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Nuclear fission yields data measurements for thermal neutron induced fission of 241Pu have been carried out at the Institut Laue Langevin (ILL) in Grenoble, using the Lohengrin mass spectrometer. Mass, isotopic and isomeric yields have been extracted for the last measurements. A focus is given in this document to the mass yield results which are obtained for almost the entire heavy peak and most of the light high yields masses, along with the covariance matrix. The mean kinetic energy as a function of the fission product mass has also been extracted from the measurements. The total mean kinetic energy pre and post neutron emission have been assessed and compared to other works showing a rather good agreement.

The simulation of the de-excitation of nuclei requires some models and data in order to construct the nuclear level scheme and the associated transition intensities. The aim of this work is to focus on nuclear structure data used at low energy where electromagnetic transitions can be measured. The RIPL3 database linked to the FIFRELIN Monte Carlo code contains such data and their influence on fission observables is reviewed.

Fission yields are essential for nuclear reactor studies (decay heat, fuel inventory…) and constitute also one of the main observables needed to improve our understanding of the fission process. The symmetric mass region is of particular interest due to various intriguing properties of the fission fragments already reported in the literature : inversion of the nuclear charge polarization, large width of the fission fragment kinetic energy distribution, strong change of the prompt neutron multiplicity, etc. Recently, measurements of fission yields and kinetic energy distributions in the symmetric mass region were achieved at the LOHENGRIN mass spectrometer of the Institut Laue-Langevin (ILL). This experimental work is challenging due to the low counting rate and the appearance of contaminant masses, leading to pronounced components in the fission fragment kinetic energy distribution. Despite removing the undesirable contributions, the fission fragment kinetic energy distributions still show two components, indicating that the fission process could be modal. To go further and better characterize these components a comparison between our experimental data and Monte Carlo calculations (FIFRELIN code) simulating the de-excitation of the fission fragments for different fission channels will be presented and discussed.

A large array of Ge detectors installed at ILL, around a 235U target irradiated with cold neutrons, (EXILL) allowed measurement of prompt gamma-ray cascades occurring in fission fragments with an unambiguous determination of fragments. Here we present preliminary results of a systematic comparison between experimental γ-ray intensities and those obtained from the Monte-Carlo simulation code FIFRELIN, which is dedicated to the de-excitation of fission fragments. Major γ-ray intensities in the 142Ba and 92Kr fission products, extracted from EXILL data, were compared to FIFRELIN, as well as to reported values (when available) obtained with EUROGAM2 in the spontaneous fission of 248Cm. The evolution of γ-ray intensities in 92Kr versus the complementary partner in fission (i.e. versus the total number of evaporated neutrons by the fission pair) was then extracted and compared to FIFRELIN.

The study of nuclear fission and in particular the correlation between the produced fragments and the associated neutrons is encountering renewed interest since new models are available on the market and a large set of applications show a rather stringent demand on high quality nuclear data. The future Neutrons For Science installation, being presently built at GANIL (Caen, France) in the framework of the SPIRAL2 project, will produce high intensity neutron beams from hundreds of keV up to 40 MeV. In view of this opportunity, the development of an experimental setup called FALSTAFF (Four Arm cLover for the Study of Actinide Fission Fragments) has been undertaken since 2011. This novel apparatus is meant to provide a full characterization of fission fragments in terms of mass, nuclear charge and kinetic energy. Moreover, it will provide a measurement of the mass before and after neutron evaporation, leading to the determination of the neutron multiplicity as a function of the fragmentation. The FALSTAFF setup is presently in its R&D phase in order to achieve the required specifications, especially in terms of time, space and energy resolution of the different detectors.

