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A program to investigate the unitarity of the Cabibbo-Kobayashi-Maskawa (CKM) quark-mixing matrix by studying super-allowed mixed mirror β decays has been initiated at the TwinSol facility at Notre Dame. These mixed Fermi/Gamow-Teller (F-GT) decays, occurring between T=1/2 isospin doublets in mirror nuclei, provide a complimentary check on the data from super-allowed pure Fermi decays from 0+to 0+ states. The first part of the program, involving the measurement of the lifetimes of the relevant nuclei to the required accuracy of one part in 103 or better, has nearly been completed. However, the additional complication introduced by F-GT mixing requires the use of an ion trap to measure the mixing ratio ρ with similar accuracy. The lifetime measurements, as well as progress in installing an ion trap at TwinSol, will be discussed. In addition, since the ion trap will require a dedicated beam line for its operation, an opportunity presented itself to greatly improve the performance of TwinSol for reaction studies with exotic nuclei. This took the form of an added dipole switching magnet coupled to a third solenoid to form the new TriSol facility currently under construction. The expected properties of TriSol, and its application to reaction studies of interest for nuclear astrophysics, will also be discussed.

Type-I x-ray bursts can reveal the properties of an accreting neutron star system when compared with astrophysics model calculations. However, model results are sensitive to a handful of uncertain nuclear reaction rates, such as ^{22}Mg(α,p). We report the first direct measurement of ^{22}Mg(α,p), performed with the Active Target Time Projection Chamber. The corresponding astrophysical reaction rate is orders of magnitude larger than determined from a previous indirect measurement in a broad temperature range. Our new measurement suggests a less-compact neutron star in the source GS1826-24.

The half-life of $^{15}\mathrm{O}$ was measured using the $\ensuremath{\beta}$-Counting Station at the University of Notre Dame's Nuclear Science Laboratory. Our new result, ${t}_{1/2}=122.308(49)$ s, is the most precise determination to date for $^{15}\mathrm{O}$, and improves the world average by a factor of 4, yielding ${t}_{1/2}^{\text{world}}=122.27(6)$ s. This more precise value will be important for future determinations of ${V}_{\text{ud}}$ using superallowed $T=1/2$ mirror transitions.

Carbon and oxygen burning reactions, in particular, $^{12}\mathrm{C}+^{12}\mathrm{C}$ 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-$\ensuremath{\gamma}$ coincidence techniques with SAND (a silicon detector array) at the high-intensity 5U Pelletron accelerator. New results for $^{12}\mathrm{C}+^{12}\mathrm{C}$ 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.

A new precision half-life measurement of $^{29}\mathrm{P}$ was conducted using the TwinSol $\ensuremath{\beta}$-counting station at the University of Notre Dame Nuclear Science Laboratory. The resulting value of ${t}_{1/2}^{\mathrm{new}}=4.1055(44)\phantom{\rule{0.28em}{0ex}}\mathrm{s}$ is the most precise $^{29}\mathrm{P}$ half-life measurement to date. Utilizing this measurement and reevaluating the world data leads to a new world average of ${t}_{1/2}^{\mathrm{world}}=4.1031(58)\phantom{\rule{0.28em}{0ex}}\mathrm{s}$, which improves the Birge ratio from 3.11 to 1.45 and is 2.3 times more precise than the previous world value. The new Cabibbo-Kobayashi-Maskawa matrix element ${V}_{\mathrm{ud}}$ for $^{29}\mathrm{P}$ shifts closer into agreement with the superallowed pure Fermi value. The uncertainty in the mixed transition value of ${V}_{\mathrm{ud}}$, however, is still dominated by the Fermi to Gamow-Teller mixing ratio $\ensuremath{\rho}$. Using the new world half-life and assuming the validity of the standard model, a new predicted value for $\ensuremath{\rho}$ and its associated correlation parameters have been evaluated in order to guide future determination of $\ensuremath{\rho}$.

This book presents a history of cosmology, covering the scientific developments from the time of the early Greek philosophers until the present day. It introduces the most important discoveries in cosmology, and how they altered our perceptions of the origin, size, structure, and evolution of the universe.

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 14O(α,p)17F reaction is an important trigger reaction to the α-p process in X-ray bursts. The most stringent experimental constraints on its astrophysical rate come from measurements of the time-inverse reaction, 17F(p,α)14O. Previous studies of this inverse reaction have sufficiently characterized the high-energy dependence of the cross section but there are still significant uncertainties at lower energies. A new measurement of the 17F(p,α)14O cross section is underway at the Twin Solenoid (TwinSol) facility at the University of Notre Dame using an in-flight secondary 17F beam. The initial results are promising but improvements are needed to complete the measurement. The initial data and plans for an improved measurement are presented in this manuscript.

