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[en] Exact calculations for the trajectories of α particles emitted during the fission of ²³⁶U are presented. The forces acting on the fragments and on the α particles are computed taking into account the time evolution of the shape of the fissioning nucleus. The resulting final directions and kinetic energies of the α particles are compared with those obtained with the traditional three-point-charge approximation. Various initial conditions, including pre-scission α emissions, are considered

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[en] The excitation function of the ²³¹Pa(n,f) reaction has been measured from 130 to 450 keV with a neutron energy resolution of 5 keV. This measurement confirmed the existence of two structures observed at Esub(n) = 200 keV and Esub(n) = 330 keV and put into evidence a narrow resonance at Esub(n) = 160 keV. The use of this 2 keV energy resolution has shown that the resonance width is <= 2 keV. The fission fragments angular distributions have been measured around these three structures with a 5 keV energy resolution. The excitation function and the angular distributions were simultaneously reproduced with a statistical model showing the competition between the different exit channels (neutron emission, γ emission, fission barrier at two maxima). This analysis shows that the narrow resonance at 160 keV presents all the characteristics of a pure vibration resonance (KJπ) = (33⁺). The 200 keV and 330 keV resonances are interpretated as correspondance to the vibrations Kπ = 0⁺ and Kπ = 0^-

[en] A method to obtain experimental angular distributions of fission fragments for (n,f) reactions is described. Fission fragments are detected in thin foils of polycarbonate plastic (Makrafol). The detectors are scanned by the spark method. Etching conditions and spark scanning conditions have been studied to obtain the best signal to noise ratio. This method is used for fission study of strong alpha-emitter actinides like ²³⁰Th and ²³¹Pa

[en] A fast circuit breaker operated by an electromagnetic command has been realized. It can open very high currents in times in order of a few microseconds. By means of electromagnetic forces, a conductor is sent against rods and thus cut. The current is then transferred onto a fuse placed in parallel. The explosion of the fuse opens the circuit. A simplified set up has permitted to test some performances of the switch. A 240kA current has been opened in 6μs and a 5kV peak voltage simultaneously generated (half-width : 3μs). The transfer of a 130kA current has been realized in a time as small as 2μs

[en] Fast neutrons up to 2.5 MeV have been used to induce light particle accompanied fission in ²³⁵U, ²³⁸U and ²³⁹Pu targets. The energy spectra and relative intensities of ³H and ⁴He have been measured with a ΔE-E telescope. Absolute particle yields were derived from the number of ⁴He particle per 1000 binary fissions of ²³⁵U and ²³⁹Pu by thermal neutrons measured under the same geometrical conditions. They observe that all the energy distributions are well reproduced by gaussian lineshape, the mean energies of which remain constant while varying the neutron incident energy. (For all nuclei, the ⁴He mean energies lie close to 16 MeV and the corresponding energies for ³H particle at about 8-9 MeV). The production rates of ³H and ⁴he in fast neutron fission of ²³⁵U decrease smoothly with the incident neutron energy up to En = 2.5 MeV. The decrease never exceeds 30% of the thermal neutron production rate. Conversely the ³H and ⁴He particle yields obtained in fast neutron fission of ²³⁹Pu are very close to the thermal neutron production rate. Therefore the corresponding particle yields for fast neutron induced fission of ²³⁸U remain constant between En = 1.5 MeV and En = 2.5 MeV. Some possible explanations for these observations are briefly and qualitatively explored

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[en] Important progress have been performed during the last years in nuclear fission; some results are presented to illustrate these progress