The beta -decaying states of 70 , 72 Co were studied at the National Superconducting Cyclotron Laboratory using the VANDLE neutron time -of -flight array. The (6 - , 7 - ) beta -decaying state in 70 Co is near -spherical with a lifetime of 113 +/- 7 ms, and the low -spin (1 + , 2 + ) beta -decaying state is postulated to be the prolate deformed ground state with a lifetime of 508 +/- 7 ms. Both decay predominantly to the bound states of 70 Ni. For the first time neutron -emissions from neutron unbound states from both the (6 - , 7 - ) and (1 + , 2 + ) beta decays were measured. Even with the low statistics data, we were able to disentangle the neutron emission from both decays, which enabled a determination of beta -decay strength above the neutron separation energy of 70 Ni. Neutron emission probabilities were measured to be 7 . 1 +/- 1 . 5% and 9 . 4 +/- 1 . 7%, respectively, for the (6 - , 7 - ) and (1 + , 2 + ) decays. The decay pattern of the 70 Co is driven by neutron f 5 / 2 to proton f 7 / 2 Gamow-Teller transformation. The observed population of neutron unbound states is attributed to the conversion of p 1 / 2 and p 3 / 2 neutrons to p 3 / 2 and p 1 / 2 protons excited across the Z = 28 closed shell.

We observed a new isomeric gamma transition at 168 keV in $^{36}$Mg, with a half-life of T$_{1/2}$=[130-500]$(\pm40)(^{+800}_{-20})_{sys}$ ns. We propose that the observed transition de-excites a new 0$^+$ isomeric state and populates the previously known first 2$^+$ state. The existence of this isomer is consistent with the predictions of the large-scale shell model calculations of $^{36}$Mg using the sdpf-u-mix interaction. The observed excitation energy of the second 0$^+$ state is caused by the small energy separation between two prolate-deformed configurations where the intruder configuration corresponds to two neutron excitations from the {\it sd} to the {\it pf} shell. Within this interpretation, $^{36}$Mg becomes the crossing point between nuclei in which ground state deformed/superdeformed configurations are caused by the dominance of N=20 intruders ($^{32,34}$Mg) and nuclei where deformed configurations are associated with N=28 intruders ($^{38}$Mg and beyond). We found the lack of three-body monopole corrections in other effective interactions results in a predominance of N=20 intruder configurations past $^{38}$Mg incompatible with our observation. We conclude that $^{36}$Mg bridges the N=20 and N=28 islands of inversion, forming the so-called Big Island of Deformation.

The astrophysical origin for the chemical elements between the first and second r-process peaks is a matter of intense debate, with a number of nucleosynthesis processes at explosive stellar environments possibly contributing to their production. Reliable data on the trends of neutron separation energies of neutron-rich isotopes are required to model neutron-capture processes that would produce these elements. Masses of 104Y, 106Zr, 112Mo, and 115Tc have been measured with the time-of-flight-magnetic-rigidity (ToF-B rho) technique at the National Superconducting Cyclotron Laboratory at Michigan State University. The experiment is the first application of the ToF-B rho technique at the S800 spectrograph that reached the mass region relevant to heavy-element nucleosynthesis. The two-neutron separation energy deduced from the measured masses exhibits a smooth trend consistent with the theoretical predictions within the range of experimental uncertainty, indicating that there is no sudden shape transition in these isotopes as hinted at by previous data.

We observed a new isomeric gamma transition at 168 keV in $^{36}$Mg, with a half-life of T$_{1/2}$=[130-500]$(\pm40)(^{+800}_{-20})_{sys}$ ns. We propose that the observed transition de-excites a new 0$^+$ isomeric state and populates the previously known first 2$^+$ state. The existence of this isomer is consistent with the predictions of the large-scale shell model calculations of $^{36}$Mg using the sdpf-u-mix interaction. The observed excitation energy of the second 0$^+$ state is caused by the small energy separation between two prolate-deformed configurations where the intruder configuration corresponds to two neutron excitations from the {\it sd} to the {\it pf} shell. Within this interpretation, $^{36}$Mg becomes the crossing point between nuclei in which ground state deformed/superdeformed configurations are caused by the dominance of N=20 intruders ($^{32,34}$Mg) and nuclei where deformed configurations are associated with N=28 intruders ($^{38}$Mg and beyond). We found the lack of three-body monopole corrections in other effective interactions results in a predominance of N=20 intruder configurations past $^{38}$Mg incompatible with our observation. We conclude that $^{36}$Mg bridges the N=20 and N=28 islands of inversion, forming the so-called Big Island of Deformation.

