### Regular Series

#### Zakopane Conference on Nuclear Physics Extremes of the Nuclear Landscape

Octupole Correlations in a Symmetry Conserving Framework

Acta Phys. Pol. B 48, 249 (2017)

page 249 •

abstract

Octupole correlations are described in a microscopic framework involving angular momentum, parity and particle number projected intrinsic Hartree–Fock–Bogoliubov states. Linear combinations of those symmetry restored states are considered to account for collective positive and negative parity states in the nucleus $^{144}$Ba. The well-known Gogny D1S interaction is used in the calculations. A strong octupole collectivity is observed in the negative parity states justifying the assignment of $^{144}$Ba as an octupole deformed nucleus. Higher lying excited states are studied and its structure is identified by looking at the collective wave functions obtained in the calculations. An oblate-spherical $0^{+}$ shape isomer and a two-phonon octupole multiplet are described in detail.

all authors

P. Bączyk, J. Dobaczewski, M. Konieczka, T. Nakatsukasa, K. Sato, W. Satuła

Mirror and Triplet Displacement Energies Within Nuclear DFT: Numerical Stability

Acta Phys. Pol. B 48, 259 (2017)

page 259 •

abstract

Isospin-symmetry-violating class II and III contact terms are introduced into the Skyrme energy density functional to account for charge dependence of the strong nuclear interaction. The two new coupling constants are adjusted to available experimental data on triplet and mirror displacement energies, respectively. We present preliminary results of the fit, focusing on its numerical stability with respect to the basis size.

Does the Gogny Interaction Need a Third Gaussian?

Acta Phys. Pol. B 48, 265 (2017)

page 265 •

abstract

By considering infinite matter constraints only, we suggest in this paper that the Gogny interaction should benefit from a third Gaussian in its central part. A statistical analysis is given to select the possible ranges which are compatible with these constraints and which minimize a $\chi ^2$ function.

Ab Initio Optical Potentials and Nucleon Scattering on Medium Mass Nuclei

Acta Phys. Pol. B 48, 273 (2017)

page 273 •

abstract

We show the first results for the elastic scattering of neutrons off oxygen and calcium isotopes obtained from ab initio optical potentials. The potential is derived using self-consistent Green’s function theory (SCGF) with the saturating chiral interaction NNLO$_{\textrm {sat}}$. Our calculations are compared to available scattering data and show that it is possible to reproduce low-energy scattering observables in medium mass nuclei from first principles.

GCM+GOA Electromagnetic Multipole Transition Operators and Symmetries of Generating Functions

Acta Phys. Pol. B 48, 281 (2017)

page 281 •

abstract

An idea of symmetry-dependent form of the electromagnetic transition operators is presented by making use of the Generator Coordinate Method and the Gaussian Overlap Approximation. Using this approximation, it turns out that the form of electromagnetic transition operators acting in the collective nuclear space can be helpful in recognition of symmetries in nuclear spectra.

QRPA Calculations of Stellar Weak-interaction Rates

Acta Phys. Pol. B 48, 287 (2017)

page 287 •

abstract

Weak-decay rates under various stellar density and temperature conditions are studied in several mass regions including neutron-deficient medium-mass waiting-point nuclei involved in the rp-process, neutron-rich medium-mass isotopes involved in the r-process, and $pf$-shell nuclei of special importance as constituents in presupernova formations. Weak rates are relevant to understand the late stages of the stellar evolution, as well as the nucleosynthesis of heavy nuclei. The nuclear structure involved in the weak-decay processes is described within a microscopic deformed quasiparticle random-phase approximation (QRPA) based on a selfconsistent mean field obtained from Skyrme Hartree–Fock + BCS calculations. This approach reproduces reasonably well both the experimental $\beta$-decay half-lives and the Gamow–Teller strength distributions measured under terrestrial conditions.

Nuclear Structure Calculations in $^{20}$Ne with No-Core Configuration–Interaction Model

Acta Phys. Pol. B 48, 293 (2017)

page 293 •

abstract

Negative parity states in $^{20}$Ne and the Gamow–Teller strength distribution for the ground-state beta decay of $^{20}$Na are calculated for the very first time using recently developed No-Core Configuration–Interaction model. The approach is based on the multi-reference density functional theory involving isospin and angular-momentum projections. Advantages and shortcomings of the method are briefly discussed.

r-process Calculations with a Microscopic Description of the Fission Process

Acta Phys. Pol. B 48, 299 (2017)

page 299 •

abstract

We computed the fission properties of nuclei in the range of $84\le Z\le 120$ and $118\le N\le 250$ using the Barcelona–Catania–Paris–Madrid (BCPM) Energy Density Functional (EDF). For the first time, a set of spontaneous and neutron-induced fission rates were obtained from a microscopic calculation of nuclear collective inertias. These fission rates were used as a nuclear input in the estimation of nucleosynthesis yields on neutron star mergers. We founded that the increased stability against the fission process predicted by the BCPM allows the formation of nuclei up to $A=286$. This constitutes a first step in a systematic exploration of different sets of fission rates on r-process abundance predictions.

Nuclear Energy Density Functional for KIDS

Acta Phys. Pol. B 48, 305 (2017)

page 305 •

abstract

The density functional theory (DFT) is based on the existence and uniqueness of a universal functional $E[\rho ]$, which determines the dependence of the total energy on single-particle density distributions. However, DFT says nothing about the form of the functional. Our strategy is to first look at what we know, from independent considerations, about the analytical density dependence of the energy of nuclear matter and then, for practical applications, to obtain an appropriate density-dependent effective interaction by reverse engineering. In a previous work on homogeneous matter, we identified the most essential terms to include in our “KIDS” functional, named after the early-stage participating institutes. We now present first results for finite nuclei, namely the energies and radii of $^{16,28}$O, $^{40,60}$Ca.

Study of $N = 16$ Shell Closure Within RMF+BCS Approach

Acta Phys. Pol. B 48, 309 (2017)

page 309 •

abstract

We have employed RMF+BCS (relativistic mean field plus BCS) approach to study behaviour of $N = 16$ shell closure with the help of ground state properties of even–even nuclei. Our present investigations include single-particle energies, deformations, separation energies as well as pairing energies etc. As per recent experiments showing neutron magicity at $N = 16$ for O isotopes, our results indicate a strong shell closure at $N = 16$ in $^{22}$C and $^{24}$O. A large gap is found between neutron $2s_{1/2}$ and $1d_{3/2}$ states for $^{22}$C and $^{24}$O. These results are also supported by a sharp increase in two neutron shell gap, zero pairing energy contribution and with an excellent agreement with available experimental data.

all authors

A. Boso, S.M. Lenzi, F. Recchia, J. Bonnard, S. Aydin, M.A. Bentley, B. Cederwall, E. Clement, G. De France, A. Di Nitto, A. Dijon, M. Doncel, F. Ghazi-Moradi, A. Gottardo, T. Henry, T. Hüyük, G. Jaworski, P.R. John, K. Juhász, I. Kuti, B. Melon, D. Mengoni, C. Michelagnoli, V. Modamio, D.R. Napoli, B.M. Nyakó, J. Nyberg, M. Palacz, J.J. Valiente-Dobón

Isospin Symmetry Breaking in Mirror Nuclei $^{23}$Mg–$^{23}$Na

Acta Phys. Pol. B 48, 313 (2017)

page 313 •

abstract

Mirror energy differences (MED) are a direct consequence of isospin symmetry breaking. Moreover, the study of MED has proved to give valuable information of several nuclear structure properties. We present the results of an experiment performed in GANIL to study the MED in mirror nuclei $^{23}$Mg–$^{23}$Na up to high spin. The experimental values are compared with state-of-the-art shell model calculations. This permits to enlighten several nuclear structure properties, such as the way in which the nucleons alignment proceeds, the radius variation with $J$, the role of the spin-orbit interaction and the importance of isospin symmetry breaking terms of nuclear origin.

all authors

V. Tokić, N. Soić, S. Blagus, S. Fazinić, D. Jelavić-Malenica, T. Mijatović, Đ. Miljanić, L. Prepolec, N. Skukan, S. Szilner, M. Uroić, M. Milin, A. Di Pietro, P. Figuera, J.P. Fernández-García, M. Fisichella, M. Lattuada, V. Scuderi, E. Strano, D. Torresi, S. Bailey, N. Curtis, M. Freer, R. Smith, J. Walshe, V. Ziman, L. Acosta, I. Martel, G. Marquinez-Durán, A.M. Sánchez-Benítez, E. Fioretto

Structure of $^{24}$Mg Excited States and Their Influence on Nucleosynthesis

Acta Phys. Pol. B 48, 319 (2017)

page 319 •

abstract

The main idea of the two presented experiments is to study the decay of resonances in $^{24}$Mg at excitation energies above the $^{12}$C+$^{12}$C decay threshold, in the astrophysical energy region of interest. The measurement of the $^{12}$C($^{16}$O,$\alpha$)$^{24}$Mg* reaction was performed at INFN-LNS in Catania. Only the $\alpha$+$^{20}$Ne decay channel of $^{24}$Mg is presented here, because it was a motivation for conducting a new experiment, a study of the$^{4}$He($^{20}$Ne,$^{4}$He)$^{20}$Ne reaction, performed at INFN-LNL in Legnaro. Some preliminary results of this measurement are also presented.

