The precise quantification of fusion suppression in heavy-projectile induced reactions is obscured by dominant noncompound processes, limited data, and uncertain models. Mass-total kinetic energy (MTKE) distributions for the reaction ^{54}Cr+^{209}Bi were measured at three beam energies, E_{beam}=261, 271, and 278 MeV. The fission fragments were detected using the newly developed TOSCA spectrometer setup. This Letter reveals, for the first time, two asymmetric mass modes at ∼80  u (complementary ∼183  u), and ∼105 u (complementary ∼158  u), likely associated with the spherical N=50 shell and the deformed Z≈42/N≈94 shells, respectively. At the lowest energy, the symmetric mode exhibits a narrow, super-short-like width and high correlated TKE caused likely by Z=50, N=82 shells. The fusion probability (P_{CN}) from multi-Gaussian fits to gated mass (and TKE) distributions using a refined tail-subtraction approach to remove the quasifission background remains robust despite model dependence. P_{CN} peaks near the barrier and decreases on either side, with a slower decrease at the above-barrier energy, differing from the sub-barrier fusion enhancement reported in [Phys. Rev. Lett. 122, 232503 (2019)PRLTAO0031-900710.1103/PhysRevLett.122.232503] and indicating an open question for further study.

The XT03 beamline at the HIE-ISOLDE facility provides a flexible platform for a broad range of non-permanent reaction experiments with accelerated radioactive ion beams. At its focal plane, the Scattering Experiment Chamber (SEC) offers a large, modular volume capable of hosting diverse internal detector setups. We present an overview of the SEC installation, mechanical layout, and integrated beam-diagnostic systems, together with a summary of the detector configurations deployed during the first decade of operation. Representative physics highlights illustrate the versatility and performance of the XT03-SEC infrastructure.

A large-area, position-sensitive, passing-through detector unit, named TOSCA (Time-Of-flight-sub-nano-second Spectrometer for Charged radiation Applications), has been developed for use in Time-Of-Flight (TOF) spectrometers. The detector provides simultaneous measurements of timing and two-dimensional impact position of traversing ions by detecting secondary electrons emitted from a thin conversion foil. The electrons are guided by electrostatic optics toward a microchannel plate amplification stage and collected on a pads-and-strips anode integrated into a printed circuit board, replacing conventional wire-based delay-line readout systems. Position resolutions of the order of 1 mm and intrinsic time resolutions better than 100 ps have been achieved when coupled to fast sampling electronics. The passing-through architecture ensures that only electrons reach the microchannel plates, resulting in improved radiation hardness and extended detector lifetime. The use of identical, fully position-sensitive TOSCA units as both Start and Stop detectors removes the functional asymmetry typical of conventional TOF spectrometers and enables multi-point trajectory measurements within a single TOF arm. This approach allows the realization of compact and flexible two-arm TOF spectrometers based on four identical detector modules. In-beam tests with heavy ions demonstrate the performance and potential of the TOSCA concept for high-resolution mass and energy measurements in heavy-ion reaction studies.

Many observations strongly support the hypothesis that nuclei may fission through several independent fission modes (multimodal fission) interpreted as different prescission shapes and fission paths in a multidimensional potential energy landscape where shell effects are dominant. Mass distributions of the fission fragments are sensitive to the potential energy landscape and appear to be single humped (symmetric) or double humped (asymmetric). In many cases a mixture of both modes is observed. We propose here our study on 180Hg. Binary fission fragments formed in the reaction 68Zn + 112Sn → 180Hg at different excitation energies around the Coulomb barrier were detected using the double-arm time-of-flight technique with the spectrometers CORSET. The experiment was performed at JYFL (Jyvaskyla, Finland). We will discuss an analysis of the mass distributions in terms of fission modes predicted by a five-dimensional fission model. We have found out that the mass distributions can be well reproduced by considering a symmetric fission mode and two asymmetric modes at (AL ≈ 80, AH ≈ 100) and (AL ≈ 70 and AH ≈ 110).

