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Carbon burning is a key step in the evolution of massive stars, Type 1a supernovae and superbursts in x-ray binary systems. Determining the C12+C12 fusion cross section at relevant energies by extrapolation of direct measurements is challenging due to resonances at and below the Coulomb barrier. A study of the Mg24(α,α′)Mg24 reaction has identified several 0+ states in Mg24, close to the C12+C12 threshold, which predominantly decay to Ne20(ground state)+α. These states were not observed in Ne20(α,α0)Ne20 resonance scattering suggesting that they may have a dominant C12+C12 cluster structure. Given the very low angular momentum associated with sub-barrier fusion, these states may play a decisive role in C12+C12 fusion in analogy to the Hoyle state in helium burning. We present estimates of updated C12+C12 fusion reaction rates.

Lifetimes or lifetime limits of a small number of excited states of the sulfur isotopes with mass numbers A=35, 36, 37, and 38 have been measured using the differential recoil-distance method. The isotopes of sulfur were populated in binary grazing reactions initiated by a beam of 36S ions of energy 225 MeV incident on a thin 208Pb target which was mounted in the Cologne plunger apparatus. The combination of the PRISMA magnetic spectrometer and an early implementation of the AGATA γ-ray tracking array was used to detect γ rays in coincidence with projectile-like nuclear species. Lifetime measurements of populated states were measured within the range from about 1 to 100 ps. The number of states for which lifetime measurements or lifetime limits were possible was limited by statistics. For 35S, the lifetime was determined for the first 1/2+ state at 1572 keV ; the result is compared with a previous published lifetime value. The lifetime of the 3− state of 36S at 4193 keV was determined and compared with earlier measurements. No previous lifetime information exists for the (6+) state at 6690 keV ; a lifetime measurement with large associated error was made in the present work. For 37S, the states for which lifetime limits were established were those at 646 keV with Jπ=3/2− and at 2776 keV with Jπ=11/2− ; there are no previously published lifetime values for excited states of 37S. Finally, a lifetime limit was established for the Jπ=(6+) state of 38S at 3675 keV ; no lifetime information exists for this state in the literature. Measured lifetime values were compared with the results of state-of-the-art shell-model calculations based on the PSDPF, SDPF-U, and FSU effective interactions. In addition, nuclear magnetic-dipole and electric-quadrupole moments, branching ratios, mixing ratios, and electromagnetic transition rates, where available, have been compared with shell-model values. The current work suffers from poor statistics ; nevertheless, lifetime values and limits have been possible, allowing a useful discussion of the ability of state-of-the-art shell-model calculations to reproduce the experimental results.

Lifetimes or lifetime limits of a small number of excited states of the sulfur isotopes with mass numbers A=35, 36, 37, and 38 have been measured using the differential recoil-distance method. The isotopes of sulfur were populated in binary grazing reactions initiated by a beam of 36S ions of energy 225 MeV incident on a thin 208Pb target which was mounted in the Cologne plunger apparatus. The combination of the PRISMA magnetic spectrometer and an early implementation of the AGATA γ-ray tracking array was used to detect γ rays in coincidence with projectile-like nuclear species. Lifetime measurements of populated states were measured within the range from about 1 to 100 ps. The number of states for which lifetime measurements or lifetime limits were possible was limited by statistics. For 35S, the lifetime was determined for the first 1/2+ state at 1572 keV; the result is compared with a previous published lifetime value. The lifetime of the 3− state of 36S at 4193 keV was determined and compared with earlier measurements. No previous lifetime information exists for the (6+) state at 6690 keV; a lifetime measurement with large associated error was made in the present work. For 37S, the states for which lifetime limits were established were those at 646 keV with Jπ=3/2− and at 2776 keV with Jπ=11/2−; there are no previously published lifetime values for excited states of 37S. Finally, a lifetime limit was established for the Jπ=(6+) state of 38S at 3675 keV; no lifetime information exists for this state in the literature. Measured lifetime values were compared with the results of state-of-the-art shell-model calculations based on the PSDPF, SDPF-U, and FSU effective interactions. In addition, nuclear magnetic-dipole and electric-quadrupole moments, branching ratios, mixing ratios, and electromagnetic transition rates, where available, have been compared with shell-model values. The current work suffers from poor statistics; nevertheless, lifetime values and limits have been possible, allowing a useful discussion of the ability of state-of-the-art shell-model calculations to reproduce the experimental results.

Background: Superdeformed (SD) bands are suggested by theory around Ca40 and in lighter alpha-conjugate nuclei such as Mg24, Si28, and S32. Such predictions originate from a number of theoretical models including mean-field models and antisymmetrized molecular dynamics (AMD) calculations. While SD bands have been identified in Ca40 and its near neighbors, evidence of their existence in the lighter, midshell nuclei is circumstantial at best. The key evidence of superdeformation would be the observation of transitions with high B(E2) transition strengths connecting states in a rotational sequence. This is challenging information to obtain since the bands lie at a high excitation energy and competition from out-of-band decay is dominant. Purpose: The purpose of the present study is to establish a new methodology to circumvent the difficulties in identifying and quantifying in-band transitions through directly populating candidate states in the SD band in Si28 through inelastic alpha scattering, selecting such states with a spectrometer, and measuring their gamma-ray decay with a large array of high-purity germanium detectors, allowing direct access to electromagnetic transition strengths. Methods: Excited states in Si28 were populated in the Si28(α,α′) reaction using a 130-MeV He4 beam from the K140 AVF cyclotron at the Research Center for Nuclear Physics. Outgoing alpha particles were analyzed using the Grand Raiden spectrometer positioned at an angle of 9.1° to favor the population of states with J≈4. Coincident gamma rays were detected with the CAGRA array of 12 HPGe clover detectors augmented by a set of four large LaBr3 detectors. Results: Data analysis showed that it was possible to identify additional low-energy transitions in competition with high-energy decays from excited states in Si28 in the vicinity of 10 MeV. However, while the candidate 4+ SD state at 10.944 MeV was populated, a 1148-keV transition to the candidate 2+ SD state at 9.796 MeV was not observed, and only an upper limit for its transition strength of B(E2)