all authors

A. Ertoprak, B. Cederwall, U. Jakobsson, B.M. Nyakó, J. Nyberg, P. Davies, M. Doncel, G. De France, I. Kuti, D.R. Napoli, R. Wadsworth, S.S. Ghugre, R. Raut, B. Akkus, H. Al-Azri, A. Algora, G. de Angelis, A. Atac, T. Bäck, A. Boso, E. Clément, D.M. Debenham, Zs. Dombrádi, S. Erturk, A. Gadea, F. Ghazi Moradi, A. Gottardo, T. Huyuk, E. Ideguchi, G. Jaworski, H. Li, C. Michelagnoli, V. Modamio, M. Palacz, C.M. Petrache, F. Recchia, M. Sandzelius, M. Siciliano, J. Timár, J.J. Valiente-Dobón, Z.G. Xiao

Lifetime Measurements with the Doppler Shift Attenuation Method Using a Thick Homogeneous Production Target — Verification of the Method

Acta Phys. Pol. B 48, 325 (2017)

page 325 •

abstract

Doppler Shift Attenuation Method (DSAM) analysis of excited-state lifetimes normally employs thin production targets mounted on a thick stopper foil (“backing”) serving to slow down and stop the recoiling nuclei of interest in a well-defined manner. Use of a thick, homogeneous production target leads to a more complex analysis as it results in a substantial decrease in the energy of the incident projectile which traverses the target with an associated change in the production cross section of the residues as a function of penetration depth. Here, a DSAM lifetime analysis using a thick homogeneous target has been verified using the Doppler broadened lineshapes of $\gamma$ rays following the decay of highly excited states in the semi-magic ($N=50$) nucleus $^{94}$Ru. Lifetimes of excited states in the $^{94}$Ru nucleus have been obtained using a modified version of the LINESHAPE package from the Doppler broadened lineshapes resulting from the emission of the $\gamma$ rays, while the residual nuclei were slowing down in the thick (6 mg/cm$^2$) metallic $^{58}$Ni target. The results have been validated by comparison with a previous measurement using a different (RDDS) technique.

all authors

M. Siciliano, J.J. Valiente-Dobón, A. Goasduff, D. Bazzacco, N. Alahari, G. Benzoni, T. Braunroth, N. Cieplicka, F.C.L. Crespi, E. Clement, G. De France, M. Doncel, S. Ertürk, C. Fransen, A. Gadea, G. Georgiev, A. Goldkuhle, U. Jakobsson, G. Jaworski, P.R. John, I. Kuti, A. Lemasson, A. Lopez-Martens, H. Li, S. Lunardi, T. Marchi, D. Mengoni, C. Michelagnoli, T. Mijatovic, C. Müller-Gatermann, D.R. Napoli, J. Nyberg, M. Palacz, R.M. Pérez-Vidal, M. Rejmund, B. Saygi, D. Sohler, S. Szilner, D. Testov

Study of Quadrupole Correlations in $N=Z=50$ Region via Lifetime Measurements

Acta Phys. Pol. B 48, 331 (2017)

page 331 •

abstract

During the AGATA campaign at GANIL, the neutron-deficient Sn region was populated via a multi-nucleon transfer reaction in order to directly measure the lifetime of the first excited states with a plunger device, providing complementary information to previous results obtained with Coulomb excitation experiments. The AGATA $\gamma$-ray array was used together with the VAMOS$++$ spectrometer to study the nuclei of interest.

all authors

S.K. Chamoli, A. Rohilla, C.K. Gupta, R.P. Singh, S. Muralithar, S. Chakraborty, H.P. Sharma, A. Kumar, I.M. Govil, D.C. Biswas

Investigating Prolate–Oblate Shape Inversion in Pt Nuclei Near $A \sim 188$

Acta Phys. Pol. B 48, 337 (2017)

page 337 •

abstract

Lifetimes have been measured of the low- and intermediate-spins states in $^{188}$Pt nucleus using the recoil distance Doppler shift technique at IUAC, Delhi. The nuclear states of interest were populated via $^{174}$Yb$(^{18}$O,$4n)^{188}$Pt reaction at a beam energy of 79 MeV provided by 15 UD Pelletron accelerator. The extracted $B$(E2) values show an increase up to $4^+$ state and then a near constant behavior with spin along yrast band, indicating change of the nuclear shape in $^{188}$Pt at low spins. The average absolute $\beta _2 = 0.20 (3)$ obtained from measured $B$(E2) values matches well the values predicted by CHFB and IBM calculations for oblate $(\beta _2 \sim -0.19)$ and prolate ($\beta _2 \sim 0.22$) shapes.

all authors

J. Ndayishimye, E.A. Lawrie, O. Shirinda, J.L. Easton, S.M. Wyngaardt, R.A. Bark, S.P. Bvumbi, T.R.S. Dinoko, P. Jones, N.Y. Kheswa, J.J. Lawrie, S.N.T. Majola, P.L. Masiteng, D. Negi, J.N. Orce, P. Papka, J.F. Sharpey-Schafer, M. Stankiewicz, M. Wiedeking

Chiral Bands in $^{193}$Tl

Acta Phys. Pol. B 48, 343 (2017)

page 343 •

abstract

A $\gamma$-spectroscopy study to search for chirality in $^{193}$Tl was conducted. Three negative-parity bands with close excitation energies and almost equal $B$(M1)/$B$(E2) values were identified. These bands were associated with the same $\pi h_{9/2} \otimes {\nu i_{13/2}}^{2}$ configuration which is suitable for chiral symmetry. Analysis of the properties of these bands suggested that one or two chiral systems are formed in $^{193}$Tl.

all authors

S.P. Noncolela, T.D. Bucher, E.A. Lawrie, T.R.S. Dinoko, J.L. Easton, N. Erasmus, J.J. Lawrie, S.H. Mthembu, W.X. Mtshali, O. Shirinda, J.N. Orce

Proportional Crosstalk for the iThemba LABS Clover Detector

Acta Phys. Pol. B 48, 347 (2017)

page 347 •

abstract

Measurements of the proportional crosstalk were performed for the iThemba LABS segmented clover detector. More than 1000 crosstalk parameters were determined and a crosstalk correction algorithm was implemented successfully.

all authors

M. Rudigier, S. Lalkovski, E.R. Gamba, A.M. Bruce, Zs. Podolyak, P.H. Regan, M. Carpenter, S. Zhu, A.D. Ayangeakaa, J.T. Anderson, T. Berry, S. Bottoni, I. Burrows, R. Carroll, P. Copp, D. Cullen, T. Daniel, L. Fraile, M. Carmona Gallardo, A. Grant, J.P. Greene, L.A. Guegi, D. Hartley, R. Ilieva, S. Ilieva, R.V.F. Janssens, F.G. Kondev, T. Kröll, G.J. Lane, T. Lauritsen, I. Lazarus, G. Lotay, G. Fernandez Martinez, V. Pucknell, M. Reed, J. Rohrer, J. Sethi, D. Seweryniak, C.M. Shand, J. Simpson, M. Smolen, E. Stefanova, V. Vedia, O. Yordanov

Fast Timing Measurement Using an LaBr$_3$(Ce) Scintillator Detector Array Coupled with Gammasphere

Acta Phys. Pol. B 48, 351 (2017)

page 351 •

abstract

A fast-timing experiment was performed at the Argonne National Laboratory in December 2015 and January 2016, measuring decay radiation of fission products from a $^{252}$Cf fission source. Details of the set-up, integration with Digital Gammasphere, and the data acquisition system are presented. The timing performance of the set-up, capable of measuring lifetimes from the nanosecond region down to tens of picoseconds, is discussed. First preliminary results from the fast-timing analysis of the fission fragment data are presented.

Recent Results with the Active Target MAYA

Acta Phys. Pol. B 48, 359 (2017)

page 359 •

abstract

The active target MAYA, built at GANIL in the beginning of the years 2000, is a Time Projection Chamber (TPC) for low-energy nuclear reactions where the gas is employed as a target. By increasing the luminosity, it allowed several type of experiments, in particular with secondary beams, from resonance scattering to fission study. We will present here some of the last results, focusing on the study of giant resonances in exotic nuclei. Preliminary results of the prototype of the future active target: the “ACTive TARget and Time Projection Chamber” (ACTAR TPC) built with a denser (16384 pixels) pad plane and digital electronic is also discussed.

