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The α resonant scattering on 18Ne was measured in inverse kinematics to understand the α-clustering of proton-rich 22Mg nucleus, performed at the CNS Radio-Isotope Beam Separator (CRIB) of Center for Nuclear Study, University of Tokyo, located at the RIBF of RIKEN Nishina Center. The excitation function of 22Mg was obtained for the excitation energies of 10–16 MeV by adopting the thick-target method. Several resonances were evident in the present work, which implies the existence of energy levels with large α widths. Since energy levels were not clearly observed at the astrophysically important energy range, upper limits on the 18Ne (α, α)18Ne cross section were set. The astrophysical impact was also investigated by estimating the 18Ne (α, p)21Na cross section.

The rapid proton capture process (rp-process) is believed to be responsible for energy production and the synthesis of elements in X-ray bursts. Although understanding the $$(p,\gamma )$$ – $$(\gamma ,p)$$ equilibrium for a wide range of masses during the process is essential, it is hampered by the large uncertainties of several key isotopes participating in the rp-process. In the present work, we investigate the impacts of mass uncertainties on $$(p,\gamma )$$ – $$(\gamma ,p)$$ equilibria in the rp-process, which strongly affects the reaction paths, the isotopic abundances of nuclei with $$A > 65$$ , the effective lifetimes of waiting points, and the luminosity of X-ray bursts. The results show that current mass uncertainties still result in rather large deviations up to two orders of magnitude in many astrophysical photodisintegration rates. The numbers of isotopes and the values of the mass resolving power required for precise mass measurements using the multi-reflection time-of-flight (MR-TOF) technique are estimated for future experiments at modern radioactive ion beam facilities, including the RAON in Korea.

In this paper, we theoretically investigate 21 projectile-target combinations of stable isotopes for the pre-synthesis parameters and production cross sections of the unknown superheavy 309,312126 nuclei. It is found that 61Ni + 248Cf and 64Ni + 248Cf combinations are the best candidates for the synthesis of the 309,312126 isotopes due to their largest cross sections of 0.03 and 3.6 pb, respectively. Besides, the results in the present and previous works indicate that the uncertainty, from pb to zb, in the synthesis cross sections of superheavy nuclei should be narrowed for a decision of measurements using the presently available facilities. This study, thus, provides valuable data for the synthesis of 126th element.

The 24Mg(p,α)21 Na transfer reaction has been previously studied for a spectroscopic study of 21Na [Cha et al., Phys. Rev. C 96, 025810 (2017)]. In this follow-up analysis, the proton decays of the excited states of the radionuclide 21Na, which were measured simultaneously, are reported. By investigating the coincidence between the reaction α-particles and decay protons, we were able to identify three groups of events that are associated with the energy levels in 20Ne. The 20Ne excitation energy plot was obtained as a result. The four lowest known energy levels in 20Ne (the ground state and excited states at Ex = 1.633, 4.247 and 4.966 MeV) were clearly observed.

The direct transfer reaction is a powerful tool in nuclear spectroscopy because the single particle properties of populated energy levels can be studied through the measurement. Furthermore, the transfer reaction using radioactive heavy ion beams in inverse kinematics has become crucial for the study of nuclei far from stability. For the design of a detector system including a scattering chamber for the transfer reaction measurements, the calculations including relativistic kinematics, stopping power, and Gamow window need to be performed many times. To make these calculations easier, we developed a new toolkit written in the Java programming language.

We report the first (in)elastic scattering measurement of ^{25}Al+p with the capability to select and measure in a broad energy range the proton resonances in ^{26}Si contributing to the ^{22}Mg(α,p) reaction at type I x-ray burst energies. We measured spin-parities of four resonances above the α threshold of ^{26}Si that are found to strongly impact the ^{22}Mg(α,p) rate. The new rate advances a state-of-the-art model to remarkably reproduce light curves of the GS 1826-24 clocked burster with mean deviation

