abstract

On August 17, 2017 the LIGO–Virgo Collaboration detected, for the first time, gravitational waves from the binary merger of two neutron stars (GW170817). Unlike the merger of two black holes, the associated electromagnetic radiation was also detected by a host of telescopes operating over a wide range of frequencies — opening a brand new era of multimessenger astronomy. This historical detection is providing fundamental new insights into the astrophysical site for the r-process and on the nature of dense matter. In this contribution, we examine the impact of GW170817 on the equation of state of neutron rich matter, particularly on the density dependence of the symmetry energy. Limits on the tidal polarizability extracted from GW170817 seem to suggest that the symmetry energy is soft, thereby excluding models that predict overly large stellar radii.

abstract

We discuss several recent developments connecting the fundamental theory of the strong interactions and bare nuclear forces to nuclear structure and reactions. In particular, we review recent results in the area of nuclear lattice simulations based on chiral effective field theory by the Nuclear Lattice EFT Collaboration. The topics we cover are lattice interactions with improved rotational properties, nuclear physics near a quantum phase transition, seeing nuclear structure through pinholes, and a computational method called eigenvector continuation.

abstract

The effects of the residual interaction in the particle–particle channel on \(\beta \)-decay characteristics and the multi-neutron emission probabilities in the \(\beta \)-decay of \(^{130,132}\)Cd are studied within the quasiparticle random phase approximation with the Skyrme interaction. The coupling between one- and two-phonon terms in the wave functions of the low-energy 1\(^{+}\) states of the daughter nuclei is taken into account. It is shown that the inclusion of the spin–isospin interaction in the particle–particle channel leads to the reduction of half-lives and redistribution of one- and two-neutron emission probabilities. The competition of tensor interaction and neutron–proton pairing contribution in \(\beta \)-decay characteristics of the neutron-rich Cd isotopes is discussed.

abstract

We take an additional step towards the optimization of the novel finite-range pseudopotential at a constrained Hartree–Fock–Bogolyubov level and implement an optimization procedure within an axial code using harmonic oscillator basis. We perform the optimization using three different numbers of the harmonic oscillator shells. We apply the new parameterizations in the O–Kr part of the nuclear chart and isotopic chain of Sn, and we compare the results with experimental values and those given by a parameterization obtained using a spherical code.

abstract

In recent measurements of prompt \(\gamma \) rays from the spontaneous fission of \(^{252}\)Cf, the focus was put on the study of angular correlations between \(\gamma \) rays and the nuclei from which they were emitted, and the dependence between prompt fission \(\gamma \)-ray characteristics and fission fragment mass, respectively. First preliminary results are presented and compared to results from other experiments as well as from model calculations.

abstract

The structure of the \(^{131}\)Sn nucleus was studied at the Institut Laue-Langevin by prompt-delayed \(\gamma \)-ray spectroscopy across the 0.3-\(\mu \)s, 23/2\(^-\) isomeric state at 4670 keV, following cold-neutron-induced fission of \(^{235}\)U and \(^{241}\)Pu targets. New \(\gamma \)-ray transitions are observed and the results are compared with theoretical calculations performed with the Hybrid Configuration Mixing Model. The latter suggests that the majority of the states can be well-described in terms of couplings between single-hole degrees of freedom and \(^{132}\)Sn core excitations, pointing to a robust neutron shell closure at \(N=82\).

abstract

With an aim to study different aspects of heavy-ion induced reactions following the evolution of compound nucleus formed via complete and/or incomplete fusion, the production cross sections of evaporation residues and fission-like fragments were measured in \(^{12}\)C+\(^{169}\)Tm reaction at \(E_{\rm lab}= 77.18\), 83.22, and 89.25 MeV. The recoil-catcher activation technique followed by offline \(\gamma \) spectroscopy was employed to measure the cross sections. Herein, we present the production cross sections of 26 fission-like fragments identified in this work. An attempt has been made to study the isotopic yield distribution and the mass distribution of fission-like fragments to discern various reaction mechanisms. The mass distribution of fission-like fragments was found to be symmetric and broad substantiating their formation from compound nuclear processes. The mass variances (\(\sigma _{M}^{2}\)) has been found to increase monotonically with excitation energy above the Coulomb barrier for deformed \(^{169}\)Tm target, and with increase in mass asymmetry of the system.

abstract

The \(\nu \)-ball is a high-efficiency hybrid spectrometer which consists of both germanium (Ge) detectors and associated anti-Compton BGO shields, coupled to lanthanum bromide (LaBr\(_3\)) detectors. The hybrid configuration provides a combination of both excellent energy and timing resolutions. The \(\nu \)-ball geometry allows the coupling with the LICORNE directional neutron source at the ALTO facility of the IPN, Orsay. This opens the possibility to perform precise spectroscopy of neutron induced reactions and was used for two experiments during the recent experimental campaign. These two experiments are described here: 1. Spectroscopy of the neutron-rich fission fragments produced in the \(^{238}\)U(\(n,f\)) and \(^{232}\)Th(\(n,f\)) reactions; 2. Spectroscopy above the shape isomer in \(^{238}\)U. The \(^{238}\)U(\(n,f\)) and \(^{232}\)Th(\(n,f\)) reactions produce hundreds of neutron-rich nuclei on which gamma-ray spectroscopy can be performed. The main goal of the experiment aiming to populate the shape isomer in \(^{238}\)U is the measurement of the gamma-ray and fission decay branches as well as determination of level scheme in the super-deformed minimum. The shape isomer is populated by \(^{238}\)U(\(n,n'\)) reaction, which gives a very advantageous population cross section over other reactions. More detailed descriptions of these two \(\nu \)-ball experiments will be presented here.

abstract

Evaporation chains in the fusion reaction \(^{13}\)C+\(^{12}\)C at 95 MeV have been measured. Events complete in charge have been detected with the large acceptance GARFIELD+RCo apparatus at INFN-LNL and the features of the decay of the excited \(^{25}\)Mg compound nuclei have been compared with predictions of statistical models. Some deviations from these predictions have been found, especially for the chains mainly containing \(\alpha \) particles.