The total cross section of the $^{82}$Kr(p,$\gamma$)$^{83}$Rb reaction was measured for the first time at effective center-of-mass energies between 2.4 and 3.0 MeV, within the relevant Gamow window for the astrophysical $\gamma$ process. The experiment took place at the National Superconducting Cyclotron Laboratory at Michigan State University using the ReA facility. A $^{82}$Kr beam was directed onto a hydrogen gas cell located at the center of the Summing NaI(Tl) (SuN) detector. The obtained spectra were analyzed using the $\gamma$-summing technique and the extracted cross section was compared to standard statistical model calculations using the \textsc{non-smoker} and \textsc{talys} codes. The comparison indicates that standard statistical model calculations tend to overproduce the cross section of the $^{82}$Kr(p,$\gamma$)$^{83}$Rb reaction relative to the experimentally measured values. Furthermore, the experimental data was used to provide additional constraints on the nuclear level density and $\gamma$-ray strength function used in the statistical model calculations.

We explore the use of machine learning techniques to remove the response of large volume $\gamma$-ray detectors from experimental spectra. Segmented $\gamma$-ray total absorption spectrometers (TAS) allow for the simultaneous measurement of individual $\gamma$-ray energy (E$_\gamma$) and total excitation energy (E$_x$). Analysis of TAS detector data is complicated by the fact that the E$_x$ and E$_\gamma$ quantities are correlated, and therefore, techniques that simply unfold using E$_x$ and E$_\gamma$ response functions independently are not as accurate. In this work, we investigate the use of conditional generative adversarial networks (cGANs) to simultaneously unfold $E_{x}$ and $E_{\gamma}$ data in TAS detectors. Specifically, we employ a \texttt{Pix2Pix} cGAN, a generative modeling technique based on recent advances in deep learning, to treat \rawmatrix~ matrix unfolding as an image-to-image translation problem. We present results for simulated and experimental matrices of single-$\gamma$ and double-$\gamma$ decay cascades. Our model demonstrates characterization capabilities within detector resolution limits for upwards of 93% of simulated test cases.

One of the biggest questions in nuclear astrophysics is understanding where the elements come from and how they are made. This work focuses on the p process, a nucleosynthesis process that consists of a series of photodisintegration reactions responsible for producing stable isotopes on the proton-rich side of stability. These nuclei, known as the p nuclei, cannot be made through the well-known neutron-capture processes. Currently p-process models rely heavily on theory to provide the relevant reaction rates to predict the final p-nuclei abundances and more experimental data is needed. The present work reports on an experiment performed with the SuN detector at the National Superconducting Cyclotron Laboratory, NSCL, at Michigan State University using the ReA facility to measure the $^{84}$Kr(p,$\gamma$)$^{85}$Rb reaction cross section in inverse kinematics. The reverse $^{85}$Rb($\gamma$,p)$^{84}$Kr reaction is a branching point in the p-process reaction network that was highlighted as an important reaction in sensitivity studies in the production of the $^{78}$Kr p nucleus. A new hydrogen gas target was designed and fabricated and a new analysis technique for background subtraction and efficiency calculations of the detector were developed. The experimental cross section is compared to standard statistical model calculations using the NON-SMOKER and TALYS codes.

The beta decay of Zn-57 and Zn-58 was investigated in an experiment at the National Superconducting Cyclotron Laboratory of Michigan State University. For the first time beta-delayed proton emission from Zn-58 was observed with a branching ratio of 0.7(1)%. The proton-energy spectrum allowed for probing the Gamow-Teller strength distribution above the proton-separation energy in the daughter nucleus. Moreover, the absolute branching ration for delayed-proton emission from Zn-57 was found to be compatible with 100%.