RESUMEN: INCENFA-SCALE es un proyecto de cinco años financiado por el programa Horizonte 2020 de la Comisión Europea,sucesor del proyecto INCEFA-PLUS. El objetivo de este proyecto es mejorar la capacidad para pronosticar la vida útil de los componentes de centrales nucleares sometidos a fatiga asistida por el ambiente. EPRI está llevando a cabo una serie de ensayos de fatiga ambiental a escala de componente, que se espera que avancen significativamente en la disponibilidad de datos. Sin embargo, la capacidad de abordar la aplicabilidad de los datos de ensayos en laboratorio a componentes con geometría y cargas reales sigue estando restringida por el limitado número de datos. Este déficit de conocimiento es abordado por INCEFA-SCALE mediante: 1) la comprensión mecánica mediante un examen detallado de probetas ensayadas a fatiga y análisis de datos (INCEFA-PLUS, USNRC, EPRI, MHI y AdFaM); 2) ensayos centrados en aspectos particulares de las cargas cíclicas aplicadas a componentes. En paralelo, se llevará a cabo una campaña de ensayos para cubrir las necesidades detectadas. Finalmente, el proyecto proporcionará una guía para aplicar en componentes a escala real los datos obtenidos en laboratorio. Este artículo describe los antecedentes del proyecto y los avances realizados en el análisis de datos, comportamiento mecánico y necesidades de ensayo. ABSTRACT: INCENFA-SCALE is a five-year project funded by the EC Horizon2020 programme, successor of the INCEFA-PLUS project. INCEFA-SCALE started in October 2020. The objective of this project is to improve the ability of predicting the lifetime of NPPs components subjected to environmental assisted fatigue. EPRI is developing a series of component-scale environmental fatigue tests, which are expected to significantly advance data availability. However, the ability to address the applicability of laboratory test data to components with real geometry and loads remains restricted by the limited number of data. INCEFA-SCALE addressed this knowledge gap by: 1) developing a comprehensive mechanical understanding through detailed examination of fatigue-tested specimens and data analysis (INCEFA-PLUS, USNRC, EPRI, MHI and AdFaM); 2) conducting tests focused on particular aspects of cyclical loads applied to components. At the same time, a test campaign will be carried out to cover the detected needs. Finally, the project will provide a guidance for using the laboratory data in full-scale components. This article describes the background of the project and the advances made in data analysis, mechanical understanding and testing needs. Este proyecto ha recibido financiación del programa de investigación y formación de Euratom 2019-2020, bajo el acuerdo de subvención nº 945300. También se reconoce la significativa contribución de los miembros del proyecto INCEFA-SCALE.

This work presents new $^{12}$C + $^{12}$C reaction rates in the form of numerical tables with associated uncertainty estimation, as well as analytical formulae that can be directly implemented into stellar evolution codes. This article further describes the impact of these new rates on C-burning in stars. We determine reaction rates for two cross-section extrapolation models: one based on the fusion-hindrance phenomenon, and the other on fusion-hindrance plus a resonance, and compare our results to previous data. Using the GENEC stellar evolution code, we study how these new rates impact the C-burning phases in two sets of stellar models for stars with 12 M$_{\odot}$ and 25 M$_{\odot}$ initial masses chosen to be highly representative of the diversity of massive stars. The effective temperatures of C-burning in both sets of stellar models are entirely covered by the sensitivity of the present experimental data, and no extrapolation of the rates is required. Although, the rates may differ by more than an order of magnitude for temperatures typical of C-burning, the impacts on the stellar structures during that phase remain modest. This is a consequence of the readjustment of the stellar structure to a change of nuclear reaction rate for reactions important for energy production. For the hindrance case, the C-burning phase is found to occur at central temperatures 10\% higher than with the hindrance plus resonance rate. Its C-burning lifetime is reduced by a factor of two. This model, nevertheless, loses more entropy than the other one thus enters earlier into the degeneracy regime which will impact the last stages of the evolution at the pre-core collapse time. The hindrance model produces up to 60% more neon. The impact of the different rates on the s-process occurring during the C-burning phase is modest, changing final abundances of s-processed elements by at most 20% (cobalt)., Comment: 13 pages, 9 figures

International audience; Prompt and delayed γ-ray spectroscopy of the neutron-rich 94Kr was performed, as part of the fission campaign at the ALTO facility of the IPN Orsay, using the fast-neutron-induced fission reaction 238U(n,f) in combination with the ν-Ball array, a novel hybrid γ spectrometer for energy and lifetime measurements. Several new yrast and nonyrast transitions were observed for the first time, extending the previously known level scheme. Additionally, we report on the observation of a new short-lived isomer at 3444 keV with a half-life of 32(3) ns. The analysis of the Nilsson orbitals obtained from Gogny cranked Hartree-Fock-Bogoliubov calculations suggests a (9−) spin and an oblate deformation for this isomer corresponding to a two-quasineutron state, indicating an isomeric structure very similar to that of the neighboring isotones 96Sr and 92Se

International audience; We report on the measurement of lifetimes of excited states in the near-mid-shell nuclei Dy164,166 using the gamma-ray coincidence fast-timing method. The nuclei of interest were populated using reactions between an O18 beam and a gold-backed isotopically enriched Dy164 target of thickness 6.3mg/cm2 at primary beam energies of 71, 76, and 80 MeV from the IPN-Orsay laboratory, France. Excited states were populated in Dy164, Dy166, and W178,179 following Coulomb excitation, inelastic nuclear scattering, two-neutron transfer, and fusion-evaporation reaction channels respectively. Gamma rays from excited states were measured using the ν-Ball high-purity germanium (HPGe)-LaBr3 hybrid γ-ray spectrometer with the excited state lifetimes extracted using the fast-timing coincidence method using HPGe-gated LaBr3-LaBr3 triple coincident events. The lifetime of the first Iπ=2+ excited state in Dy166 was used to determine the transition quadrupole deformation of this neutron-rich nucleus for the first time. The experimental methodology was validated by showing consistency with previously determined excited state lifetimes in Dy164. The half-lives of the yrast 2+ states in Dy164 and Dy166 were 2.35(6) and 2.3(2) ns, respectively, corresponding to transition quadrupole moment values of Q0=7.58(9) and 7.5(4) eb, respectively. The lifetime of the yrast 2+ state in Dy166 is consistent with a quenching of nuclear quadrupole deformation at β≈0.35 as the N=104 mid-shell is approached.