The precise modeling of the de-excitation of Gd isotopes is of great interest for experimental studies of neutrinos using Gd-loaded organic liquid scintillators. The FIFRELIN code was recently used within the purposes of the STEREO experiment for the modeling of the Gd de-excitation after neutron capture in order to achieve a good control of the detection efficiency. In this work, we report on the recent additions in the FIFRELIN de-excitation model with the purpose of enhancing further the de-excitation description. Experimental transition intensities from the EGAF database are now included in the FIFRELIN cascades, in order to improve the description of the higher energy part of the spectrum. Furthermore, the angular correlations between γ rays are now implemented in FIFRELIN, to account for the relative anisotropies between them. In addition, conversion electrons are now treated more precisely in the whole spectrum range, while the subsequent emission of X rays is also accounted for. The impact of the aforementioned improvements in FIFRELIN is tested by simulating neutron captures in various positions inside the STEREO detector. A repository of up-to-date FIFRELIN simulations of the Gd isotopes is made available for the community, with the possibility of expanding for other isotopes which can be suitable for different applications. [ABSTRACT FROM AUTHOR]

Fission fragments from neutron-induced fission of 235 produced at the high-flux reactor of the Institut Laue-Langevin, Grenoble, were separated with the Lohengrin separator to provide a beam of neutron-rich 85As nuclei. The &bgr;- decay of 85As to 85Se was studied using &ggr;-&ggr; and &bgr;-&ggr; coincidence techniques. 85Se was also studied using the prompt-&ggr; coincidence data from spontaneous fission of 248Cm and 252Cf measured with the Eurogam2 and Gammasphere Ge arrays, respectively. The combination of &bgr; decay and prompt-&ggr; data enabled the determination of spins and parities of low-energy excited states in 85Se. There are new arguments supporting the 5/2- assignment for the ground state of 85As. [ABSTRACT FROM AUTHOR]

Abstract: The LOHENGRIN fission fragment separator uses actinide targets in a neutron flux of about in an in-pile position of the high-flux reactor of ILL Grenoble. For fission yield measurements relatively thin targets (tens of ) are used, while for nuclear spectroscopy applications targets up to are employed. This leads to fission rates up to . The targets are heated by the fission power in vacuum to temperatures of up to . The radiation damage caused by the fission fragments can reach 50 dpa (displacements per atom) per day, an extremely high value comparable to that caused by irradiation with intense heavy ion beams. Therefore the thick targets that were produced with different methods (painting, spray-painting, electrolysis and molecular plating) all suffer from a burnup that is much quicker than explainable by nuclear transmutation. We discuss physical effects responsible for this additional decrease in fission fragment rate and ways to improve the situation. [Copyright &y& Elsevier]

Abstract: We analyzed the experimental data of the pre-scission neutron multiplicity in connection with fission fragments in the reaction 58Ni+ 208Pb at the incident energy corresponding to the excitation energy of the compound nucleus , which was performed by DéMoN group. The relation between the pre-scission neutron multiplicity and each reaction process having different reaction time is investigated. In order to study the fusion–fission process accompanied by neutron emission, the fluctuation–dissipation model combined with a statistical model is employed. It is found that the fusion–fission process and the quasi-fission process are clearly distinguished in correlation with the pre-scission neutron multiplicity. [Copyright &y& Elsevier]

Numerous measurements of fission product yields were performed since the discovery of the nuclear fission process. However, more precise and reliable fission product yields are requested. Lack of covariance matrices make difficult to use it for specific application purposes such as the propagation uncertainty of decay heat. In this work, we propose to measure independently the fission product mass yields for the whole heavy peak (including the symmetric mass region) for the 233 U (n th , f) reaction. Both average values and experimental covariance is provided. The fission product mass yields are measured with the LOHENGRIN recoil mass spectrometer of the ILL using an ionization chamber located at the focal plane. A new procedure of data taking has been developed in order to minimize the biases. Concretely several ionic charges and kinetic energy distributions have been measured for each mass. Particular attention has been considered in the monitoring of the target time evolution. Additional corrections were necessary in the symmetry mass region due to contaminants coming from the LOHENGRIN recoil mass spectrometer. A complex Monte Carlo analysis has been developed in order to better propagate all the uncertainties. The fission product mass yields of the 233 U (n th , f) and its associated covariance matrix has been produced. An overall good agreement has been observed with ENDF/B-VIII.0 in contrast with the JEFF-3.3 evaluation. A precision around 2% for the heavy peak has been measured. The experimental covariance matrix was also computed. In the symmetry mass region, two components were observed in the kinetic energy distribution. One of this component was considered as an artifact and was ruled-out. [ABSTRACT FROM AUTHOR]