The elastic scattering of the radioactive proton-rich carbon isotope $^{10}\mathrm{C}$ has been investigated. A full differential angular distribution for the elastic scattering of $^{10}\mathrm{C}$ on a $^{58}\mathrm{Ni}$ target has been measured at ${E}_{\mathrm{Lab}}=35.3$ MeV, which is just above the Coulomb barrier for this system (${V}_{B}=27$ MeV). The obtained angular distribution was analyzed in terms of coupled-channels, coupled-reaction-channels, and continuum-discretized coupled-channels calculations. In the coupled-channels calculation, several inelastic transitions of the target and the first (${2}^{+}$) excited state of the $^{10}\mathrm{C}$ projectile were considered. The coupling to the first (${2}^{+}$) excited state of $^{10}\mathrm{C}$ was shown to be very important to describe the rising of the cross section at backward angles. We also performed an analysis with the continuum-discretized coupled channels, considering the $^{9}\mathrm{B}+p$ and $^{6}\mathrm{Be}+\ensuremath{\alpha}$ channels, which indicated a strong cluster configuration for the $^{10}\mathrm{C}$ projectile.

Electromagnetic observables are able to give insight into collective and emergent features in nuclei, including nuclear clustering. These observables also provide strong constraints for ab initio theory, but comparison of these observables between theory and experiment can be difficult due to the lack of convergence for relevant calculated values, such as $E2$ transition strengths. By comparing the ratios of $E2$ transition strengths for mirror transitions, we find that a wide range of ab initio calculations give robust and consistent predictions for this ratio. To experimentally test the validity of these ab initio predictions, we performed a Coulomb excitation experiment to measure the $B(E2;3/{2}^{\ensuremath{-}}\ensuremath{\rightarrow}1/{2}^{\ensuremath{-}})$ transition strength in $^{7}\mathrm{Be}$ for the first time. A $B(E2;3/{2}^{\ensuremath{-}}\ensuremath{\rightarrow}1/{2}^{\ensuremath{-}})$ value of $26{(6)}_{\mathrm{stat}}{(3)}_{\mathrm{syst}}\phantom{\rule{0.16em}{0ex}}{e}^{2}{\mathrm{fm}}^{4}$ was deduced from the measured Coulomb excitation cross section. This result is used with the experimentally known $^{7}\mathrm{Li}\phantom{\rule{4pt}{0ex}}B(E2;3/{2}^{\ensuremath{-}}\ensuremath{\rightarrow}1/{2}^{\ensuremath{-}})$ value to provide an experimental ratio to compare with the ab initio predictions. Our experimental value is consistent with the theoretical ratios within $1\ensuremath{\sigma}$ uncertainty, giving experimental support for the value of these ratios. Further work in both theory and experiment can give insight into the robustness of these ratios and their physical meaning.

We report a new precision half-life measurement of $^{20}\mathrm{F}$, performed using the $\ensuremath{\beta}$-counting station of the University of Notre Dame's Nuclear Science Laboratory. The measured half-life of $11.0160{(41)}_{\text{stat}}{(155)}_{\text{sys}}$ s resulting from this work will help resolve the longstanding discrepancy between two earlier sets of high-precision half-life measurements.

Much effort has been made to understand the origins of 18F in novae. Due to its relatively long half-life (~2 hours), 18F can survive until the nova envelope is transparent, and therefore can provide a sensitive diagnostic of nova nucleosynthesis. It is likely produced through the beta decay of 18Ne, which is itself produced (primarily) through the 17F(p,γ) reaction. Understanding the direct capture contribution to the 17F(p,γ) reaction is important to accurately calculate it. As such, the proton spectroscopic strengths of low-lying states in 18Ne are needed. At the University of Notre Dame a measurement of the 17F(d,n) reaction has been performed using a beam produced by the TwinSol low energy radioactive beam facility. Preliminary data analysis is presented.

Unexpected and challenging experimental results, at below barrier energies for weakly bound nuclei, are briefly reviewed in this article. The emphasis will be on our recent breakup results for 8B+208Pb at deep sub-barrier energies, indicating a dominance of direct mechanisms at this low energy regime. We will also present, a preliminary analysis of the 4He and 3He - particle production events for the 7Be + 208Pb reaction. These data were collected at the same experiment and at similar deep sub-barrier energies, exhibiting large yields compatible with cluster transfer processes. To confirm these results a new experiment to be performed at TriSol is planned, as soon as the upgrading of this facility will be completed.

