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A previous analysis of the charge (Z) correlations in the ΔZ−〈Z〉plane for 129Xe+natSn central collisions at 32 MeV/n has shown an enhancement in the production of equally sized fragments (low ΔZ) which was interpreted as an evidence for spinodal decomposition. However, the signal is weak and rises the question of the estimation of the uncorrelated yield. After a critical analysis of its robustness, we propose in this paper a new technique to build the uncorrelated yield in the charge correlation function. The application of this method to 129Xe+natSn central collision data at 32, 39, 45 and 50 MeV/n does not show any particular enhancement of the correlation function in any ΔZ bin. [Copyright &y& Elsevier]

Ar + Ni and Ni + Ni collisions are investigated between 32 and around 100A MeV incident energy with the 4π multidetector INDRA. Fusion cross-sections are found to decrease from ∼ 180mb at 32A MeV to zero above 50A MeV. Other experimental results, for light systems, are compared. Moreover, theoretical works are discussed and fusion cross-sections, calculated from two dynamical simulations based on nuclear Boltzmann equation (Boltzmann-Nordheim-Vlasov and Landau-Vlasov models), are also compared to experimental results. [ABSTRACT FROM AUTHOR]

Abstract: The low-lying spectroscopy of 6He was investigated via the 2-neutron transfer reaction with the 8He beam delivered by the SPIRAL facility at . The light charged particles produced by the direct reactions were measured using the MUST2 Si-strip telescope array. Above the known state, two new resonances were observed: at (width ) and at with . Through the analysis of the angular distributions, they correspond to a state and to an state, respectively. These new states, challenging the nuclear theories, could be used as benchmarks for checking the microscopic inputs of the newly improved structure models, and should trigger development of models including the treatments of both core excitation and continuum coupling effects. [Copyright &y& Elsevier]

We present a new experimental method to correlate the isotopic composition of intermediate mass fragments (IMF) emitted at mid-rapidity in semi-peripheral collisions with the emission timescale: IMFs emitted in the early stage of the reaction show larger values of (N/Z) isospin asymmetry, stronger angular anisotropies and reduced odd-even staggering effects in neutron to proton ratio (N/Z) distributions than those produced in sequential statistical emission. All these effects support the concept of isospin "migration", that is sensitive to the density gradient between participant and quasi-spectator nuclear matter, in the so called neck fragmentation mechanism. By comparing the data to a Stochastic Mean Field (SMF) simulation we show that this method gives valuable constraints on the symmetry energy term of nuclear equation of state at subsaturation densities. An indication emerges for a linear density dependence of the symmetry energy. [ABSTRACT FROM AUTHOR]

The article discusses the experimental developments in nuclear physics. It presents the study which examined the correlations between emission timescale of fragments and isospin dynamics in 124tin (Sn) + 64nickel (Ni) and 112Sn + 58Ni reactions at 35 A megaelectron volt (MeV). Based on the study, intermediate mass fragments (IMF) emitted in the early stage of the reaction show bigger values of (N/Z) isospin asymmetry, among others.

Decay modes of excited nuclei are investigated in 78,82Kr+40Ca reactions at 5.5 MeV/nucleon. Charged products were measured by means of the 4π INDRA array. Kinetic-energy spectra and angular distributions of fragments with atomic number 3 ⩽Z⩽ 28 indicate a high degree of relaxation and are compatible with a fissionlike phenomenon. Persistence of structure effects is evidenced from elemental cross sections (σZ) as well as a strong odd-even staggering (o-e-s) of the light-fragment yields. The magnitude of the staggering does not significantly depend on the neutron content of the emitting system. Fragment-particle coincidences suggest that the light partners in very asymmetric fission are emitted either cold or at excitation energies below the particle emission thresholds. The evaporation residue cross section of the 78Kr+40Ca reaction is slightly higher than the one measured in the 82Kr+40Ca reaction. The fissionlike component is larger by ~25% for the reaction having the lowest neutron-to-proton ratio. These experimental features are confronted to the predictions of theoretical models. The Hauser-Feshbach approach including the emission of fragments up to Z = 14 in their ground states as well as excited states does not account for the main features of σZ. For both reactions, the transition-state formalism reasonably reproduces the Z distribution of the fragments with charge 12 ⩽Z⩽ 28. However, this model strongly overestimates the light-fragment cross sections and does not explain the o-e-s of the yields for 6 ⩽Z⩽ 10. The shape of the whole Z distribution and the o-e-s of the light-fragment yields are satisfactorily reproduced within the dinuclear system framework which treats the competition among evaporation, fusion-fission, and quasifission processes. The model suggests that heavy fragments come mainly from quasifission while light fragments are predominantly populated by fusion. An underestimation of the cross sections for 16 ⩽Z⩽ 22 could signal a mechanism in addition to the capture process. [ABSTRACT FROM AUTHOR]