This article reports the measurement of the 235U-induced antineutrino spectrum shape by the Stereo experiment. 43 000 antineutrinos have been detected at about 10 m from the highly enriched core of the ILL reactor during 118 full days equivalent at nominal power. The measured inverse beta decay spectrum is unfolded to provide a pure 235U spectrum in antineutrino energy. A careful study of the unfolding procedure, including a cross-validation by an independent framework, has shown that no major biases are introduced by the method. A significant local distortion is found with respect to predictions around Eν ≃ 5.3 MeV. A Gaussian fit of this local excess leads to an amplitude of A = 12.1 ± 3.4% (3.5σ). [ABSTRACT FROM AUTHOR]

Quantitative neutron studies of cultural heritage objects provide access to microscopic, mesoscopic, and macroscopic structures in a nondestructive manner. In this paper we present a neutron diffraction investigation of a Ghiberti Renaissance gilded bronze relief devoted to the measurement of cavities and inhomogeneities in the bulk of the sample, along with the bulk phase composition and residual strain distribution. The quantitative measurements allowed the determination of the re-melting parts extension, as well as improving current knowledge about the manufacturing process. The study provides significant and unique information to conservators and restorators about the history of the relief. [ABSTRACT FROM AUTHOR]

The lifetime of the state of 135Te has been measured to be τ = 809(22) ps, corresponding to a reduced transition rate of =6.6(2) W.u. The experiment was performed at the focal point of the Lohengrin spectrometer and μs-delayed γ rays from mass-selected A = 135 ions were detected by four LaBr3(Ce) scintillators. This allowed the fast-timing technique to be used to access lifetimes in the 10s-of-ps to ns time region. The value is typical of a vibrational transition, despite 135Te possessing only one valence neutron and two valence protons. Shell model calculations performed with the state-of-the-art effective interaction predict a B(E2) value close to the experimental one and show that contributions from the π(g7/2, d5/2)νf7/2 couplings are coherent. [ABSTRACT FROM AUTHOR]

The Daya Bay, Double Chooz and RENO experiments recently observed a significant distortion in their detected reactor antineutrino spectra, being at odds with the current predictions. Although such a result suggests to revisit the current reactor antineutrino spectra modeling, an alternative scenario, which could potentially explain this anomaly, is explored in this letter. Using an appropriate statistical method, a study of the Daya Bay experiment energy scale is performed. While still being in agreement with the γ calibration data and B 12 measured spectrum, it is shown that a O ( 1 % ) deviation of the energy scale reproduces the distortion observed in the Daya Bay spectrum, remaining within the quoted calibration uncertainties. Potential origins of such a deviation, which challenge the energy calibration of these detectors, are finally discussed. [ABSTRACT FROM AUTHOR]

The Fission Product Prompt γ -ray Spectrometer (FIPPS) is a new instrument of the Institut Laue-Langevin (ILL) for the spectroscopy of nuclei produced after neutron induced reactions. The future upgrade of the instrument aims to explore the neutron-rich region of the nuclear chart with higher selectivity by identifying the fragments produced after neutron induced fission. The Gas-Filled-Magnet (GFM) technique has been chosen in order to obtain a good mass separation (<4 amu at A = 150) and a large geometrical and momentum acceptance (>50 msr and Δ P/P > 10%). A GFM design consisting of a 1/r magnetic field index and Thales circle-shaped entrance and exit magnet edges is proposed. The characteristic of the magnet is presented with realistic magnetic field calculations and Monte-Carlo simulations. [ABSTRACT FROM AUTHOR]

