AGATA Collaboration(Avigo, R. et al), Domingo-Pardo, C., Gadea, A., & Gonzalez, V. (2020). Low-lying electric dipole gamma-continuum for the unstable Fe-62(,)64 nuclei: Strength evolution with neutron number. Phys. Lett. B, 811, 135951–6pp.
Abstract: The gamma-ray emission from the nuclei Fe-62,Fe-64 following Coulomb excitation at bombarding energy of 400-440 AMeV was measured with special focus on E1 transitions in the energy region 4-8 MeV. The unstable neutron-rich nuclei Fe-62,Fe-64 were produced at the FAIR-GSI laboratories and selected with the FRS spectrometer. The gamma decay was detected with AGATA. From the measured gamma-ray spectra the summed E1 strength is extracted and compared to microscopic quasi-particle phonon model calculations. The trend of the E1 strength with increasing neutron number is found to be fairly well reproduced with calculations that assume a rather complex structure of the 1(-) states (three-phonon states) inducing a strong fragmentation of the E1 nuclear response below the neutron binding energy.
|
Pasqualato, G. et al, Gadea, A., & Jurado, M. (2023). An alternative viewpoint on the nuclear structure towards 100Sn: Lifetime measurements in 105Sn. Phys. Lett. B, 845, 138148–7pp.
Abstract: This work aims at presenting an alternative approach to the long standing problem of the B(E2) values in Sn isotopes in the vicinity of the N=Z double-magic nucleus Sn-100, until now predominantly measured with relativistic and intermediate-energy Coulomb excitation reactions. The direct measurement of the lifetime of low-lying excited states in odd-even Sn isotopes provides a new and precise guidance for the theoretical description of the nuclear structure in this region. Lifetime measurements have been performed in Sn-105 for the first time with the coincidence Recoil Distance Doppler Shift technique. The lifetime results for the 7/2(1)(+) first excited state and the 11/2(1)(+) state, 2(+)(Sn-104) circle times nu 1g(7/2) multiplet member, are discussed in comparison with state-of-the-art shell model and mean field calculations, highlighting the crucial contribution of proton excitation across the core of Sn-100. The reduced transition probability B(E2) of the 11/2(1)(+) core-coupled state points out an enhanced staggering with respect to the B(E2; 2(1)(+) -> 0(1)(+)) in the even-mass Sn-104 and Sn-106 isotopes.
|
Fernandez, A., Hufschmidt, D., Colaux, J. L., Valiente-Dobon, J. J., Godinho, V., Jimenez de Haro, M. C., et al. (2020). Low gas consumption fabrication of He-3 solid targets for nuclear reactions. Mater. Des., 186, 108337–10pp.
Abstract: Nanoporous solids that stabilize trapped gas nanobubbles open new possibilities to fabricate solid targets for nuclear reactions. A methodology is described based on the magnetron sputtering (MS) technique operated under quasistatic flux conditions to produce such nanocomposites films with He-3 contents of up to 16 at.% in an amorphous-silicon matrix. In addition to the characteristic low pressure (3-6 Pa) needed for the gas discharge, the method ensures almost complete reduction of the process gas flow during film fabrication. The method could produce similar materials to those obtained under classical dynamic flux conditions for MS. The drastic reduction (>99.5%) of the gas consumption is fundamental for the fabrication of targets with scarce and expensive gases. Si:He-3 and W:He-3 targets are presented together with their microstructural (scanning and transmission electron microscopy, SEM and TEM respectively) and compositional (Ion Beam Analysis, IBA) characterization. The He-3 content achieved was over 1 x 10(18) at/cm(2) for film thicknesses between 1.5 and 3 μm for both Si and W matrices. First experiments to probe the stability of the targets for nuclear reaction studies in inverse kinematics configurations are presented.
|
Fomichev, A. S., Mukha, I., Stepantsov, S. V., Grigorenko, L. V., Litvinova, E. V., Chudoba, V., et al. (2011). Lifetime of (26)S and a limit for its 2p decay energy. Int. J. Mod. Phys. E, 20(6), 1491–1508.
Abstract: The unknown isotope (26)S, expected to decay by two-proton (2p) emission, was studied theoretically and searched experimentally. The structure of this nucleus was examined within the relativistic mean field (RMF) approach. A method for taking into account the many-body structure in the three-body decay calculations was developed. The results of the RMF calculations were used as an input for the three-cluster decay model optimized for the study of a possible 2p decay branch of this nucleus. The experimental search for (26)S was performed by fragmentation of a 50.3 A MeV (32)S beam. No events of a particles table (26)S or (25)P (a presumably proton-unstable subsystem of (26)S) were observed. Based on the obtained production systematics, an upper half-life limit of T(1/2) < 79 ns was established from the time-of-flight through the fragment separator. Together with the theoretical lifetime estimates for two-proton decay, this gives a decay energy limit of Q(2p) > 640 keV for (26)S. Analogous limits for (25)P are found as T(1/2) < 38 ns and Q(p) > 110 keV. In the case that the one-proton emission is the main branch of the (26)S decay, a limit Q(2p) > 230 keV would follow for this nucleus. According to these limits, it is likely that (26)S resides in the picosecond life time range
|
Tain, J. L., Agramunt, J., Algora, A., Aprahamian, A., Cano-Ott, D., Fraile, L. M., et al. (2015). The sensitivity of LaBr3:Ce scintillation detectors to low energy neutrons: Measurement and Monte Carlo simulation. Nucl. Instrum. Methods Phys. Res. A, 774, 17–24.
Abstract: The neutron sensitivity of a cylindrical circle minus 1.5 in x 1.5 in LaBr3:Ce scintillation detector was measured using quasi-monoenergetic neutron beams in the energy range from 40 keV to 2.5 MeV. In this energy range the detector is sensitive to gamma-rays generated in neutron inelastic and capture processes. The experimental energy response was compared with Monte Carlo simulations performed with the Geant4 simulation toolkit using the so-called High Precision Neutron Models. These models rely on relevant information stored in evaluated nuclear data libraries. The performance of the Geant4 Neutron Data Library as well as several standard nuclear data libraries was investigated. In the latter case this was made possible by the use of a conversion tool that allowed the direct use of the data from other libraries in Geant4. Overall it was found that there was good agreement with experiment for some of the neutron data bases like ENDF/B-VII.0 or JENDL-3.3 but not with the others such as ENDF/B-VI.8 or JEFF-3.1.
|