Isospin diffusion is probed as a function of the dissipated energy by studying two systems 58Ni+58Ni and 58Ni+197Au, over the incident energy range 52-74A MeV. Experimental data are compared with the results of a microscopic transport model with two different parameterizations of the symmetry energy term. A better overall agreement between data and simulations is obtained when using a symmetry term with a potential part linearly increasing with nuclear density. The isospin equilibration time at 52 A MeV is estimated to 130 ± 10 fm/c. [ABSTRACT FROM AUTHOR]

A new detector system dedicated for very/super heavy elements (VHE/SHE) detection that decay by spontaneous fission is presented. Such a decay mode of nuclei can be found e.g. in the region of Z≈100 (Fermium). Future experiments realized in the frame of French-Polish collaboration at the cyclotrons in GANIL and in the Heavy Ion Laboratory (HIL), University of Warsaw, is described. The results of test measurements made in the HIL for reactions 20Ne(8 A.MeV)+120Sn, 179Au are presented. [ABSTRACT FROM AUTHOR]

For fragments emitted in the reactions 124Sn + 64Ni and 112Sn + 58Ni at 35 AMeV, isotopic composition and velocity correlations have been studied as a function of the centrality of the collision, using the 4π Chimera multidetector. We have investigated the time scale for fragments formation, in order to distinguish between prompt dynamical and sequential statistical emission. Promptly emitted light fragments (Z ≤9) produced in the mid-rapidity domain are characterised by larger N/Z ratio and stronger angular anisotropies than those produced in sequential statistical emission. Results are compared with stochastic BNV code simulations obtained for primary fragments. Valuable information on the symmetry term of the nuclear equation of state at sub-saturation densities are obtained. [ABSTRACT FROM AUTHOR]

In the paper we present scintillation-ionization detector (SID) -- a new device for support of the superheavy elements (SHE) identification in the standard, complete fusion methods. We highlight problems with background effects in SHE production and their minimization by introducing SID to the detection set-up at GANIL. We also point possible application of this detector in alternative approach for superheavy elements production. [ABSTRACT FROM AUTHOR]

Investigations on the influence of the neutron enrichment on the decay channels of excited nuclei are presented. Characteristics of fragments with charge 6 ≤ Z ≤ 28 emitted in 78,82Kr+40Ca at 5.5 MeV/A reactions were measured at the GANIL facility. Data are compatible with an emission process from compound nucleus and are discussed in the framework of the transition state model. [ABSTRACT FROM AUTHOR]

Abstract: Fragment properties of hot fragmenting sources of similar sizes produced in central and semi-peripheral collisions are compared in the excitation energy range . For semi-peripheral collisions a method for selecting compact quasi-projectiles sources in velocity space similar to those of fused systems (central collisions) is proposed. The two major results are related to collective energy. The weak radial collective energy observed for quasi-projectile sources is shown to originate from thermal pressure only. The larger fragment multiplicity observed for fused systems and their more symmetric fragmentation are related to the extra radial collective energy due to expansion following a compression phase during central collisions. A first attempt to locate where the different sources break in the phase diagram is proposed. [Copyright &y& Elsevier]

Cross sections, kinetic energy and angular distributions of fragments with charge 6 ≤ Z ≤ 28 emitted in 78,82Kr+40C at 5.5 MeV/A reactions were measured at the GANIL facility using the INDRA apparatus. This experiment aims to investigate the influence of the neutron enrichment on the decay mechanism of excited nuclei. Data are discussed in comparison with predictions of transition state and Hauser-Feshbach models. [ABSTRACT FROM AUTHOR]

Abstract: Unstable 10C nuclei are produced as quasi-projectiles in 12C+ 24Mg collisions at and 95 MeV. The decay of their short-lived states is studied with the INDRA multidetector array via multi-particle correlation functions. The obtained results show that heavy-ion collisions can be used as a tool to access spectroscopic information of unbound states in exotic nuclei, such as their energies and the relative importance of different sequential decay widths. [Copyright &y& Elsevier]

Abstract: We analyzed the 93Nb on natMg reaction at 30 MeV/nucleon in the aim of disentangling binary sequential decay and multifragmentation decay close to the energy threshold, i.e. ≃3 MeV/nucleon. Using the backtracing technique applied to the statistical models GEMINI and SMM we reconstruct simulated charge, mass and excitation energy distributions and compare them to the experimental ones. We show that data are better described by SMM than by GEMINI in agreement with the fact that multifragmentation is responsible for fragment production at excitation energies around 3 MeV/nucleon. [Copyright &y& Elsevier]