Low-spin excited levels in 8635Br51 and 8636Kr50, populated following β− decay and the neutron-induced fission of 235U, were measured using the Lohengrin fission-fragment separator and the EXILL array of Ge detectors at the PF1B cold-neutron facility of the Institute Laue-Langevin Grenoble. Improved populations of excited levels in 86Br remove inconsistencies existing in the literature on this nucleus. Directional-linear-polarization correlations, analyzed using newly developed formulas, as well as precise angular correlations allowed the unique 1− and 2− spin and parity assignments to the ground state of 86Br and the 4016.3-keV level in 86Kr, respectively. Based on these results we propose that the Gamow-Teller β− decays of 86Se and 86Br involve the νg7/2→πg9/2 transition in addition to the νp3/2→πp3/2 transition proposed earlier. In 86Kr we have identified 1+1, 2+3, and 3+1 levels, analogous to the mixed-symmetry states in 94Mo, which in 86Kr are from proton excitations, only. Large-scale, shell-model calculations with refined interactions reproduce well excitations in 86Br and 86Kr and support our interpretations. [ABSTRACT FROM AUTHOR]

The Fission Product Prompt γ -ray Spectrometer, FIPPS, is under development to enable prompt γ -ray spectroscopy correlated with fission fragment identification. This will open new possibilities in the study of fission and of nuclear structure of neutron rich nuclei. FIPPS will consist of an array of γ and neutron detectors coupled with a fission fragment filter. The chosen solution for the filter is a Gas Filled Magnet (GFM). Both experimental and modeling work was performed in order to extract the key parameters of such a device and design the future GFM of the FIPPS project. Experiments performed with a GFM behind the LOHENGRIN spectrometer demonstrated the capability of additional beam purification. [ABSTRACT FROM AUTHOR]

The 88Kr nucleus has been reinvestigated with prompt-y-ray-spectroscopy methods using the Gammasphere Ge array to measure y rays following spontaneous fission of 252 Cf. The order of some of the transitions, reported previously, has been changed and new levels were introduced. Angular correlation analysis allowed the assignment of spins to several levels in 88Kr. These data, together with the shell-model calculations, explained the near-yrast structure of 88Kr, which is similar to the structure of the N = 52, 90Sr, and 92Zr isotones. The regular systematics obtained for the three isotones suggests that the spin of the 2073.4-keV level in the 86Se isotone is different from the l = 6 value reported previously. Using data from prompt y-ray measurement of spontaneous fission of 248Cm, we reinvestigated the 86Se nucleus. A new candidate for the level in 86Se has been proposed, which is supported by shell-model calculations. Energies of the 21+ and 41+ levels in the 82Zn nucleus have been predicted using a novel systematics. [ABSTRACT FROM AUTHOR]

A delayed, 76.5-keV transition has been observed in coincidence with 97Rb at the Lohengrin mass spectrometer via y-ray and conversion-electron spectroscopy. The multipolarity of the delayed transition was determined to be El and its measured half-life is 5.1(4) /xs. Comparisons with the results of Hartree-Fock-Bogoliubov and quasiparticle-rotor model calculations allow a spin and parity of (1/2, 3/2)- to be assigned to this state. The isomer is likely to be one of the low-lying prolate-deformed 3/2- [312], or oblate-deformed 1/2- [321], 3/2- [321] quasiparticle excitations. A new decay branch of the (9/2+), 830.8-keV isomer of 97Sr has also been observed in the same experiment, allowing a spin of (5/2)+ to be assigned to the 522.5-keV state. This level is likely to have a high-seniority spherical configuration [ABSTRACT FROM AUTHOR]

Abstract: The neutron detection efficiency of a DEMON detector, averaged over the whole volume, was calculated using GEANT and applied to determine neutron multiplicities in an intermediate heavy ion reaction. When a neutron source is set at a distance of about 1m from the front surface of the detector, the average efficiency, , is found to be significantly lower (20–30%) than the efficiency measured at the center of the detector, . In the GEANT simulation the ratio was calculated as a function of neutron energy. The experimental central efficiency multiplied by R was then used to determine the average efficiency. The results were applied to a study of the 64Zn+112Sn reaction at 40 A MeV which employed 16 DEMON detectors. The neutron multiplicity was extracted using a moving source fit. The derived multiplicities are compared well with those determined using the neutron ball in the NIMROD detector array in a separate experiment. Both are in good agreement with multiplicities predicted by a transport model calculation using an antisymmetric molecular dynamics (AMD) model code. [Copyright &y& Elsevier]