A MICROMEGAS (MICRO Mesh GASeous) detector is developed to monitor neutrons with a continuous energy spectra generated by bombarding protons on a thick Be target at the MC-50 cyclotron of the Korea Institute of Radiological and Medical Sciences (KIRAMS). Two different neutron spectra are produced by protons of 20 and 40 MeV, and are detected by using the MICROMEGAS detector with a boron converter. Boron carbides (B4C) are deposited on the cathode of the detector and are used as a neutron-to-charged particle converter. α particles and 7Li nuclei produced by the 10B(n,α)7Li reaction are detected by using the MICROMEGAS detector. Monte Carlo simulations for the detector system are performed to compare the experimental data with the simulation results. For measuring the energies of the α particles and the 7Li nuclei, we vary the geometry of detector in both the simulations and the experiments to fully stop the α particles and the 7Li nuclei in the detector. The changes of the positions of the α and the 7Li peaks observed in the distribution of the deposited energy for different detector geometries agree more or less with those from the simulation results. The neutron conversion efficiency of the detector is studied.

A fast ionization chamber with a high counting rate was commissioned at the 8 MV tandem accelerator complex of Kyushu University in Japan. Heavy ion beams consisting of 12C and 16O with Ebeam = 36 MeV were used to investigate the detector performance. By using various beam intensities ranging from 103 to 106 particles per second (pps), the maximum counting rate of the ion counter was measured to be about 8 × 105 pps. The detector performance under different gases was also investigated using two common gases in the ionization chamber: isobutane and P-10 gases. The results show that the negative effects due to pileups, which are often observed at high counting rates, can be greatly reduced when P-10 gas is used.

Decay protons from excited states in $^{21}\mathrm{Na}$ populated through a previously reported $^{24}\mathrm{Mg}(p,\ensuremath{\alpha})^{21}\mathrm{Na}$ transfer reaction [Cha et al., Phys. Rev. C 96, 025810 (2017)] were analyzed to extract the proton branching ratios of the energy levels. By utilizing 31-MeV proton beams from the Holifield Radioactive Ion Beam Facility of Oak Ridge National Laboratory and isotopically enriched $^{24}\mathrm{Mg}$ solid targets, the decay protons were detected in coincidence with $\ensuremath{\alpha}$ particles from the $(p,\ensuremath{\alpha})$ reaction using a silicon strip detector array. Proton decay branching ratios of several $^{21}\mathrm{Na}$ levels were deduced for the $p0$ and $p1$ decay channels to the ground and first excited states in $^{20}\mathrm{Ne}$, respectively.

In this paper, we examined the β −-decay half-lives of 94 extremely neutron-rich isotopes with Z = 26 − 57 close to the neutron drip line, which are important for the r-process calculations. The half-lives were calculated using four semi-empirical models and compared to those based on the FRDM+QRPA approach and available measured data. The impact of the difference in the models on the half-life predictions was investigated. We found that theoretical calculations for the β-decay half-life have a large deviation, up to 60%, which is mostly similar to that in measurements. The half-lives of the investigated nuclei are ranging from a few to hundreds of milliseconds. The r-process abundances in various astrophysical scenarios were calculated by using the predicted half-lives. The half-life uncertainty due to different models results in a large deviation in the isotopic abundance, specially for the isotopes in the mass range of A > 210. The shell closures in 76Fe is still a doubt due to the discrepancy in the trends of the half-life and paring gap while a closed-shell at N = 82 in 127Rh is possible. The results of this study also notice that it is a challenge for measuring precisely the masses of 106Rb, 116,117Nb, 122Tc, and 128Rh because of their short half-lives.

Energy production in Type Ia x-ray bursts depends on a number of nuclear reactions that become efficient in a hot environment (up to 2 GK). Model sensitivity studies have been performed in an effort to better identify the reactions that have the largest effect, but these efforts are hampered by the high level of complexity of the astrophysical model and large nuclear physics uncertainties. In a recent study, the $^{24}\mathrm{Mg}(\ensuremath{\alpha},p)^{27}\mathrm{Al}$ reaction was found to significantly affect the energy generation in x-ray bursts. This manuscript reports the first study of the $^{24}\mathrm{Mg}(\ensuremath{\alpha},{p}_{1,2}\ensuremath{\gamma})^{27}\mathrm{Al}$ reaction at energies relevant for x-ray bursts. The branches to the $^{27}\mathrm{Al}$ excited states increase to a small degree the estimates of the total astrophysical $^{24}\mathrm{Mg}(\ensuremath{\alpha},p)^{27}\mathrm{Al}$ reaction rate.