The Use of Storage Rings in the Study of Reactions at Low-momentum Transfers

Acta Phys. Pol. B 48, 365 (2017)

page 365 •

abstract

A few aspects of the nucleus manifest themselves in direct reactions where the transferred momentum to the nucleus is very small. In the study of radioactive isotopes, one has to use inverse kinematics in which the radioactive ion impinges on a stable target. When the momentum transfer is low, one has to do these reactions with either an active target or in a storage-ring environment. In this contribution, the latter method will be discussed in some detail as the active targets are discussed in other contributions. The pilot studies performed by the EXL Collaboration in 2012 lead to the first ever measurements of reactions employing radioactive isotopes in the ring. In this contribution, the first results will be presented. The outlook will indicate in which directions the future of this field will be headed.

FAZIA: A Versatile Detection System for EoS Studies

Acta Phys. Pol. B 48, 377 (2017)

page 377 •

abstract

In this paper, we describe the main results obtained by the FAZIA Collaboration during its R&D phase devoted to the design of a versatile and modular detector array, meant for a possible 4$\pi$ angular coverage, necessary for studies of heavy-ion collisions with radioactive nuclear beams. The basic module of the array and the solutions devised to get its final performances are described. The obtained improvements with respect to existing detectors are due to a better understanding of the involved detection mechanisms, to the technical solutions introduced accordingly on the detector material and construction, and to the purposely developed digital techniques for Pulse Shape Analysis. Finally, a significant effort has been dedicated to the Front End Electronics (FEE) and Data Acquisition and Transfer (DAQ). The FAZIA Demonstrator, i.e. the first working array composed by the FAZIA basic modules, is now in operation. After its commissioning at LNS, it will be coupled next year with INDRA detector for a physics campaign at GANIL.

all authors

D.R. Napoli, G. Maggioni, S. Carturan, J. Eberth, V. Boldrini, D. De Salvador, E. Napolitani, P. Cocconi, G. Della Mea, M. Gelain, R. Gunnella, M.G. Grimaldi, M. Loriggiola, G. Mariotto, N. Pinto, W. Raniero, S.J. Rezvani, S. Riccetto, D. Rosso, F. Sgarbossa, S. Tati

New Developments in HPGe Detectors for High Resolution Detection

Acta Phys. Pol. B 48, 387 (2017)

page 387 •

abstract

High-Purity Germanium (HPGe) detectors continue to be a fundamental tool in nuclear gamma spectroscopy. The tracking of the gamma interactions inside the HPGe crystals is opening a new era in the use of these detectors for both basic science and applications, but they have also shown that new R&D is necessary for the production of even better and more reliable highly segmented detectors. In this work, we present recent results obtained in the framework of a multidisciplinary research program in HPGe detector technologies and we discuss the influence of these studies on the use of HPGe detectors.

all authors

J.N. Wilson, M. Lebois, L. Qi, P. Amador-Celdran, D. Bleuel, J.A. Briz, R. Carroll, W. Catford, H. De Witte, D. Doherty, R. Eloirdi, G. Georgiev, A. Gottardo, A. Goasduff, K. Hadynska-Klek, K. Hauschild, M. Hess, V. Ingeberg, T. Konstantinopoulos, J. Ljungvall, A. Lopez-Martens, G. Lorusso, R. Lozeva, R. Lutter, P. Marini, I. Matea, T. Materna, L. Mathieu, A. Oberstedt, S. Oberstedt, S. Panebianco, Z. Podolyak, A. Porta, P.H. Regan, P. Reiter, K. Rezynkina, S.J. Rose, E. Sahin, M. Seidlitz, R. Shearman, B. Siebeck, S. Siem, A.G. Smith, G.M. Tveten, D. Verney, N. Warr, F. Zeiser, M. Zielinska

Production and Study of Neutron-rich Nuclei Using the LICORNE Directional Neutron Source

Acta Phys. Pol. B 48, 395 (2017)

page 395 •

abstract

We have recently successfully demonstrated a new technique for production and study of many of the most exotic neutron-rich nuclei at moderate spins. LICORNE, a newly developed directional inverse-kinematic fast neutron source at the IPN Orsay, was coupled to the MINIBALL high resolution $\gamma$-ray spectrometer to study nuclei the furthest from stability using the $^{238}$U$(n,f)$ reaction. This reaction and $^{232}$Th$(n,f)$ are the most neutron-rich fission production mechanisms achievable and can be used to simultaneously populate hundreds of neutron-rich nuclei up to spins of $\approx 16\,\hbar$. High selectivity in the experiment was achieved via triple $\gamma$-ray coincidences and the use of a 400 ns period pulsed neutron beam, a technique which is unavailable to other population mechanisms such as $^{235}$U$(n_{\rm th},f)$ and $^{252}$Cf(SF). The pulsing allows time correlations to be exploited to separate delayed $\gamma$ rays from isomeric states in the hundreds of nuclei produced, which are then used to cleanly select a particular nucleus and its exotic binary partners. In the recent experiment, several physics cases are simultaneously addressed such as shape coexistence, the evolution of shell closures far from stability, and the spectroscopy of nuclei in the r-process path near $N=82$. Preliminary physics results on anomalies in the $^{238}$U$(n,f)$ fission yields and the structure of the $^{138}$Te and $^{100}$Sr nuclei will soon be published. A future project, $\nu$-ball, to couple LICORNE with a hybrid escape-suppressed spectrometer to refine further the technique and achieve a large increase in the observational limit is discussed.

all authors

D.M. Cox, J. Pakarinen, P. Papadakis, P.A. Butler, P.T. Greenlees, J. Konki, R.-D. Herzberg, G.G. O'Neill, P. Rahkila

Commissioning of the SPEDE Spectrometer with Stable Beams

Acta Phys. Pol. B 48, 403 (2017)

page 403 •

abstract

The SPectrometer for Electron DEtection (SPEDE) has been construc-ted for in-beam nuclear structure studies using radioactive ion beams. SPEDE employs a silicon detector for detecting conversion electrons. It is designed to be used in conjunction with the MINIBALL spectrometer at HIE-ISOLDE, CERN.

all authors

E. Miyata, M. Takechi, T. Ohtsubo, M. Fukuda, D. Nishimura, K. Abe, K. Aoki, A. Ikeda, T. Izumikawa, H. Oikawa, K. Ohnishi, S. Ohmika, I. Kato, Y. Kanke, N. Kanda, R. Kanbe, H. Kikuchi, A. Kitagawa, S. Sato, H. Shimamura, J. Shimaya, S. Suzuki, T. Suzuki, R. Takagaki, H. Takahashi, Y. Takei, Y. Takeuchi, T. Takenouchi, N. Tadano, M. Tanaka, Y. Tanaka, K. Chikaato, H. Du, J. Nagumo, K. Nishizuka, T. Nishimura, S. Fukuda, M. Machida, A. Mizukami, M. Mihara, J. Muraoka, S. Yagi, S. Yamaoka, T. Yamaguchi, K. Yokoyama

Development of High Resolution TOF Detector for RI Beams Using Cherenkov Radiation

Acta Phys. Pol. B 48, 409 (2017)

page 409 •

abstract

We have developed a high time resolution time-of-flight (TOF) detector that detects the Cherenkov light emitted when an RI beam passes through a high refractive index glass. $^{58}$Ni and $^{132}$Xe beams of energies of 200 $A$–500 $A$ MeV and secondary beams produced with those beams have been used for the test of the Cherenkov detectors. The time resolution of $\sigma =5$ ps with the inclusion of system resolution has been achieved with a 420 $A$ MeV $^{132}$Xe beam.

all authors

B. Wasilewska, M. Kmiecik, A. Maj, J. Łukasik, P. Pawłowski, M. Ciemała, M. Ziębliński, P. Lasko, J. Grębosz, F.C.L. Crespi, A. Bracco, S. Brambilla, A. Giaz, I. Ciepał, B. Fornal, K. Guguła, Ł.W. Iskra, M. Krzysiek, M. Matejska-Minda, K. Mazurek, P. Napiorkowski, W. Parol, B. Sowicki, A. Szperłak, A. Tamii

The First Results from Studies of Gamma Decay of Proton-induced Excitations at the CCB Facility

Acta Phys. Pol. B 48, 415 (2017)

page 415 •

abstract

A new accelerator facility — Cyclotron Centre Bronowice (CCB) — was opened two years ago in Kraków, Poland. Aside from cancer therapy, a scientific program of the nuclear structure research making use of proton beams in the energy range of 70–230 MeV plays a significant role as well. Lead and graphite targets were used to prove the feasibility of exclusive experiments on collective modes in various nuclei. The experimental technique consists of simultaneous energy measurement of scattered beam particles in coincidence with $\gamma$ rays emitted from excited nuclei. This article describes the set-up and the method of analysis used for the experiment.

all authors

P. Lasko, J. Brzychczyk, P. Hirnyk, J. Łukasik, P. Pawłowski, K. Pelczar, A. Snoch, A. Sochocka, Z. Sosin

KATANA — a Charge-sensitive Triggering/Veto System for the S$\pi$RIT Experiment

Acta Phys. Pol. B 48, 419 (2017)

page 419 •

abstract

KATANA — the Kraków Array for Triggering with Amplitude discrimiNAtion, has been built and used as a trigger and Veto detector for the S$\pi$RIT TPC at RIKEN. Its construction allows for operation in magnetic field and provides a fast response for ionizing particles giving the approximate forward multiplicity and charge information. Depending on this information, trigger and veto signals are generated. The Multi-Pixel Photon Counters were used as light sensors for plastic scintillators. Performance of the detector is presented.

