensuremath{\gamma})^{18}\mathrm{Ne}$ reaction.Method: The $^{17}\mathrm{F}(d,n)^{18}\mathrm{Ne}$ reaction is measured in inverse kinematics using a beam of the short-lived isotope $^{17}\mathrm{F}$ and a compact setup of neutron, proton, $\ensuremath{\gamma}$-ray, and heavy-ion detectors called resoneut.Results: The spectroscopic factors for the lowest $l=0$ proton resonances at ${\mathrm{E}}_{\mathrm{c}.\mathrm{m}.}=0.60$ and 1.17 MeV are determined, yielding results consistent within $1.4\ensuremath{\sigma}$ of previous proton elastic-scattering measurements. The asymptotic normalization coefficients of the bound ${2}_{1}^{+}$ and ${2}_{2}^{+}$ states in $^{18}\mathrm{Ne}$ are determined and the resulting direct-capture reaction rates are extracted.Conclusions: The direct-capture component of the $^{17}\mathrm{F}(p,\ensuremath{\gamma})^{18}\mathrm{Ne}$ reaction is determined for the first time from experimental data on $^{18}\mathrm{Ne}$.

Reactions on certain proton-rich, radioactive nuclei have been shown to have a significant influence on X-ray bursts. We provide an overview of two recent measurements of important X-ray burst reactions using in-flight radioactive ion beams from the RESOLUT facility at the J. D. Fox Superconducting Accelerator Laboratory at Florida State University. The 17 F(d,n) 18 Ne reaction was measured, and Asymptotic Normalization Coefficients were extracted for bound states in 18 Ne that determine the direct-capture cross section dominating the 17 F(p, γ ) 18 Ne reaction rate for T≲ 0.45 GK. Unbound resonant states were also studied, and the single-particle strength for the 4.523-MeV (3 + ) state was found to be consistent with previous results. The 19 Ne(d,n) 20 Na proton transfer reaction was used to study resonances in the 19 Ne(p, γ ) 20 Na reaction. The most important 2.65-MeV state in 20 Na was observed to decay by proton emission to both the ground and first-excited states in 19 Ne, providing strong evidence for a 3 + spin assignment and indicating that proton capture on the thermally-populated first-excited state in 19 Ne is an important contributor to the 19 Ne(p, γ ) 20 Na reaction rate.

The $^{19}\mathrm{Ne}(p,\ensuremath{\gamma})^{20}\mathrm{Na}$ reaction is the second step of a reaction chain which breaks out from the hot CNO cycle, following the $^{15}\mathrm{O}(\ensuremath{\alpha},\ensuremath{\gamma})^{19}\mathrm{Ne}$ reaction at the onset of x-ray burst events. We investigate the spectrum of the lowest proton-unbound states in $^{20}\mathrm{Na}$ in an effort to resolve contradictions in spin-parity assignments and extract reliable information about the thermal reaction rate. The proton-transfer reaction $^{19}\mathrm{Ne}(d,n)^{20}\mathrm{Na}$ is measured with a beam of the radioactive isotope $^{19}\mathrm{Ne}$ at an energy around the Coulomb barrier and in inverse kinematics. We observe three proton resonances with the $^{19}\mathrm{Ne}$ ground state, at 0.44, 0.66, and 0.82 MeV c.m. energies, which are assigned ${3}^{+}$, ${1}^{+}$, and (${0}^{+}$), respectively. In addition, we identify two resonances with the first excited state in $^{19}\mathrm{Ne}$, one at 0.20 MeV and one, tentatively, at 0.54 MeV. These observations allow us for the first time to experimentally quantify the astrophysical reaction rate on an excited nuclear state. Our experiment shows an efficient path for thermal proton capture in $^{19}\mathrm{Ne}(p,\ensuremath{\gamma})^{20}\mathrm{Na}$, which proceeds through ground state and excited-state capture in almost equal parts and eliminates the possibility for this reaction to create a bottleneck in the breakout from the hot CNO cycle.

Resonance scattering with rare isotope beams provides direct access to continuum properties of exotic nuclei and can serve as a stringent test for modern theoretical approaches. Properties of neutron deficient isotope 8B, that were studied using resonance scattering of protons of 7Be, are discussed and compared to the predictions of the ab initio theories. New experimental data on clustering in 10Be studied using 6He+α resonance elastic scattering is presented.

Many astrophysical events, such as novae and X-ray bursts, are powered by reactions with radioactive nuclei. Studying the properties of these nuclei in the laboratory can therefore further our understanding of these astrophysical explosions. The TwinSol separator at the University of Notre Dame has recently been used to produce intense (~106 pps) beams of 17F. In this article, some of the first measurements with these beams are discussed.