Single-step Coulomb excitation of 46,48,49,50Ti is presented. A complete set of E2 matrix elements for the quintuplet of states in 49Ti, centred on the 2+ core excitation, was measured for the first time. A total of nine E2 matrix elements are reported, four of which were previously unknown. 2249Ti27 shows a 20% quenching in electric quadrupole transition strength as compared to its semi-magic 2250Ti28 neighbour. This 20% quenching, while empirically unprecedented, can be explained with a remarkably simple two-state mixing model, which is also consistent with other ground-state properties such as the magnetic dipole moment and electric quadrupole moment. A connection to nucleon transfer data and the quenching of single-particle strength is also demonstrated. The simplicity of the 49Ti-50Ti pair (i.e., approximate single-j 0f7/2 valence space and isolation of yrast states from non-yrast states) provides a unique opportunity to disentangle otherwise competing effects in the ground-state properties of atomic nuclei, the emergence of collectivity, and the role of proton-neutron interactions.

Single-neutron adding data was collected in order to determine the distribution of the single-neutron strength of the 0f_7/2 , 1p_3/2 , 1p_1/2 and 0f_5/2 orbitals outside of Z=16, N=18 , ^34 S. The ^34 S(d,p) ^35 S reaction has been measured at 8 MeV/u to investigate cross sections to excited states in ^35 S. Outgoing proton yields and momenta were analyzed by the Super-Enge Split-Pole Spectrograph in conjunction with the CeBrA demonstrator located at the John D. Fox Laboratory at Florida State University. Angular distributions were compared with Distorted Wave Born Approximation calculations in order to extract single-neutron spectroscopic overlaps. Spectroscopic overlaps and strengths were determined for states in ^35 S up through 6 MeV in excitation energy. Each orbital was observed to have fragmented strength where a single level carried the majority. The single-neutron centroids of the 0f_7/2 , 1p_3/2 , 1p_1/2 and 0f_5/2 orbitals were determined to be 2360^+90_-40 keV, 3280^+80_-50 keV, 4780^+60_-40 keV, and ≳ 7500 keV, respectively. A previous discrepancy in the literature with respect to the distribution of the neutron 1p_1/2 strength was resolved. The integration of the normalized spectroscopic strengths, up to 5.1 MeV in excitation energy, revealed fully-vacant occupancies for the 0f_7/2 , 1p_3/2 , and 1p_1/2 orbitals, as expected. The spacing in the single-neutron energies highlighted a reduction in the traditional N=28 shell-gap, relative to both the 1p spin-orbit energy difference ( N=32 ) and the lower limit on the N=34 shell spacing.

We report on a highly selective experimental setup for particle-γ coincidence experiments at the Super-Enge Split-Pole Spectrograph (SE-SPS) of the John D. Fox Superconducting Linear Accelerator Laboratory at Florida State University (FSU) using fast CeBr3 scintillators for γ-ray detection. Specifically, we report on the results of characterization tests for the first five CeBr3 scintillation detectors of the CeBr3 Array (CeBrA) with respect to energy resolution and timing characteristics. We also present results from the first particle-γ coincidence experiments successfully performed with the CeBrA demonstrator and the FSU SE-SPS. We show that with the new setup, γ-decay branching ratios and particle-γ angular correlations can be measured very selectively using narrow excitation energy gates, which are possible thanks to the excellent particle energy resolution of the SE-SPS. In addition, we highlight that nuclear level lifetimes in the nanoseconds regime can be determined by measuring the time difference between particle detection with the SE-SPS focal-plane scintillator and γ-ray detection with the fast CeBrA detectors. Selective excitation energy gates with the SE-SPS exclude any feeding contributions to these lifetimes.