all authors

F. Giacoppo, K. Blaum, M. Block, P. Chhetri, Ch.E. Düllmann, C. Droese, S. Eliseev, P. Filianin, S. Götz, Y. Gusev, F. Herfurth, F.P. Hessberger, O. Kaleja, J. Khuyagbaatar, M. Laatiaoui, F. Lautenschläger, C. Lorenz, G. Marx, E. Minaya Ramirez, A. Mistry, Yu.N. Novikov, W.R. Plass, S. Raeder, D. Rodríguez, D. Rudolph, L.G. Sarmiento, C. Scheidenberger, L. Schweikhard, P. Thirolf, A. Yakushev

Recent Upgrades of the SHIPTRAP Setup: On the Finish Line Towards Direct Mass Spectroscopy of Superheavy Elements

Acta Phys. Pol. B 48, 423 (2017)

page 423 •

abstract

With the Penning-trap mass spectrometer SHIPTRAP at GSI, Darmstadt, it is possible to investigate exotic nuclei in the region of the heaviest elements. Few years ago, challenging experiments led to the direct measurements of the masses of neutron-deficient isotopes with $Z=102,103$ around $N=152$. Thanks to recent advances in cooling and ion-manipulation techniques, a major technical upgrade of the setup has been recently accomplished to boost its efficiency. At present, the gap to reach more rare and shorter-lived species at the limits of the nuclear landscape has been narrowed.

Physical Origin of the Transition from Symmetric to Asymmetric Fission Fragment Charge Distribution

Acta Phys. Pol. B 48, 431 (2017)

page 431 •

abstract

Using the improved scission-point model, the isotopic trends of the charge distribution of fission fragments are studied in induced fission of even–even Th isotopes at low- and high-excitation energies.

all authors

G.G. Adamian, N.V. Antonenko, A.N. Bezbakh, R.V. Jolos, L.A. Malov, K. Wang, S.-G. Zhou, H. Lenske

Influence of Properties of Superheavy Nuclei on Their $\alpha$ Decays

Acta Phys. Pol. B 48, 441 (2017)

page 441 •

abstract

The structure of superheavy nuclei is considered with the microscopic–macroscopic approach based on the two-center shell model. The shell effects are compared with those obtained in the self-consistent approaches. The $\alpha$-decay chains of $^{291,293}$Ts and $^{288}$Mc are considered.

Potential Energy Surfaces of Thorium Isotopes in the 4D Fourier Parametrisation

Acta Phys. Pol. B 48, 451 (2017)

page 451 •

abstract

The recently developed extremely flexible and rapidly converging Fourier shape parametrisation is used to evaluate the potential energy surfaces of $^{210}$Th–$^{238}$Th even–even isotopes within the macroscopic–microscopic method. A vast sample of 4D landscapes is analysed, searching for absolute and local extrema, ridges and valleys. The expected fission-fragment mass distribution obtained from different Th isotopes at low excitation energy is illustrated by a static analysis of the potential energy landscape. Quadrupole moments in the relevant minima are also evaluated.

all authors

A. Di Pietro, J.P. Fernandez-Garcia, M. Fisichella, M. Alcorta, M.J.G. Borge, T. Davinson, F. Ferrera, P. Figuera, A.M. Laird, M. Lattuada, A.C. Shotter, N. Soic, O. Tengblad, D. Torresi, M. Zadro

Investigation of Cluster States in $^{13}$B Using the $^{9}$Li–$\alpha$ Resonant Elastic Scattering

Acta Phys. Pol. B 48, 455 (2017)

page 455 •

abstract

The excitation function of the resonant reaction $^4$He($^9$Li,$\alpha$) was measured with the aim of investigating the compound nucleus $^{13}$B. These measurements were performed in inverse kinematics at center-of-mass scattering angles close to 180$^ \circ$ by using a thick $^4$He gas target and a $^9$Li beam. The $^{13}$B excitation energy region explored was 14–20 MeV where $^9$Li–$\alpha$ configurations of $^{13}$B are predicted by Antysimmetrised Molecular Dynamics calculations. The measured excitation function at $\theta _{\rm cm} =180^\circ$ shows different clear structures in a $^{13}$B excitation energy region which was experimentally unknown.

all authors

M. Tanaka, M. Fukuda, D. Nishimura, M. Takechi, S. Suzuki, H. Du, Y. Tanaka, K. Aoki, S. Fukuda, A. Honma, T. Izumikawa, Y. Kamisho, N. Kanda, I. Kato, Y. Kanke, A. Kitagawa, J. Kohno, M. Machida, K. Matsuta, M. Mihara, E. Miyata, Y. Morita, J. Muraoka, D. Murooka, T. Nagai, M. Nagashima, K. Ohnishi, J. Ohno, T. Ohtsubo, H. Oikawa, S. Sato, H. Shimamura, T. Sugihara, T. Suzuki, N. Tadano, R. Takagaki, Y. Takei, A. Takenouchi, S. Yagi, T. Yamaguchi, S. Yamaki, S. Yamaoka

Reaction Cross Sections for $^{13-15}$B and One-neutron Halo in $^{14}$B

Acta Phys. Pol. B 48, 461 (2017)

page 461 •

abstract

We have measured reaction cross sections ($\sigma _{\rm R}$) for $^{13,14,15}$B on Be, C, Al, and proton targets. In addition to the conventional method of deducing nucleon density distributions based on the Glauber-type calculation, the recently developed method for deducing point-proton and neutron density distributions separately from $\sigma _{\rm R}$ on proton targets were utilized for these nuclei. The result suggests the necessity for $^{14}$B of a large tail in its neutron density distribution, which can be referred to as a one-neutron halo. Root-mean-square point-proton, neutron and matter radii for $^{13,14,15}$B were also derived. From present systematic studies for $^{13,14,15}$B, a large enhancement of matter and neutron radii in $^{14}$B was found for the first time.

Structure of $^{13}$C Excited States with Low-energy Reactions of $\alpha$ Particles on $^{9}$Be Nuclei

Acta Phys. Pol. B 48, 467 (2017)

page 467 •

abstract

We report results on the spectroscopy of $^{13}$C obtained by analysing experimental data on $^9$Be($\alpha$,$\alpha$) and $^9$Be($\alpha ,n$) reactions at low energies ($E_\alpha \approx 2$–10 MeV). A comprehensive R-matrix fit of several excitation functions has allowed to improve the spectroscopy of $^{13}$C states in the excitation energy region $E_x\approx 12$–18 MeV. Preliminary results on the structure of several excited states are discussed.

all authors

H. Du, M. Fukuda, D. Nishimura, M. Takechi, T. Suzuki, Y. Tanaka, I. Kato, M. Tanaka, K. Abe, T. Izumikawa, H. Oikawa, T. Ohtsubo, J. Ohno, Y. Kanke, H. Kikuchi, A. Kitagawa, S. Sato, U. Sayama, J. Shimaya, S. Suzuki, Y. Takeuchi, T. Takemoto, N. Tadano, R. Tamura, J. Nagumo, K. Nishizuka, S. Fukuda, K. Hori, S. Matsunaga, A. Mizukami, M. Mihara, E. Miyata, D. Murooka, S. Yamaoka, T. Yamaguchi

Nuclear Structure of $^{15,16}$C via Reaction Cross-section Measurements

Acta Phys. Pol. B 48, 473 (2017)

page 473 •

abstract

Reaction cross sections for $^{15,16}$C on nuclear targets (Be, C, Al) and proton target are systematically measured in the intermediate energy range. Nucleon density distributions of $^{15,16}$C were deduced from the analyses of present data with existing experimental data using the Glauber-type calculation. Proton and neutron density distributions were also deduced separately from proton target data. Results of root-mean-square radii show a good agreement with theoretical calculations for both isotopes.

all authors

I. Ciepał, I. Skwira-Chalot, St. Kistryn, A. Kozela, A. Magiera, E. Stephan

Probing Three- and Four-Nucleon Interactions with the Deuteron Breakup Reaction

Acta Phys. Pol. B 48, 481 (2017)

page 481 •

abstract

Research in the domain of few-nucleon systems concerns reactions involving a small number of nucleons in which observables can be compared directly to exact computational methods — rigorous solutions of the Faddeev equations. The investigations of such systems reveal existence of various dynamical ingredients such as the three-nucleon force, the Coulomb force or relativistic effects. A large set of the cross-section data of the $^{1}$H$(d,pp)n$ breakup reaction obtained at energy of 130 MeV was used to trace the Coulomb force effects. Comparisons of the cross-section data with the predictions using the realistic Argonne 18 potential are presented. The new set of invariants was introduced to describe the process with three nucleons in the final state.