Prompt and delayed γ-ray spectroscopy of the neutron-rich 94Kr was performed, as part of the fission campaign at the ALTO facility of the IPN Orsay, using the fast-neutron-induced fission reaction 238U(n,f) in combination with the ν-Ball array, a novel hybrid γ spectrometer for energy and lifetime measurements. Several new yrast and nonyrast transitions were observed for the first time, extending the previously known level scheme. Additionally, we report on the observation of a new short-lived isomer at 3444 keV with a half-life of 32(3) ns. The analysis of the Nilsson orbitals obtained from Gogny cranked Hartree-Fock-Bogoliubov calculations suggests a (9−) spin and an oblate deformation for this isomer corresponding to a two-quasineutron state, indicating an isomeric structure very similar to that of the neighboring isotones 96Sr and 92Se.

We present 12C+12C direct fusion measurements with STELLA UKFATIMA, that reach into the region of astrophysics interest relevant to massive stars (M⊙ ≈ 25) using self-supporting thin rotating carbon foils [1]. We demonstrate that detecting gammas and light charged particles in coincidence with nanosecond timing is key for effective background reduction achieving reliable measurements in the sub-nanobarn range. We give details about core developments of the detection apparatus as well as the coincidence-analysis procedure of low count statistics. The present data largely follows the phenomenological hindrance interpolation and shows indication for resonant behaviour at the lowest energy explored.

We report on the first measurement of the half-lives of Kπ=11− and 12+ four-quasiparticle states in the even-even nucleus $^{178}$W. The sub-nanosecond half-lives were measured by applying the centroid shift method to data taken with LaBr$_{3}$(Ce) scintillator detectors of the NuBall array at the ALTO facility in Orsay, France. The half-lives of these states only became experimentally accessible by the combination of several experimental techniques - scintillator fast timing, isomer spectroscopy with a pulsed beam, and the event-by-event calorimetry information provided by the NuBall array. The measured half-lives are 476(44)ps and 275(65)ps for the Iπ=11− and 12+ states, respectively. The decay transitions include weakly hindered E1 and E2 branches directly to the ground-state band, bypassing the two-quasiparticle states. This is the first such observation for an E1 transition. The interpretation of the small hindrance hinges on mixing between the ground-state band and the t-band.

International audience; We studied multinucleon transfer (MNT) processes in the $^{197}$Au + $^{130}$Te at E$_{lab}$=1.07 GeV system coupling the PRISMA magnetic spectrometer to NOSE, an ancillary particle detector. We constructed a mass correlation matrix associating to each light fragment identified in PRISMA the corresponding mass distribution of the heavy partner detected in NOSE and, through the comparison with Monte Carlo simulations, we could infer about the role of neutron evaporation in multinucleon transfer reactions for the population of neutron-rich heavy nuclei.

International audience; Lifetimes of excited states of the phosphorus isotopes 1533,34,35,36P have been measured by using the differential recoil-distance method. The isotopes of phosphorus were populated in binary grazing reactions initiated by a beam of S36 ions of energy 225 MeV incident on a thin Pb208 target mounted in the Cologne plunger apparatus. The combination of the PRISMA magnetic spectrometer and an early implementation of the AGATA γ-ray tracking array was used to detect γ rays in coincidence with projectile-like nuclear species. Lifetime measurements of populated states were made within the range from about 1 to 100 ps. The number of states for which lifetime measurements were possible was limited by statistics. For P33, lifetime limits were determined for the first 3/2+ and 5/2+ states at 1431 and 1848 keV, respectively; the results are compared with previous published lifetime values. The lifetime of the first 2+ state of P34 at 429 keV was determined and compared with earlier measurements. For P35, the states for which lifetimes, or lifetime limits, were determined were those at 2386, 3860, 4101, and 4493 keV, with Jπ values of 3/2+, 5/2+, 7/21−, and 7/22−, respectively. There have been no previous published lifetimes for states in this nucleus. A lifetime was measured for the stretched π(1f7/2)⊗ν(1f7/2)Jπ=(7+) state of P36 at 5212 keV and a lifetime limit was established for the stretched π(1d3/2)⊗ν(1f7/2)Jπ=(5−) state at 2030 keV. There are no previously published lifetimes for states of P36. Measured lifetime values were compared with the results of state-of-the-art shell-model calculations based on the PSDPF effective interaction. In addition, measured branching ratios, published mixing ratios, and electromagnetic transition rates, where available, have been compared with shell-model values. In general, there is good agreement between experiment and the shell model; however there is evidence that the shell-model values of the M1 transition rates for the 3/21+→1/2+ (ground state) and 5/21+→3/21+ transitions in P33 underestimate the experimental values by a factor between 5 and 10. In P35 there are some disagreements between experimental and shell-model values of branching ratios for the first and second excited 7/2− states. In particular, there is a serious disagreement for the decay characteristics of the second 7/2− state at 4493 keV, for which the shell-model counterpart lies at 4754 keV. In this case, the shell-model competing electromagnetic decay branches are dominated by E1 and M1 transitions.