True ternary fission, the fission of a nucleus into three fragments of nearly equal mass, is an elusive and poorly known process influenced by shell effects. An increase in the probability of this process with respect to binary fission, which is very low in spontaneous and neutron-induced fission, has been envisaged. Heavy-ion-induced reactions are adopted due to the possibility of an increase in the fissility parameter and the excitation energy of the compound nuclei. Nuclei with mass number around A = 250, accessible in heavy-ion-induced reactions, are favorable and should be investigated. It is still debated if the process takes place in a single step, direct ternary fission, or in a two step, sequential ternary fission. The purpose of this work is to define experimental conditions and observables that allow the disentangling of the products from the direct and sequential ternary fission, as well as from the usual most probable binary fission. This step is essential for gaining insights into the ternary fission dynamics and the binary to ternary fission competition. The method proposed here is for simulating the kinematics of the ternary and binary fission processes to compute the energy distributions and angular correlations of direct and sequential ternary fission products, as well as those of binary fission. The reaction taken as a benchmark is 40Ar + 208Pb at 230 MeV and is supposed to form the 248Fm* compound nucleus. The simulation results have been filtered by considering the response function of a multi-coincidence detection system virtually constructed using the Geant4 simulation toolkit. The simulations support the possibility of separating the products of different multimodal fission decays with the proposed setup that consequently represents an effective tool to obtain insights into ternary fission from the observables selected.

Background: Nuclear fission is influenced by shell effects. Fission modes are a strong signature of the compound nucleus formation in heavy ion induced reactions. The evolution of the relative strengths of the fission modes with excitation energy is a matter of intense interest. Purpose: We investigate the signatures of fission modes in Np-238 populated by the Li-6 + Th-232 reaction through the mass-total kinetic energy distribution. Method: The mass-total kinetic energy distributions of fission fragments of the reaction Li-6 + Th-232 are measured at four laboratory energies, Elab = 28.5, 40, 45, and 62.5 MeV. Mass-total kinetic energy distributions of Li-6 + Th-232 are described by the multimodal random neck rupture model. Results: Channel probabilities of different fission modes are obtained obtained through a two-dimensional fitting procedure. The contribution of the standard 1 (S1) mode is found to become approximate to 2% at E-lab = 40 MeV. The heavy fragments of S1 and standard 2 (S2) modes are found to be associated with Z approximate to 52 and Z approximate to 55 shells, respectively. The slope of the asymmetric to symmetric fission yields ratio with the excitation energy of Li-6 + Th-232 is found to be similar to that of O-18 + Pb-208 (previously reported). Conclusions: The analysis of mass-total kinetic energy distribution data reveals the presence of fission modes in Li-6 + Th-232. The average kinetic energy release in fission obtained from Viola systematic matches well with the one of the of S2 mode. The liquid -drop -like broad symmetric (SL) mode is found to peak at a lower energy than predicted by Viola systematic. This is associated with the decrease of the total kinetic energy in the asymmetric fission mode due to the fading out of shell effects with increasing excitation energy.

The nuclear properties of 36Ar composite alpha-like nuclei produced at 46.72 MeV of excitation energy via the 24Mg + 12C reaction were investigated. In the past, at this excitation energy, resonant structures with peak-tovalley variation of 50-100 mb have been observed for this system and associated with fusion cross sections. To reveal the nature of this phenomenon the fusion channel observable was investigated. Exclusive measurements of alpha particles and evaporation residues were carried out at Laboratori Nazionali di Legnaro using the 8 pi LP apparatus coupled to an evaporation residue detector. Then the experimental data were interpreted through the comparison with statistical model predictions. The energy spectra in coincidence with evaporation residues evidence the limitation of the statistical model assuming nuclear shape of the compound nucleus according to the rotating liquid drop model. To reproduce the experimental data very elongated nuclear shapes and reduced barriers for light particle emission have to be considered, with a major to minor axis ratio up to 3 at higher angular momenta. This large value for the axis ratio is selected in agreement with the predictions of the cranked cluster model and is consistent with previous findings for alpha-like nuclei.

Space missions with humans expose the crews to ionizing radiation, mainly due to the galactic cosmic radiation (GCR). All radiation protection programs in space aim to minimize crews' exposure to radiation. The radiation protection of astronauts can be achieved through the use of shields. The shields could serve as a suit to reduce GCR exposure and, in an emergency, as a radiation shelter to perform necessary interventions outside the space habitat in case of a solar proton event (SPE). A space radiation shielding that is suitable for exploration during space missions requires particular features and a proper knowledge of the radiation type. This study shows the results of numerical simulations performed with the Geant4 toolkit-based code DOSE. Calculations to evaluate the performance of Nomex, an aramidic fiber with high mechanical resistance, in terms of dose reduction to crews, were performed considering the interaction between protons with an energy spectrum ranging from 50 to 1100 MeV and a target slab of 20 g/cm2. This paper shows the properties of secondary products obtained as a result of the interaction between space radiation and a Nomex target and the properties of the secondary particles that come out the shield. The results of this study show that Nomex can be considered a good shield candidate material in terms of dose reductions. We also note that the secondary particles that provide the greatest contribution to the dose are protons, neutrons and, in a very small percentage, α-particles and Li ions.