Nuclear reactions play a key role in the framework of the Big Bang Nucleosynthesis. A network of 12 principal reactions has been identified as the main path that drove the elemental nucleosynthesis in the first 20 min of the history of the Universe. Among them an important role is played by neutron-induced reactions, which, from an experimental point of view, are usually a difficult task to be measured directly. Nevertheless big efforts in the last decades have led to a better understanding of their role in the primordial nucleosynthesis network. In this work we apply the Trojan Horse Method to extract the cross section at astrophysical energies for the $$^3\text {He}$$ (n,p) $$^3\text {H}$$ reaction after a detailed study of the $$^2\hbox {H}$$ ( $$^3\text {He}$$ ,pt)H three-body process. Data extracted from the present measurement are compared with other published sets.

We report the first (in)elastic scattering measurement of ^{25}Al+p with the capability to select and measure in a broad energy range the proton resonances in ^{26}Si contributing to the ^{22}Mg(α,p) reaction at type I x-ray burst energies. We measured spin-parities of four resonances above the α threshold of ^{26}Si that are found to strongly impact the ^{22}Mg(α,p) rate. The new rate advances a state-of-the-art model to remarkably reproduce light curves of the GS 1826-24 clocked burster with mean deviation9% and permits us to discover a strong correlation between the He abundance in the accreting envelope of the photospheric radius expansion burster and the dominance of ^{22}Mg(α,p) branch.

The $^{7}\mathrm{Li}(\ensuremath{\gamma},t)^{4}\mathrm{He}$ ground state cross section was measured for the first time using monoenergetic $\ensuremath{\gamma}$ rays with energies between 4.4 and 10 MeV at the High Intensity Gamma-ray Source. The reaction is important for the primordial Li problem and for testing our understanding of the mirror $\ensuremath{\alpha}$-capture reactions $^{3}\mathrm{H}(\ensuremath{\alpha},\ensuremath{\gamma})^{7}\mathrm{Li}$ and $^{3}\mathrm{He}(\ensuremath{\alpha},\ensuremath{\gamma})^{7}\mathrm{Be}$. Although over the last 30 years most measurements of the $^{3}\mathrm{H}(\ensuremath{\alpha},\ensuremath{\gamma})^{7}\mathrm{Li}$ reaction have concentrated in an energy range below ${E}_{\ensuremath{\gamma}}=3.65$ MeV, measurements at higher energies could potentially restrict the extrapolation to astrophysically important energies. The experimental arrangement for measuring the $^{7}\mathrm{Li}(\ensuremath{\gamma},t)^{4}\mathrm{He}$ reaction included a large-area silicon detector array and several beam characterization instruments. The experimental astrophysical $S$ factor of $^{3}\mathrm{H}(\ensuremath{\alpha},\ensuremath{\gamma})$ calculated from the present data was fitted using the $R$-matrix formalism. The results are in disagreement with previous experimental measurements in the same energy range but the extrapolated $S$ factor agrees with the potential model calculation and lower energy experimental data.

The $$^{22}\hbox {Na}(p,\gamma )^{23}\hbox {Mg}$$ reaction is responsible for destruction of the long-lived radionuclide $$^{22}\hbox {Na}$$ produced during nova explosions. Since the reaction proceeds through resonances from levels in $$^{23}\hbox {Mg}$$ above the proton threshold at 7.581 MeV, the properties of these levels such as excitation energies, spins, and parities are crucial ingredients to determine the $$^{22}\hbox {Na}(p,\gamma )^{23}\hbox {Mg}$$ reaction rate. Despite recent studies of these levels, their spins are not well constrained in many cases. We have measured the $$^{24}\mathrm{Mg}(p,d)^{23}\hbox {Mg}$$ transfer reaction to determine spectroscopic properties of these levels at the Holifield Radioactive Ion Beam Facility at Oak Ridge National Laboratory. The spin of the $$E_{x}$$ = 7.788 MeV level in $$^{23}\hbox {Mg}$$ is constrained to be $$J^{\pi }$$ = (3/2$$^+$$, 5/2$$^+$$) through the present work. The astrophysical $$^{22}\hbox {Na}(p,\gamma )^{23}\hbox {Mg}$$ reaction rate at nova temperatures is updated accordingly. Nova nucleosynthesis model calculations using the newly updated $$^{22}\hbox {Na}(p,\gamma )^{23}\hbox {Mg}$$ reaction rate shows that the final weighted abundance of the radionuclide $$^{22}\hbox {Na}$$ is increased by 42% compared to that obtained by using the previous $$^{22}\hbox {Na}(p,\gamma )^{23}\hbox {Mg}$$ reaction rate of Sallaska et al. for a 1.35 $$M_{\odot }$$ ONeMg white dwarf.