The 25Al(p, gamma ) 26Si reaction is part of a reaction network with impact on the observed galactic 26Al abundance. A new determination of the proton strength of the lowest = 0 proton resonance in 26Si is required to more precisely calculate the thermal reaction rate. To this end, the 25Al(d, n) 26Si proton -transfer reaction is measured in inverse kinematics using an in-flight radioactive beam at the RESOLUT facility. Excitation energies of the lowest 26Si proton resonances are measured and cross sections are determined for the lowest = 0 resonance associated with the 3+3 state at 5.92(2) MeV. Coupled reaction channels calculations using FRESCO are performed to extract the = 0 spectroscopic factor for the 3+3 state. The proton width for the 3+3 state in 26Si is determined to be rp= 2.19(45) eV and the (p, gamma) resonance strength for the 3+3 state is extracted as 0.026(10) eV. This resonance dominates the 25Al(p, gamma) 26Si reaction rate above 0.2 GK.

The $\mathrm{^{25}Al(p,\gamma)^{26}Si}$ reaction is part of a reaction network with impact on the observed galactic $^{26}$Al abundance. A new determination of the proton strength of the lowest $\ell=0$ proton-resonance in $^{26}$Si is required to more precisely calculate the thermal reaction rate. To this end, the $\mathrm{^{25}Al(d,n)^{26}Si}$ proton-transfer reaction is measured in inverse kinematics using an in-flight radioactive beam at the RESOLUT facility. Excitation energies of the lowest $^{26}$Si proton resonances are measured and cross sections are determined for the lowest $\ell=0$ resonance associated with the $3^{+}_{3}$ state at 5.92(2) MeV. Coupled reaction channels (CRC) calculations using FRESCO are performed to extract the $\ell=0$ spectroscopic factor for the $3^{+}_{3}$ state. The proton width for the $3^{+}_{3}$ state in $^{26}$Si is determined to be $\Gamma_{p}$=2.19(45) eV and the $(p,\gamma)$ resonance strength for the $3^{+}_{3}$ state is extracted as 26(10) meV. This resonance dominates the $\mathrm{^{25}Al(p,\gamma)^{26}Si}$ reaction rate above 0.2 GK.

The $^{25}\mathrm{Al}(p,\ensuremath{\gamma})^{26}\mathrm{Si}$ reaction is part of a reaction network with impact on the observed galactic $^{26}\mathrm{Al}$ abundance. A new determination of the proton strength of the lowest $\ensuremath{\ell}=0$ proton resonance in $^{26}\mathrm{Si}$ is required to more precisely calculate the thermal reaction rate. To this end, the $^{25}\mathrm{Al}(d,n)^{26}\mathrm{Si}$ proton-transfer reaction is measured in inverse kinematics using an in-flight radioactive beam at the RESOLUT facility. Excitation energies of the lowest $^{26}\mathrm{Si}$ proton resonances are measured and cross sections are determined for the lowest $\ensuremath{\ell}=0$ resonance associated with the ${3}_{3}^{+}$ state at 5.92(2) MeV. Coupled reaction channels calculations using fresco are performed to extract the $\ensuremath{\ell}=0$ spectroscopic factor for the ${3}_{3}^{+}$ state. The proton width for the ${3}_{3}^{+}$ state in $^{26}\mathrm{Si}$ is determined to be ${\mathrm{\ensuremath{\Gamma}}}_{p}=2.19(45)$ eV and the $(p,\ensuremath{\gamma})$ resonance strength for the ${3}_{3}^{+}$ state is extracted as 0.026(10) eV. This resonance dominates the $^{25}\mathrm{Al}(p,\ensuremath{\gamma})^{26}\mathrm{Si}$ reaction rate above 0.2 GK.