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This paper briefly reviews the first results of a coordinated study aimed at the clarification of the interplay between spectator fragmentation and electromagnetic phenomena in ultrarelativistic heavy-ion collisions at CERN SPS energies. The available experimental and phenomenological results are put in the context of recent theoretical calculations.

abstract

An in-flight zero-angle mass separator, MARA, has been recently constructed and commissioned at the University of Jyväskylä, Finland. MARA is a double focusing device, consisting of a quadrupole driplet, electrostatic deflector, and magnetic dipole. This separator is built for nuclear structure studies to be performed around the \(N{\sim }Z\) line and at beyond the proton drip line.

abstract

The Extreme Light Infrastructure is a major European undertaking with the aim of constructing a set of facilities that can produce the worlds highest intensity laser beams as well as unique high-brilliance, narrow-bandwidth gamma-ray beams using laser-based inverse Compton scattering. The latter will be one of the unique features of the facility in Bucharest-Măgurele, Romania, where the scientific focus will be towards nuclear physics and nuclear photonics both with high intensity lasers and gamma beams individually, as well as combined. One of the main instruments being constructed for the nuclear physics and applications with high-brilliance gamma-beams research activity is the ELIADE \(\gamma \)-ray detector array. This array consists of eight segmented HPGe clover detectors as well as large-volume LaBr\(_{3}\) detectors. The nuclear physics topics are expected to cover a large range including, but not limited to, properties of pygmy resonance and collective scissors mode excitations, parity violation in nuclear excitations, and matrix elements for neutrinoless double-beta decay. However, the uniqueness of the environment in which ELIADE will operate presents several challenges in the design and construction of the array. Here, we discuss some of these challenges and how we plan to overcome them, as well as the current status of implementation.

abstract

The scintillator Cs\(_2\)LiYCl\(_6\) (CLYC) has emerged as a versatile detector for both gammas and neutrons, with excellent pulse shape discrimination. Originally developed as a thermal neutron counter, the discovery of its unexpected and unprecedented \(\sim 10\)% pulse height resolution for fast neutrons in the few MeV range has prompted studies to benchmark its use in low-energy nuclear science and applications. Since the typical long time-of-flight arms are not needed for achieving good energy resolution, geometrical efficiency can be enhanced by positioning the detectors much closer to the target. We have constructed a 16-element array of 1”\(\,\times \,\)1” \(^7\)Li-enriched C\(^7\)LYC, to eliminate the dominant peak in the spectrum from thermal neutron capture on \(^6\)Li, leaving the energy region above 3 MeV with a clean baseline for fast neutron spectroscopy. We have also procured the first ever 3”\(\,\times \,\)3” C\(^7\)LYC crystal. Test experiments under way with C\(^7\)LYC include elastic and inelastic neutron scattering cross sections at Los Alamos with a pulsed white neutron source, efficiency measurements using mono-energetic neutron beams up to a few MeV at UMass Lowell, and fission neutron measurements with GRETINA and CHICO detector arrays at Argonne. Beta-delayed neutron spectroscopy experiments have also been initiated at the CARIBU and NSCL facilities, to evaluate C\(^7\)LYC as a possible candidate for auxiliary scintillator arrays for stopped beam physics at the next generation rare isotope accelerators.

abstract

Based on computed tomography (CT) scans of the interior of a patient’s body, it is possible to precisely locate planning target volume (PTV) and organs at risk (OARs) for radiotherapy. Constant development of this kind of imaging techniques has led to the emergence of dual-energy CT, which in conjunction with Metal Artifact Reduction software (MARs) allows to restore the structures and compensate the disorders resulting from the presence of metallic implants in the patient’s body. Such implants cause artifacts in the CT image which carries false information about the area between endoprosthesis. The aim of this thesis is evaluation of usefulness of dual-energy CT in radiotherapy planning for patients with hip endoprosthesis in comparison to manual method of reduction. This method relies heavily on estimating where a given tissue passes into another and inflicting one average HU (Hounsfield Units) value for the artifact site, based on the HU measurement for several neighboring tissues. Treatment plans were created using TPS (Treatment Planning System) Eclipse. Calculated dose distributions were imported into the Sun Nuclear application and subjected to gamma analysis. It can be concluded that the MARs algorithm is very useful for treatment planning, but it should be used with at most care.

abstract

The experiment was performed at CCB IFJ PAN in Kraków with the use of the BINA detector. The experimental program and data analysis of proton-induced deuteron breakup reaction at 108 MeV are presented.