Lifetimes of excited states of the phosphorus isotopes 33 , 34 , 35 , 36 15 P have been measured by using the differential recoil-distance method. The isotopes of phosphorus were populated in binary grazing reactions initiated by a beam of 36 S ions of energy 225 MeV incident on a thin 208 Pb target mounted in the Cologne plunger apparatus. The combination of the PRISMA magnetic spectrometer and an early implementation of the AGATA γ -ray tracking array was used to detect γ rays in coincidence with projectile-like nuclear species. Lifetime measurements of populated states were made within the range from about 1 to 100 ps. The number of states for which lifetime measurements were possible was limited by statistics. For 33 P , lifetime limits were determined for the first 3/2+ and 5/2+ states at 1431 and 1848 keV, respectively; the results are compared with previous published lifetime values. The lifetime of the first 2+ state of 34 P at 429 keV was determined and compared with earlier measurements. For 35 P , the states for which lifetimes, or lifetime limits, were determined were those at 2386, 3860, 4101, and 4493 keV, with Jπ values of 3/2+, 5/2+, 7/2− 1 , and 7/2− 2 , respectively. There have been no previous published lifetimes for states in this nucleus. A lifetime was measured for the stretched π ( 1 f 7 / 2 ) ⊗ ν ( 1 f 7 / 2 ) J π = ( 7 + ) state of 36 P at 5212 keV and a lifetime limit was established for the stretched π ( 1 d 3 / 2 ) ⊗ ν ( 1 f 7 / 2 ) J π = ( 5 − ) state at 2030 keV. There are no previously published lifetimes for states of 36 P . Measured lifetime values were compared with the results of state-of-the-art shell-model calculations based on the PSDPF effective interaction. In addition, measured branching ratios, published mixing ratios, and electromagnetic transition rates, where available, have been compared with shell-model values. In general, there is good agreement between experiment and the shell model; however there is evidence that the shell-model values of the M1 transition rates for the 3/2+1→ 1 / 2 + (ground state) and 5/2+1→ 3 / 2 + 1 transitions in 33 P underestimate the experimental values by a factor between 5 and 10. In 35 P there are some disagreements between experimental and shell-model values of branching ratios for the first and second excited 7/2− states. In particular, there is a serious disagreement for the decay characteristics of the second 7/2− state at 4493 keV, for which the shell-model counterpart lies at 4754 keV. In this case, the shell-model competing electromagnetic decay branches are dominated by E1 and M1 transitions.

Prompt-fission γ-ray spectra (PFGS) have been measured for the U238(n,f) reaction using fast neutrons produced by the LICORNE directional neutron source. Fission events were detected with an ionization chamber containing actinide samples placed in the neutron beam, and the coincident prompt-fission γ rays were measured using a number of LaBr3 scintillation detectors and a cluster of nine phoswich detectors from the PARIS array. Prompt-fission γ rays (PFGs) were discriminated from prompt-fission neutrons using the time-of-flight technique over distances of around 35 cm. PFG emission spectra were measured at two incident neutron energies of 1.9 and 4.8 MeV for U238(n,f) and also for Cf252(sf) as a reference. Spectral characteristics of PFG emission, such as mean γ multiplicity and average total γ-ray energy per fission, as well as the average γ-ray energy, were extracted. The sensitivity of these results to the width of the time window and the type of spectral unfolding procedure used to correct for the detector responses was studied. Iteration methods were found to be more stable in low-statistics data sets. The measured values at En=1.9MeV were found to be the mean γ multiplicity Mγ=6.54±0.19, total released energy per fission Eγ,tot=5.25±0.20 MeV, and the average γ-ray energy ϵγ=0.80±0.04 MeV. Under similar conditions, the values at En=4.8MeV were measured to be Mγ=7.31±0.46, Eγ,tot=6.18±0.65 MeV, and ϵγ=0.84±0.11 MeV.

Carbon burning is a critical phase for nucleosynthesis in massive stars. The conditions for igniting this burning stage, and the subsequent isotope composition of the resulting ashes, depend strongly on the reaction rate for C12+C12 fusion at very low energies. Results for the cross sections for this reaction are influenced by various backgrounds encountered in measurements at such energies. In this paper, we report on a new measurement of C12+C12 fusion cross sections where these backgrounds have been minimized. It is found that the astrophysical S factor exhibits a maximum around Ecm=3.5-4.0 MeV, which leads to a reduction of the previously predicted astrophysical reaction rate.

International audience; Prompt-fission γ-ray spectra (PFGS) have been measured for the U238(n,f) reaction using fast neutrons produced by the LICORNE directional neutron source. Fission events were detected with an ionization chamber containing actinide samples placed in the neutron beam, and the coincident prompt-fission γ rays were measured using a number of LaBr3 scintillation detectors and a cluster of nine phoswich detectors from the PARIS array. Prompt-fission γ rays (PFGs) were discriminated from prompt-fission neutrons using the time-of-flight technique over distances of around 35 cm. PFG emission spectra were measured at two incident neutron energies of 1.9 and 4.8 MeV for U238(n,f) and also for Cf252(sf) as a reference. Spectral characteristics of PFG emission, such as mean γ multiplicity and average total γ-ray energy per fission, as well as the average γ-ray energy, were extracted. The sensitivity of these results to the width of the time window and the type of spectral unfolding procedure used to correct for the detector responses was studied. Iteration methods were found to be more stable in low-statistics data sets. The measured values at En=1.9MeV were found to be the mean γ multiplicity M¯γ=6.54±0.19, total released energy per fission Eγ,tot=5.25±0.20 MeV, and the average γ-ray energy εγ=0.80±0.04 MeV. Under similar conditions, the values at En=4.8MeV were measured to be M¯γ=7.31±0.46, Eγ,tot=6.18±0.65 MeV, and εγ=0.84±0.11 MeV.

Background: The fusion reaction 12C+30Si is a link between heavier cases studied in recent years, and the light heavy-ion systems, e.g., 12C+12C, 16O+16O that have a prominent role in the dynamics of stellar evolution. 12C+30Si fusion itself is not a relevant process for astrophysics, but it is important to establish its behavior below the barrier, where couplings to low-lying collective modes and the hindrance phenomenon may determine the cross sections. The excitation function is presently completely unknown below the barrier for the 12C+30Si reaction, thus no reliable extrapolation into the astrophysical regime for the C+C and O+O cases can be performed. Purpose: Our aim was to carry out a complete measurement of the fusion excitation function of 12C+30Si from well below to above the Coulomb barrier, so as to clear up the consequence of couplings to low-lying states of 30Si, and whether the hindrance effect appears in this relatively light system which has a positive Q value for fusion. This would have consequences for the extrapolated behavior to even lighter systems. Methods: The inverse kinematics was used by sending 30Si beams delivered from the XTU Tandem accelerator of INFN-Laboratori Nazionali di Legnaro onto thin 12C (50μg/cm2) targets enriched to 99.9% in mass 12. The fusion evaporation residues (ER) were detected at very forward angles, following beam separation by means of an electrostatic deflector. Angular distributions of ER were measured at Ebeam=45, 59, and 80 MeV, and they were angle integrated to derive total fusion cross sections. Results: The fusion excitation function of 12C+30Si was measured with high statistical accuracy, covering more than five orders of magnitude down to a lowest cross section ≃3μb. The logarithmic slope and the S factor have been extracted and we have convincing phenomenological evidence of the hindrance effect. These results have been compared with the calculations performed within the model that considers a damping of the coupling strength well inside the Coulomb barrier. Conclusions: The experimental data are consistent with the coupled-channels calculations. A better fit is obtained by using the Yukawa-plus-exponential potential and a damping of the coupling strengths inside the barrier. The degree of hindrance is much smaller than the one in heavier systems. Also a phenomenological estimate reproduces quite closely the hindrance threshold for 12C+30Si, so that an extrapolation to the C+C and O+O cases can be reliably performed.