At low-energy nuclear physics facilities, the in-flight fragmentation method is often employed to produce radioactive ion beams. This technique often involves a stable ion beam at high intensity and a gas cell target. Since the parameters for the production reaction are usually chosen to take advantage of a large cross section of the resonance reaction, a slight change in the center-of-mass energy due to the reduced target density may significantly affect the rare isotope production rate. Therefore, to estimate the heating effect due to beam particles on the target thickness, a new and more comprehensive semi-empirical model is developed by employing a heating factor function. The estimated heating factors were consistent with experimental data, which were obtained from various reaction measurements at wide ranges of heat densities.

The solar neutrino is a good probe for understanding the internal structure and the energy production mechanism of stars with masses of about that of the sun because it does not interact with other materials of the star. The production rate of the solar neutrino is largely uncertain due to the lack of nuclear structure information on the 8B nucleus. In the search for resonances in the highly unstable nucleus 8B, which affect the production of solar neutrino, the 2H(7Be, p+3He+4He)n reaction was studied by using a radioactive 7Be beam produced at the Holifield Radioactive Ion Beam Facility of the Oak Ridge National Laboratory. Two layers of annular silicon strip detectors were used for particle identification, and the excitation energy of 8B was reconstructed by requiring triple coincidence for p, 3He, and 4He.

The α-clusterization of an atomic nucleus has been studied for a long time, even from the earliest days of nuclear physics. Our understanding of the α-cluster structure is, however, mainly limited to the self-conjugate A = 4n (n = 2, 3, 4, · · · ) light nuclei and some of the neutron-rich radionuclides such as 10Be, 11B, and 14C. In order to study the α-cluster structure of a neutron-deficient 22Mg nucleus, we have measured the 18Ne(α, α)18Ne scattering in inverse kinematics by using radioactive 18Ne beams and the 4He gas target at the Center for Nuclear Study radioactive ion beam separator of the University of Tokyo. Recoiling α particles from the scattering were detected by using silicon strip detectors, which constitute ΔE-E telescopes for particle identification. By adopting a thick target method, we were able to investigate a wide range of excitation energies Ex = 9.9 - 16.5 MeV in 22Mg in this work.

A silicon detector combined with a thin polyethylene converter and a collimator is designed as a simple proton recoil telescope (PRT) detector for detecting 2.45 MeV neutrons from a D-D neutron generator. Monte Carlo simulations are performed for a quantitative optimization of the geometrical parameters of the detector that determine the statistics and the spectrum of recoil protons. On the basis of the optimized geometry, a 15 μm polyethylene converter and a 2.5 mm thick stainless steel collimator are chosen for the design of a PRT. A test experiment is done by using 2.45 MeV neutrons from a D-D generator at the Korea Research Institute of Standards and Science. Energy calibration of the silicon detector is done by using proton beams from the MC-50 cyclotron at the Korea Institute of Radiological & Medical Sciences. A peak corresponding to 2.45 MeV neutrons is observed. Neutron detection efficiency of our PRT detector for 2.45 MeV neutrons is found to be about 3 × 10 −6.

Direct measurements of ( α , p ) reactions of astrophysical interest with radioactive beams presents serious challenges because of the difficult nature of helium targets and the typical low intensities of the beams. To address this, a new technique has been developed for measurements of low-energy ( α , p ) reactions with heavy ion beams using an extended 4 He gas target and a newly developed gas recirculating system. The system was used to measure the 4 He(19F, 1 H)22Ne reaction as a demonstration. Excitation functions of the 19F( α , p )22Ne and 19F( α , p ′ )22Ne ∗ reactions were successfully measured to show the viability of this technique. Details of the approach and future plans are given.