abstract

The elastic nucleon–deuteron (\(Nd\)) scattering process at nucleon laboratory energies up to 200 MeV can be used to study the three-nucleon interaction (\(3N\)). In order to draw final conclusions based on the comparison of theoretical predictions and data, an estimation of theoretical uncertainties is necessary. We focus here on the statistical uncertainties of theoretical predictions. We use the One-Pion-Exchange Gaussian (OPE-Gaussian) nucleon–nucleon (\(NN\)) potential and compare our predictions for the \(3N\) observables with results based on the AV18 potential and results obtained with chiral potentials as well as with available data. We give examples of polarization observables at \(E=135\) MeV and discuss magnitudes of some theoretical uncertainties.

abstract

In this contribution, we present an overview of the “three-dimensional” (3D) approach that can be used to describe few-nucleon systems. Instead of relying on the partial wave decomposition of quantum mechanical operators related to a specific problem, the 3D approach works directly with the (three-dimensional) momentum degrees of freedom of the nucleons. Using this approach is, in principle, equivalent to using all partial wave at once and does not require a numerical implementation of heavily oscillating functions. In practice, these beneficial properties are limited by the available computing resources. Nonetheless, some recent results suggest that 3D calculations can be used in situations where traditional calculations are problematic. We briefly describe nucleon–nucleon scattering, and three-nucleon (\(3N\)) bound state calculations within the 3D approach. We also provide some preliminary results for the \(^{3}\)He bound state with a screened Coulomb interaction.

abstract

We present the results of our measurements using proton beams to address two different problems, namely, inelastic scattering of proton by \(^{12}\)C and radiative capture of proton by deuteron. The \(^{12}\)C(\(p,p'\gamma \))\(^{12}\)C reaction was carried out with proton-beam energies ranging from 8 to 22 MeV. The differential and total cross section of \(\gamma \) rays from the 4.438, 9.64, 12.7 and 15.1 MeV states were measured at all the beam energies and compared with detailed Optical Model calculations. We report, for the first time, the cross section and the branching ratio of the 9.64 MeV state. In a different experiment, cross sections and astrophysical \(S(E)\) factors for \(p+d\) capture reaction were measured for the first time at CM energies of 66, 116 and 166 keV. The measured values at these three new energies are found to be in good agreement with global set of data and in nice agreement with recent theoretical calculations.

abstract

We discuss effects of shock propagation on neutrino \((\nu )\) oscillation in supernova environment, which affects directly \(\nu \)-induced nucleosynthesis. Since electron number density varies rapidly behind and in front of the shock, multiple resonances of mixing angles by adiabatic and/or non-adiabatic electron density change can occur during the shock propagation. In this work, we report detailed analysis of the \(\nu \) oscillation in matter and the \(\nu \)-induced nucleosynthesis by the shock propagation. The shock effects increase abundances by about 16\(\%\) of \(^{138}\)La, 14\(\%\) of \(^{92}\)Nb and 7\(\%\) of \(^{98}\)Tc, whose main synthesized region is O–Ne–Mg layer in our supernova model. Here, we adopt a simple thermal bomb hydrodynamic model and the normal \(\nu \)-mass hierarchy.

abstract

The \(^{19}\)F(\(p,\alpha )^{16}\)O reaction has a twofold importance: it allows to investigate the spectroscopy of low angular momentum high-energy states in the self-conjugate \(^{20}\)Ne nucleus and, at low energy, it is important to astrophysical models aiming at describing the nucleosynthesis of fluorine in stars. In this proceeding, we discuss preliminary results of a comprehensive R-matrix analysis of the \(^{19}\)F(\(p,\alpha _0)^{16}\)O and \(^{19}\)F(\(p,\alpha _\pi )^{16}\)O reactions and \(p+^{19}\)F elastic cross-section data.

abstract

The two-proton radioactivity is a unique tool to study the nuclear structure beyond the proton drip-line. Since its discovery in 2002, the known emitters have been \(^{19}\)Mg, \(^{45}\)Fe, \(^{48}\)Ni, \(^{54}\)Zn and \(^{67}\)Kr. \(^{67}\)Kr was observed for the first time at the RIKEN Nishina Center in 2015. Its decay energy was measured at \(1690(17)\) keV with a branching ratio of \(37(14)\)%. The half-life, \(7.4(30)\) ms, was found in contradiction with theoretical calculations, pointing out effects of decay dynamics and nuclear deformation.

abstract

A systematic investigation of the argon and chlorine isotopes located by two and three mass units beyond the proton drip line was performed recently at the FRS. A state-of-the-art tracking technique with silicon micro-strip detectors allowed for measurement of the trajectories of argon and chlorine in-flight decay products. These data were used to reconstruct angular correlations between decay products, which allowed to assign the energy levels to \(^{31}\)Ar and \(^{30}\)Cl for the first time. On the basis of the observed excited states in \(^{31}\)Ar and a new estimation of its two-proton separation energy \(S_{2p}\) of a few keV, the prospects for further studies of low-binding effects of this nucleus are presented.

abstract

In order to gain further information on the electromagnetic properties of the low-lying states in \(^{45}\)Sc, a Coulomb excitation measurement was carried out at the IUAC, New Delhi. The \(^{45}\)Sc target nuclei were Coulomb excited by the 70 MeV \(^{32}\)S beam from the 15UD tandem accelerator. The \(\gamma \)-rays depopulating Coulomb excited states in \(^{45}\)Sc were detected by four Clover detectors in coincidence with the forward scattered ions. The main aim of the experiment was to determine the \(B(\)E3\(; 7/2^- \rightarrow 3/2^+)\) and \(B(\)E3\(; 7/2^- \rightarrow 5/2^+)\) transition probabilities, as well as the transitional electromagnetic matrix elements for low-lying intruder states.