The total fusion excitation function for 10 Be+ 40 Ar has been measured over the center-of-momentum (c.m.) energy range from 12 to 24 MeV using a time-projection chamber (TPC). The main purpose of this experiment, which was carried out in a single run of duration 90 h using a ≈100 particle per second (pps) 10 Be beam, was to demonstrate the capability of an active-target TPC to determine fusion excitation functions for extremely weak radioactive ion beams. Cross sections as low as 12 mb were measured with acceptable (50%) statistical accuracy. It also proved to be possible to separate events in which charged particles were emitted from the fusion residue from those in which only neutrons were evaporated. The method permits simultaneous measurement of incomplete fusion, break-up, scattering, and transfer reactions, and therefore fully exploits the opportunities presented by the very exotic beams that will be available from the new generation of radioactive beam facilities.

Helical spectrometers, such as the HELIOS device at Argonne National Laboratory, have proven to be a powerful tool for the study of nuclear spectroscopy (Lighthall, 2010). However, due to the expense in procuring a large bohr solenoid, relatively few of these devices exist. However, at the University of Notre Dame, TwinSol , is composed of two such magnets. The availability of intense light-ion beams from the Notre Dame Nuclear Science Laboratory (NSL) in combination with a large-bore superconducting solenoids provides an excellent opportunity to develop a new solenoid spectrometer at the University of Notre Dame, one optimized for measurements in normal kinematics.

We have surveyed a series of elastic scattering measurements from the literature involving tightly bound (9Li, 10Be, 12C, 16O, 19F), weakly bound (6Li, 7Li, 8Li, 8He, 9Be, 17F), and exotic (6He and 11Li) nuclei on a 208Pb target at energies close to the Coulomb barrier. The corresponding data were then converted and analyzed in terms of the interaction distance, where critical-interaction and strong-absorption distances were extracted. Larger values were obtained for the exotic 6He and 11Li nuclei, as compared with both weakly bound and tightly bound projectiles. The influence of long-range nuclear interactions and Coulomb dipole polarizability are discussed. A correlation between the critical interaction distance and binding energy for a given configuration is observed.

Background: The precise determination of the $\mathcal{F}t$ value in $T=1/2$ mixed mirror decays is an important avenue for testing the standard model of the electroweak interaction through the determination of ${V}_{ud}$ in nuclear $\ensuremath{\beta}$ decays. $^{11}\mathrm{C}$ is an interesting case, as its low mass and small ${Q}_{EC}$ value make it particularly sensitive to violations of the conserved vector current hypothesis. The present dominant source of uncertainty in the $^{11}\mathrm{C}\phantom{\rule{4pt}{0ex}}\mathcal{F}t$ value is the half-life.Purpose: A high-precision measurement of the $^{11}\mathrm{C}$ half-life was performed, and a new world average half-life was calculated.Method: $^{11}\mathrm{C}$ was created by transfer reactions and separated using the TwinSol facility at the Nuclear Science Laboratory at the University of Notre Dame. It was then implanted into a tantalum foil, and $\ensuremath{\beta}$ counting was used to determine the half-life.Results: The new half-life, ${t}_{1/2}=1220.27(26)$ s, is consistent with the previous values but significantly more precise. A new world average was calculated, ${t}_{1/2}^{\text{world}}=1220.41(32)$ s, and a new estimate for the Gamow-Teller to Fermi mixing ratio $\ensuremath{\rho}$ is presented along with standard model correlation parameters.Conclusions: The new $^{11}\mathrm{C}$ world average half-life allows the calculation of a $\mathcal{F}{t}^{\text{mirror}}$ value that is now the most precise value for all superallowed mixed mirror transitions. This gives a strong impetus for an experimental determination of $\ensuremath{\rho}$, to allow for the determination of ${V}_{ud}$ from this decay.

Ab-initio calculations have been able to reproduce emergent phenomena such as the formation of clusters in nuclei, a prominent feature in light nuclei. A number of ab-initio methods have made predictions for the B(E2; 3/2− → 1/2−) transition strength in the radioactive nucleus 7Be where a prominent α-3 He structure is expected. In order to test and guide these ab-inito methods, we have performed a Coulomb excitation experiment to measure the B(E2; 3/2− → 1/2−) in 7Be. Our current results point to the importance of reproducing cluster features in our nuclear models.Ab-initio calculations have been able to reproduce emergent phenomena such as the formation of clusters in nuclei, a prominent feature in light nuclei. A number of ab-initio methods have made predictions for the B(E2; 3/2− → 1/2−) transition strength in the radioactive nucleus 7Be where a prominent α-3 He structure is expected. In order to test and guide these ab-inito methods, we have performed a Coulomb excitation experiment to measure the B(E2; 3/2− → 1/2−) in 7Be. Our current results point to the importance of reproducing cluster features in our nuclear models.