The intense γ-rays from classical novae are emitted due to the β-decay of 18F which is produced by the Hot-CNO cycle. The reaction rate of 18F(p,α)15O affects the prediction of the abundance of 18F. The main contribution to this reaction rate is from the resonances in 19Ne near and above the proton threshold. Hence, many experiments and theoretical works have been performed on the low-lying 18F+p resonances. One of the methods for investigating 19Ne parameters is studying the mirror nucleus 19F. α elastic scattering experiment was performed with a 7 MeV/u 15N beam for investigating the resonance parameters in 19F using the thick target method in inverse kinematics at the radioactive beam facility CRIB of the Center for Nuclear Study, the University of Tokyo. The excitation function of 19F was obtained for the excitation energy Ex = 6.7 - 7.7 MeV, and the parameters of the resonance states in 19F were determined using an R-matrix analysis.

We conducted a measurement of 18Ne + α scattering in inverse kinematics , in order to search for experimental evidence of α -cluster structure in 22Mg above the alpha threshold ( E thr = 8 . 14 MeV ) and determine the astrophysical rates of the 18Ne( α , p)21Na reaction under the conditions of break-out from the Hot-CNO cycle. A high intensity 18 Ne beam at 2.54 AMeV was successfully produced at CRIB (CNS Radioactive Ion Beam separator) of the Center for Nuclear Study, the University of Tokyo. This paper presents the in-flight production of the radioactive 18Ne beam by using the production reaction 3He(16O, 18Ne)n with a windowed cryogenic gas target, which was employed in the mentioned resonant α -scattering experiment.

The β −-decay half-lives of extremely neutron-rich nuclei are important for understanding nucleosynthesis in the rapid neutron capture process (r-process). However, most of their half-lives are unknown or very uncertain, leading to the need for reliable calculations. In this study, we updated the coefficients in recent semi-empirical formulae using the newly updated mass (AME2020) and half-life (NUBASE2020) databases to improve the accuracy of the half-life prediction. In particular, we developed a new empirical model for better calculations of the β −-decay half-lives of isotopes ranging in Z = 10–80 and N = 15–130. We examined the β −-decay half-lives of the extremely neutron-rich isotopes at and around the neutron magic numbers of N = 50, 82, and 126 using either five different semi-empirical models or finite-range droplet model and quasi-particle random phase approximation method. The β −-decay rates derived from the estimated half-lives were used in calculations to evaluate the impact of the half-life uncertainties of the investigated nuclei on the abundance of the r-process. The results show that the half-lives mostly range in 0.001 < T 1/2 < 100 s for the nuclei with a ratio of N/Z < 1.9; however, they differ significantly for those with the ratio of N/Z > 1.9. The half-life differences among the models were found to range from a few factors (for N/Z < 1.9 nuclei) to four orders of magnitude (for N/Z > 1.9). These discrepancies lead to a large uncertainty, which is up to four orders of magnitude, in the r-process abundance of isotopes. We also found that the multiple-reflection time-of-flight technique is preferable for precise mass measurements because its measuring timescale applies to the half-lives of the investigated nuclei. Finally, the results of this study are useful for studies on the β-decay of unstable isotopes and astrophysical simulations.

The level structure of a radionuclide 23Mg has been studied by using the 24Mg(p, d)23Mg one nucleon transfer reaction measurement for the astrophysical 19Ne(α, γ)23Mg reaction rate. A 41 MeV proton beam was produced and accelerated at the 25 MV tandem accelerator of the Holifield Radioactive Ion Beam Facility of the Oak Ridge National Laboratory in the United States. The beam particles impinged on an isotopically-enriched 24Mg solid target. Angular distributions of recoiling deuterons were extracted by using a large area silicon strip detector array. By comparing the experimentally-obtained angular distributions with zero range distorted wave Born approximation calculations, spins and parities of three energy levels of 23Mg could be constrained for the first time, which is very important information needed to understand the 19Ne(α, γ)23Mg reaction rate.