Background: The lowest-lying shape oscillations of deformed nuclei have been described as quadrupole in nature (lambda = 2), resulting in two types of vibrations or oscillations: beta vibrations with oscillations along the symmetry axis (K pi = 0+) and gamma vibrations breaking axial symmetry with a projection of K pi = 2+ on the symmetry axis. The gamma vibration seems to be well characterized as the first K pi = 2+1 (or 2+gamma) band in deformed nuclei and exhibits a systematic behavior across the region. The nature of the K pi = 0+ excitations, however, has remained poorly understood and has been open to debate for some decades.Purpose: The goal of this work is to understand the nature of 0+ states observed in 168Er through measurements of the lifetimes of these states and to determine if they are consistent with oscillations built on a deformed ground state, the minima of other coexisting shapes, single-particle states, or a mixture of effects.Method: Lifetimes of excited states in the 168Er nucleus were measured with the Doppler shift attenuation method (DSAM) and the inelastic neutron scattering reaction, (n, n'gamma), at the University of Kentucky Accelerator Laboratory.Results: Numerous 0+ states had been observed by the (p, t) reaction [D. Bucurescu et al., Phys. Rev. C 73, 064309 (2006).]. We confirm the 0+ states at 1217.2, 1421.5, 1833.6, 2364.9, 2392.1, and 2643.0 keV in 168Er. We could not, however, support the previous assignments of 0+ levels at 2114.1, 2200.6, 2572.5, and 2617.4 keV. We report measured lifetimes for six confirmed 0+ excitations and additional members of 0+ bands.Conclusions: The results for 168Er show that it is the third excited K pi = 0+ (0+4 ) excitation that carries the collective strength and, therefore, the potential to be an oscillation on the ground state. This result is similar to the case in 166Er, where it was also the 0+4 state that exhibited greater collectivity than the first excited K pi = 0+ band. The Delaroche et al. [J.-P Delaroche et al., Phys. Rev. C 81, 014303 (2010).] prediction for a collective K pi = 0+ band is at ET = 1.818 MeV, which corresponds the third excited K pi = 0+ band.

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.

A measurement of the Ti(d,p)Ti reaction at 16 MeV was performed using a Super Enge Split Pole Spectrograph to measure the magnitude of the N = 32 subshell gap in Ti. Seven states were observed that had not been observed in previous (d,p) measurements, and the L transfer values for six previously measured states were either changed or measured for the first time. The results were used to determine single neutron energies for the p3/2, p1/2 and f5/2 orbitals. The resulting single neutron energies in Ti confirm the existence of the N = 32 gap in Ti. These single neutron energies and those from previous measurements in Ca, Cr and Fe are compared to values from a covariant density functional theory calculation.

The National Ignition Facility (NIF) provides the opportunity to study nuclear reactions under controlled conditions at high temperatures and pressures at a level never before achieved. However, the timescale of the deuterium-tritium (DT) implosion is only a few nanoseconds, making data collection and diagnostics very challenging. One method that has been proposed for obtaining additional information about the conditions of the implosion is to activate a dopant material using the alpha particles produced from the DT fuel as a diagnostic. The yield of the activated material can give a measure of the mixing that occurs in the capsule. One of the reactions that has been proposed is B-10(alpha, n) N-13 as it produces a radioactive reactant product with a convenient half-life of approximate to 10 min. Although this reaction has several advantages for the application at hand, it has not seen much study in the present literature, resulting in large uncertainties in the cross section. Furthermore, for the current application, the cross section must be well characterized. With this motivation, the B-10 (alpha, n) N-13 cross section has been remeasured for 2.2 < E-alpha, < 4.9 MeV with the angle-integrated ground-state cross section reported for the first time. The present results, combined with previous measurements, allow for a determination of the cross section to a significantly higher degree of accuracy and precision than obtained previously and are shown to be consistent with thick-target measurements. Preliminary calculations are performed to test the feasibility of this reaction as a diagnostic for a NIF implosion.

Q. Liu,1 M. Febbraro,2 R. J. deBoer,1 A. Boeltzig,1,* Y. Chen,1 C. Cerjan,3 M. Couder,1 B. Frentz,1 J. Görres,1 E. A. Henry,3 E. Lamere,1,† K. T. Macon,1,4 K. V. Manukyan,1 L. Morales,1 P. D. O’Malley,1 S. D. Pain,2 W. A. Peters,2 D. Schneider,3 C. Seymour,1 G. Seymour,1,‡ E. Temanson,2 R. Toomey,5 B. Vande Kolk,1 J. Weaver,6 and M. Wiescher1 1Department of Physics, The Joint Institute for Nuclear Astrophysics, University of Notre Dame, Notre Dame, Indiana 46556, USA 2Oak Ridge National Laboratory, Oak Ridge, Tennessee 37830, USA 3Lawrence Livermore National Laboratory, Livermore, California 94550, USA 4Department of Physics and Astronomy, Louisiana State University, Baton Rouge, Louisiana 70803, USA 5Department of Physics and Astronomy, Rutgers University, New Brunswick, New Jersey 08901, USA 6Material Measurement Laboratory, National Institute of Standards and Technology, Gaithersburg, Maryland 20899, USA