abstract

The last stable tellurium nucleus on the neutron-deficient side, \(^{120}\)Te, was Coulomb excited using two different projectiles. The low-lying collective states were populated in a multi-step Coulomb excitation process. Magnitudes and relative signs of the reduced E2 matrix elements were determined using the GOSIA code. The resulting set of E2 matrix elements was analysed using the quadrupole sum rules approach to determine the quadrupole deformation parameters for the \(0_{1}^{+}\) and \(2_{1}^{+}\) states.

abstract

In 2017–2018, the ALTO facility hosted an experimental campaign using a \(\gamma \) spectrometer called \(\nu \)-ball. This device is an hybrid array combining the excellent energy resolution of high purity germanium detectors with the excellent time resolution of new generation of scintillators LaBr\(_{3}\). Despite the short duration of the campaign, \(3\,200\) hours of beam time distributed over eight experimental project have been provided. In this paper, a description of the progress of the campaign as a short description of the \(\nu \)-ball array will be given.

abstract

The study of nuclei in the region around the \(N=Z\) doubly-magic nucleus \(^{100}\)Sn has been of long standing interest for the nuclear structure and nuclear astrophysics. Recently, Park et al.  have reported on properties of \(\gamma \)-decaying isomers and isomeric ratios in the vicinity of \(^{100}\)Sn. That experiment was performed at the Radioactive Ion Beam Factory (RIBF) of the RIKEN Nishina Center in Japan as a part of the EURICA campaign. Neutron-deficient nuclei were produced in a fragmentation reaction of a \(^{124}\)Xe primary beam on a \(^9\)Be target at an energy of 345 MeV/\(A\). Secondary ions were separated and identified in the BigRIPS fragment separator and implanted in the silicon detector array WAS3ABi. The data presented here were obtained in another experiment performed at the RIBF using the same reaction but slightly different separator settings. New results of ratios of isomeric population and half-lives of \(\gamma \)-decaying isomers populated in the experiment are presented.

abstract

Fine structure of giant resonances (GRs) has been established in recent years as a global phenomenon across the nuclear chart and for different types of resonances. A quantitative description of the fine structure in terms of characteristic scales derived by wavelet techniques is discussed. By comparison with microscpic calculations of GR strength distributions, one can extract information on the role of different decay mechanisms contributing to the width of GRs. The observed cross-section fluctuations contain information on the level density (LD) of states with a given spin and parity defined by the multipolarity of the GR.

abstract

A comprehensive study of the evolution of the GDR properties from \(E^*=150\) MeV to \(E^*=430\) MeV has been undertaken in nuclei of mass \(A = 120 \div 132\). The experimental investigation was performed using MEDEA detector. An onset of a quenching of the GDR gamma yield was found at \(E^*=270\) MeV comparing the experimental gamma-ray spectrum with statistical model calculation. The quenching effect increases at \(E^*=330\) MeV and is even more pronounced when the analysis is extended to higher excitation energies using data from previously performed experiments. The comparison with phenomenological models describing the quenching phenomenon gives a qualitative explanation for the effect but is not able to reproduce its detailed features as a function of excitation energy. A smooth cut-off approach describes reasonably well the progressive disappearance of the dipole strength, which occurs around 220–230 MeV excitation energy, and shows that the GDR quenching is a rather sharp effect.

abstract

Experiments investigating the fine structure of the Isovector Giant Dipole Resonances (IVGDR) have been carried out on target nuclei \(^{40,42,44,48}\)Ca with 200 MeV proton inelastic scattering reactions using the high-energy resolution capability and the zero-degree set-up at the K600 magnetic spectrometer of the iThemba LABS, Cape Town, South Africa. Quasi-free scattering background contributions in the experimental data have been removed by applying a novel method of Discrete Wavelet Transform (DWT) analysis. Energy scales extracted are compared with the state-of-the-art theoretical calculations within the framework of the Quasiparticle-RPA and Relativistic Quasiparticle Time Blocking Approximation (RQTBA). For \(^{40,48}\)Ca, these calculations consider all major processes (Landau damping, escape width, spreading width) contributing to the damping of the IVGDR.

abstract

A very first experiment in the field of nuclear structure at the Cyclotron Centre Bronowice (CCB) facility in Kraków, Poland has been performed recently. The medical cyclotron IBA Proteus C-235 located at CCB produces proton beams in the energy range of 70–230 MeV, that can be used for experimental purposes as well. In the reported measurement, the energy of scattered protons at the incident beam energy of 85 MeV and emitted \(\gamma \) rays from the excited \(^{208}\)Pb target were measured in coincidence. During the experiment excitations in the energy region of the Giant Quadrupole and Dipole Resonances, as well as the Pygmy Dipole States were observed. By applying different conditions on the data, spectra corresponding to \(\gamma \) decays of excited states to selected low-lying levels in \(^{208}\)Pb were obtained, allowing a look into the Brink–Axel hypothesis.

abstract

An inelastic proton scattering experiment was performed with the combined setup SONIC@HORUS at a beam energy of 15 MeV in Cologne. First results for the deduced branching ratios as well as the E1 strength distribution obtained with the \(^{124}\)Sn(\(p,p'\gamma \)) reaction are presented. Additionally, a qualitative comparison to excitations in experiments with different probes like (\( \alpha ,\alpha '\gamma \)) and (\( \gamma ,\gamma '\)) will be discussed.

