Dilator, J. M., Jaworski, G., Goasduff, A., Gonzalez, V., Gadea, A., Palacz, M., et al. (2025). Reconstruction of pile-up events using a one-dimensional convolutional autoencoder for the NEDA detector array. Nucl. Sci. Tech., 36(2), 32–9pp.
Abstract: Pulse pile-up is a problem in nuclear spectroscopy and nuclear reaction studies that occurs when two pulses overlap and distort each other, degrading the quality of energy and timing information. Different methods have been used for pile-up rejection, both digital and analogue, but some pile-up events may contain pulses of interest and need to be reconstructed. The paper proposes a new method for reconstructing pile-up events acquired with a neutron detector array (NEDA) using an one-dimensional convolutional autoencoder (1D-CAE). The datasets for training and testing the 1D-CAE are created from data acquired from the NEDA. The new pile-up signal reconstruction method is evaluated from the point of view of how similar the reconstructed signals are to the original ones. Furthermore, it is analysed considering the result of the neutron-gamma discrimination based on charge comparison, comparing the result obtained from original and reconstructed signals.
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Dudouet, J. et al, Gadea, A., & Perez-Vidal, R. M. (2024). High-resolution spectroscopy of neutron-rich Br isotopes and signatures for a prolate-to-oblate shape transition at N=56. Phys. Rev. C, 110(3), 034304–16pp.
Abstract: The first systematic experimental study of the neutron-rich Br isotopes with two complementary state-ofthe-art techniques is presented. These isotopes were populated in the fission process at two different facilities, GANIL and ILL. New spectroscopic information was obtained for odd-even Br87-93 isotopes and the experimental results were compared with state-of-the-art large scale shell model (LSSM) and discrete nonorthogonal (DNO) shell model calculations. As a result of such theoretical approaches, a transition from prolate (Br-87,Br-89) to oblate (Br-91,Br-93) shapes is obtained from the subtle balance between proton and neutron quadrupole deformations, as a clear signature of a pseudo-SU3 quadrupole regime.
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Bottoni, S. et al, Gadea, A., & Perez-Vidal, R. M. (2024). Search for the γ decay of the narrow near-threshold proton resonance in 11B. Phys. Lett. B, 855, 138851–4pp.
Abstract: The y decay of the elusive narrow, near-threshold proton resonance in 11 B was investigated at Laboratori Nazionali di Legnaro (INFN) in a particle-y coincidence experiment, using the 6 Li( 6 Li,py) fusion-evaporation reaction and the GALILEO-GALTRACE setup. No clear signature was found for a possible E1 decay to the 1/2-1, – 1 , first-excited state of 11 B, predicted by the Shell Model Embedded in the Continuum (SMEC) with a branching of 0.98+167 +167 -69 x 10-3 -3 with respect to the dominant particle-decaying modes. The statistical analysis of the y-ray spectrum provided an average upper limit of 2.37 x 10-3 -3 for this y-ray branching, with a global significance of 5 sigma. On the other hand, by imposing a global confidence level of 3 sigma, a significant excess of counts was observed for Ey y = 9300(20) keV, corresponding to a resonance energy of 11429(20) keV (namely 200(20) keV above the proton separation energy of 11 B) and a y-ray branching of 1.12(35) x10-3. -3 . This result is compatible with the SMEC calculations, potentially supporting the existence of a near-threshold proton resonance in 11 B.
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Jungclaus, A. et al, Gadea, A., & Montaner-Piza, A. (2024). Excited-State Half-Lives in 130 Cd and the Isospin Dependence of Effective Charges. Phys. Rev. Lett., 132(22), 222501–7pp.
Abstract: The known I pi = 8 & thorn; 1 , E x = 2129-keV isomer in the semimagic nucleus 130 Cd 82 was populated in the projectile fission of a 238 U beam at the Radioactive Isotope Beam Factory at RIKEN. The high counting statistics of the accumulated data allowed us to determine the excitation energy, E x = 2001.2(7) keV, and half-life, T 1 =2 = 57(3) ns, of the I pi = 6 & thorn; 1 state based on gamma gamma coincidence information. Furthermore, the halflife of the 8 & thorn; 1 state, T 1 =2 = 224(4) ns, was remeasured with high precision. The new experimental information, combined with available data for 134 Sn and large-scale shell model calculations, allowed us to extract proton and neutron effective charges for 132 Sn, a doubly magic nucleus far -off stability. A comparison to analogous information for 100 Sn provides first reliable information regarding the isospin dependence of the isoscalar and isovector effective charges in heavy nuclei.
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Zanon, I. et al, Domingo-Pardo, C., & Gadea, A. (2023). High-Precision Spectroscopy of O-20 Benchmarking Ab Initio Calculations in Light Nuclei. Phys. Rev. Lett., 131(26), 262501–7pp.
Abstract: The excited states of unstable O-20 were investigated via.-ray spectroscopy following the O-19(d, p)O-20 reaction at 8 AMeV. By exploiting the Doppler shift attenuation method, the lifetimes of the 2(2)(+) and 3(1)(+) states were firmly established. From the gamma-ray branching and E2/M1 mixing ratios for transitions deexciting the 2(2)(+) and 3(1)(+) states, the B(E2) and B(M1) were determined. Various chiral effective field theory Hamiltonians, describing the nuclear properties beyond ground states, along with a standard USDB interaction, were compared with the experimentally obtained data. Such a comparison for a large set of gamma-ray transition probabilities with the valence space in medium similarity renormalization group ab initio calculations was performed for the first time in a nucleus far from stability. It was shown that the ab initio approaches using chiral effective field theory forces are challenged by detailed high-precision spectroscopic properties of nuclei. The reduced transition probabilities were found to be a very constraining test of the performance of the ab initio models.
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