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[en] The invention concerns a neutron detector adapted for use in the core instrumentation of nuclear reactors. It comprises an emitter electrode which, upon irradiation with neutrons, emits electrons by means of (n,γ) processes, a collector electrode, and a dielectric disposed between the emitter and the collector electrode. Thulium 169 or terbium 159 is used as the emitter substance. With this emitter substance a prompt signal is obtained, the magnitude of which hardly changes for years;any delayed signals that may build up and any interference currents due to them are so small that they can be compensated for by simple, known means. (Official Gazette)
[en] The magnetic dipole (M1) response of the 169Tm nucleus is investigated from a theoretical point of view. The theoretical tool used in this study is the Rotational Invariant Quasiparticle Phonon Nuclear Model (RI-QPNM) which gives a possibility to eliminate spurious contributions in the M1 spectrum. In the framework of this model, both the low-lying and high-lying parts of the M1 excitation spectrum of 169Tm are calculated. The result shows that the low-lying excitations have almost pure orbital character and can be interpreted as scissors mode, whereas the high-lying transitions can be read as spin-flip mode because of its spin nature. The reduced transition probability summed up in the energy range 2–4 MeV is found to be which agrees with the available experimental data. The fragmentation of the low-energy M1 strength is also well reproduced. This is also the first study in which both the low-lying and high-lying M1 spectrum of the 169Tm nucleus is theoretically investigated.
[en] We have observed in thulium phosphate TmPO4 an ordered structure of the nuclear spins of 169Tm in high magnetic field. This structure is transverse in the rotating frame, and thus precessing in the laboratory frame
[fr]Nous avons observe dans le phosphate de thulium TmPO4 une structure ordonnee des spins nucleaires de 169Tm en champ magnetique eleve. Cette structure est transversale dans le referentiel tournant et precesse donc dans le systeme du laboratoire