abstract

The breaking of isospin symmetry caused by the Coulomb interaction can be measured by the study of E1 \(\gamma \) decay. The Isovector Giant Dipole Resonance (IVGDR) was measured in \(^{60}\)Zn and \(^{62}\)Zn at two different excitation energies \(E^* = 47\) MeV and \(E^* = 58\) MeV with the goal of deducing the isospin mixing term. A fusion–evaporation reaction, with a beam of \(^{32}\)S and a target of \(^{28}\)Si, was used to produce \(^{60}\)Zn. We also produced the compound nucleus \(^{62}\)Zn using the reaction \(^{32}\)S + \(^{30}\)Si. This last reaction is required because, for the produced nucleus, the statistical model analysis is much less sensitive to the isospin mixing, and this allows to extract the GDR parameters and use them for isospin mixing sensitive reaction populating neighboring nucleus with \(N=Z\). The experimental setup was composed of GALILEO array (germanium detectors) coupled to the large-volume LaBr\(_{3}\):Ce detectors for the \(\gamma \)-rays measuring and by two ancillary arrays, EUCLIDES and the Neutron Wall for the detection of particles and neutrons, respectively. An overview on the ongoing analysis and on preliminary results is presented.

abstract

The Coordinated Research Project of the International Atomic Energy Agency (IAEA CRP-F41032) was launched with a goal to publish two compilations of an updated photonuclear data library and a reference database of photon strength functions. The PHOENIX (PHOto-Excitation and Neutron emIssion cross [X] sections) Collaboration has been established for the IAEA-CRP in the \(\gamma \)-ray beam line GACKO (GAmma Collaboration hutch of KOnan university) of the NewSUBARU synchrotron radiation facility in Japan. The collaboration provides (\(\gamma ,xn\)) cross-section data to resolve the long-standing discrepancy between the Livermore and Saclay data on partial photoneutron cross sections. For the IAEA-CRP, a flat-efficiency neutron detector (FED) for (\(\gamma ,xn\)) cross-section measurements was developed. The detector consists of \(^{3}\)He counters arranged in three concentric rings embedded in a polyethylene moderator. Due to the fact that the efficiency of the detector is constant for the neutron energies up to several MeV, it is possible to determine the partial photoneutron reactions cross sections using direct neutron-multiplicity sorting technique. The paper gives details of the experimental setup and data analysis, and preliminary results of total neutron-production cross sections in monochromatic approximation for \(^{165}\)Ho nucleus.

abstract

Collisions of actinides are analyzed in the paper on the basis of the multidimensional dynamical model based on the Langevin equations as the method of production of neutron-enriched isotopes of heavy elements.

abstract

Competition between the two reaction channels: sequential breakup and neck fragmentation has been studied in peripheral and semi-peripheral collisions of the \(^{197}\)Au+\(^{197}\)Au system at bombarding energy of \(23A\) MeV. It was found that the emission of heavy (\(A\lt 50\)) neck-originating fragments occurs in about \(22\%\) of ternary breakup events, making this reaction channel highly competitive with the sequential breakup of the projectile- or target-like fragment (\(78\%\) of events).

abstract

Applying the microscopic nuclear physics ideas to macroscopic stellar systems, we study the evolution of the compact di-stars in mass asymmetry (transfer) coordinate. Depending on the internal structure of constituent stars, the initial mass asymmetry, total mass, and orbital angular momentum, the close di-star system can either exist in symmetric configuration or fuse into mono-star. The limitations for the formation of stable symmetric binary stars are analyzed. The role of symmetrization of asymmetric binary star in the transformation of potential energy into internal energy of binary star and the release of a large amount of energy is revealed.

abstract

After more than half a century of research addressing the synthesis and nuclear structure of superheavy nuclei (SHN), a boost for its progress is expected from the advent of new instrumentation. An order of magnitude in beam intensity increase is envisaged to be provided by new powerful accelerators such as the new DC280 cyclotron at the SHE factory of FLNR/JINR or the superconducting linac at SPIRAL2 of GANIL. In addition, new ion-optical installations like the separator-spectrometer set-up S\(^3\) with two complementary detection systems SIRIUS and LEB will provide a substantial sensitivity increase for classically pursued routes like decay spectroscopy after separation (DSAS), and alternative and complementary methods such as high precision mass measurements and laser spectroscopy. Decay spectroscopy has proven in the past to be a powerful tool to study the low-lying nuclear structure of heavy and superheavy nuclei. Single particle levels and other structure features like \(K\) isomerism, being important in the fermium–nobelium region as well as for the route towards spherical shell stabilised SHN, have been investigated almost up to the limit posed by the sensitivity of the present-day instrumentation. Precision mass measurements and laser spectroscopy will offer the possibility to study alternative features such as binding energies, charge radii and quadrupole moments. At the magnetic spectrometer VAMOS of GANIL with the recently improved mass resolution and the development of \(Z\) identification, deep-inelastic reactions like multi-nucleon transfer can be used to reach more neutron-rich nuclei in the region of light actinides, possibly being extended towards higher \(Z\).