In-flight fission of a 345 MeV per nucleon 238U primary beam on a 2 mm thick 9Be target has been used to produce and study the decays of a range of neutron-rich nuclei centred around the doubly mid-shell nucleus 170Dy at the RIBF Facility, RIKEN, Japan. The produced secondary fragments of interest were identified eventby- event using the BigRIPS separator. The fragments were implanted into the WAS3ABI position sensitive silicon active stopper which allowed pixelated correlations between implants and their subsequent β-decay. Discrete γ-ray transitions emitted following decays from either metastable states or excited states populated following beta decay were identified using the 84 coaxial high-purity germanium (HPGe) detectors of the EURICA spectrometer, which was complemented by 18 additional cerium-doped lanthanum bromide (LaBr3)

A gas-filled ionization chamber is well suited for low energy nuclear physics applications such as measuring beam intensities and detecting heavy recoils from nuclear reactions. Recently developed multi-electrode ionization chamber shows great performance in terms of the energy resolution and the maximum counting rate. It requires, however, iterative energy loss calculations for certain applications mainly due to its complex geometry. For easier energy loss calculations, a stopping power calculation code called the Multi-electrode Ionization Chamber Energy Loss Calculator (MICE) has been developed by utilizing the Java programming language. The development procedure, usage, and application of the MICE are reported.

It is a well-known fact that a cluster of nucleons can be formed in the interior of an atomic nucleus, and such clusters may occupy molecular-like orbitals, showing characteristics similar to normal molecules consisting of atoms. Chemical molecules having a linear alignment are commonly seen in nature, such as carbon dioxide. A similar linear alignment of the nuclear clusters, referred to as linear-chain cluster state (LCCS), has been studied since the 1950s, however, up to now there is no clear experimental evidence demonstrating the existence of such a state. Recently, it was proposed that an excess of neutrons may offer just such a stabilizing mechanism, revitalizing interest in the nuclear LCCS, specifically with predictions for their emergence in neutron-rich carbon isotopes. Here we present the experimental observation of {\alpha}-cluster states in the radioactive 14C nucleus. Using the 10Be+{\alpha} resonant scattering method with a radioactive beam, we observed a series of levels which completely agree with theoretically predicted levels having an explicit linear-chain cluster configuration. We regard this as the first strong indication of the linear-chain clustered nucleus., Comment: 15 pages, 3 figures

Results are presented from the first neutron-transfer measurement on $^{80}\mathrm{Ge}$ using an exotic beam from the Holifield Radioactive Ion Beam Facility at Oak Ridge National Laboratory. Newly measured spins and spectroscopic factors of low-lying states of $^{81}\mathrm{Ge}$ are determined, and the neutron capture cross section on $^{80}\mathrm{Ge}$ was calculated in a direct-semidirect model to provide a more realistic ($n,\ensuremath{\gamma}$) reaction rate for $r$-process simulations. Furthermore, a region of shape coexistence around $N\ensuremath{\approx}50$ is confirmed and implications for the magic nature of $^{78}\mathrm{Ni}$ are discussed.

The β-delayed γ-ray spectroscopy of neutron-rich 123;125Ag isotopes is investigated at the Radioactive Isotope Beam Factory of RIKEN and the long-predicted 1/2¯ β-emitting isomers in 123;125Ag are identified for the first time. With the new experimental results, the systematic trend of energy spacing between the lowest 9/2+ and 1/2¯ levels is extended in Ag isotopes up to N = 78, providing a clear signal for the reduction of the Z = 40 subshell gap in Ag towards N = 82. Shellmodel calculations with the state-of-the-art VMU plus M3Y spin-orbit interaction give a satisfactory description of the low-lying states in 123;125Ag. The tensor force is found to play a crucial role in the evolution of the size of the Z = 40 subshell gap. The observed inversion of the single particle levels around 123Ag can be well interpreted in terms of the monopole shift of the π1g9/2 orbitals mainly caused by the increasing occupation of ʋ1h11/2 orbitals.