The next years will see the completion of the radioactive ion beam facility SPES (Selective Production of Exotic Species) and the upgrade of the accelerators complex at Istituto Nazionale di Fisica Nucleare – Legnaro National Laboratories (LNL) opening up new possibilities in the fields of nuclear structure, nuclear dynamics, nuclear astrophysics, and applications. The nuclear physics community has organised a workshop to discuss the new physics opportunities that will be possible in the near future by employing state-of-the-art detection systems. A detailed discussion of the outcome from the workshop is presented in this report.

The nuclear properties of $^{36}\mathrm{Ar}$ composite $\ensuremath{\alpha}$-like nuclei produced at 46.72 MeV of excitation energy via the $^{24}\mathrm{Mg}+^{12}\mathrm{C}$ reaction were investigated. In the past, at this excitation energy, resonant structures with peak-to-valley variation of 50--100 mb have been observed for this system and associated with fusion cross sections. To reveal the nature of this phenomenon the fusion channel observable was investigated. Exclusive measurements of $\ensuremath{\alpha}$ particles and evaporation residues were carried out at Laboratori Nazionali di Legnaro using the $8\ensuremath{\pi}\mathrm{LP}$ apparatus coupled to an evaporation residue detector. Then the experimental data were interpreted through the comparison with statistical model predictions. The energy spectra in coincidence with evaporation residues evidence the limitation of the statistical model assuming nuclear shape of the compound nucleus according to the rotating liquid drop model. To reproduce the experimental data very elongated nuclear shapes and reduced barriers for light particle emission have to be considered, with a major to minor axis ratio up to 3 at higher angular momenta. This large value for the axis ratio is selected in agreement with the predictions of the cranked cluster model and is consistent with previous findings for $\ensuremath{\alpha}$-like nuclei.

Background: Nuclear fission is influenced by shell effects. Fission modes are a strong signature of the compound nucleus formation in heavy ion induced reactions. The evolution of the relative strengths of the fission modes with excitation energy is a matter of intense interest.Purpose: We investigate the signatures of fission modes in $^{238}\mathrm{Np}$ populated by the $^{6}\mathrm{Li}+^{232}\mathrm{Th}$ reaction through the mass--total kinetic energy distribution.Method: The mass--total kinetic energy distributions of fission fragments of the reaction $^{6}\mathrm{Li}+^{232}\mathrm{Th}$ are measured at four laboratory energies, ${E}_{\text{lab}}=28.5$, 40, 45, and 62.5 MeV. Mass--total kinetic energy distributions of $^{6}\mathrm{Li}+^{232}\mathrm{Th}$ are described by the multimodal random neck rupture model.Results: Channel probabilities of different fission modes are obtained obtained through a two-dimensional fitting procedure. The contribution of the standard 1 (S1) mode is found to become $\ensuremath{\approx}2%$ at ${E}_{\text{lab}}=40$ MeV. The heavy fragments of S1 and standard 2 (S2) modes are found to be associated with $Z\ensuremath{\approx}52$ and $Z\ensuremath{\approx}55$ shells, respectively. The slope of the asymmetric to symmetric fission yields ratio with the excitation energy of $^{6}\mathrm{Li}+^{232}\mathrm{Th}$ is found to be similar to that of $^{18}\mathrm{O}+^{208}\mathrm{Pb}$ (previously reported).Conclusions: The analysis of mass--total kinetic energy distribution data reveals the presence of fission modes in $^{6}\mathrm{Li}+^{232}\mathrm{Th}$. The average kinetic energy release in fission obtained from Viola systematic matches well with the one of the of S2 mode. The liquid-drop-like broad symmetric (SL) mode is found to peak at a lower energy than predicted by Viola systematic. This is associated with the decrease of the total kinetic energy in the asymmetric fission mode due to the fading out of shell effects with increasing excitation energy.

The next years will see the completion of several new facilities at Istituto Nazionale di Fisica Nucleare – Laboratori Nazionali del Sud (LNS) opening up new possibilities in the fields of nuclear structure, nuclear dynamics, nuclear astrophysics and applications. These include a new line for high-intensity cyclotron beams, a new facility for in-flight production of radioactive ion beams, the PANDORA plasma trap for multidisciplinary studies and a high-power laser for basic science and applied physics. The nuclear physics community has organized a workshop to discuss the new physics opportunities that will be possible in the middle term (5–7 years) by employing state-of-the-art detection systems. A detailed discussion of the outcome from the workshop is presented in this report.