all authors

A. Rusnok, I. Ciepał, B. Jamróz, N. Kalantar-Nayestanaki, G. Khatri, St. Kistryn, B. Kłos, A. Kozela, J. Kuboś, P. Kulessa, A. Liptak, W. Parol, I. Skwira-Chalot, E. Stephan, A. Wilczek, B. Włoch, J. Zejma

Experimental Study of Three-nucleon Dynamics in Proton–Deuteron Breakup Reaction

Acta Phys. Pol. B 48, 485 (2017)

page 485 •

abstract

A measurement of the differential cross sections for the proton–deuteron elastic scattering and the deuteron breakup in collision with a proton was carried out at Cyclotron Center Bronowice using the BINA detection system. The very preliminary analysis of the experimental data taken at three proton beam energies: 108, 135 and 160 MeV is presented.

all authors

M. Kaczmarski, K. Czerski, D. Weissbach, A.I. Kilic, G. Ruprecht, A. Huke

Threshold Resonance Contribution to the Thick Target $^2$H$(d,p)^3$H Reaction Yield

Acta Phys. Pol. B 48, 489 (2017)

page 489 •

abstract

Thick target yield of the $^2$H$(d,p)^3$H reaction has been measured at very low energies under ultra-high vacuum conditions using deuteron-implanted Zr targets. Increase of enhancement factors observed for lowering deuteron energies could not be explained only by the electron screening effect. Assuming an additional contribution resulting from a single-particle threshold resonance, we are able to describe the energy dependence of the experimental reaction yield correctly. The theoretical calculations performed within the T-matrix approach allows also to study interference effects between different reaction amplitudes and predict a saturation of the threshold resonance strength at deuteron energies below 5 keV.

all authors

N. Burtebayev, S.B. Sakuta, A.K. Morzabayev, Zh.K. Kerimkulov, N. Amangeldi, A.A. Temerbayev, B. Mauyey, Ye. Kok, A.S. Aimaganbetov

Elastic Scattering of $^{15}$N Ions by $^{16}$O at the Energy 11.59 MeV

Acta Phys. Pol. B 48, 495 (2017)

page 495 •

abstract

The main purpose of this work is to find optimal optical parameters and to investigate the transfer mechanism at low energy, close to the Coulomb barrier energy for $^{15}$N$\,+\,^{16}$O nuclear systems. Angular distributions were measured at the energy $E_{\rm cm} =11.59$ MeV using stable $^{15}$N beams and target Al$_2$O$_3$ with thickness 30 $\mu$g/cm$^2$. The beam of $^{15}$N was accelerated on cyclotron DC-60 (INP, Astana). Registration and identification of charged particles was conducted by $\Delta E$–$E$ method. The data were analyzed within the optical model (OM) and coupled reaction channels (CRC) method. The CRC calculation was used by the program code Fresco [I.J. Thompson, Comput. Phys. Rep. 7, 167 (1988)].

all authors

D. Dell'Aquila, L. Acosta, L. Auditore, G. Cardella, E. De Filippo, S. De Luca, L. Francalanza, B. Gnoffo, G. Lanzalone, I. Lombardo, N.S. Martorana, S. Norella, A. Pagano, E.V. Pagano, M. Papa, S. Pirrone, G. Politi, L. Quattrocchi, F. Rizzo, P. Russotto, A. Trifirò, M. Trimarchi, G. Verde, M. Vigilante

Experimental Studies of the Structure of $^{16}$C with Reactions at Intermediate Energy

Acta Phys. Pol. B 48, 499 (2017)

page 499 •

abstract

The possible existence of cluster structures in $^{16}$C has been investigated by inspecting their breakup (induced on CH$_2$ targets) in $^{10}$Be+$^{6}$He events. The excitation energy of the projectile nucleus prior to decay is obtained via an invariant mass analysis of identified fragments. The experiment has been carried out at the FRIBs facility of INFN-LNS, by using a fragmentation cocktail beam at intermediate energies ($\approx 55$ MeV/nucleon) and the CHIMERA $4\pi$ multi-detector. A non-vanishing yield in the $^{10}$Be+$^{6}$He correlations is reported at an excitation energy of about 20.5 MeV in $^{16}$C, in analogy with previous works. To improve these results, we recently performed a new experiment by coupling CHIMERA and FARCOS at forward angles. Preliminary details of the new experiment are reported in the text.

all authors

B.C. Rasco, A. Fijałkowska, K.P. Rykaczewski, M. Wolińska-Cichocka, M. Karny, R.K. Grzywacz, K.C. Goetz, C.J. Gross, D.W. Stracener, E.F. Zganjar, J.C. Batchelder, J.C. Blackmon, N.T. Brewer, T. King, K. Miernik, S.V. Paulauskas, M.M. Rajabali, J.A. Winger

$\beta$ Decays of $^{92}$Rb, $^{96\mathrm {gs}}$Y, and $^{142}$Cs Measured with the Modular Total Absorption Spectrometer and the Influence of $\gamma$ Multiplicity on Total Absorption Spectrometry Measurements

Acta Phys. Pol. B 48, 507 (2017)

page 507 •

abstract

Total absorption spectroscopy is a technique that helps obtain reliable $\beta$-feeding patterns of complex decays important for nuclear structure and astrophysics modeling as well as decay heat analysis in nuclear reactors. The need for improved measurements of $\beta$-feeding patterns from fission decay products has come to the forefront of experiments that use nuclear reactors as a source of antineutrinos. Here we present more detailed results, in particular the $\beta$-decay measurements of $^{96\mathrm {gs}}$Y, and demonstrate the impact of the $\beta$-delayed $\gamma$ multiplicity on the overall efficiency of Modular Total Absorption Spectrometer used at Oak Ridge National Laboratory to study the decays of fission products abundant during a nuclear fuel cycle.

all authors

R. Caballero-Folch, I. Dillmann, J. Agramunt, J.L. Taín, C. Domingo-Pardo, A. Algora, J. Äysto, F. Calvino, L. Canete, G. Cortès, T. Eronen, E. Ganioglu, W. Gelletly, D. Gorelov, V. Guadilla, J. Hakala, A. Jokinen, A. Kankainen, V. Kolhinen, J. Koponen, M. Marta, E. Mendoza, A. Montaner-Pizá, I. Moore, Ch. Nobs, S. Orrigo, H. Penttilä, I. Pohjalainen, J. Reinikainen, A. Riego, S. Rinta-Antila, B. Rubio, P. Salvador-Castineira, V. Simutkin, A. Voss

First Evidence of Multiple $\beta$-delayed Neutron Emission for Isotopes with $A\gt 100$

Acta Phys. Pol. B 48, 517 (2017)

page 517 •

abstract

The $\beta$-delayed neutron emission probability, $P_n$, of very neutron-rich nuclei allows us to achieve a better understanding of the nuclear structure above the neutron separation energy, $S_n$. The emission of neutrons can become the dominant decay process in neutron-rich astrophysical phenomena such as the rapid neutron capture process (r-process). There are around 600 accessible isotopes for which $\beta$-delayed one-neutron emission ($\beta 1n$) is energetically allowed, but the branching ratio has only been determined for about one third of them. $\beta 1n$ decays have been experimentally measured up to the mass $A\sim 150$, plus a single measurement of $^{210}$Tl. Concerning two-neutron emitters ($\beta 2n$), $\sim 300$ isotopes are accessible and only 24 have been measured so far up to the mass $A=100$. In this contribution, we report recent experiments which allowed the measurement of $\beta 1n$ emitters for masses beyond $A\gt 200$ and $N\gt 126$ and identified the heaviest $\beta 2n$ emitter measured so far, $^{136}$Sb.

all authors

P.E. Garrett, B. Jigmeddorj, A.D. MacLean, H. Bidaman, V. Bildstein, C. Burbadge, G.A. Demand, A. Diaz Varela, M. Dunlop, R. Dunlop, B. Hadinia, B. Olaizola, C.E. Svensson, J. Turko, T. Zidar, A.B. Garnsworthy, M. Bowry, P.C. Bender, G.C. Ball, R. Caballero-Folch, I. Dillmann, G. Hackman, J. Henderson, W.J. Mills, M. Moukaddam, J. Park, C.J. Pearson, P. Ruotsalainen, J. Smallcombe, J.K. Smith, C. Andreoiu, D.S. Cross, J.L. Pore, K. Starosta

High-statistics $\beta$-decay Measurements at TRIUMF-ISAC and the Transition from the $8\pi$ Spectrometer to GRIFFIN

Acta Phys. Pol. B 48, 523 (2017)

page 523 •

abstract

Over a 12 year period, the $8\pi$ $\gamma$-ray spectrometer at the TRIUMF-ISAC facility was a world unique device for $\beta$-decay studies. Equipped with a variety of auxiliary devices, it was used in studies of Fermi superallowed $\beta ^+$ emitters, and nuclear structure studies far from stability and those employing high-statistics measurements. In the present contribution, this latter use is highlighted with examples of recent data obtained in the decay of $^{122}$Cs to $^{122}$Xe. The $8\pi$ spectrometer was replaced with the much more powerful GRIFFIN facility in 2014, ensuring world-leading capability for $\gamma$-ray spectroscopy following $\beta$ decay at TRIUMF-ISAC for the next generation. Examples that highlight GRIFFIN’s capabilities are given.