Abstract: Freeze-out properties of multifragmentation events produced in central 129Xe+ natSn collisions at different beam energies (32, 39, 45 and 50 A MeV) were estimated by means of a simulation based on the experimental data collected by the 4π INDRA multidetector. A rapid increase (between 32 and 45 A MeV) of the fraction of particles emitted at freeze-out is deduced. The existence of a limitation of excitation energy for fragments around 3.0–3.5 A MeV is confirmed. A comparison with the results of a microcanonical statistical model is also performed to verify the overall physical coherence of the present approach. [Copyright &y& Elsevier]

Abstract: Correlation functions, constructed from directional projections of the relative velocities of fragments, are used to determine the shape of the breakup volume in coordinate space. For central collisions of 129Xe+ natSn at 50 MeV per nucleon incident energy, measured with the 4π multidetector INDRA at GSI, a prolate shape aligned along the beam direction with an axis ratio of is deduced. The sensitivity of the method is discussed in comparison with conventional fragment–fragment velocity correlations. [Copyright &y& Elsevier]

The blocking technique in single crystals has been applied to reaction time measurements for the 238U + Ge system at 6.1 MeV/nucleon. Backed up with a reaction mechanism analysis using the INDRA 4π detector, it provides a direct experimental evidence for Z = 124 compound nuclei living longer than 10-18 s, indicating thus very high fission barriers for this element. [ABSTRACT FROM AUTHOR]

Abstract: Multifragmentation properties measured with INDRA are studied for single sources produced in Xe + Sn reactions in the incident energy range 32–50 A MeV and quasi-projectiles from Au + Au collisions at 80 A MeV. A comparison for both types of sources is presented concerning Fisher scaling, Zipf law, fragment size and fluctuation observables. A Fisher scaling is observed for all the data. The pseudo-critical energies extracted from the Fisher scaling are consistent between Xe + Sn central collisions and Au quasi-projectiles. In the latter case it also corresponds to the energy region at which fluctuations are maximal. The critical energies deduced from the Zipf analysis are higher than those from the Fisher analysis. [Copyright &y& Elsevier]

Abstract: We have observed a bimodal behaviour of the distribution of the asymmetry between the charges of the two heaviest products resulting from the decay of the quasi-projectile released in binary and collisions from 60 to 100 MeV/u. Event sorting has been achieved through the transverse energy of light charged particles emitted on the quasi-target side, thus avoiding artificial correlations between the bimodality signal and the sorting variable. Bimodality is observed for intermediate impact parameters for which the quasi-projectile is identified. A simulation shows that the deexcitation step rather than the geometry of the collision appears responsible for the bimodal behaviour. The influence of mid-rapidity emission has been verified. The two bumps of the bimodal distribution correspond to different excitation energies and similar temperatures. It is also shown that it is possible to correlate the bimodality signal with a change in the distribution of the heaviest fragment charge and a peak in potential energy fluctuations. All together, this set of data is coherent with what would be expected in a finite system if the corresponding system in the thermodynamic limit exhibits a first order phase transition. [Copyright &y& Elsevier]

The odd- Z isotope 255Lr, its daughter 251Md and grand-daughter 247Es were studied in two experiments performed at GANIL and the University of Jyväskylä. The 255Lr nuclei were produced using the cold fusion-evaporation reaction 209Bi(48Ca, 2n)255Lr at a bombarding energy of 217MeV. The single-particle structure and decay properties were investigated using α, γ and electron spectroscopy. The ground-state spin and parity could be assigned for 255Lr (1/2-) and 251Md (7/2-). States corresponding to the 7/2+[633], 7/2-[514] and 1/2-[521] Nilsson orbitals were observed. Results are compared to experimental data obtained in neighbouring isotopes and to Hartree-Fock-Bogoliubov calculations using the Skyrme interaction SLy4 and a density-dependent pairing interaction. The position of the 1/2-[521] orbital from the spherical 2 f 5/2 shell is discussed. [ABSTRACT FROM AUTHOR]

Abstract: Results on projectile fragment–fragment coincidences in the forward direction and for the reaction 40Ar+ 27Al at 44 A MeV are presented and compared with the predictions of two different entrance channel models, a two-body and a three-body mechanism both followed by a binary multisequential decay including fission. This analysis shows that many features of the projectile decay products are well accounted for by the binary multisequential decay model. However the results depend critically upon the initial masses and excitation energies of the primary projectile fragments. In this respect, the three-body approach underestimates the excitation energy imparted to the primary fragments whereas the two-body scenario overestimates it. The present data put strong constraints on the initial excitation energy imparted to the primary fragments which appears to be intermediate between the predictions of the two models. [Copyright &y& Elsevier]