Since the code LILITA was presented in 1981 by Gomez Del Campo and Stockstad (1981)[1] and used to simulate the emission of light particles in the decay of a compound nucleus, relevant improvements have been made. Revisions leading to LILITA_N97 were begun by G. La Rana (Naples), M. Kaplan (CMU, Pittsburgh, PA), J.M. Alexander (Stony Brook, NY) and continued by the Naples Group (Moro et al., 2012) [2]. In this work new key features of the code consisting of the implementation of transmission coefficients based on global parametrization of the optical model potential, a description of the nuclear shape based on the nuclear stratosphere model, the parallelization of the code and a graphical user interface are presented. We expect that the new code version, LILITA_N21, makes it possible a better reproduction of wide data set from literature. In order to illustrate how this could be achieved, the standard statistical model predictions have been compared with those obtained with the new code features. A single set of parameters of the new code simultaneously well reproduces the neutron, proton and alpha-particle energy spectra, angular distributions, and multiplicities in the fusion-evaporation channel. By way of example, here the calculations are compared with experimental data of the reaction Ni-60+Mo-100 at the excitation energy of about 280 MeV (Charity et al., 2003) [3]. The capability to reduce the execution time by exploiting the code parallelization is also discussed.

The study of suitable materials to shield astronauts from Galactic Cosmic Rays (GCR) is a topic of fundamental importance. The choice of the material must take into account both the secondary radiation produced by the interaction between primary radiation and material and its shielding ability. The physics case presented here deals with the interaction of a proton beam with a Nomex shield, namely, a target material with a mass thickness of 20 g cm−2. The study was conducted with the simulation code DOSE based on the well-known simulation package Geant4. This article shows the properties of secondary radiations produced in the target by the interaction of a proton beam in an energy range characterizing the GCR spectrum. We observed the production of ions of masses and charges lower than the chemical elements that make up Nomex, and also a significant production of neutrons, protons, and 𝛼 particles.

The excitation of the dynamical dipole mode was explored in the formation of a heavy composite system with mass A similar or equal to 190, by investigating its fission channel. The composite system was produced through the charge asymmetric reaction, Ca-40 + Sm-152, and the nearly charge symmetric one, Ca-48 + Sm-144, at E-lab = 11 and 10.1 MeV/nucleon, respectively. High-energy gamma rays and light charged particles were detected in coincidence with the two fission fragments by means of the MEDEA multidetector array coupled to two parallel plate avalanche counters. The kinetic energy spectra of the light charged particles measured at different angles were used to infer the average excitation energy, the average mass, and the average charge of the produced nuclei whereas the time of flight and the emission angle of the fragments were employed to reconstruct the fission dynamics. The study of the gamma-ray spectra and angular distributions for the selected fission events, allowed us to establish (i) the excitation of the giant dipole resonance in the composite system of both reactions and (ii) the excitation of the dynamical dipole mode in the dinucleus of the charge asymmetric reaction by isolating its prompt gamma radiation through the difference technique. The present results on the dynamical dipole mode were compared with the experimental findings for the evaporation channel of the Ca-40 + Sm-152 reaction and moreover with calculations based on a collective bremsstrahlung analysis of the reaction dynamics. Interesting hints connecting the dynamical dipole gamma radiation with the superheavy element quest are given.

The excitation of the dynamical dipole mode was explored in the formation of a heavy composite system with mass $A\ensuremath{\simeq}$ 190, by investigating its fission channel. The composite system was produced through the charge asymmetric reaction, $^{40}\mathrm{Ca} + ^{152}\mathrm{Sm}$, and the nearly charge symmetric one, $^{48}\mathrm{Ca} +^{144}\mathrm{Sm}$, at ${E}_{\text{lab}}$ = 11 and 10.1 MeV/nucleon, respectively. High-energy $\ensuremath{\gamma}$ rays and light charged particles were detected in coincidence with the two fission fragments by means of the MEDEA multidetector array coupled to two parallel plate avalanche counters. The kinetic energy spectra of the light charged particles measured at different angles were used to infer the average excitation energy, the average mass, and the average charge of the produced nuclei whereas the time of flight and the emission angle of the fragments were employed to reconstruct the fission dynamics. The study of the $\ensuremath{\gamma}$-ray spectra and angular distributions for the selected fission events, allowed us to establish (i) the excitation of the giant dipole resonance in the composite system of both reactions and (ii) the excitation of the dynamical dipole mode in the dinucleus of the charge asymmetric reaction by isolating its prompt $\ensuremath{\gamma}$ radiation through the difference technique. The present results on the dynamical dipole mode were compared with the experimental findings for the evaporation channel of the $^{40}\mathrm{Ca} + ^{152}\mathrm{Sm}$ reaction and moreover with calculations based on a collective bremsstrahlung analysis of the reaction dynamics. Interesting hints connecting the dynamical dipole $\ensuremath{\gamma}$ radiation with the superheavy element quest are given.