abstract

The influence of the mechanisms of nuclear reactions on the population of isomeric states \(^{44m}\)Sc (6\(^+\)), \(^{196m}\)Au (12\(^-\)), \(^{198m}\)Au (12\(^-\)), \(^{195m}\)Hg (13/2\(^+\)), \(^{197m}\)Hg (13/2\(^+\)), \(^{198m}\)Tl (7\(^+\)), \(^{196m}\)Tl (7\(^+\)) obtained in reactions induced by beams of weakly bound and radioactive nuclei \(^{3}\)He, \(^{6}\)Li, \(^{6}\)He are studied. In direct reactions involving cluster transfer, the isomeric ratio is lower than in reactions, where fusion with evaporation of nucleons occurs. In the case of charge exchange reactions with beams of weakly bound nuclei, the isomeric ratios change only slightly. If the reaction \(Q\)-value is positive, neutron transfer is observed with high probability in interactions of all weakly bound nuclei with both light and heavy stable target nuclei. Cross sections and their isomeric ratios differ for nucleon stripping and pickup channels owing to the difference in population of excited single-particle and collective states.

abstract

The potential-energy surfaces of even–even super-heavy nuclei are evaluated within the LSD macroscopic–microscopic approach with a Yukawa-folded mean-field potential using the Fourier shape parametrization. The calculations are performed in a four-dimensional deformation space, defined by quadrupole, octupole, hexadecapole and nonaxiality degrees of freedom. It is shown that the both pear-like and nonaxial deformation modes are important when evaluating fission barrier heights.

abstract

We apply the importance-truncation procedure in the framework of the ab initio symmetry-adapted no-core shell model. We study efficacy of this new method for the description of energies and E2 transitions of the ground-state rotational band in \(^{12}\)C. We demonstrate that the coupling SU(3)-scheme basis with the perturbative relevance estimate leads to a dramatic reduction in dimensionality of the nuclear eigenvalue problem.

abstract

The structures of continuum states for the \(s_{1/2}\), \(p_{3/2}\) and \(p_{1/2}\) waves of \(^5\)Li and \(^5\)He mirror nuclei are studied in the complex scaled \(\alpha + N\) (\(N=\) neutron or proton) two-body model. The resonant, continuum and total terms of the continuum level density and the phase shifts are calculated.

abstract

Different Skyrme functional parametrizations were tested for Te, Xe, Ba and Ce isotopes for \(N \gt 82\). For the SVsym34 parametrization, which best fits the experimental binding energy, potential energy curves obtained from constrained \(\beta _2\), \(\beta _ 3\) and \(\beta _4\) Hartree–Fock+BCS calculations were investigated. Positions of the lowest quadrupole and octupole vibrational states and the lowest \(2^+\) rotational states in deformed nuclei were obtained within the Skyrme QRPA and compared to existing experimental data.

abstract

The phonon structure and spectral properties of states in \(^{110}\)Cd are addressed by including proton excitations in the phonon basis and exploiting a partial dynamical symmetry that mixes only certain classes of states and maintains the vibrational character in the majority of normal states.

abstract

Based on both the time-dependent Hartree–Fock (TDHF) and the time-dependent density matrix (TDDM) methods, we adopt a macroscopic reduction procedure to investigate the dissipation dynamics of nuclear fusion reactions. The TDDM method is an extension of TDHF, in the sense that it goes beyond the mean-field concept and takes into account two-body correlations explicitly. To investigate the effect of correlations on dissipation, the collective trajectories as well as the friction coefficients for the reaction \(^{16}\mathrm {O}+^{16}\mathrm {O} \rightarrow ^{32}\)S are extracted. Our results suggest that two-body correlations play a relevant role in the fusion process.

abstract

A new fast ionization chamber has been designed and built at the National Laboratories of Legnaro (LNL) to ensure a high counting rate particle identification for fusion studies involving exotic beams up to \(10^5\) pps. To reduce the response time of the ionization chamber, a design using a series of tilted electrodes has been adopted. The readout of the fast IC was optimized and extensive tests using stable heavy-ion beams demonstrated its ability to operate at high counting rates. This feature and the much larger solid angle coverage will allow to detect fusion–evaporation residues with very high efficiency.

abstract

We present a dedicated experimental setup which is currently used to search for long-lived super-heavy elements (SHE) implanted in catcher scintillators which were irradiated by reaction products of \(^{197}\)Au (7.5 \(A\) MeV) projectile and \(^{232}\)Th target collisions during our experiment performed at the Cyclotrone Institute, Texas A\(\&\)M University in 2015. The built-in novel measuring apparatus consists of \(\Delta E\)–\(E\) detector pairs which are able to register \(\alpha \) or spontaneous fission (SF) decays of heavy-reaction products deposited in the catcher scintillators. Their unique feature is that the examined catcher scintillators are at the same time \(\Delta E\) part of each of \(\Delta E\)–\(E\) detector pair while \(E\) part is a silicon detector. Our apparatus is dedicated to search for SHEs which have a lifetime of a year till tens of years. Results of commissioning tests of our setup are presented.

abstract

A new neutron multiplicity filter NEDA, after a decade of design, R&D and construction, was employed in its first physics campaign with the AGATA spectrometer. Properties and performance of the array are discussed.

abstract

Low Temperature Nuclear Orientation (LTNO) experiments can probe magnetic properties of nuclei. The presence of PolarEx at the ALTO facility allows to perform these kind of on-line experiments with neutron rich beams. This paper presents the formalism of the LTNO technique and the set-up of PolarEx. It focuses on the analysis process for multipolarity mixing ratio extraction.