Synchrotron radiation (μ-XRF) was applied to the study of organic-rich phosphatized limestones of NW Greece (Epirus). The results revealed uranium accumulation in areas of the material containing, among others, carbonate apatite (francolite) and organic matter. Uranium-bearing francolite crystals were separated from the rock and characterized by Raman spectroscopy and microprobe analysis. The analysis of francolite crystals also indicated the presence of sodium and sulfur. The ULIII-edge of μ-XANES spectra showed that uranium is present in tetravalent form. The uranium presence in the crystals was also visualized, after neutron irradiation and etching, by the observation of the fission tracks. Figure: Preliminary UL3-edge μ-XANES spectra. http://epublishing.ekt.gr | e-Publisher: EKT | Downloaded at 02/10/2020 15:32:05 | γ-ray spectrometry practices in the deep ocean C. Tsabaris 1 , D. L. Patiris 1 , E.G. Androulakaki 1,2 , G. Eleftheriou 1,2 , F.K. Pappa 1,2 , S. Alexakis 1 and C.A. Kalfas 3 1 Hellenic Centre for Marine Research, Institute of Oceanography, P.O. Box 712, GR-19013 Anavyssos, Greece 2 National Technical University of Athens, Department of Physics, Zografou Campus, GR-15780 Athens, Greece 3 National Centre for Scientific Research ‘‘Demokritos’’, Institute of Nuclear Physics, GR-15310 Agia Paraskevi, Greece

Cross section measurements of the Hf(n,2n)Hf and Hf(n,2n)Hf reactions have been performed at the VdG Tandem accelerator of NCSR “Demokritos” in Athens, in the neutron energy region from 8.8 to 11.5 MeV, using the activation technique. Statistical model calculations based on the Hauser Feshbach theory have also been implemented by using the code EMPIRE-II with different sets of input parameters. The predictions were compared to the data of the present work as well as data from literature.

To better understand the process of nucleosynthesis in stars today, advanced nuclear physics techniques are needed. At the National Superconducting Cyclotron Laboratory, at Michigan State University, a new tape transport system has been developed for this purpose. Radioactive nuclei can be implanted on the tape system, and after detecting the products of their decay, the tape rotates to remove any remaining unwanted activity. The present work focuses on the development of software to be used for calculating the optimum settings for experiments using the tape transport system.

Toward complete spectroscopy using β decay: The example of Cl(βγ )S E. Aboud,1,2,* M. B. Bennett,1,2,3,† C. Wrede,1,2,‡ M. Friedman,2 S. N. Liddick,2,4 D. Pérez-Loureiro,1,2 D. W. Bardayan,5 B. A. Brown,1,2 A. A. Chen,6 K. A. Chipps,7,8 C. Fry,1,2,3 B. E. Glassman,1,2 C. Langer,2,3 E. I. McNeice,6 Z. Meisel,1,2,3 W.-J. Ong,1,2,3 P. D. O’Malley,5 S. D. Pain,7 C. J. Prokop,2,4 H. Schatz,1,2,3 S. B. Schwartz,1,2,9 S. Suchyta,2,4 P. Thompson,7,8 M. Walters,6 and X. Xu1,2 1Department of Physics and Astronomy, Michigan State University, East Lansing, Michigan 48824, USA 2National Superconducting Cyclotron Laboratory, Michigan State University, East Lansing, Michigan 48824, USA 3Joint Institute for Nuclear Astrophysics, Michigan State University, East Lansing, Michigan 48824, USA 4Department of Chemistry, Michigan State University, East Lansing, Michigan 48824, USA 5Department of Physics, University of Notre Dame, Notre Dame, Indiana 46556, USA 6Department of Physics and Astronomy, McMaster University, Hamilton, Ontario L8S 4M1, Canada 7Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, USA 8Department of Physics and Astronomy, University of Tennessee, Knoxville, Tennessee 37996, USA 9Department of Geology and Physics, University of Southern Indiana, Evansville, Indiana 47712, USA