all authors

V. Guadilla, A. Algora, J.L. Tain, J. Agramunt, J. Äystö, J.A. Briz, A. Cucoanes, T. Eronen, M. Estienne, M. Fallot, L.M. Fraile, E. Ganioğlu, W. Gelletly, D. Gorelov, J. Hakala, A. Jokinen, D. Jordan, A. Kankainen, V. Kolhinen, J. Koponen, M. Lebois, T. Martinez, M. Monserrate, A. Montaner-Pizá, I. Moore, E. Nácher, S.E.A. Orrigo, H. Penttilä, I. Pohjalainen, A. Porta, J. Reinikainen, M. Reponen, S. Rinta-Antila, B. Rubio, K. Rytkönen, T. Shiba, V. Sonnenschein, A.A. Sonzogni, E. Valencia, V. Vedia, A. Voss, J.N. Wilson, A.-A. Zakari-Issoufou

Study of the $\beta$ Decay of Fission Products with the DTAS Detector

Acta Phys. Pol. B 48, 529 (2017)

page 529 •

abstract

Total Absorption Spectroscopy measurements of the $\beta$ decay of $^{103}$Mo and $^{103}$Tc, important contributors to the decay heat summation calculation in reactors, are reported in this work. The analysis of the experiment, performed at IGISOL with the new DTAS detector, show new $\beta$ intensity that was not detected in previous measurements with Ge detectors.

The Blocking Effect on the $\beta$-decay Properties of the Neutron-rich Ni Isotopes

Acta Phys. Pol. B 48, 533 (2017)

page 533 •

abstract

The $Q_{\beta }$-window has been studied within the Skyrme HF–BCS calculations including the blocking effect of unpaired neutron and proton in cases of the even–odd and odd–odd nuclei. Using the energy-density functional T45 containing the tensor terms, we analyze this effect on the $\beta$-transition rates of the neutron-rich nuclei $^{72-80}$Ni.

From Chiral $NN(N)$ Interactions to Giant and Pygmy Resonances via Extended RPA

Acta Phys. Pol. B 48, 537 (2017)

page 537 •

abstract

The properties of giant and pygmy resonances are calculated starting from chiral two- and three-nucleon interactions. The aim is to assess the predictive power of modern Hamiltonians and especially the role of the three-nucleon force. Methods based on the random-phase approximation (RPA) provide an optimal description of the modes of interest with minimal computational requirements. Here, we discuss the giant resonances (GRs) of $^{40,48}$Ca isotopes and their low-energy dipole response. A comparison with previous results obtained with a transformed Argonne V18 two-nucleon potential points to certain improvements.

On Jacobi and Poincaré Shape Transitions in Rotating Nuclei

Acta Phys. Pol. B 48, 541 (2017)

page 541 •

abstract

A recently developed Fourier shape parametrisation has been used to evaluate the potential energy surfaces of rotating nuclei including, in particular, the non-axiality degree of freedom. Our analysis has been performed in a 4D deformation space, but the effect of two additional deformation degrees of freedom of higher multipolarity has been taken into account. The calculations were performed using the Lublin–Strasbourg Drop model (LSD), but without taking microscopic correction into account. No sign of a Poincaré shape transition has been observed.

all authors

M. Scheck, S. Mishev, V.Yu. Ponomarev, O. Agar, T. Beck, A. Blanc, R. Chapman, U. Gayer, L.P. Gaffney, E.T. Gregor, J. Keatings, P. Koseoglou, U. Köster, K.R. Mashtakov, D. O'Donnell, H. Pai, N. Pietralla, D. Savran, J.F. Smith, P. Spagnoletti, G.S. Simpson, M. Thürauf, V. Werner

$\beta$ Decay as a New Probe for the Low-energy E1 Strength

Acta Phys. Pol. B 48, 547 (2017)

page 547 •

abstract

In this contribution, it is evaluated whether high $Q$-value $\beta$ decays from mothers with low ground-state spin are suitable to probe the structure of $1^-$ levels associated with the pygmy dipole response. A comparison of data from the exemplary $^{136}$I $\rightarrow ^{136}$Xe $\beta$ decay and the $^{136}$Xe($\gamma ,\gamma ^{\prime }$) reaction reveals that some 1$^{-}$ levels are populated in both reactions but with a different pattern. An investigation within the microscopic quasiparticle phonon model shows that the pattern is related to the population of different parts of the wave functions of these $1^-$ levels establishing $\beta$ decay as a novel probe.

Effects of Phonon–Phonon Coupling on Properties of Pygmy Resonance in $^{40-48}$Ca

Acta Phys. Pol. B 48, 553 (2017)

page 553 •

abstract

Starting from the Skyrme interaction SLy5, we study the effect of pho-non–phonon coupling on the low-energy electric dipole response in $^{40-48}$Ca. This effect leads to the fragmentation of the E1 strength to a lower energy and improves the agreement with available experimental data.

all authors

D. Choudhury, D.L. Balabanski, A. Krasznahorkay, L. Csige, J. Gulyas, M. Csatlos, P. Constantin, S. Coban

Prospectives of Photofission Studies with High-brilliance Narrow-width Gamma Beams at the New ELI–NP Facility

Acta Phys. Pol. B 48, 559 (2017)

page 559 •

abstract

Simulations providing estimates of the ELI–NP gamma-beam energy bandwidths and beam spot dimensions for the collimated beams, and expected fission rates with the narrow-width $\gamma$ beams of bandwidth 0.3% and 0.5% on actinide targets, $^{238}$U and $^{232}$Th, are reported. These estimates support the feasibility of precise transmission resonance measurements with the narrow-width ELI–NP $\gamma$ beams. The status of the design and construction of a state-of-the-art experimental array, consisting of four double-sided, Frisch-gridded Bragg ionization chambers, coupled to $\Delta E$–$E$ detectors, is reported.

Influence of Dipole Deformations on Electric Transitions in $^{156}$Gd Nucleus

Acta Phys. Pol. B 48, 565 (2017)

page 565 •

abstract

The aim of this work is to show the importance of the center-of-mass motion generated by the octupole modes and connected with these induced dipole deformations on $^{156}$Gd nucleus in its ground-state configuration. The investigation is performed within a quadrupole–octupole collective approach in the presence of rotational motion.

Microscopic Study of Nuclear Quadrupole Collective Motions in Terms of the Boson Expansion Theory

Acta Phys. Pol. B 48, 573 (2017)

page 573 •

abstract

Structures of the collective wave functions of the normal-ordered linked-cluster boson expansion theory (NOLC-BET) are investigated. Numerical results are presented for some low-lying collective states in neutron-deficient barium isotopes, and properties of excited $0^+$ states and an evolution of the collective mode as the neutron number changes are discussed.

all authors

N. Cieplicka-Oryńczak, G. Bocchi, S. Leoni, B. Fornal, S. Bottoni, M. Jentschel, U. Köster, P. Mutti, T. Soldner, A. Blanc, G. De France, G.S. Simpson, A. Türler, W. Urban, C.A. Ur

Study of $^{41}$Ca via Cold Neutron Capture

Acta Phys. Pol. B 48, 577 (2017)

page 577 •

abstract

The low-spin structure of the $^{41}$Ca isotope, populated by neutron capture, has been investigated by high resolution $\gamma$-spectroscopy techniques. The experiment was performed at the PF1B cold neutron facility at the Institut Laue–Langevin (Grenoble, France) employing the EXILL array, consisting of 46 HPGe crystals. Several new $\gamma$ rays have been observed and two excited states were newly established.

all authors

Ł.W. Iskra, G. Bocchi, B. Fornal, S. Leoni, S. Bottoni, N. Cieplicka-Oryńczak, M. Jentschel, U. Köster, C. Michelagnoli, P. Mutti, T. Soldner, A. Blanc, G. De France, G.S. Simpson, C.A. Ur, W. Urban

Yrast Structure Above the 9.6 s $8^+$ Isomer in $^{96}$Y Isotope

Acta Phys. Pol. B 48, 581 (2017)

page 581 •

abstract

High- and medium-spin structures have been investigated in neutron-rich $^{96}$Y isotope produced in the cold-neutron-induced fission of $^{235}$U and $^{241}$Pu targets. The study significantly extended the existing level scheme of this isotope. In the current work, particular attention was devoted to the structure which has been identified above the long 9.6 s, (8$^+$) isomer, up to the excitation energy of 4813 keV. The angular correlation analysis, together with obtained decay pattern, allowed to propose spin values for some of the newly observed states.

