[en] To study the n+d→p+n+n breakup reaction the experimental setup allowing registration of all secondary particles in different kinematical arrangements was installed at the neutron channel of the Moscow Meson Factory of the Institute for Nuclear Research. The experiment is performed in broad energy range of neutrons (20-100 MeV) incident on deuterium target. The first preliminary data on neutron-neutron scattering length a_nn obtained in the final state interaction (FSI) geometry are presented. For E_n = 40 MeV and ΔΘ = 6° the value a_nn = -17.9 ± 1.0 fm is obtained. Test measurements in the np quasi-free scattering (QFS) arrangement showed that we are able to obtain data on nn QFS in a broad range of neutron energy.

[en] The possibility of reconstructing the neutron flux density of a W-Be photoneutron source using neutron activation analysis of Ag, Mn, Fe, Mn, and Ti samples is considered. The use of simple functions as AE^–B, describing particular regions of the spectrum, as a reconstruction option is discussed. The dependence of the deviation of the measured reaction rates on those calculated in this study on the parameters of approximating functions is investigated. The convergence of the reconstruction results is obtained by increasing the amount of experimental data. This reconstruction method can be used for the operational measurement of the thermal neutron flux density of the photoneutron source and for the optimization of the source parameters.

[en] The possibility of experimentally studying the structure of halo nuclei in reactions induced by quasifree proton scattering on clusters of these nuclei is considered. Quasifree proton scattering on "6He, "4He, "4n, "2n, and n clusters in inverse kinematics is considered for the example of the "8He nucleus. Angular and energy distributions of secondaries are obtained for various representations of the cluster structure of the "8He nucleus. It is clearly shown that, in the angular and energy distributions of secondaries, one can single out regions that receive dominant contributions from reactions on specific clusters and which correspond to concrete cluster configurations of halo nuclei. Possible relevant experiments are proposed

[en] Experimental results on the excitation of isomeric nuclear states in the reactions ¹¹¹Cd(γ, γ′)^111mCd, ¹¹³In(γ, γ′)^113mIn, and ¹¹⁵In(γ, γ′)^115mIn studied by the activation method at photon energies of up to 8 MeV are presented. The respective experiments were performed at the LUE-8 linear electron accelerator of the Institute for Nuclear Research (INR, Moscow). A method for calculating cross sections per equivalent photon was developed with the aid of a simulation on the basis of the GEANT-4 code. The data obtained in this way are discussed from the point of view of the possibility of studying collective nuclear excitations of various multipolarity near the threshold.

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[en] An analysis of the most recent data on the reaction nd → pnn revealed a serious discrepancy between theoretical predictions and cross sections measured for this reaction in various configurations where the role of neutron-neutron interactions is important. In view of this, it seems necessary both to develop theoretical approaches and to obtain new experimental data. For this purpose, a setup for studying the neutron-deuteron breakup reaction was created at the Institute for Nuclear Research on the basis of the neutron beam in the RADEX channel and deuterium targets. This facility makes it possible to perform experiments over a broad region of primary-neutron energies (10–60 MeV) and in various (final-state interaction, quasifree scattering, and spatial-star) configurations. Preliminary results of the respective experiment were obtained for configurations of final-state neutron-neutron interaction and quasifree neutron-neutron scattering

[en] An experimental method based on an analysis of the neutron-neutron correlations in reactions induced by halo nuclei in nuclear photoemulsion is proposed for studying the two-neutron halo structure. Photoemulsion stacks were exposed to a beam of radioactive ⁶He nuclei. Preliminary data on interaction of the ⁶He halo nucleus to hydrogen are compared with the results of the kinematic calculation for the reaction of quasi-free proton scattering from clusters making up the ⁶He halo nucleus. A fraction of quasi-free scattering events with 'survival' of the dineutron is evaluated for scattering of protons by the dineutron configuration of the ⁶He nucleus.

[en] An experimental investigation of the reaction of core pickup from ⁶He and ¹¹Li two-neutronhalo nuclei is proposed. In such experiments, neutron–neutron correlations in a halo nucleus will be assessed on the basis of the energy of a neutron–neutron quasibound state. A detailed kinematical simulation of the reaction ⁶He + ²H → ⁶Li + (nn) →⁶ Li + n + n is performed. It is shown that the energy of the quasibound state in question can determined from the shape of the energy spectrum of neutrons originating from the breakup of this state. In the proposed exclusive experiment, a beam of ⁶He (¹¹Li) nuclei with an energy of about 5 to 10 MeV per nucleon interacts with a deuterated-polyethylene target. This will permit detecting charged particles (⁶Li and ¹¹Be) and a neutron. On the basis of determining the energy of the neutron–neutron quasibound state, it will become possible to estimate the effective attraction between the valence neutrons in the field of the third particle (core).

[en] We report the first results of a kinematically complete experiment on measurement of nd breakup reaction yield at neutron beam RADEX of Institute for Nuclear Research. In the experiment two neutrons are detected in geometry of neutron-neutron final-state interaction which allow one to determine the ¹S₀ neutron-neutron scattering length a_nn. Experimental dependence of the reaction yield on relative energy of two secondary neutrons was compared with predictions of Watson-Migdal theory. For ∆Θ=6° and E_n=40 MeV the value of neutron-neutron scattering length a_nn = -17.9 ± 1.0 fm is obtained. The further improving of experimental uncertainty will allow one to remove the existing difference of results obtained in various experiments. (author)