Background: The nature of asymmetric fission of preactinides is not yet understood in detail, despite intense experimental and theoretical studies carried out at present.Purpose: The study of asymmetric and symmetric fission of $^{180,182,183}\mathrm{Hg}$ and $^{178}\mathrm{Pt}$ nuclei as a function of their excitation energy and isospin.Methods: Mass-energy distributions of fission fragments of $^{180}\mathrm{Hg}, ^{178}\mathrm{Pt}$ (two protons less than $^{180}\mathrm{Hg}$), and $^{182}\mathrm{Hg}$ (two neutrons more than $^{180}\mathrm{Hg}$) formed in the $^{36}\mathrm{Ar}+^{144}\mathrm{Sm}, ^{142}\mathrm{Nd}$, and $^{40}\mathrm{Ca}+^{142}\mathrm{Nd}$ reactions were measured at energies near and above the Coulomb barrier. Fission of $^{183}\mathrm{Hg}$ obtained in the reaction of $^{40}\mathrm{Ca}$ with $^{143}\mathrm{Nd}$ was also investigated to see if one extra neutron could lead to dramatic changes in the fission process due to the shape-staggering effect in radii, known in $^{183}\mathrm{Hg}$.The measurements were performed with the double-arm time-of-flight spectrometer CORSET.Results: The observed peculiarities in the fission fragment mass-energy distributions for all studied nuclei may be explained by the presence of a symmetric fission mode and three asymmetric fission modes, manifested by the different total kinetic energies and fragment mass splits. The yield of symmetric mode grows with increasing excitation energy of compound nucleus.Conclusions: The investigated properties of asymmetric fission of $^{180,182,183}\mathrm{Hg}$ and $^{178}\mathrm{Pt}$ nuclei point out the existence of well-deformed proton shell at $Z\ensuremath{\approx}36$ and a less deformed proton shell at $Z$ \ensuremath{\approx} 46.

n Erratum to this paper has been published: https://doi.org/10.3103/S1062873822340019

In this paper, light charged particle emission in the evaporation residue channel for the 190 MeV 40Ar + 27Al reaction leading to 67Ga composite nuclei at Ex = 91 MeV and angular momentum up to 46 ℏ has been re-analyzed. The main goal was to study the decay of 67Ga on the basis of an extended set of observables in order to provide a description of the evaporative decay cascades using the multistep Monte Carlo approach. The proton and α-particle energy spectra along with their angular distributions and ratios of differential multiplicities have been considered. The measured observables were compared with statistical model calculations. Having used a single-step Monte Carlo approach and standard parameters decades ago, the model does not provide a good description of the full dataset. Only a subset of the data was reproduced by assuming emitting nuclei with very large deformed shapes in a previous work published in the late 1980s. In the reported analysis, better agreement has been observed. Using the new transmission coefficients from the Optical Model, the parameters of which have recently been derived, the multi-step approach and the introduction of a nuclear shape description based on the nuclear stratosphere allowed us to realize a significant improvement.

Background: The nature of asymmetric fission of preactinides is not yet understood in detail, despite intense experimental and theoretical studies carried out at present. Purpose: The study of asymmetric and symmetric fission of Hg-180,Hg-182,Hg-183 and Pt-178 nuclei as a function of their excitation energy and isospin. Methods: Mass-energy distributions of fission fragments of Hg-180, Pt-178 (two protons less than Hg-180), and Hg-182 (two neutrons more than Hg-180) formed in the( 36)Ar+Sm-144, Nd-142, and Ca-40+Nd-142 reactions were measured at energies near and above the Coulomb barrier. Fission of Hg-183 obtained in the reaction of Ca-40 with Nd-143 was also investigated to see if one extra neutron could lead to dramatic changes in the fission process due to the shape-staggering effect in radii, known in Hg-183. The measurements were performed with the double-arm time-of-flight spectrometer CORSET. Results: The observed peculiarities in the fission fragment mass-energy distributions for all studied nuclei may be explained by the presence of a symmetric fission mode and three asymmetric fission modes, manifested by the different total kinetic energies and fragment mass splits. The yield of symmetric mode grows with increasing excitation energy of compound nucleus. Conclusions: The investigated properties of asymmetric fission of Hg-180,Hg-182,Hg-183 and Pt-178 nuclei point out the existence of well-deformed proton shell at Z approximate to 36 and a less deformed proton shell at Z approximate to 46.