The National Ignition Facility provides the opportunity to study nuclear reactions under controlled conditions at high temperatures and pressures at a level never before achieved. However, the time scale of the deuterium-tritium (DT) implosion is only a few nanoseconds, making data collection and diagnostics very challenging. One method that has been proposed for obtaining additional information about the conditions of the implosion is to activate a dopant material using the α particles produced from the DT fuel as a diagnostic. The yield of the activated material can give a measure of the mixing that occurs in the capsule. One of the reactions that has been proposed is 10 B( α, n ) 13 N, as it produces a radioactive reactant product with an convenient half-life of ≈ 10 minutes. While this reaction has several advantages for the application at hand, it has not seen much study in the present literature, resulting in large uncertainties in the cross section. Further, for the current application, the cross section must be well characterized. With this motivation, the 10 B( α, n ) 13 N cross section has been remeasured from 2.2 < E α < 4.9 MeV, with the angle integrated ground state cross section reported for the first time. The present results, combined with previous measurements, allow for a determination of the cross section to a significantly higher degree of accuracy and precision than obtained previously, and are shown to be consistent with thick-target measurements. Preliminary calculations are performed to test the feasibility of this reaction as a diagnostic for a NIF implosion.

The National Ignition Facility (NIF) provides the opportunity to study nuclear reactions under controlled conditions at high temperatures and pressures at a level never before achieved. However, the timescale of the deuterium-tritium (DT) implosion is only a few nanoseconds, making data collection and diagnostics very challenging. One method that has been proposed for obtaining additional information about the conditions of the implosion is to activate a dopant material using the $\ensuremath{\alpha}$ particles produced from the DT fuel as a diagnostic. The yield of the activated material can give a measure of the mixing that occurs in the capsule. One of the reactions that has been proposed is $^{10}\mathrm{B}(\ensuremath{\alpha},n)\phantom{\rule{0.16em}{0ex}}^{13}\mathrm{N}$ as it produces a radioactive reactant product with a convenient half-life of $\ensuremath{\approx}10\phantom{\rule{0.16em}{0ex}}\mathrm{min}$. Although this reaction has several advantages for the application at hand, it has not seen much study in the present literature, resulting in large uncertainties in the cross section. Furthermore, for the current application, the cross section must be well characterized. With this motivation, the $^{10}\mathrm{B}(\ensuremath{\alpha},n)\phantom{\rule{0.16em}{0ex}}^{13}\mathrm{N}$ cross section has been remeasured for $2.2<{E}_{\ensuremath{\alpha}}<4.9\phantom{\rule{0.28em}{0ex}}\mathrm{MeV}$ with the angle-integrated ground-state cross section reported for the first time. The present results, combined with previous measurements, allow for a determination of the cross section to a significantly higher degree of accuracy and precision than obtained previously and are shown to be consistent with thick-target measurements. Preliminary calculations are performed to test the feasibility of this reaction as a diagnostic for a NIF implosion.

An array of neutron detectors based on liquid scintillator technology has been developed for nuclear reaction studies, in particular measurements with radioactive ion beams (RIBs). Reaction measurements with RIBs often involve low reaction yields and high gamma-induced backgrounds, which requires high solid angle coverage, high efficiency, and background reduction capability. The kinematics of the reaction neutrons require energy and position determination with good resolution, but preferably without a large number of readouts to minimize cost. To address these requirements, the Scintillation Array of Bars for Reaction Experiments (SABRE) consists of five 12” long, 2” diameter bar detectors filled with organic liquid scintillator and capped at both ends with individually read-out superbialkali photomultiplier tubes (PMTs). In-house purification of the scintillator mixtures resulted in improved light collection. Discussion of the liquid scintillator development and the design and commissioning of SABRE will be presented.