Reaccelerated radioactive beams near the Coulomb barrier, which are starting to be available from the ReA3 accelerator at NSCL and in next future at FRIB, will open up new opportunities for the study of nuclear structure near the drip lines. Efficient measurement techniques must be developed to compensate for the limited intensity of the most exotic beams. The Active-Target Time Projection Chamber (AT-TPC) constructed at MSU solves this problem by providing the increased luminosity of a thick target while maintaining a good energy resolution by tracking the reaction vertex over an essentially 4 π solid angle. The AT-TPC and similar detectors allow us to take full advantage of the radioactive ion beams at present and future nuclear physics facilities to explore the frontier of rare isotopes.

Deuterated scintillators have been used as a tool for neutron spectroscopy without Neutron Time-of-Flight (n-ToF) for more than 30 years. This article will provide a brief historical overview of the technique and current uses of deuterated scintillators in the UM-DSA and DESCANT arrays. Pulse-shape discrimination and spectrum unfolding with the maximum-likelihood expectation maximization algorithm will be discussed. Experimental unfolding and cross section results from measurements of (d,n), ( 3 He,n) and (α,n) reactions are shown.

A cosmic-ray veto shield for the University of Notre Dame neutron wall has been constructed in order to carry out low-rate neutron time-of-flight (TOF) measurements. The veto detector employs plastic scintillator embedded with wavelength-shifting fibers and is read out by a versatile coupling to standard photomultiplier tubes (PMTs). This veto shield is effective at reducing the muon background by about one order of magnitude and therefore increases the sensitivity for experiments with low neutron yields. The 26Mg(3He,n)28Si reaction was used as a testbed for the veto.

TwinSol , a pair of coupled, superconducting solenoids, was one of the first devices capable of producing beams of radioactive nuclei at energies near the Coulomb barrier. A primary beam from University of Notre Dame (UND) tandem accelerator is used to bombard a primary target producing a secondary beam in flight. TwinSol is used to gather, separate, and focus the recoils. Since it was commissioned at the UND in 1997, at least 58 publications have reported data from its use and there have been hundreds of collaborators from many different countries that use this device. Currently, plans are in place at the UND to provide several upgrades to TwinSol , including a multi-cell gas production target and the possible addition of a third solenoid. Upgrades currently in progress will be discussed along with future plans.

Evaporation-proton yields were measured for the fusion of the weakly bound nucleus $^{6}\mathrm{Li}$ on a $^{58}\mathrm{Ni}$ target at six near- or sub-barrier bombarding energies. Effects of the one-neutron transfer reaction were estimated and corrections made. Total-fusion cross sections were deduced using calculated proton multiplicities. The resulting fusion excitation function shows a considerable enhancement with respect to calculations for a bare potential. Inelastic couplings are estimated to have insignificant effects on such fusion. The sum of total fusion plus one-neutron transfer cross sections nearly saturates the total reaction cross section in the energy region measured. Comparison with previous results appropriately scaled for the $^{6}\mathrm{Li}+(^{59}\mathrm{Co}, ^{64}\mathrm{Ni}, ^{64}\mathrm{Zn})$ systems shows good consistency except for some data spread at the lower energies.

A new precision half-life measurement of $^{25}\mathrm{Al}$ was conducted using the TwinSol $\ensuremath{\beta}$-counting station at the University of Notre Dame. The new measured value of ${t}_{1/2}^{\mathrm{new}}=7.1657(24)$ s is in good agreement with the most recent measurement, while being 3 times more precise. Using these new measurements, an evaluation of the $^{25}\mathrm{Al}$ half-life has been performed, leading to an average half-life of ${t}_{1/2}^{\mathrm{world}}=7.1665(26)$ s, which is 5 times more precise than it's predecessor and has a more satisfactory Birge ratio of 1.1. To aid in future measurements of correlation parameters, a new Fermi to Gamow-Teller mixing ratio $\ensuremath{\rho}$ and correlation parameters for this mixed transition have been calculated assuming the standard model validity using the new world half-life.