We report on a γγ angular-correlation experiment investigating 200Hg after cold-neutron capture. The experiment was performed using eight high-purity germanium detectors mounted on an array installed at the PF1B neutron beam line of the research reactor of the Institut Laue-Langevin in Grenoble, France. The geometry of the array allows γγ angular-correlation analyses that can be used for the determination of level spins and multipole mixing ratios in 200Hg. We present multipole mixing ratios for secondary γ rays and investigate the nature of the 200Hg neutron-capture state by analyzing the observed primary γ rays of this nucleus. [ABSTRACT FROM AUTHOR]

This paper describes measurements on the isotopes 75,77,78Cu by the technique of in-source laser spectroscopy, at the ISOLDE facility, CERN. The role of this technique is briefly discussed in the context of this and other, higher resolution, methods applied to copper isotopes in the range 57-78Cu. The data, analyzed in comparison with previous results on the lighter isotopes 59,63Cu, establish the ground-state nuclear spin of 75,77Cu as 5/2 and yield their magnetic dipole moments as +1.01(5)/µN and +1.61(5)µN, respectively. The results on 78Cu show no evidence for long-lived isomerism at this mass number and are consistent with a spin in the range 3-6 and moment of 0.0(4)µN. [ABSTRACT FROM AUTHOR]

Despite the huge number of fission yield data available in the different evaluated nuclear data libraries, such as JEFF-3.1.1, ENDF/B-VII.0, and JENDL-4.0, more accurate data are still needed both for nuclear energy applications and for our understanding of the fission process itself. It is within the framework of this that measurements on the recoil mass spectrometer Lohengrin (at the Institut Laue-Langevin, Grenoble, France) was undertaken, to determine isotopic yields for the heavy fission products from the 239Pu(nth,f) reaction. In order to do this, a new experimental method based on γ-ray spectrometry was developed and validated by comparing our results with those performed in the light mass region with completely different setups. Hence, about 65 fission product yields were measured with an uncertainty that has been reduced on average by a factor of 2 compared to that previously available in the nuclear data libraries. In addition, for some fission products, a strongly deformed ionic charge distribution compared to a normal Gaussian shape was found, which was interpreted as being caused by the presence of a nanosecond isomeric state. Finally, a nuclear charge polarization has been observed in agreement, with the one described on other close fissioning systems. [ABSTRACT FROM AUTHOR]

Abstract: The detector system used at the first focus of the BigSol superconducting solenoid beam line at the Texas A & M superconducting cyclotron is presented. The system is composed of a position sensitive PPAC followed by an ionization chamber (IC) with a YAP(Ce) array in its back plane. The position sensitivity of the PPAC as well the energy resolution of the IC is investigated as a function of the counting rate. Pulse height, pulse height resolution and time resolution of the YAP(Ce) crystals are studied for a variety of heavy ion beams ranging from 20Ne to 197Au at energies from 15AMeV to 40AMeV. The pulse shape discrimination method using a Flash ADC is also explored, in order to identify decay products (alpha particles and electron/gamma) from the fragments implanted in the scintillator. [Copyright &y& Elsevier]

The 4H resonance was investigated in the transfer reactions 2H(t, p)4H and 3H(t, d)4H using cryogenic liquid targets of deuterium and tritium and 58 MeV triton beam. The multidetector system with a large angular acceptance was used to measure the recoil protons and deuterons in coincidences with tritons or neutrons from the decay of 4H. Data analysis involved careful considerations made for the competing processes of final state interaction and quasifree scattering. The experimental data show a peak with resonance parameters Eres=3.05±0.19 MeV and Γobs=4.18±1.02 MeV. The pole of S-matrix corresponding to the physical values of energy and width, E0=1.99±0.37 MeV and Γ0=2.85±0.3 MeV, has been extracted. [Copyright &y& Elsevier]

