2019, Fomichev, A. S., Bezbakh, A. A., Wolski, R., Gazeeva, E. M., Belogurov, S. G., Grigorenko, L. V., Белогуров, Сергей Геннадьевич, Григоренко, Леонид Валентинович

© 2019, Allerton Press, Inc.Abstract: Characteristics of a new separator of radioactive ion beams (RIBs) are described. It was recently commissioned at the Flerov Laboratory of Nuclear Reactions (FLNR JINR) and is in operation at the primary beam line of the U-400M heavy ion cyclotron providing RIBs in energy range of 10–50 MeV/nucleon. Preliminary results obtained in the first experiments performed with this separator in 2018 are presented. A medium-term program of scientific research is discussed.

2023, Nikolskii, E. Y., Muzalevskii, I. A., Krupko, S. A., Bezbakh, A. A., Belogurov, S. G., Grigorenko, L. V., Белогуров, Сергей Геннадьевич, Григоренко, Леонид Валентинович

The extremely neutron-rich systems 7H, 6H were studied in the 2H(8He, 3He)7H and 2H(8He, 4He)6H proton and deuteron pickup reactions with a 26 AMeV secondary 8He beam produced at the new ACCULINNA-2 fragment separator. In addition, the same proton and deuteron pickup reactions were generated using the 42 AMeV 10Be beam, and the population of low-lying 9Li and 8Li states was measured in reactions 2H(10Be,3He)9Li and 2H(10Be,4He)8Li, respectively. The latter were used as reference measurements in order to check the setup calibration over the excitation energy of 7,6H and to determine the real experimental energy resolution which was compared with Monte Carlo calculations. The corresponding results obtained for the superheavy hydrogen systems 7H, 6H are presented and discussed. Typical excitation spectra of the 9Li and 8Li nuclei are also shown.

2023, Bezbakh, A. A., Belogurov, S. G., Chudoba, V., Grigorenko, L. V., Белогуров, Сергей Геннадьевич, Григоренко, Леонид Валентинович

2021, Muzalevskii, I. A., Bezbakh, A. A., Nikolskii, E. Yu., Chudoba, V., Belogurov, S. G., Grigorenko, L. V., Белогуров, Сергей Геннадьевич, Григоренко, Леонид Валентинович

© 2021 American Physical Society.The extremely neutron-rich system H7 was studied in the direct H2(He8,He3)H7 transfer reaction with a 26 AMeV secondary He8 beam [Bezbakh et al., Phys. Rev. Lett. 124, 022502 (2020)PRLTAO0031-900710.1103/PhysRevLett.124.022502]. The missing mass spectrum and center-of-mass angular distributions of H7, as well as the momentum distribution of the H3 fragment in the H7 frame, were constructed. In addition, we carried out another experiment with the same beam but a modified setup, which was cross-checked by the study of the H2(Be10,He3)Li9 reaction. A solid experimental evidence is provided that two resonant states of H7 are located in its spectrum at 2.2(5) and 5.5(3)MeV relative to the H3+4n decay threshold. Also, there are indications that the resonant states at 7.5(3) and 11.0(3)MeV are present in the measured H7 spectrum. Based on the energy and angular distributions, obtained for the studied H2(He8,He3)H7 reaction, the weakly populated 2.2(5)-MeV peak is ascribed to the H7 ground state. It is highly plausible that the firmly ascertained 5.5(3)-MeV state is the 5/2+ member of the H7 excitation 5/2+-3/2+ doublet, built on the 2+ configuration of valence neutrons. The supposed 7.5-MeV state can be another member of this doublet, which could not be resolved in Bezbakh et al. [Phys. Rev. Lett. 124, 022502 (2020)PRLTAO0031-900710.1103/PhysRevLett.124.022502]. Consequently, the two doublet members appeared in the spectrum of H7 in the work mentioned above as a single broad 6.5-MeV peak.