Spectroscopic Properties and Collectivity Beyond $^{132}$Sn

Acta Phys. Pol. B 48, 587 (2017)

page 587 •

abstract

Recent shell-model advances in the mass region above the doubly closed core $^{132}$Sn are reported in the present work. Using an effective interaction based on the N3LO potential, the low-lying spectra, E2 and M1 transition strengths are calculated for the following nuclei: $^{134,136,138}$Te, $^{136,138,140}$Xe, $^{138,140,142}$Ba, $^{140,142,144}$Ce and $^{142,144,146}$Nd. We focus in the discussion on the collectivity in the $N=86$ isotones characterized by development of triaxial $\gamma$ bands.

all authors

G. Bocchi, S. Leoni, B. Fornal, G. Colò, P.F. Bortignon, D. Bazzacco, A. Blanc, S. Bottoni, N. Cieplicka-Oryńczak, F.C.L. Crespi, G. De France, M. Jentschel, U. Koster, C. Michelagnoli, P. Mutti, J.-M. Régis, G. Simpson, T. Soldner, B. Szpak, C.A. Ur, W. Urban

Interplay Between Particle and Core Excitations in $^{133}$Sb

Acta Phys. Pol. B 48, 595 (2017)

page 595 •

abstract

The $\gamma$ decay of the one-proton valence nucleus $^{133}$Sb is studied using the cold-neutron induced fission of $^{235}$U and $^{241}$Pu targets. The experiment is performed at the ILL reactor in Grenoble, using a highly efficient HPGe array, also coupled to fast LaBr$_3$(Ce) scintillators. High-spin excited states above the 16.6 $\mu$s isomer are observed, and the lifetime of the 13/2$^{+}$ and 15/2$^{+}$ states is measured by fast-timing techniques, revealing a complex nature of the wave functions. The experimental results are well-interpreted by a newly developed microscopic model which takes into account the coupling between the valence proton and excitations (both collective and non-collective) of the doubly magic $^{132}$Sn core.

all authors

L.A. Gurgi, P.H. Regan, P.-A. Söderström, H. Watanabe, P.M. Walker, Zs. Podolyák, S. Nishimura, T.A. Berry, P. Doornenbal, G. Lorusso, T. Isobe, H. Baba, Z.Y. Xu, H. Sakurai, T. Sumikama, W.N. Catford, A.M. Bruce, F. Browne, G.J. Lane, F.G. Kondev, A. Odahara, J. Wu, H.L. Liu, F.R. Xu, Z. Korkulu, P. Lee, J.J. Liu, V.H. Phong, A. Yagi, G.X. Zhang, T. Alharbi, R.J. Carroll, K.Y. Chae, Zs. Dombradi, A. Estrade, N. Fukuda, C. Griffin, E. Ideguchi, N. Inabe, H. Kanaoka, I. Kojouharov, T. Kubo, S. Kubono, N. Kurz, I. Kuti, S. Lalkovski, E.J. Lee, C.S. Lee, G. Lotay, C.B. Moon, I. Nishizuka, C.R. Nita, Z. Patel, O.J. Roberts, H. Schaffner, C.M. Shand, H. Suzuki, H. Takeda, S. Terashima, Zs. Vajta, S. Kanaya, J.J. Valiente-Dobón

Isomer Spectroscopy of Neutron-rich $^{165,167}$Tb

Acta Phys. Pol. B 48, 601 (2017)

page 601 •

abstract

We present information on the excited states in the prolate-deformed, neutron-rich nuclei $^{165,167}$Tb$_{100,102}$. The nuclei of interest were synthesised following in-flight fission of a 345 MeV per nucleon $^{238}$U primary beam on a 2 mm $^{9}$Be target at the Radioactive Ion-Beam Factory (RIBF), RIKEN, Japan. The exotic nuclei were separated and identified event-by-event using the BigRIPS separator, with discrete energy gamma-ray decays from isomeric states with half-lives in the $\mu$s regime measured using the EURICA gamma-ray spectrometer. Metastable-state decays are identified in $^{165}$Tb and $^{167}$Tb and interpreted as arising from hindered E1 decay from the $\frac {7}{2}^-[523]$ single quasi-proton Nilsson configuration to rotational states built on the $\frac {3}{2}^-[411]$ single quasi-proton ground state. These data correspond to the first spectroscopic information in the heaviest, odd-$A$ terbium isotopes reported to date and provide information on proton Nilsson configurations which reside close to the Fermi surface as the $^{170}$Dy doubly-midshell nucleus is approached.

all authors

F. Galtarossa, L. Corradi, E. Fioretto, D. Montanari, S. Szilner, T. Mijatović, G. Pollarolo, D. Ackermann, D. Bourgin, S. Courtin, A. Goasduff, J. Grebosz, F. Haas, H.M. Jia, D. Jelavić-Malenica, S. Jeong, P.R. John, M. Milin, G. Montagnoli, F. Scarlassara, N. Skukan, N. Soić, A.M. Stefanini, E. Strano, V. Tokić, C.A. Ur, J.J. Valiente-Dobón, Y. Watanabe

Neutron-rich Nuclei Populated in Multi-nucleon Transfer Reactions: the $^{197}$Au+$^{130}$Te System

Acta Phys. Pol. B 48, 609 (2017)

page 609 •

abstract

An experiment was performed at LNL to obtain information concerning the yield distributions in both the $^{132}$Sn ($N=82$) and the $^{208}$Pb ($N=126$) regions of the nuclide chart. The experimental set-up was composed of the large-acceptance magnetic spectrometer PRISMA to detect the light partner of the reaction, in conjunction with a recently installed ancillary set-up to detect the heavy partner.

all authors

E. Strano, D. Torresi, M. Mazzocco, N. Keeley, A. Boiano, C. Boiano, P. Di Meo, A. Guglielmetti, M. La Commara, P. Molini, C. Manea, C. Parascandolo, D. Pierroutsakou, C. Signorini, F. Soramel, D. Filipescu, A. Gheorghe, T. Glodariu, J. Grebosz, S. Jeong, Y.H. Kim, J.A. Lay, H. Miyatake, M. Nicoletto, A. Pakou, K. Rusek, O. Sgouros, V. Soukeras, L. Stroe, N. Toniolo, A. Vitturi, Y. Watanabe, K. Zerva

Discrimination of Processes and Optical Model Analysis in the $^{17}$O+$^{58}$Ni Collision Around the Coulomb Barrier

Acta Phys. Pol. B 48, 615 (2017)

page 615 •

abstract

The $^{17}$O+$^{58}$Ni collision was studied by means of a detailed analysis of the experimental spectra based on Monte Carlo simulations. The elastic scattering angular distributions were measured at five near-barrier energies in the range of 40–50 MeV and were investigated within the framework of the Optical Model, observing a relation between the imaginary radius parameter and the target mass. The Optical Model potential trend shows a normal Threshold Anomaly whereas the total reaction cross section, compared to the $^{16}$O+$^{58}$Ni case, is in agreement with the theoretical predictions.

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G. Kaur, B.R. Behera, A. Jhingan, R. Dubey, M. Thakur, P. Sharma, R. Mahajan, T. Banerjee, Khushboo, N. Saneesh, A. Kumar, S. Mandal, B.K. Nayak, A. Saxena, P. Sugathan, N. Rowley

Influence of Positive $Q$-value Neutron Transfer Coupling on Fusion Enhancement in $^{28}$Si+$^{154}$Sm Reaction

Acta Phys. Pol. B 48, 619 (2017)

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abstract

Recently, the barrier distribution (BD) for the $^{28}$Si+$^{154}$Sm system has been measured by our group using the quasi-elastic scattering technique. Here, we present the results of coupled-channel calculations performed to reproduce the measured BD. The inelastic excitation of target and projectile alone explains the experimentally observed BD very well, even though the system studied has large positive $Q$-value for neutron transfer channels. Hence, the results reveal no significant influence of positive $Q$-value neutron transfer channels on fusion enhancement for the $^{28}$Si+$^{154}$Sm system.

Structural Effects Through Nuclear Charge Radius in Mass Asymmetric Collisions

Acta Phys. Pol. B 48, 623 (2017)

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abstract

The structural effects through nuclear charge radius on the multifragmentation and nuclear stopping have been studied for mass symmetric and asymmetric collisions using Isospin-dependent Quantum Molecular Dynamics (IQMD) model. Our analysis shows that the role of increase in radius is more pronounced in mass symmetric collisions compared to asymmetric collisions. Moreover, we explicitly studied the influence of radius on the contribution of projectile and target nuclei in the nuclear stopping.

Analysis of Spontaneous Fission in Superheavy Mass Region Using the Dynamical Cluster-decay Model

Acta Phys. Pol. B 48, 629 (2017)

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abstract

Based on the dynamical cluster-decay model (DCM), we have extended our earlier study on $\alpha$-decay chains of superheavy nuclei (SHN), to address the phenomenon of spontaneous fission (SF) in $^{267}$Rf occurring as an end product of the decay chain of $^{291}$116$^*$ formed via $^{245}$Cm+$^{48}$Ca reaction after $2n$ emission. Interestingly, the most probable decay fragment $^{133}$Te (and the corresponding daughter $^{134}$Te) lie in the neighborhood of doubly shell closure, which in DCM is justified in terms of a minimum in fragmentation potential and the maximum in preformation factor. The half-life times are estimated using $\beta _2$-deformed choice of fragments, with calculated half-lives finding decent agreement with available experimental data.