International audience; We studied multinucleon transfer reactions in the Au197+Te130 system at Elab=1.07 GeV by employing the PRISMA magnetic spectrometer coupled to a coincident detector. For each light fragment we constructed, in coincidence, the distribution in mass of the heavy partner of the reaction. With a Monte Carlo method, starting from the binary character of the reaction, we simulated the de-excitation process of the produced heavy fragments to be able to understand their final mass distribution. The total cross sections for pure neutron transfer channels have also been extracted and compared with calculations performed with the grazing code.

International audience; Background: The fusion reaction C12+Si30 is a link between heavier cases studied in recent years, and the light heavy-ion systems, e.g., C12+C12, O16+O16 that have a prominent role in the dynamics of stellar evolution. C12+Si30 fusion itself is not a relevant process for astrophysics, but it is important to establish its behavior below the barrier, where couplings to low-lying collective modes and the hindrance phenomenon may determine the cross sections. The excitation function is presently completely unknown below the barrier for the C12+Si30 reaction, thus no reliable extrapolation into the astrophysical regime for the C+C and O+O cases can be performed. Purpose: Our aim was to carry out a complete measurement of the fusion excitation function of C12+Si30 from well below to above the Coulomb barrier, so as to clear up the consequence of couplings to low-lying states of Si30, and whether the hindrance effect appears in this relatively light system which has a positive Q value for fusion. This would have consequences for the extrapolated behavior to even lighter systems. Methods: The inverse kinematics was used by sending Si30 beams delivered from the XTU Tandem accelerator of INFN-Laboratori Nazionali di Legnaro onto thin C12 (50μg/cm2) targets enriched to 99.9% in mass 12. The fusion evaporation residues (ER) were detected at very forward angles, following beam separation by means of an electrostatic deflector. Angular distributions of ER were measured at Ebeam=45, 59, and 80 MeV, and they were angle integrated to derive total fusion cross sections. Results: The fusion excitation function of C12+Si30 was measured with high statistical accuracy, covering more than five orders of magnitude down to a lowest cross section ≃3μb. The logarithmic slope and the S factor have been extracted and we have convincing phenomenological evidence of the hindrance effect. These results have been compared with the calculations performed within the model that considers a damping of the coupling strength well inside the Coulomb barrier. Conclusions: The experimental data are consistent with the coupled-channels calculations. A better fit is obtained by using the Yukawa-plus-exponential potential and a damping of the coupling strengths inside the barrier. The degree of hindrance is much smaller than the one in heavier systems. Also a phenomenological estimate reproduces quite closely the hindrance threshold for C12+Si30, so that an extrapolation to the C+C and O+O cases can be reliably performed.

International audience; As many countries are now working to extend the life of their existing power plants, a thorough inventory of the various effects that could potentially represent a hazard to a safe long term operation is necessary. These structures, often of large dimensions, are subjected during their life to complex loading combining varying mechanical loads, multiaxial, with non-zero mean values associated with temperature fluctuations and also PWR environment. Before applying the concepts and methods observed on uniaxial analytical specimens, it is necessary to consolidate the implementation of tests on almost structures.In the framework of upgrading the fatigue design rules (RCC-M, RCC-MRx), the uniaxial reference fatigue curve was altered by taking into account effects like Multiaxiality, Mean stress or strain, Surface roughness (polished or ground), Scale effect, Loading History. In addition to this effect, Environmentally Assisted Fatigue is also receiving nowadays an increased level of attention.To formally integrate these effects, and to obtain fatigue data under structural loading, biaxial test means with and without PWR environment were developed at LISN. Two kinds of fatigue device have been developed. Within the same specimen geometry, structural loads can be applied in varying only the PWR environment. The first device (FABIME2) is devoted to study the effect of biaxiality and mean strain/stress on the fatigue life. A second and new device based on FABIME2 is for the study of the impact of the environmental effect. With these new experimental results, we will highlight a PWR effect on the fatigue life of stainless austenitic steels.

International audience; As many countries are now working to extend the life of their existing power plants, a thorough inventory of the various effects that could potentially represent a hazard to a safe long term operation is necessary. These structures, often of large dimensions, are subjected during their life to complex loading combining varying mechanical loads, multiaxial, with non-zero mean values associated with temperature fluctuations and also PWR environment. Before applying the concepts and methods observed on uniaxial analytical specimens, it is necessary to consolidate the implementation of tests on almost structures.In the framework of upgrading the fatigue design rules (RCC-M, RCC-MRx), the uniaxial reference fatigue curve was altered by taking into account effects like Multiaxiality, Mean stress or strain, Surface roughness (polished or ground), Scale effect, Loading History. In addition to this effect, Environmentally Assisted Fatigue is also receiving nowadays an increased level of attention.To formally integrate these effects, and to obtain fatigue data under structural loading, biaxial test means with and without PWR environment were developed at LISN. Two kinds of fatigue device have been developed. Within the same specimen geometry, structural loads can be applied in varying only the PWR environment. The first device (FABIME2) is devoted to study the effect of biaxiality and mean strain/stress on the fatigue life. A second and new device based on FABIME2 is for the study of the impact of the environmental effect. With these new experimental results, we will highlight a PWR effect on the fatigue life of stainless austenitic steels.

The fusion excitation function for the positive-Q-value system 12 C+30 Si (Qfus = +14.1 MeV) has been measured in inverse kinematics down to the μ b level and compared with standard coupled-channel calculations. The appearance of the fusion hindrance phenomenon and the evidence of a S-factor maximum have been observed. This result can be significant to extrapolate the behavior of lighter astrophysical relevant systems at deep sub-barrier energies, where existing experimental data are still contradicting and affected by large errors.