Using the 4π CHIMERA detector system we have observed a dynamical, non-equilibrated fission of projectile-like fragments as well as an equilibrated fission component in collisions 124Sn + 64Ni and 112Sn + 58Ni at 35A MeV. The velocity and angular distributions of projectile-like fission fragments were analyzed. The contribution of the "dynamical fission" component is larger in the neutron rich 124Sn + 64Ni system than in the neutron poor 112Sn + 58Ni one. [ABSTRACT FROM AUTHOR]

Abstract: Two-particle correlation functions, involving protons, deuterons, tritons, and α-particles, have been measured at very forward angles (), in order to study projectile-like fragment (PLF) emission in = 44 and 77 MeV 40Ar + 27Al collisions. The observed correlations are similar for the two reactions at and 77 MeV, except for peaks originating from resonance decays, which are larger at the lower bombarding energy. Particle-velocity gated correlation functions are presented, and possible implications on the time sequence of the light charged particles, emitted from the PLF, are discussed. [Copyright &y& Elsevier]

Abstract: The spectroscopy of 27Ne has been investigated through the one-neutron transfer reaction 26Ne()27Ne in inverse kinematics at 9.7 MeV/nucleon. The results strongly support the existence of a low-lying negative parity state in 27Ne, which is a signature of a reduced sd–fp shell gap in the neutron-rich region, at variance with stable nuclei. [Copyright &y& Elsevier]

Abstract: Kinetic energy spectra and fragment velocity correlations, simulated by means of stochastic mean-field calculations, are successfully confronted with experimental data for single multifragmenting sources prepared at the same excitation energy per nucleon in 32 A MeV 129Xe+ natSn and 36 A MeV 155Gd+ natU central collisions. Relying thus on simulations, average freeze-out times of 200–240 fm/c are estimated. The corresponding spatial distributions of fragments are more compact for the lighter system ( vs. ). [Copyright &y& Elsevier]

Abstract: An estimate of the average freeze-out volume for multifragmentation events is presented. Values of volumes are obtained by means of a simulation using the experimental charged product partitions measured by the 4π multidetector INDRA for 129Xe central collisions on natSn at incident energy. The input parameters of the simulation are tuned by means of the comparison between the experimental and simulated velocity (or energy) spectra of particles and fragments. [Copyright &y& Elsevier]

Abstract: Directed and elliptic flow for the 197Au + 197Au system at incident energies between 40 and 150 MeV per nucleon has been measured using the INDRA 4π multi-detector. For semi-central collisions, the elliptic flow of particles switches from in-plane to out-of-plane enhancement at around 100 MeV per nucleon, in good agreement with the result reported by the FOPI Collaboration. The directed flow changes sign at a bombarding energy between 50 and 60 MeV per nucleon and remains negative at lower energies. The conditions for the appearance and possible origins of the observed antiflow are discussed. [Copyright &y& Elsevier]

Low-energy π+ (Eπ ≲ 35 MeV) from 12C + 197Au collisions at incident energies from 300 to 1800 MeV per nucleon were detected with the Si-Si(Li)-Csl(TI) calibration telescopes of the INDRA multidetector. The inclusive angular distributions are approximately isotropic, consistent with multiple rescattering in the target spectator. The multiplicity correlations of the low-energy pions and of energetic protons (Ep ≳ 150 MeV) with intermediate-mass fragments were determined from the measured coincidence data. The deduced correlation functions 1 + R ≈ 1.3 for inclusive event samples reflect the strong correlations evident from the common impact parameter dependence of the considered multiplicities. For narrow impact parameter bins (based on charged-particle multiplicity), the correlation functions are close to unity and do not indicate strong additional correlations. Only for pions at high particle multiplicities (central collisions) a weak anticorrelation is observed, probably due to a limited competition between these emissions. Overall, the results are consistent with the equilibrium assumption made in statistical multifragmentation scenarios. Predictions obtained with intranuclear-cascade models coupled to the Statistical Multifragmentation Model are in good agreement with the experimental data. [ABSTRACT FROM AUTHOR]

Directed flow in symmetric heavy ion collisions has been studied using the 197Au+ 197Au reactions at incident energies between 40 and 150 A MeV. The reactions have been measured with the 4π multi-detector INDRA at the GSI facility. In particular, the bombarding energy at which the elliptic flow switches from in-plane to out-of-plane enhancement has been determined to be clearly above 100 A MeV in good agreement with the result obtained by the FOPI Collaboration. The new data also allows to extend the experimental excitation function of v2 to lower energies. [Copyright &y& Elsevier]