abstract

Measurements of the angular correlation function \(W\)(\(\theta \)) were performed with the iThemba LABS segmented clover detector. A set of measurements with radioactive sources and irradiated targets was carried out to check the performance of the detector. At short detector-to-source distance, the detector covers the whole range of angles needed for precise angular correlation measurements. Preliminary results show that our detector can measure precisely angular correlation functions, including for transitions with large multipole order such as E3, M4, E4, etc., and deliver mixing ratios \(\delta \) of mixed magnetic and electric nature.

abstract

A systematic investigation of the shape coexistence phenomenon in the Ni isotopic chain, from \(A=62\) to \(A=66\), is being performed by using gamma-ray spectroscopy and employing sub-Coulomb barrier transfer reactions. The aim is to shed light on the microscopic origin of nuclear deformation along the Ni isotopic chain. The experiments were performed at the Tandem Accelerator Laboratory in Bucharest and IPN-Orsay, following the first observation of a shape-isomer-like structure at spin zero in \(^{66}\)Ni. The study has been inspired by various mean-field theoretical approaches as well as by the state-of-the-art Monte Carlo Shell Model (MCSM) calculations, all pointing to \(^{66}\)Ni as the lightest nucleus with a pronounced secondary prolate minimum in the nuclear potential energy surface, at spin zero, although other examples of shape isomerism in this mass region are not excluded. Preliminary results are discussed for \(^{64}\)Ni, in comparison with MCSM predictions, together with perspectives for similar searches in \(^{62}\)Ni.

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An experiment aiming at measuring lifetimes of the second 2\(^+\) excited states in neutron-rich C and O isotopes was recently performed at the GANIL laboratory, in France. In these nuclei, recent ab initio calculations provide a detailed description of the nuclear excited states, predicting a strong sensitivity of the electromagnetic transition probabilities to the details of the nucleon–nucleon interactions, especially in connection with the role played by the three-body (NNN) forces. Thus, the measurement of 2\(^{+}\) states lifetimes in this region will be a stringent test of the importance of including the NNN forces in describing the electromagnetic properties of selected nuclear states. This contribution reports on the status of the experimental analysis for the case of lifetimes in \(^{20}\)O.

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Recent ab initio calculations pointed out the importance of the three-body terms of the nuclear interaction, in the description of the structure of \(n\)-rich systems. The state lifetimes in light \(n\)-rich carbon and oxygen nuclei have been predicted to be sensitive to the three-body terms and, in this context, an experiment, aiming at the measurement of these lifetimes, was performed in GANIL in July 2017 with the AGATA and PARIS arrays coupled to the VAMOS\(+\!+\) magnetic spectrometer. Details on the AGATA preliminary data analysis are presented.

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Reduced quadrupole transition probabilities for low-lying transitions in neutron-rich \(N = 52\) isotones \(^{88}\)Kr and \(^{86}\)Se were investigated with a recoil distance Doppler shift (RDDS) experiment. The experiment was performed at GANIL (Caen, France) using the Orsay Universal Plunger System (OUPS) for the RDDS technique and the AGATA array for the \(\gamma \)-ray detection coupled to the VAMOS\(++\) magnetic spectrometer for an event-by-event particle identification. In \(^{88}\)Kr, the lifetimes of seven levels were determined and in \(^{86}\)Se, the lifetimes of five levels were determined. The deduced \(B({\rm E}2;2^+_1 \rightarrow 0^+_1)\) are compared with mean-field and shell-model calculations.

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The development of in-flight separators has opened up fascinating opportunities for studying exotic nuclei in isomeric states. At the Radioactive-Isotope Beam Factory (RIBF) in RIKEN Nishina Center, which has come online in 2007 as the first \(3^{\mathrm {rd}}\)-generation in-flight separator facility, more than 400 species of rare isotopes have been explored in experimental programs dedicated to radioactive-decay measurements performed in the last decade. Some selected topics relevant to characteristic isomers, such as seniority, spin-trap, and \(K\) isomers, are presented.

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For a better understanding of the nature of isomer depletion via the nuclear excitation by electron capture (NEEC) process, we have presented here, for the long-lived (T\(_{1/2}\) \(\sim \) 6.85 h) \(^{93m}\)Mo isomer, the results of high-precision multiconfiguration Dirac–Fock calculations concerning the dependence of the energy released by electron capture into different atomic subshells of the N, M, and L shells on the specific charge state. These energy values can be understood as benchmarks, i.e. , reference parameters, which are crucial for implementations of the proposed beam-based scenario approach for different stopping targets. The authors believe that this detailed analysis of the atomic conditions for the NEEC process should be a first step to applied research, which aims to allow the controlled release of energy stored in the nuclear isomer of selected elements. The presented studies may contribute to the development of the concept of new, unconventional, and ultra-energy-dense nuclear power sources.

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The reaction of a pulsed \(^{18}\)O beam on a \(^{164}\)Dy target was studied in the first experiment with the NuBall array at the IPN Orsay, France. Excited state half-lives were measured using the fast timing method with 20 LaBr\(_3\)(Ce) detectors. The timing characteristics of the fully digital acquisition system is briefly discussed. A value for the previously unknown half-life of the first excited 4\(^+\) state in \(^{178}\)W is presented.