2023, Nikolskii, E. Y., Krupko, S. A., Muzalevskii, I. A., Bezbakh, A. A., Belogurov, S. G., Grigorenko, L. V., Белогуров, Сергей Геннадьевич, Григоренко, Леонид Валентинович

2020, Bezbakh, A. A., Chudoba, V., Krupko, S. A., Biare, D., Belogurov, S. G., Grigorenko, L. V., Белогуров, Сергей Геннадьевич, Григоренко, Леонид Валентинович

© 2020 American Physical Society.The H7 system was populated in the H2(He8,He3)H7 reaction with a 26 AMeV He8 beam. The H7 missing mass energy spectrum, the H3 energy and angular distributions in the H7 decay frame were reconstructed. The H7 missing mass spectrum shows a peak, which can be interpreted either as unresolved 5/2+ and 3/2+ doublet or one of these states at 6.5(5) MeV. The data also provide indications of the 1/2+ ground state of H7 located at 1.8(5) MeV with quite a low population cross section of ∼25 μb/sr within angular range θc.m.≃(17°-27°).

2022, Nikolskii, E. Yu., Muzalevskii, I. A., Bezbakh, A. A., Chudoba, V., Belogurov, S. G., Grigorenko, L. V., Белогуров, Сергей Геннадьевич, Григоренко, Леонид Валентинович

© 2022 American Physical Society.The extremely neutron-rich system H6 was studied in the direct H2(He8,He4)H6 transfer reaction with a 26A MeV secondary He8 beam. The measured missing mass spectrum shows a broad bump at ≈4-8 MeV above the H3+3n decay threshold. This bump can be interpreted as a broad resonant state in H6 at 6.8(5) MeV. The population cross section of such a presumably p-wave state (or it may be few overlapping states) in the energy range from 4 to 8 MeV is dσ/dωc.m.≃190-80+40μb/sr in the angular range 5°<θc.m.<16°. The obtained missing mass spectrum is practically free of H6 events below 3.5 MeV (dσ/dωc.m. 5μb/sr in the same angular range). The steep rise of the H6 missing mass spectrum at ≈3 MeV allows us to derive the lower limit for the possible resonant-state energy in H6 to be 4.5(3) MeV. According to the paring energy estimates, such a 4.5(3) MeV resonance is a realistic candidate for the H6 ground state (g.s.). The obtained results confirm that the decay mechanism of the H7 g.s. (located at 2.2 MeV above the H3+4n threshold) is the "true"(or simultaneous) 4n emission. The resonance energy profiles and the momentum distributions of fragments of the sequential H6→H5(g.s.)+n→H3+3n decay were analyzed by the theoretically updated direct four-body-decay and sequential-emission mechanisms. The measured momentum distributions of the H3 fragments in the H6 rest frame indicate very strong "dineutron-type"correlations in the H5 ground state decay.

2024, Krupko, S. A., Belogurov, S. G., Bezbakh, A. A., Fomichev, A. S., Grigorenko, L. V., Белогуров, Сергей Геннадьевич, Григоренко, Леонид Валентинович

2020, Muzalevskii, I. A., Chudoba, V., Bezbakh, A. A., Biare, D., Belogurov, S. G., Grigorenko, L. V., Белогуров, Сергей Геннадьевич, Григоренко, Леонид Валентинович

© 2020, Allerton Press, Inc.Abstract: Investigation of the 7H-system in the experiment conducted at the fragment separator ACCULINNA-2 in the 8He(2H,3He)7H reaction requires to detect the recoil 3He ions with energy down to 6 MeV. For this purpose two ∆ E-E particle telescopes are used, with each telescope having in front a thin (20-μm) Si strip detector (∆E-SSD). The maps of thickness heterogeneity of the thin detectors were determined by measuring the energy losses of the 226Ra α-particles. The adopted thickness normalization method provides a good identification of the 3He nuclei being recorded in the presence of a high 4He background. Two approaches were used for calculating the energy losses of the identified 3He and 4He reaction ejectiles and reconstructing their energy values available at the exit from the deuterium target. The developed techniques were applied for the 7H missing-mass reconstruction.