The C-12+C-12 fusion reaction is one of the most important for nuclear astrophysics since it determines the carbon ignition in stellar environments. Two experiments which make use of the gamma-particle coincidence technique to measure the C-12+C-12 S-factors at deep sub barrier energies are discussed. Results are presented showing a decrease of the S-factor below E-c.m. = 3 MeV.

WOS: 000310091000001, The level structures of the N = 50 As-83, Ge-82, and Ga-81 isotones have been investigated by means of multi-nucleon transfer reactions. A first experiment was performed with the CLARA PRISMA setup to identify these nuclei. A second experiment was carried out with the GASP array in order to deduce the gamma-ray coincidence information. The results obtained on the high-spin states of such nuclei are used to test the stability of the N = 50 shell closure in the region of Ni-78 (Z = 28). The comparison of the experimental level schemes with the shell-model calculations yields an N = 50 energy gap value of 4.7(3) MeV at Z = 28. This value, in a good agreement with the prediction of the finite-range liquid-drop model as well as with the recent large-scale shell model calculations, does not support a weakening of the N = 50 shell gap down to Z = 28. (c) 2012 Elsevier B.V. All rights reserved., NSF [PHY0244389, PHY0555396]; European Commission within the Sixth Framework Programme through I3-EURONS [RII3-CT-2004-506065]; DGF (Germany) [DE 1516/-1]; Science and Technology Facilities Council [ST/G000689/1 NuSTAR, ST/F004052/1, ST/G000689/1, ST/J000108/1], We thank O. Sorlin for the useful discussions and the accelerator crews of LNL for the excellent support. A.F.L. acknowledges partial support of this work from NSF grants PHY0244389 and PHY0555396. This work has been partially supported by the European Commission within the Sixth Framework Programme through I3-EURONS (contract No. RII3-CT-2004-506065) and the DGF (Germany under contract No. DE 1516/-1).

International audience; We performed a γ -particle coincidence experiment for the 60Ni+116Sn system to investigate whether thepopulation of the two-neutron pickup channel leading to 62Ni is mainly concentrated in the ground-state transition,as has been found in a previous work [D. Montanari et al., Phys. Rev. Lett. 113, 052501 (2014)]. The experimenthas been performed by employing the PRISMA magnetic spectrometer coupled to theAdvanced Gamma TrackingArray (AGATA) demonstrator. The strength distribution of excited states corresponding to the inelastic, one- andtwo-neutron transfer channels has been extracted.We found that in the two-neutron transfer channel the strengthto excited states corresponds to a fraction (less than 24%) of the total, consistent with the previously obtainedresults that the 2n channel is dominated by the ground-state to ground-state transition.

Preliminary experimental data for nucleon transfer reactions of the 40Ca+58Ni and 40Ca+64Ni systems are analyzed with the coupled- channels approach. It is shown that a simple treatment for the transfer in the coupled-channels method cannot reproduce simultaneously the transfer probabilities and the sub-barrier enhancement of fusion cross sections., Comment: 5 pages, 2 figures, Proceeding of the "International Workshop on Multi facets of EOS and Clustering"

Background: Heavy-ion fusion reactions at energies near the Coulomb barrier are influenced by couplings between the relative motion and nuclear intrinsic degrees of freedom of the colliding nuclei. The time-dependent Hartree-Fock (TDHF) theory, incorporating the couplings at the mean-field level, as well as the coupled-channels (CC) method are standard approaches to describe low energy nuclear reactions. Purpose: To investigate the effect of couplings to inelastic and transfer channels on the fusion cross sections for the reactions $^{40}$Ca+$^{58}$Ni and $^{40}$Ca+$^{64}$Ni. Methods: Fusion cross sections around and below the Coulomb barrier have been obtained from coupled-channels (CC) calculations, using the bare nucleus-nucleus potential calculated with the frozen Hartree-Fock method and coupling parameters taken from known nuclear structure data. The fusion thresholds and neutron transfer probabilities have been calculated with the TDHF method. Results: For $^{40}$Ca+$^{58}$Ni, the TDHF fusion threshold is in agreement with the most probable barrier obtained in the CC calculations including the couplings to the low-lying octupole $3_1^{-}$ state for $^{40}$Ca and to the low-lying quadrupole $2_1^{+}$ state for $^{58}$Ni. This indicates that the octupole and quadrupole states are the dominant excitations while neutron transfer is shown to be weak. For $^{40}$Ca+$^{64}$Ni, the TDHF barrier is lower than predicted by the CC calculations including the same inelastic couplings as those for $^{40}$Ca+$^{58}$Ni. TDHF calculations show large neutron transfer probabilities in $^{40}$Ca+$^{64}$Ni which could result in a lowering of the fusion threshold. Conclusions: Inelastic channels play an important role in $^{40}$Ca+$^{58}$Ni and $^{40}$Ca+$^{64}$Ni reactions. The role of neutron transfer channels has been highlighted in $^{40}$Ca+$^{64}$Ni.

We performed a gamma-particle coincidence experiment for the 60Ni+116Sn system in order to investigate whether the population of the two-neutron pick-up channel leading to 62Ni is mainly concentrated in the ground state transition, as has been found in a previous work. The experiment has been performed by employing the PRISMA magnetic spectrometer coupled to the Advanced Gamma Tracking Array (AGATA) demonstrator. The strength distribution of excited states corresponding to the inelastic, one- and two-neutron transfer channels has been extracted. We found that in the two-neutron transfer channel the strength to excited states corresponds to a fraction (less than 24%) of the total, consistent with the previously obtained results that the 2n channel is dominated by the ground to ground state transition.