Delayed γ-ray and conversion-electron spectroscopy is performed on A=152 fission fragments, at the Lohengrin spectrometer of the Institut Laue-Langevin, providing a new decay scheme for 152Pr. The quasiparticle phonon model, combined with the particle-rotor model, which allows octupole correlations and Coriolis mixing to be taken into account, is applied to analyze its low-energy structure. The main configurations are found to be (π3/2[422]⊗ν5/2[642])1+ for the isomer and (π3/2[541]⊗ν3/2[521])3+ for the ground state. [ABSTRACT FROM AUTHOR]

The fission fragment yield distribution has been measured in the 239Pu(nth,f) reaction in the mass region of A=126 to 150 using the Lohengrin recoil-mass spectrometer. Three independent experimental campaigns were performed, allowing a significant reduction of the uncertainties compared to evaluated nuclear data libraries. The long-standing discrepancy of around 10% for the relative yield of A=134 reported in JEF-2.2 and JEFF-3.1.1 data libraries is finally solved. Moreover, the measured mass distribution in thermal neutron-induced fission does not show any significant dip around the shell closure (A=136) as seen in heavy-ion fission data of 208Pb(18O, f) and 238U(18O, f) reactions. Lastly, comparisons between our experimental data and the predictions from Monte Carlo codes (gef and fifrelin) are presented and discussed. [ABSTRACT FROM AUTHOR]

Ratios of differential chemical potential values relative to the temperature, (µn - µp)/T, extracted from isotope yields of 13 reaction systems at 40 MeV/nucleon are compared to those of a quantum statistical model to determine the temperature and symmetry energy values of the fragmenting system. The experimental (µn - µp)/T values are extracted based on the modified Fisher model. Using the density value of ρ/ρ0 = 0.56 from the previous analysis, the temperature and symmetry energy values of T = 4.6 ± 0.4 MeV and asym = 23.6 ± 2.1 MeV are extracted in a framework of a quantum statistical model. These values agree well with those of the previous work, in which a self-consistent method was utilized with antisymmetrized molecular dynamics simulations. The extracted temperature and symmetry energies are discussed together with other experimental values published in literature. [ABSTRACT FROM AUTHOR]

Any experiment aiming to measure rare events, like Coherent Elastic neutrino-Nucleus Scattering (CE ν NS) or hypothetical Dark Matter scattering, via nuclear recoils in cryogenic detectors relies crucially on a precise detector calibration at sub-keV energies. The Crab collaboration developed a new calibration technique based on the capture of thermal neutrons inside the target crystal. Together with the Nucleus experiment, first measurements with a moderated 252 Cf neutron source and a cryogenic CaWO 4 detector were taken. We observed for the first time the 112eV peak caused by the 182 W(n, γ ) 183 W capture reaction and subsequent nuclear recoils. Currently, Crab is preparing a precision measurement campaign based on a monochromatic flux of thermal neutrons from the 250-kW Triga-mark II nuclear reactor at TU Wien. In this contribution, we introduce the Crab technique, present the first measurement of the 112eV peak, report the preparations for the precision measurement campaign, and give an outlook on the impact on the field of cryogenic detectors., Competing Interests: Conflict of interestThe authors have no relevant financial or non-financial interests to disclose., (© The Author(s) 2024.)

Coherent elastic neutrino-nucleus scattering and low-mass dark matter detectors rely crucially on the understanding of their response to nuclear recoils. We report the first observation of a nuclear recoil peak at around 112 eV induced by neutron capture. The measurement was performed with a CaWO&#95;{4} cryogenic detector from the NUCLEUS experiment exposed to a ^{252}Cf source placed in a compact moderator. We identify the expected peak structure from the single-γ de-excitation of ^{183}W with 3σ and its origin by neutron capture with 6σ significance. This result demonstrates a new method for precise, in situ, and nonintrusive calibration of low-threshold experiments.