The astrophysical $S$-factor for the radiative proton capture reaction on $^7$Be ($S_{17}$) at low energies is affected by the $s$-wave scattering lengths. We report the measurement of elastic and inelastic scattering cross sections for the $^7$Be+p system in the center-of-mass energy range 0.474 - 2.740 MeV and center-of-mass angular range of 70$^\circ$- 150$^\circ$. A radioactive $^7$Be beam produced at Oak Ridge National Laboratory's (ORNL) Holifield Radioactive Ion Beam Facility was accelerated and bombarded a thin polypropylene (CH$_{2}$)$_\text n$ target. Scattered ions were detected in the segmented Silicon Detector Array. Using an $\textit{R}$-matrix analysis of ORNL and Louvain-la-Neuve cross section data, the $s$-wave scattering lengths for channel spins 1 and 2 were determined to be 17.34$^{+1.11}_{-1.33}$ and -3.18$^{+0.55}_{-0.50}$ fm, respectively. The uncertainty in the $s$-wave scattering lengths reported in this work is smaller by a factor of 5-8 compared to the previous measurement, which may reduce the overall uncertainty in $S_{17}$ at zero energy. The level structure of $^8$B is discussed based upon the results from this work. Evidence for the existence of 0$^+$ and 2$^+$ levels in $^8$B at 1.9 and 2.21 MeV, respectively, is observed.

Half of the elements heavier than iron are believed to be produced through the rapid neutron-capture process ($r$ process). The astrophysical environment(s) where the $r$ process occurs remains an open question, even after recent observations of neutron-star mergers and the associated kilonova. Features in the abundance pattern of $r$-process ashes may provide critical insight for distinguishing contributions from different possible sites, including neutron-star mergers and core-collapse supernovae. In particular, the largely unknown neutron-capture reaction rates on neutron-rich unstable nuclei near $^{132}\mathrm{Sn}$ could have a significant impact on the final $r$-process abundances. To better determine these neutron-capture rates, the $(d,p)$ reaction has been measured in inverse kinematics using radioactive ion beams of $^{126}\mathrm{Sn}$ and $^{128}\mathrm{Sn}$ and a stable beam of $^{124}\mathrm{Sn}$ interacting with a ${({\mathrm{CD}}_{2})}_{n}$ target. An array of position-sensitive silicon strip detectors, including the Super Oak Ridge Rutgers University Barrel Array, was used to detect light reaction products. In addition to the present measurements, previous measurements of $^{130,132}\mathrm{Sn}(d,p)$ were reanalyzed using state-of-the-art reaction theory to extract a consistent set of spectroscopic factors for $(d,p)$ reactions on even tin nuclei between the heaviest stable isotope $^{124}\mathrm{Sn}$ and doubly magic $^{132}\mathrm{Sn}$. The spectroscopic information was used to calculate direct-semidirect $(n,\ensuremath{\gamma})$ cross sections, which will serve as important input for $r$-process abundance calculations.

The $^{15}$O($\alpha$,$\gamma$)$^{19}$Ne reaction is responsible for breakout from the hot CNO cycle in Type I x-ray bursts. Understanding the properties of resonances between $E_x = 4$ and 5 MeV in $^{19}$Ne is crucial in the calculation of this reaction rate. The spins and parities of these states are well known, with the exception of the 4.14- and 4.20-MeV states, which have adopted spin-parities of 9/2$^-$ and 7/2$^-$, respectively. Gamma-ray transitions from these states were studied using triton-$\gamma$-$\gamma$ coincidences from the $^{19}$F($^{3}$He,$t\gamma$)$^{19}$Ne reaction measured with GODDESS (Gammasphere ORRUBA Dual Detectors for Experimental Structure Studies) at Argonne National Laboratory. The observed transitions from the 4.14- and 4.20-MeV states provide strong evidence that the $J^\pi$ values are actually 7/2$^-$ and 9/2$^-$, respectively. These assignments are consistent with the values in the $^{19}$F mirror nucleus and in contrast to previously accepted assignments.