International audience; Background: No data on the fusion excitation function of Ti-48 + Fe-58 in the energy region near the Coulomb barrier existed prior to the present work, while fusion of Ni-58 + Fe-54 was investigated in detail some years ago, down to very low energies, and clear evidence of fusion hindrance was noticed at relatively high cross sections. Ti-48 and Fe-58 are soft and have a low-lying quadrupole excitation lying at approximate to 800-900 keV only. Instead, Ni-58 and Fe-54 have a closed shell (protons and neutrons, respectively) and are rather rigid.Purpose: We aim to investigate (1) the possible influence of the different structures of the involved nuclei on the fusion excitation functions far below the barrier and, in particular, (2) whether hindrance is observed in Ti-48 + Fe-58, and to compare the results with current coupled-channels models.Methods: Ti-48 beams from the XTU Tandem accelerator of INFN-Laboratori Nazionali di Legnaro were used. The experimental setup was based on an electrostatic beam separator, and fusion-evaporation residues (ERs) were detected at very forward angles. Angular distributions of ERs were measured.Results: Fusion cross sections of Ti-48 + Fe-58 have been obtained in a range of nearly six orders of magnitude around the Coulomb barrier, down to sigma similar or equal to 2 mu b. The sub-barrier cross sections of Ti-48 + Fe-58 are much larger than those of Ni-58 + Fe-54. Significant differences are also observed in the logarithmic derivatives and astrophysical S factors. No evidence of hindrance is observed, because coupled-channels calculations using a standard Woods-Saxon potential are able to reproduce the data in the whole measured energy range. Analogous calculations for Ni-58 + Fe-54 predict clearly too large cross sections at low energies. The two fusion barrier distributions are wide and display a complex structure that is only qualitatively fit by calculations.Conclusions: It is pointed out that all these different trends originate from the dissimilar low-energy nuclear structures of the involved nuclei. In particular, the strong quadrupole excitations in Ti-48 and Fe-58 produce the relative cross section enhancement and make the barrier distribution approximate to 2 MeV wider, thus probably pushing the threshold for hindrance below the measured limit.

The β decay of the N=Z nucleus Kr72 has been studied with the total absorption spectroscopy technique at ISOLDE (CERN). A total B(GT)=0.79(4)gA2/4π has been found up to an excitation energy of 2.7 MeV. The B(GT) distribution obtained is compared with predictions from state-of-the-art theoretical calculations to learn about the ground state deformation of Kr72. Although a dominant oblate deformation is suggested by direct comparison with quasiparticle random phase approximation (QRPA) calculations, beyond-mean-field and shell-model calculations favor a large oblate-prolate mixing in the ground state, J.A.B. acknowledges the predoctoral grant BES-2008-009412 associated with the research project FPA2007-62170 funded by Ministerio de Ciencia e Innovacion (Spain). This work has been partly supported by the Spanish Ministerio de Economía y Competitividad (MINECO) through projects FPA2012- 32443, FPA2011-24553, FPA2011-29854-C04-01, FPA2013-41267-P, FPA2014-52823-C2-1-P and FIS2011-23565, by STFC-UK (Grant No. ST/F012012/1) and by the European Union by means of the European Commission within its Seventh Framework Programme (FP7) via ENSAR (Contract No. 262010)

International audience; Measurements of fusion excitation functions of Ni-58 + Sn-124 and Ni-64 + Sn-124 are extended towards lower energy to cross sections of 1 mu b and are compared to detailed coupled-channels calculations. The calculations clearly show the importance of including transfer reactions in a coupled-channels treatment for such heavy systems. This result is different from the conclusion made in a previous article which claimed that the influence of transfer on fusion is not important for fusion reactions of Ni + Sn. In the energy region studied in this experiment no indication of fusion hindrance has been observed, which is consistent with a systematic study of this behavior.

No data on the fusion excitation function of 48Ti + 58Fe in the energy region near the Coulomb barrier existed prior to the present work, while fusion of 58Ni + 54Fe was investigated in detail some years ago, down to very low energies and clear evidence of fusion hindrance was noticed at relatively high cross sections. 48Ti and 58Fe are soft and have a low-lying quadrupole excitation lying at ~800-900 keV only. Instead, 58Ni and 54Fe have a closed shell (protons and neutrons, respectively) and are rather rigid. Investigating: 1) the possible in influence of the different structure of the involved nuclei on the fusion excitation functions far below the barrier ; 2) in particular, whether hindrance is observed in 48Ti + 58Fe, and to compare the results with current CC models. Methods: 48Ti beams from the XTU Tandem accelerator of INFN-Laboratori Nazionali di Legnaro were used. The experimental set-up was based on an electrostatic beam separator, and fusion-evaporation residues (ER) were detected at very forward angles. Angular distributions of ER were measured. Fusion cross sections of 48Ti + 58Fe have been obtained in a range of nearly 6 orders of magnitude around the Coulomb barrier, down to2 microb. The sub-barrier cross sections of 48Ti + 58Fe are much larger than those of 58Ni + 54Fe. Significant differences are also observed in the logarithmic derivatives and astrophysical S-factors. No evidence of hindrance is observed, because coupled-channels calculations using a standard Woods-Saxon potential are able to reproduce the data in the whole measured energy range. Analogous calculations for 58Ni + 54Fe predict clearly too large cross sections at low energies. The two fusion barrier distributions are wide and display a complex structure that is only qualitatively fit by calculations. It is pointed out that all these different trends originate from the dissimilar low-energy nuclear structure of the involved nuclei. In particular, the strong quadrupole excitations in 48Ti and 58Fe produce the relative cross section enhancement and make the barrier distribution ~2 MeV wider, thus probably pushing the threshold for hindrance below the measured limit.

10 pags.; 11 figs.; 2 tabs.; PACS number(s): 23.40.Hc, 29.30.Kv, 27.50.+e, 21.10.Pc; Open Access funded by Creative Commons Atribution Licence 3.0, The beta decay of the N = Z nucleus Kr-72 has been studied with the total absorption spectroscopy technique at ISOLDE (CERN). A total B(GT) = 0.79(4)g(A)(2)/4 pi has been found up to an excitation energy of 2.7 MeV. The B(GT) distribution obtained is compared with predictions from state-of-the-art theoretical calculations to learn about the ground state deformation of Kr-72. Although a dominant oblate deformation is suggested by direct comparison with quasiparticle random phase approximation (QRPA) calculations, beyond-mean-field and shell-model calculations favor a large oblate-prolate mixing in the ground state. Published by the American Physical Society, J.A.B. acknowledges the predoctoral grant BES-2008-009412 associated with the research project FPA2007-62170 funded by Ministerio de Ciencia e Innovacion (Spain). This work has ´ been partly supported by the Spanish Ministerio de Economía y Competitividad (MINECO) through projects FPA2012- 32443, FPA2011-24553, FPA2011-29854-C04-01, FPA2013- 41267-P, FPA2014-52823-C2-1-P and FIS2011-23565, by STFC-UK (Grant No. ST/F012012/1) and by the European Union by means of the European Commission within its Seventh Framework Programme (FP7) via ENSAR (Contract No. 262010)