We investigate the possible origins of the reactor antineutrino anomalies in norm and shape within the framework of a summation model where β^{-} transitions are simulated by a phenomenological model of Gamow-Teller decay strength. The general trends of divergence from the Huber-Mueller model on the antineutrino side can be reproduced in both norm and shape. From the exact electron-antineutrino correspondence of the summation model, we predict similar distortions in the electron spectra, suggesting that biases on the reference spectra of fission electrons could be the cause of the anomalies.

The PROSPECT and STEREO collaborations present a combined measurement of the pure ^{235}U antineutrino spectrum, without site specific corrections or detector-dependent effects. The spectral measurements of the two highest precision experiments at research reactors are found to be compatible with χ^{2}/ndf=24.1/21, allowing a joint unfolding of the prompt energy measurements into antineutrino energy. This ν[over ¯]&#95;{e} energy spectrum is provided to the community, and an excess of events relative to the Huber model is found in the 5-6 MeV region. When a Gaussian bump is fitted to the excess, the data-model χ^{2} value is improved, corresponding to a 2.4σ significance.

Different extensions of the standard model of particle physics, such as braneworld or mirror matter models, predict the existence of a neutron sterile state, possibly as a dark matter candidate. This Letter reports a new experimental constraint on the probability p for neutron conversion into a hidden neutron, set by the STEREO experiment at the high flux reactor of the Institut Laue-Langevin. The limit is p<3.1×10^{-11} at 95% C.L. improving the previous limit by a factor of 13. This result demonstrates that short-baseline neutrino experiments can be used as competitive passing-through-walls neutron experiments to search for hidden neutrons.

We report a measurement of the antineutrino rate from the fission of ^{235}U with the STEREO detector using 119 days of reactor turned on. In our analysis, we perform several detailed corrections and achieve the most precise single measurement at reactors with highly enriched ^{235}U fuel. We measure an IBD cross section per fission of σ&#95;{f}=(6.34±0.06[stat]±0.15[sys]±0.15[model])×10^{-43}  cm^{2}/fission and observe a rate deficit of (5.2±0.8[stat]±2.3[sys]±2.3[model])% compared to the model, consistent with the deficit of the world average. Testing ^{235}U as the sole source of the deficit, we find a tension between the results of lowly and highly enriched ^{235}U fuel of 2.1 standard deviations.

The reactor antineutrino anomaly might be explained by the oscillation of reactor antineutrinos toward a sterile neutrino of eV mass. In order to explore this hypothesis, the STEREO experiment measures the antineutrino energy spectrum in six different detector cells covering baselines between 9 and 11 m from the compact core of the ILL research reactor. In this Letter, results from 66 days of reactor turned on and 138 days of reactor turned off are reported. A novel method to extract the antineutrino rates has been developed based on the distribution of the pulse shape discrimination parameter. The test of a new oscillation toward a sterile neutrino is performed by comparing ratios of cells, independent of absolute normalization and of the prediction of the reactor spectrum. The results are found to be compatible with the null oscillation hypothesis and the best fit of the reactor antineutrino anomaly is excluded at 97.5% C.L.

The neutrons for science (NFS) facility is a component of SPIRAL-2, the new superconducting linear accelerator built at GANIL in Caen (France). The proton and deuteron beams delivered by the accelerator will allow producing intense neutron fields in the 100 keV-40 MeV energy range. Continuous and quasi-mono-kinetic energy spectra, respectively, will be available at NFS, produced by the interaction of a deuteron beam on a thick Be converter and by the 7Li(p,n) reaction on thin converter. The pulsed neutron beam, with a flux up to two orders of magnitude higher than those of other existing time-of-flight facilities, will open new opportunities of experiments in fundamental research as well as in nuclear data measurements. In addition to the neutron beam, irradiation stations for neutron-, proton- and deuteron-induced reactions will be available for cross-sections measurements and for the irradiation of electronic devices or biological cells. NFS, whose first experiment is foreseen in 2018, will be a very powerful tool for physics, fundamental research as well as applications like the transmutation of nuclear waste, design of future fission and fusion reactors, nuclear medicine or test and development of new detectors.