This work presents the nuclear level scheme (NLS) of 164Dy nucleus obtained from the 163Dy(n t h ,2γ) experiment. The latter has used a γ − γ coincidence spectrometer to measure the two-step gamma cascades corresponding to the decays from the compound state to 9 low-lying states of 164Dy, whose energies are 0.0, 73.393, 242.234, 761.815, 828.215, 915.991, 976.916, 1039.309, and 1122.774 keV. Based on the measured data, the 164Dy NLS, which consists of 64 primary gamma transitions and their corresponding intermediate levels, together with 132 secondary gamma transitions, has been constructed. Among these data, 20 primary gamma transitions, 51 intermediate levels, and 63 secondary gamma transitions are found to be the same as those currently exist in the Evaluated Nuclear Structure Data File (ENSDF) database. The remaining data, which include 44 primary transitions, 13 intermediate levels, and 69 secondary transitions, are therefore, considered as an update for the NLS of 164Dy. In particular, the spin values of 57 observed intermediate levels have been tentatively assigned by means of transition rules. Furthermore, the influence of the present experimental data on the nuclear level density and radiative strength function is also discussed.

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 134 Xe 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 135 Xe, including previously unobserved states based on the orbitals above the N=82 shell closure.

Physics letters / B 762, 404 - 408 (2016). doi:10.1016/j.physletb.2016.09.058, Published by North-Holland Publ., Amsterdam

A position-sensitive ionization chamber has been constructed and commissioned at the Physics Department of Sungkyunkwan University to extract position information on incident charged particles for future nuclear reaction measurements. By utilizing the newly-designed position-sensitive anodes and the previously-commissioned portable gas-filled ionization chamber by Chae et al., position information on incident particles could be obtained. The device was tested with an 241Am α-emitting source, and the standard deviation of the fitted Gaussian distribution was measured to be 1.76 mm when a collimator with a 2 mm hole was used.

The one or few nucleon transfer reaction has been a great tool for investigating the single-particle properties of a nucleus. Both stable and exotic beams are utilized to study transfer reactions in normal and inverse kinematics, respectively. Because many energy levels of the heavy recoil from the two-body nuclear reaction can be populated by using a single beam energy, identifying each populated state, which is not often trivial owing to high level-density of the nucleus, is essential. For identification of the energy levels, a visualized kinematics code called VISKIN has been developed by utilizing the Java programming language. The development procedure, usage, and application of the VISKIN is reported.

In this paper, we estimated half-lives using semi-empirical formulae for isotopes with Z = 100 − 126 in four α-decay chains, which can appear in the syntheses of the 309−312126 nuclei. The spontaneous fission half-lives were calculated using the Anghel, Karpov, and Xu models, whereas the α-decay ones were predicted using the Viola-Seaborg, Royer, Akrawy, Brown, modified formulae of Royer, Ni, and Qian approaches. We found that there are large differences among the spontaneous fission half-lives estimated using the Xu model and those calculated using the others, which are up to 50 orders of magnitude. The α-decay half-lives also have large uncertainties due to difference in either methods or uncertainties in nuclear mass and spin-parities. Subsequently, there is an argument in determination of α-emitters, especially for the 312126 isotope. On the other hand, the α-decay half-lives are in the range from a few microseconds (309−312126) to thousands of years (257−260Fm) in the decay chains. It was found that the half-lives are very sensitive to not only the shell closure but also the angular momentum in the α decay. For experiments, with relatively long half-lives (a few milliseconds), the 289−292Lv isotopes can be observed as evidences for syntheses of the unknown super-heavy 309−312126 nuclei. Furthermore, measurements for precise mass, fission barrier, and spin-parity are necessary to improve accuracy of half-life predictions for super-heavy nuclei.

In the network of reactions present in the Big Bang nucleosynthesis, the 3He(n, p)3H reaction has an important role which impacts the final 7Li abundance. The Trojan Horse Method (THM) has been applied to the 3He(d, pt)H reaction in order to extract the astrophysical S(E)-factor of the 3He(n, p)3H reaction in the Gamow energy range. The experiment will be described in the present work together with the first preliminary results.

We performed indirect measurements of the neutron-induced reactions \(^{7}\)Be(n,p)\(^{7}\)Li and \(^{7}\)Be(n,\(\mathsf \alpha \))\(^{4}\)He simultaneously by the Trojan Horse method relevant to the cosmological \(^7\)Li problem. Preliminary excitation functions for \((n,p_0)\) and \((n,\alpha )\) are basically consistent with the previous studies, and new information about the \((n,p_1)\) contribution suggests possible enhancement of the total reaction rate.