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Our understanding of the evolution of the shell structure in nuclei far from stability is based on the study of some key nuclei. Nuclei at or next to double shell closures play a special role in this. Presently, a lot of discussion is concentrated on the neutron-rich calcium isotopes, which provide a rich testing ground for various nuclear models with several traditional and new magic numbers. \(^{60}\)Ca is now almost within reach with the most advanced radioactive beam facilities. In order to investigate the evolution of the shell gap at \(N=40\), the configuration of states in the odd–even titanium isotopes up to \(N=37\) (\(^{59}\)Ti) have been studied. In order to experimentally access the shell gap at \(N=40\), it is nowadays within the reach of the most advanced facility the investigation of neutron hole configuration states in odd–even titanium isotopes up to \(N=37\), in the \(^{59}\)Ti nucleus. Such states correspond to relatively simple configurations that constitute a challenging testing ground for effective nuclear interactions. The new data obtained in our experiment allows to place the present predictions concerning the shell closure at \(N=40\) in the calcium region on a more solid ground.

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Recently, we observed an anomalous internal pair creation for the M1 transition depopulating the 18.15 MeV isoscalar 1\(^+\) state in \(^8\)Be. The deviation from the theoretical prediction can be described by assuming the creation and subsequent decay of a new, light boson with a mass of 16.7 MeV/\(c^2\). In order to clarify the interpretation, we re-investigated the \(^8\)Be anomaly with an improved and independent setup. We have confirmed the signal of the assumed \(X\)(17) particle and constrained its mass (\(m_0c^2 = 17.01(16)\) MeV) and branching ratio compared to the \(\gamma \)-decay (\(B_x = 6(1)\times 10^{-6}\)). We investigated also the high-energy (21 MeV) \(J^\pi =0^-\rightarrow 0^+\) transition in \(^4\)He and got a consistent result for the \(X\)(17) particle.

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We report on the recent progress in the application of the group-theory criteria combined with the nuclear mean-field theory methods in the context of the experimental verification of the presence of the tetrahedral and octahedral (sometimes referred to as high-rank) symmetries in sub-atomic physics. In this article, we focus on the possible coexistence of the two classes of shapes representing the two symmetries in nuclei simultaneously as well as we discuss the possible spontaneous breaking of the octahedral O\(_{\mathrm {h}}\)-group symmetry by its tetrahedral T\(_{\mathrm {d}}\)-subgroup symmetry partner. Experimental methods which are envisaged for the identification of the discussed symmetries, the former based on the mass spectrometry and isomer detection techniques are briefly discussed.

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We investigate neutron–proton (\(np\)) pairing correlation effect on the shell evolution of ground-state energies along with the deformation for \(N = Z\) nuclei in \(sd\)- and \(pf\)-shell, such as \(^{24}\)Mg and \(^{72}\)Kr. We start from a simple shell-filling model constructed by a deformed Woods–Saxon potential characterized as \(\beta _2\) deformation, and then we include all kinds of pairing correlations in the residual interaction. In this work, like- and unlike-pairing correlation decomposed as isoscalar (IS) \(T = 0\) and isovector (IV) \(T = 1\) component are explicitly taken into account to estimate the ground-state energies. It turns out that the IS condensation can explain the oblate deformation for \(^{72}\)Kr. We also test those effects on the Gamow–Teller (GT) transition for another \(N = Z\) nucleus, \(^{56}\)Ni, which explicitly exhibits the effects by the IS condensation and the deformation.

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Angular distributions of scattered deuterons on \(^{7}\)Li nuclei with excitation of the 0.478 MeV (\(J^{\pi } = {1/2}^{-}\)) level and tritons from the \(^{7}\)Li\((d, t)^{6}\)Li reaction with transitions to the ground (\(1^{+}\)) state of \(^{6}\)Li were measured at 14.5 MeV. Analysis of the experimental data was performed in the framework of the optical model and the coupled reaction channels method with taking into account the \(\alpha \)- and \(n\)-transfer mechanisms. The values of the spectroscopic factors and the deformation parameters for the \(^{7}\)Li, \(^{6}\)Li were extracted.

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Computed tomography is a method of diagnostic radiology. The latest trend in the field of imaging using X-ray is multi-energy tomography, wherein a patient is scanned simultaneously by two energies: high (140 keV) and low (80 keV). In single-energy tomography, image in a given voxel is based on ascribing to that specific voxel value of Hounsfield Unit (HU). HU value is obtained from linear absorption coefficient in the patient’s body. Hounsfield units may, however, imprecisely reflect the composition of the structure under study, due to the effect of beam hardening. This causes the scanned field, despite its homogeneous structure, to have different CT values for different layers. The aim of this study was to evaluate the usefulness of dual-energy CT in determining the mineralogical composition of organs stones. The results obtained from the dual-energy computed tomography (DECT) were compared with the effective atomic number calculated during the IR measurements. The research material were 11 kidney stones and 16 gallstones. They were divided into 18 groups. In order to perform tomographic scans, each of the stones was placed in a phantom made of plexiglass. Then, decomposition of the stones was analyzed using infrared spectrometry.

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A model describing the ORTEC GMX-30190-P coaxial \(n\)-type HPGe detector with a thin beryllium window was created. The absolute full-energy peak efficiency calibration for measurements of activated ITER materials was performed in the gamma-energy range from 60 to 1836 keV using a semi-empirical approach employing Monte-Carlo-based efficiency transfer method. The validity of the model was shown by cross-checking against the experimental data obtained with a calibration standard of the same geometry. The additional correction factors for a self-absorption of gamma rays in different sample matrices were also calculated.