[en] The MUNU experiment measures the neutrino-electron scattering in a nuclear reactors at Bugey (France). The central detector is a gas time projection chamber surrounded by an anti-compton detector and passive shieldings. The detector is composed of liquid scintillators and photomultipliers. It allows the detection of most of the photons in interaction with the gas and generates a background noise equal to the signal. A simulation has been developed: the light collection in the anti-compton detector has been studied, the influence of the electronic conditions on the efficiency has been estimated and a standardization method is proposed. (A.L.B.)

[en] Knowledge of prompt fission gamma-ray emission has been of major interest in reactor physics for a few years. Since very few experimental spectra were ever published until now, new measurements would be also valuable to improve our understanding of the fission process. An experimental method is currently being developed to measure the prompt fission gamma-ray spectrum from some tens keV up to 10 MeV at least. The mean multiplicity and total energy could be deduced. In this method, the gamma-rays are measured with a bismuth germanate (BGO) detector which has the advantage to present a high P/T ratio and a high efficiency compared to other gamma-ray detectors. The prompt fission neutrons are rejected by the time of flight technique between the BGO detector and a fission trigger given by a fission chamber or a scintillating active target. Energy and efficiency calibration of the BGO detector were carried out up to 10.76 MeV by means of the Al-27(p, gamma) reaction. First prompt fission gamma-ray spectrum measurements performed for the spontaneous fission of Cf-252 and for 1.7 and 15.6 MeV neutron-induced fission of U-238 at the CEA, DAM, DIF Van de Graaff accelerator, will be presented. (authors)

[en] The creation of isomeric nuclei by neutron capture in the resonances energy range has been studied with the lead slowing down spectrometer CIRENE. The isomeric ratio measurement of 8 nuclei allows to determine the spin of the compound nucleus at the binding energy S_n. An experiment on ¹⁷⁷Lu underlines the role of the spin of a resonance on the isomeric state alimentation. The neutron flux measurement inside the lead pile, projections on the production of an isomeric target by this method and the pulsed working mode are also presented. (authors)

[en] Six semiconductor detectors (Si(Li) and HPGe) are calibrated in the 1-10 keV energy range by means of tuneable monochromatised synchrotron radiation. Significant improvement in the quality of the response is observed in very recent detectors. A peak shape calibration is established using a modified Hypermet-type function to model the detector response for each energy step; electron effects induce individual background and tail shapes for each detector material. Fano factors for both semiconductor materials are experimentally derived. The efficiency calibration is determined using a proportional counter as reference: the front semiconductor layer acts as a partially active zone

[en] This article presents a full program devoted to the calculation and the measurement of the neutron-induced deuteron break-up reaction cross-section between 5 and 10 MeV, and between 20 and 25 MeV. Measurements are compared with theoretical calculations based on the solution of the Faddeev equations for a realistic nuclear Hamiltonian. The experiments were performed at the Tandem 7 MV accelerator at CEA, DAM, DIF, France. The measurements were carried out with a C₆D₆ detector as active deuterium target located at the center of a 4π neutron counter (see C. Varignon et al., Nucl. Instrum. Methods B 248, 329 (2006)) which allows to count the two neutrons emitted in the ²H(n, 2n)p reaction. Comparisons of the new data and calculations are made with the existing data as well as the CENDL2, JENDL3.3 and ENDF/B-VII evaluations. (orig.)

[en] The measurement and the modeling of nuclear reactions involving a deuterium nucleus come up against the fact that a deuterium nucleus is a neutron-proton pair weakly bound that can break during the collision. The difficulty is to assess the impact of the breaking on the value of the cross-section. A dedicated experimental setting developed by Cea-Dam has allowed us to select the events involving the breaking of the neutron-proton pair: d(n,2n)p. The measurement of the corresponding cross-section has been made for an incident neutron energy ranging from a few MeV to 25 MeV. The quantum 3-body problem has been solved and the simulation agrees well with the experimental results. In the case of deuterium-nucleus reactions, taking into account the breaking of the deuterium improves the accuracy of the simulation. (A.C.)

[en] Following the decommissioning of the 7 MV tandem accelerator of CEA/DAM by the end of 2007, the present report relates the history of the accelerator from its beginning in the sixties and then the nuclear physics studies on fission, (x,xn) reactions, elastic and inelastic scattering, etc and other studies in microelectronics, biology, etc) performed with that installation. (authors)

[en] We have built a low background detector based on a gas time projection chamber surrounded by an active anti-Compton shielding. The detector is installed near a nuclear reactor at Bugey for the experimental study of ν_e bar, e^- scattering. (authors)

[en] An active and non destructive method is being established for detection of ²³⁷Np in nuclear waste barrels. The unique high-energy decay-gamma signature produced after photo-fission is analysed to deduce decay time parameters. High purity ²³⁷Np sample was irradiated with Bremsstrahlung photons and high energies gamma decay spectra were measured with BGO detectors for various irradiation durations. The analysis of decay spectra resulted in formation of five decay groups, which can reproduce the experimental decay spectra within 10 % accuracy. These parameters together with neutron decay groups are absolutely essential to quantify the nuclear material in waste barrels by photo-fission. The delayed decay gamma groups for ²³⁷Np nucleus are being reported for the first time. (authors)

[en] Investigations on neutron-induced fission of actinides and the deuteron breakup are presented. Neutron-induced fission has been studied for 10 years at the WNR (Weapons Neutron Research) neutron facility of the Los Alamos Neutron Science Center (LANSCE). Thanks to this white neutron source the evolution of the prompt fission neutron energy spectra as a function of the incident neutron energy has been characterized in a single experiment up to 200 MeV incident energy. For some isotopes the prompt neutron multiplicity has been extracted. These experimental results demonstrated the effect on the mean neutron energy of the neutron emission before scission for energies higher than the neutron binding energy. This extensive program (²³⁵U and ²³⁸U, ²³⁹Pu, ²³⁷Np and ²³²Th were measured) is completed by neutron spectra measurements on the CEA 4 MV accelerator. The D(n,2n) reaction is studied both theoretically and experimentally. The cross-section was calculated for several nucleon-nucleon interactions including the AV18 interaction. It has also been measured on the CEA 7 MV tandem accelerator at incident neutron energies up to 25 MeV. Uncertainties lower than 8% between 5 and 10 MeV were obtained. In particular these experiments have extended the measured domain for cross sections. (authors)