The nucleus-nucleus Lie`ge intranuclear-cascade+percolation+evaporation model has been applied to the 12C+197Au data measured by the INDRA-ALADIN collaboration at GSI. After the intranuclear cascade stage, the data are better reproduced when using the Statistical Multiframentation Model as afterburner. Further checks of the model are done on data from the EOS and KAOS collaborations. [Copyright &y& Elsevier]

Dedicated ionization chamber (IC) was built and installed to measure the energy loss of very heavy nuclei at 2.7 MeV/u produced in fusion reactions in inverse kinematics (beam of 208Pb). After going through the IC, products of reactions on 12C, 18O targets are implanted in a Si detector. Their identification through their α-decay chain is ambiguous when their half-life is short. After calibration with Pb and Th nuclei, the IC signal allowed us to resolve these ambiguities. In the search for rare super-heavy nuclei produced in fusion reactions in inverse or symmetric kinematics, such a chamber will provide direct information on the nuclear charge of each implanted nucleus. [Copyright &y& Elsevier]

The transport properties of the 36Ar + 58Ni system at 95 A. MeV measured with the INDRA array, are studied within the BNV kinetic equation. A general protocol of comparison between the N-body experimental fragment information and the one-body distribution function is developed using global variables, with a special focus on charge density. This procedure avoids any definition of sources and any use of an afterburner in the simulation. We shall discuss the feasibility of such an approach and the distortions induced by the finite detection efficiency and the completeness requirements of the data selection. The sensitivity of the different global observables to the macroscopic parameters of the effective nuclear interaction will be studied in detail. [ABSTRACT FROM AUTHOR]

An efficient method of energy scale calibration for the CsI(Tl) modules of the INDRA multidetector (rings 6–12) using elastic and inelastic 12C+1H scattering at E(12C)=30MeV per nucleon is presented. Background-free spectra for the binary channels are generated by requiring the coincident detection of the light and heavy ejectiles. The gain parameter of the calibration curve is obtained by fitting the proton total charge spectra to the spectra predicted with Monte-Carlo simulations using tabulated cross section data. The method has been applied in multifragmentation experiments with INDRA at GSI. [Copyright &y& Elsevier]

The influence of the entrance channel mass asymmetry upon the fragmentation process is addressed by studying heavy-ion induced reactions around the Fermi energy. The data have been recorded with the INDRA 4π array. An event selection method called the Principal Component Analysis is presented and discussed. It is applied for the selection of central events and furthermore to multifragmentation of single source events. The selected subsets of data are compared to the Statistical Multifragmentation Model (SMM) to check the equilibrium hypothesis and get the source characteristics. Experimental comparisons show the evidence of a decoupling between thermal and compressional (radial flow) component of the excitation energy stored in such nuclear systems. [Copyright &y& Elsevier]

Mass and charge identification of charged products detected with Silicon–CsI(Tl) telescopes of the Chimera apparatus are presented. An identification function, based on the Bethe–Bloch formula, is used to fit empirical correlations between ΔE and E ADC readings, in order to determine, event by event, the atomic and mass numbers of the detected charged reaction products prior to energy calibration. [Copyright &y& Elsevier]

The charged particle identification obtained by the analysis of signals coming from the CsI(Tl) detectors of the CHIMERA 4π heavy-ion detector is presented. A simple double-gate integration method, with the use of the cyclotron radiofrequency as reference time, results in low thresholds for isotopic particle identification. The dependence of the identification quality on the gate generation timing is discussed. Isotopic identification of light ions up to Beryllium is clearly seen. For the first time also the identification of Z=5 particles is observed. The identification of neutrons interacting with CsI(Tl) by (n,α) and (n,γ) reactions is also discussed. [Copyright &y& Elsevier]

Abstract: Recent important progress on the knowledge of multifragmentation and phase transition for hot nuclei, thanks to the high detection quality of the INDRA array, is reported. It concerns i) the radial collective energies involved in hot fragmenting nuclei/sources produced in central and semi-peripheral collisions and their influence on the observed fragment partitions, ii) a better knowledge of freeze-out properties obtained by means of a simulation based on all the available experimental information and iii) the quantitative study of the bimodal behaviour of the heaviest fragment distribution for fragmenting hot heavy quasi-projectiles which allows the extraction, for the first time, of an estimate of the latent heat of the phase transition. [Copyright &y& Elsevier]