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S. Valdré, S. Piantelli, G. Casini, S. Barlini, M. Ciemała, M. Kmiecik, A. Maj, K. Mazurek, M. Cinausero, F. Gramegna, V.L. Kravchuk, L. Morelli, T. Marchi, S. Appannababu, G. Baiocco, P. Bednarczyk, G. Benzoni, M. Bini, N. Blasi, A. Bracco, S. Brambilla, M. Bruno, F. Camera, M. Cicerchia, M. Colonna, F.C.L. Crespi, M. D'Agostino, M. Degerlier, D. Fabris, B. Fornal, O.V. Fotina, A. Giaz, M. Krzysiek, S. Leoni, J. Mabiala, M. Matejska-Minda, W. Męczyński, B. Million, D. Montanari, S. Myalski, R. Nicolini, A. Olmi, G. Pasquali, G. Prete, J. Styczeń, B. Szpak, E. Vardaci, B. Wasilewska, O. Wieland, M. Ziębliński

Constraining Hot Sources in Central Heavy-ion Collisions Below 20 MeV/$u$

Acta Phys. Pol. B 48, 635 (2017)

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abstract

Pre-equilibrium emissions affect the production of excited systems in nuclear reactions, thus modifying their properties which enter as input parameters in the comparison with statistical models. In this contribution, we discuss this subject referring to recent results from experiments performed at Legnaro National Laboratories (Italy) with the GARFIELD apparatus complemented with other detectors.

Microscopic Calculations of $\beta$-decay Rates for r-process

Acta Phys. Pol. B 48, 641 (2017)

page 641 •

abstract

Elements heavier than iron are being created in massive, explosive astrophysical scenarios such as core-collapse supernovae and neutron star mergers. Heavy element nucleosynthesis is a very complex process that requires the knowledge of the properties, mainly nuclear masses, neutron capture and beta-decay rates, of thousands of nuclei. However, due to the limitations of current experimental facilities, only a relatively small number of nuclei have so far been studied experimentally. Given the amount of nuclei, and the regions of the nuclear chart involved in the heavy element nucleosynthesis, it is necessary to use models that can be reliably applied to even the most exotic nuclei. Thus, the use of microscopic nuclear structure models presents itself as the logical choice, because the underlying microscopic theory of nuclear interaction is expected to be valid across the whole nuclear chart. In this manuscript, we present the results of a large-scale calculation of $\beta$-decay rates using a fully self-consistent theoretical framework based on the relativistic nuclear energy density functional. Taking into account the first-forbidden transitions, we are able to determine the regions of the nuclear chart where these transitions are critical for the description of the decay rates. Finally, we examine the $\beta$-delayed neutron emission in all neutron-rich nuclei, from the valley of stability to the limits of nuclear binding. The results of the study are applied in an r-process simulations where we obtain an improved description of the r-process abundance pattern.

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A. Bauswein, R. Ardevol Pulpillo, J.A. Clark, O. Just, S. Goriely, H.-T. Janka, N. Stergioulas

Neutron-star Mergers and Nuclear Physics

Acta Phys. Pol. B 48, 651 (2017)

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abstract

Neutron-star mergers are closely related to nuclear physics. The nuclear equation of state determines the properties of neutron-star matter and sensitively affects the dynamics of the merger. Consequently, the gravitational-wave signal carries a strong imprint of the equation of state. This, in turn, offers the possibilities to infer incompletely known properties of high-density matter from observations of gravitational waves emitted by the neutron-star mergers. For instance, the frequency of the dominant postmerger oscillation mode is strongly affected by the stiffness of nuclear matter. Furthermore, unbound matter from the neutron-star mergers provides generally favorable conditions for the formation of heavy elements through the rapid neutron-capture process. The element formation is investigated by nuclear network calculations. The amounts of ejecta are influenced by the high-density equation of state, which also implies an impact on the properties of nuclear powered electromagnetic counterparts.

Emissivity and Mean-free Paths of Neutrinos in Neutron Star Matter via Modified Urca Processes

Acta Phys. Pol. B 48, 661 (2017)

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abstract

The modified Urca processes are the most effective weak interactions that produce neutrinos in neutron star medium. Emissivity and mean-free path of electron neutrinos arising from the neutron branch of the modified Urca process are calculated supposing the neutron star matter is a beta stable one. The effect of strong nuclear interactions on the rate of this weak interaction is taken into account through the pair nuclear density-dependent correlation functions adapted from the lowest-order constrained variational (LOCV) method using the AV18 two-body potential.

Neutrino Processes with Hot Nuclei in Supernovae

Acta Phys. Pol. B 48, 667 (2017)

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abstract

In this paper, we calculate cross sections for charged-current neutrino–nucleus processes occuring under presupernova conditions. To treat thermal effects, we extend self-consistent Skyrme–QRPA calculations to finite temperature by using the formalism of thermo field dynamics. The numerical results are presented for the sample nuclei, $^{56}$Fe and $^{82}$Ge.

Test of Production of $^{198}$Au Radioisotope by Means of Typical Medical Linear Accelerators Used in Teleradiotherapy

Acta Phys. Pol. B 48, 671 (2017)

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abstract

The test of production of the $^{198}$Au radioisotope by means of Varian medical linear accelerators used in teleradiotherapy was carried out. The targets made of the natural gold (100% of the $^{197}$Au isotope) were irradiated with high-energy therapeutic 20 MV X-ray beam. $^{198}$Au was produced in the simple capture reaction $^{197}$Au($n,\gamma$)$^{198}$Au. The obtained specific activities in the saturation state are relatively low, not exceeding the value of 510.4 kBq/g, because only the high-energy part of the spectrum of 20 MV X-ray beam covers the energy range of the neutron production cross section. Low activity of the $^{198}$Au radioisotope produced by medical linear accelerators makes this technique not suitable for a massive production of $^{198}$Au for nuclear medicine, but the produced amount of $^{198}$Au is sufficient for laboratory tests of new drugs for possible clinical applications.

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A. Chrobak, A. Konefał, A. Wrońska, A. Magiera, K. Rusiecka, K. Laihem, D. Böckenhoff, S. Feyen

Comparison of Various Models of Monte Carlo Geant 4 Code in Simulations of Prompt Gamma Production

Acta Phys. Pol. B 48, 675 (2017)

page 675 •

abstract

In this paper, results of simulations of the gamma-ray production in reactions with 70 MeV protons in a target of PMMA are presented. The data obtained by means of two versions of Geant 4 software, 9.3 and 10.01, have shown significant differences in the gamma-ray spectra. The comparison between the calculated spectra and the measured ones has been carried out. The tested versions do not give satisfactory agreement with the experimental result. The reason of the performed verification was the planned application of this simulation toolkit for the preparation of in vivo dosimetry based on the prompt gamma-ray measurements for the proton therapy.

Calculation of Perturbation Factors for the PTW 23343 Markus Ionization Chamber in Proton Beams

Acta Phys. Pol. B 48, 679 (2017)

page 679 •

abstract

In this work, perturbation factors for the PTW 23343 Markus ionization chamber in proton beams were determined using Monte Carlo simulations based on the MCNPX code in version of 2.7.0. The calculations were performed for chosen proton energies from 15 MeV to 80 MeV and for various energy spread. The main conclusion is that the perturbation factors for the considered ionization chamber cannot be neglected in the region with the disturbed proton equilibrium in the above-mentioned energy range.

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S.A. Rymzhanova, L.V. Grigorenko, I.A. Egorova, A.G. Knyazev, Y.L. Parfenova, P.G. Sharov

Three-body Correlations Data Analysis Through Monte Carlo Simulation in Decay of $^{10}$He

Acta Phys. Pol. B 48, 683 (2017)

page 683 •

abstract

This work concerns the program for Monte Carlo (MC) simulation of three-body decays data. Three-body events are characterized by complicated correlations hindered by induced distortions due to finite resolution of experimental setups. The MC code is developed and tested by performing the analysis of the $^{10}$He experiment which shows the unusual order of first excited states of $^{10}$He.

all authors

U. Wiącek, M. Curyło, B. Gabańska, M. Gierlik, A. Igielski, R. Kwiatkowski, R. Prokopowicz, K. Pytel, M. Tarchalski, I. Zychor

STUMM — Test Module for a High Intensity Neutron Stripping Source

Acta Phys. Pol. B 48, 687 (2017)

page 687 •

abstract

An intense neutron source based on the stripping reaction between deuterium and lithium will produce the neutron spectrum similar to that induced by the deuterium–tritium reaction in fusion plasma reactors. This accelerator source will be built for tests prior to the operation of the future tokamaks, e.g. DEMO. As till now, no experimental results exist for such a kind of source. All parameters of the neutron and photon fields, and working conditions are foreseen based on theoretical and numerical calculations for the radiation transport. For verifying these predictions, it is necessary to build a special test module, called STUMM, that means the Start-Up Monitoring Module. This paper presents a concept of STUMM including a description of the main objective of the module, proposition of its shape and description of the foreseen experimental instrumentation.

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