43rd Zakopane Conference on Nuclear Physics -- SEP 01-07, 2008 -- Zakopane, POLAND, WOS: 000264436200022, The PARIS project is ail initiative to develop and build a high-efficiency gamma-calorimeter principally for Use at SPIRAL2. It is intended to comprise a double shell of scintillators and use the novel scintillator material LaBr3(Ce), which promises a step-change in energy and time resolutions over what is achievable using conventional scintillators. The array could be used in a stand-alone mode, in conjunction with an inner particle detection system, or with high-purity germanium arrays. Its potential physics opportunities as well as initial designs and simulations will be discussed.

International audience; An excitation function of one-and two-neutron transfer channels for the Ni-60 + 116-Sn system has been measured with the magnetic spectrometer PRISMA in a wide energy range, from the Coulomb barrier to far below it. The experimental transfer probabilities are well reproduced, for the first time with heavy ions, in absolute values and in slope by microscopic calculations which incorporate nucleon-nucleon pairing correlations.

International audience; The sub-barrier fusion excitation function of Ca-40 + Zr-96 has been measured down to cross sections similar or equal to 2.4 mu b, i.e. two orders of magnitude smaller than obtained in the previous experiment, where the sub-barrier fusion of this system was found to be greatly enhanced with respect to Ca-40 + Zr-90, and the need of coupling to transfer channels was suggested. The purpose of this work was to investigate the behavior of Ca-40 + Zr-96 fusion far below the barrier. The smooth trend of the excitation function has been found to continue, and the logarithmic slope increases very slowly. No indication of hindrance shows up, and a comparison with Ca-48 + Zr-96 is very useful in this respect. A new CC analysis of the complete excitation function has been performed, including explicitly one- and two-nucleon Q > 0 transfer channels. Such transfer couplings bring significant cross section enhancements, even at the level of a few mu b. Locating the hindrance threshold, if any, in Ca-40 + Zr-96 would require challenging measurements of cross sections in the sub-mu b range.

International audience; The fusion excitation function of Ti-48 + Fe-58 has been measured in a wide energy range around the Coulomb barrier, covering 6 orders of magnitude of the cross sections. We present here the preliminary results of this experiment, and a full comparison with the near-by system Ni-58 + Fe-54 where evidence of fusion hindrance shows up at relatively high cross sections. The sub-barrier cross sections of Ti-48 + Fe-58 are much larger than those of Ni-58 + Fe-54. Significant differences are also observed in the logarithmic derivatives, astrophysical S-factors and fusion barrier distributions. The influence of low-energy nuclear structure on all these trends is pointed out and commented. Coupled-channels calculations using a Woods-Saxon potential are able to reproduce the experimental results for Ti-48 + Fe-58. The logarithmic derivative of the excitation function is very nicely fit, and no evidence of hindrance is observed down to around 1 mu b. The fusion barrier distribution is rather wide, flat and structureless. It is only in qualitative agreement with the calculated distribution.

International audience; Background: The nuclear structure of colliding nuclei is known to influence the fusion process. Couplings of the relative motion to nuclear shape deformations and vibrations lead to an enhancement of the sub-barrier fusion cross section in comparison with the predictions of one-dimensional barrier penetration models. This enhancement is explained by coupled-channels calculations including these couplings. The sub-barrier fusion cross section is also affected by nucleon transfer channels between the colliding nuclei.Purpose: The aim of the present experiment is to investigate the influence of the projectile and target nuclear structures on the fusion cross sections in the Ca40+Ni58 and Ca40+Ni64 systems.Methods: The experimental and theoretical fusion excitation functions as well as the barrier distributions were compared for these two systems. Coupled-channels calculations were performed using the ccfull code.Results: Good agreement was found between the measured and calculated fusion cross sections for the Ca40+Ni58 system. The situation is different for the Ca40+Ni64 system where the coupled-channels calculations with no nucleon transfer clearly underestimate the fusion cross sections below the Coulomb barrier. The fusion excitation function was, however, well reproduced at low and high energies by including the coupling to the neutron pair-transfer channel in the calculations.Conclusions: The nuclear structure of the colliding nuclei influences the fusion cross sections below the Coulomb barrier for both Ca40+Ni58,64 systems. Moreover, we highlighted the effect of the neutron pair-transfer channel on the fusion cross sections in Ca40+Ni64.

Measurements of the excitation function for the fusion of Mg-24 + Si-30 (Q = 17.89 MeV)have been extended toward lower energies with respect to previous experimental data. The S-factor maximum observed in this large, positive-Q-value system is the most pronounced among such systems studied thus far. The significance and the systematics of an S-factor maximum in systems with positive fusion Q values are discussed. This result would strongly impact the extrapolated cross sections and reaction rates in the carbon and oxygen burnings and, thus, the study of the history of stellar evolution.

An excitation function of one- and two-neutron transfer channels for the 60Ni+116Sn system has been measured with the magnetic spectrometer PRISMA in a wide energy range, from the Coulomb barrier to far below it. The experimental transfer probabilities are well reproduced, for the first time with heavy ions, in absolute values and in slope by microscopic calculations which incorporate nucleon-nucleon pairing correlations.

The fusion excitation function of the system 28Si + 28Si at energies near and below the Coulomb barrier is known only down to ~15 mb. This precludes any information on both coupling effects on sub-barrier cross sections and the possible appearance of hindrance. The sub-barrier cross sections for 28Si + 28Si are overestimated by coupled-channels calculations based on a standard Woods-Saxon potential, except for the lowest energies. Calculations using the M3Y+repulsion potential are adjusted to fit the 28Si + 28Si and the existing 30Si + 30Si data. An additional weak imaginary potential is required to fit the low-energy trend of 28Si + 28Si.