The $^{15}\mathrm{O}(\ensuremath{\alpha},\ensuremath{\gamma})^{19}\mathrm{Ne}$ reaction is expected to trigger the initial path for breakout from the CNO hydrogen-burning cycles to the rapid proton capture $(rp)$ process in type I x-ray bursts on accreting neutron stars. The thermonuclear reaction rate has a major impact on models of type I x-ray burst observables and it depends on the small $\ensuremath{\alpha}$-particle branching ratio, ${\mathrm{\ensuremath{\Gamma}}}_{\ensuremath{\alpha}}/\mathrm{\ensuremath{\Gamma}}$, of the 4.03 MeV state in $^{19}\mathrm{Ne}$. Attempts to measure ${\mathrm{\ensuremath{\Gamma}}}_{\ensuremath{\alpha}}/\mathrm{\ensuremath{\Gamma}}$ by populating the 4.03 MeV state using nuclear reactions have only led to strong upper limits. In the present work, we report the first experimental evidence that the 4.03 MeV $^{19}\mathrm{Ne}$ state is populated in $^{20}\mathrm{Mg} \ensuremath{\beta}$-delayed proton emission. This new channel has the potential to provide the necessary sensitivity to detect a finite value of ${\mathrm{\ensuremath{\Gamma}}}_{\ensuremath{\alpha}}/\mathrm{\ensuremath{\Gamma}}$.

Low-lying excited states in $^{38,40}\mathrm{P}$ have been identified in the $\ensuremath{\beta}$ decay of ${T}_{z}=+5,\phantom{\rule{0.16em}{0ex}}+6, ^{38,40}\mathrm{Si}$. Based on the allowed nature of the Gamow-Teller (GT) decay observed, these states are assigned spin and parity of ${1}^{+}$ and are core-excited 1p1h intruder states with a parity opposite to the ground state. The occurrence of intruder states at low energies highlights the importance of pairing and quadrupole correlation energies in lowering the intruder states despite the $N=20$ shell gap. Configuration interaction shell model calculations with the state-of-art SDPF-MU effective interaction were performed to understand the structure of these 1p1h states in the even-$A$ phosphorus isotopes. States in $^{40}\mathrm{P}$ with $N=25$ were found to have very complex configurations involving all the $fp$ orbitals leading to deformed states as seen in neutron-rich nuclei with $N\ensuremath{\approx}28$. The calculated GT matrix elements for the $\ensuremath{\beta}$ decay highlight the dominance of the decay of the core neutrons rather than the valence neutrons.

The β-decay intensity of ^{70}Co was measured for the first time using the technique of total absorption spectroscopy. The large β-decay Q value [12.3(3) MeV] offers a rare opportunity to study β-decay properties in a broad energy range. Two surprising features were observed in the experimental results, namely, the large fragmentation of the β intensity at high energies, as well as the strong competition between γ rays and neutrons, up to more than 2 MeV above the neutron-separation energy. The data are compared to two theoretical calculations: the shell model and the quasiparticle random phase approximation (QRPA). Both models seem to be missing a significant strength at high excitation energies. Possible interpretations of this discrepancy are discussed. The shell model is used for a detailed nuclear structure interpretation and helps to explain the observed γ-neutron competition. The comparison to the QRPA calculations is done as a means to test a model that provides global β-decay properties for astrophysical calculations. Our work demonstrates the importance of performing detailed comparisons to experimental results, beyond the simple half-life comparisons. A realistic and robust description of the β-decay intensity is crucial for our understanding of nuclear structure as well as of r-process nucleosynthesis.

Sensitive searches for exotic scalar and tensor couplings in nuclear and neutron decays involve precision measurements of the shape of the β -energy spectrum. We have performed a high statistics measurement of the β -energy spectrum in the allowed Gamow-Teller decay of 6 He with the aim to first find evidence of the contribution due to the weak magnetism form factor. We review here the motivation, describe the principle of the measurement, summarize the theoretical corrections to the allowed phase space, and anticipate the expected statistical precision.