Fast-neutron-induced fission of ^{238}U at an energy just above the fission threshold is studied with a novel technique which involves the coupling of a high-efficiency γ-ray spectrometer (MINIBALL) to an inverse-kinematics neutron source (LICORNE) to extract charge yields of fission fragments via γ-γ coincidence spectroscopy. Experimental data and fission models are compared and found to be in reasonable agreement for many nuclei; however, significant discrepancies of up to 600% are observed, particularly for isotopes of Sn and Mo. This indicates that these models significantly overestimate the standard 1 fission mode and suggests that spherical shell effects in the nascent fission fragments are less important for low-energy fast-neutron-induced fission than for thermal neutron-induced fission. This has consequences for understanding and modeling the fission process, for experimental nuclear structure studies of the most neutron-rich nuclei, for future energy applications (e.g., Generation IV reactors which use fast-neutron spectra), and for the reactor antineutrino anomaly.

Conversion electron spectroscopy represents an important tool for nuclear structure analysis of medium and heavy nuclei. Two iron-free magnetic electron spectrometers of the orange type have been installed at the Institute for Nuclear Physics of the University of Cologne. The very large transmission of 15% and the very good energy resolution of 1% makes the iron-free orange spectrometer a powerful instrument. By means of fast timing techniques, lifetimes of nuclear excited states can be measured with an accuracy better than 20 ps. For the first time, the energy dependent centroid position of prompt events yielding the time-walk characteristics (the prompt curve) of the orange spectrometer fast timing setup has been measured using prompt secondary δ-electrons generated in a pulsed beam experiment. The prompt curve calibrated as a function of energy allows precise lifetime determination down to a few tens of picoseconds by the use of the centroid shift method.

We report the first confirmation of the predicted inversion between the pi2p3/2 and pi1f5/2 nuclear states in the nu(g)9/2 midshell. This was achieved at the ISOLDE facility, by using a combination of in-source laser spectroscopy and collinear laser spectroscopy on the ground states of 71,73,75Cu, which measured the nuclear spin and magnetic moments. The obtained values are mu(71Cu)=+2.2747(8)mu(N), mu(73Cu)=+1.7426(8)mu(N), and mu(75Cu)=+1.0062(13)mu(N) corresponding to spins I=3/2 for 71,73Cu and I=5/2 for 75Cu. The results are in fair agreement with large-scale shell-model calculations.

Aims: The aim of the present report was to evaluate current methods of in vitro analysis of three-dimensional (3D) scaffolds seeded with human bone marrow stromal cells (hBMSCs) from six bone marrow aspirates for tissue engineered growth of bone., Methods: A series of experiments was conducted to compare methods of cell expansion and to validate analysis of proliferation and differentiation of hBMSCs in long term cultures of up to 40 days in 3D scaffolds of calcium carbonate (CaCO(3)) and mineralized collagen. Proliferation within the seeded scaffolds was monitored using cell counting, 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl-tetrazolium bromide (MTT), neutral red (NR) and DNA fluorescence assays and compared with empty controls. Differentiation was assessed by means of ELISA for osteocalcin (OC) and real time PCR for OC and collagen I (Coll I)., Results: The results showed that the scaffold differed in seeding efficacy (CaCO(3): 53.3%, min. Coll.: 83.3%). The precise identification of the number of cells in biomaterials by MTT, NR and DNA assays was problematic, as MTT and NR assay overestimated the number of cells, whereas DNA assay grossly underestimated the number of cells on the scaffolds. Monitoring of changes over time may be biased by unspecific material-dependent background activity that has to be taken into account. Identification of osteogenic differentiation is not reliable by identifying osteogenic markers such as OC in the supernatant but has to be done on the transcriptional level., Conclusions: It is concluded that monitoring of in vitro procedures for the construction of biohybrid scaffolds requires more emphasis in order to make the cell based approach a reliable treatment option in tissue engineering.