|
|
Algora, A. et al, Jordan, D., Tain, J. L., Rubio, B., Agramunt, J., Perez-Cerdan, A. B., et al. (2010). Reactor Decay Heat in Pu-239: Solving the gamma Discrepancy in the 4-3000-s Cooling Period. Phys. Rev. Lett., 105(20), 202501–4pp.
Abstract: The beta feeding probability of Tc-102,Tc- 104,Tc- 105,Tc- 106,Tc- 107, Mo-105, and Nb-101 nuclei, which are important contributors to the decay heat in nuclear reactors, has been measured using the total absorption technique. We have coupled for the first time a total absorption spectrometer to a Penning trap in order to obtain sources of very high isobaric purity. Our results solve a significant part of a long-standing discrepancy in the gamma component of the decay heat for Pu-239 in the 4-3000 s range.
|
|
|
|
Mistry, A. K. et al, Tain, J. L., Agramunt, J., Algora, A., Guadilla, V., Morales, A. I., et al. (2022). The DESPEC setup for GSI and FAIR. Nucl. Instrum. Methods Phys. Res. A, 1033, 166662–18pp.
Abstract: The DEcay SPECtroscopy (DESPEC) setup for nuclear structure investigations was developed and commissioned at GSI, Germany in preparation for a full campaign of experiments at the FRS and Super-FRS. In this paper, we report on the first employment of the setup in the hybrid configuration with the AIDA implanter coupled to the FATIMA LaBr3(Ce) fast-timing array, and high-purity germanium detectors. Initial results are shown from the first experiments carried out with the setup. An overview of the setup and function is discussed, including technical advancements along the path.
|
|
|
|
Cabanelas, P. et al, & Nacher, E. (2020). Performance recovery of long CsI(Tl) scintillator crystals with APD-based readout. Nucl. Instrum. Methods Phys. Res. A, 965, 163845–6pp.
Abstract: CALIFA is the high efficiency and energy resolution calorimeter for the (RB)-B-3 experiment at FAIR, intended for detecting high energy light charged particles and gamma rays in scattering experiments, and is being commissioned during the Phase-0 experiments at FAIR, between 2018 and 2020. It surrounds the reaction target in a segmented configuration with 2432 detection units made of long CsI(Tl) finger-shaped scintillator crystals. CALIFA has a 10 year intended operational lifetime as the (RB)-B-3 calorimeter, necessitating measures to be taken to ensure enduring performance. In this paper we present a systematic study of two groups of 6 different detection units of the CALIFA detector after more than four years of operation. The energy resolution and light output yield are evaluated under different conditions. Tests cover the aging of the first detector units assembled and investigates recovery procedures for degraded detection units. A possible reason for the observed degradation is given, pointing to the crystal-APD coupling.
|
|
|
|
IDS Collaboration(Olaizola, B. et al), Algora, A., & Nacher, E. (2025). The 76Cu conundrum remains unsolved. Phys. Lett. B, 866, 139551–8pp.
Abstract: Near the doubly-magic nucleus Ni-78 (Z = 28, N = 50), there has been a decades-long debate on the existence of a long-lived isomer in Cu-76. A recent mass measurement claimed to have settled the debate, by measuring the energy of the isomer and shedding light on the structure of the nucleus. In this work, we present new, more accurate, and precise values of the half-lives of the isomeric and ground states in Cu-76. Our findings suggest that both states have very similar half-lives, in the 600-700 ms range, in disagreement with the literature values, implying that they cannot be differentiated by their decay curves. These results raise more questions than they answer, reopening the debate and showing that the structures in Cu-76 are still not fully understood.
|
|
|
|
Zhang, G. et al, Algora, A., Nacher, E., Orrigo, S. E. A., Perez-Vidal, R. M., & Rubio, B. (2025). Approaching 100Sn: Structural evolution in 98,100Cd via lifetime measurements. Phys. Lett. B, 863, 139378–7pp.
Abstract: The lifetimes of low-lying excited states below the 8(+) seniority isomer were directly measured using fast timing detectors in the neutron-deficient isotopes Cd-98,Cd-100. This experiment was conducted with the DEcay SPECtroscopy (DESPEC) setup at GSI, where the ions of interest were produced via a fragmentation reaction and identified using the FRagment Separator (FRS) before being implanted in the AIDA active stopper system, and the gamma rays emitted during the de-excitation of isomeric states were detected by the LaBr3 FATIMA Array. The newly deduced values for the reduced transition probabilities were compared with shell-model calculations using different interactions and effective charges. The results indicate that, while Cd-98 aligns well with a seniority scheme description, in Cd-100 the transition strengths among low-lying states are not fully reproduced, and the nature of these states remains an open problem within the present theoretical description. Ultimately, a key element in the description of this region, crucial for nuclear physics and astrophysics, appears to be the proton-neutron term of the nuclear effective interaction.
|
|
|
|
R3B Collaboration(Ponnath, L. et al), & Nacher, E. (2024). Measurement of nuclear interaction cross sections towards neutron-skin thickness determination. Phys. Lett. B, 855, 138780–6pp.
Abstract: The accuracy of reaction theories used to extract properties of exotic nuclei from scattering experiments is often unknown or not quantified, but of utmost importance when, e.g., constraining the equation of state of asymmetric nuclear matter from observables as the neutron-skin thickness. In order to test the Glauber multiple-scattering model, the total interaction cross section of C-12 on carbon targets was measured at initial beam energies of 400, 550, 650, 800, and 1000 MeV/nucleon. The measurements were performed during the first experiment of the newly constructed (RB)-B-3 (Reaction with Relativistic Radioactive Beams) experiment after the start of FAIR Phase-0 at the GSI/FAIR facility with beam energies of 400, 550, 650, 800, and 1000 MeV/nucleon. The combination of the large-acceptance dipole magnet GLAD and a newly designed and highly efficient Time-of-Flight detector enabled a precise transmission measurement with several target thicknesses for each initial beam energy with an experimental uncertainty of +/- 0.4%. A comparison with the Glauber model revealed a discrepancy of around 3.1% at higher beam energies, which will serve as a crucial baseline for the model-dependent uncertainty in future fragmentation experiments.
|
|
|
|
Jungclaus, A., Doornenbal, P., Acosta, J., Vaquero, V., Browne, F., Cortes, M. L., et al. (2024). Position of the single-particle 3/2- state in 135Sn and the N = 90 subshell closure. Phys. Lett. B, 851, 138561–5pp.
Abstract: The decay of excited states of the nucleus Sn-135, with three neutrons outside the doubly-magic Sn-132 core, was studied in an experiment performed at the Radioactive Isotope Beam Factory at RIKEN. Several gamma rays emitted from excited Sn-135 ions were observed following one-neutron and one-neutron-one-proton removal from Sn-136 and Sb-137 beams, respectively, on a beryllium target at relativistic energies. Based on the analogy to 133Sn populated via one-neutron removal from Sn-134, an excitation energy of 695(15) keV is assigned to the 3/2(-) state with strongest single-particle character in 135Sn. This result provides the first direct information about the evolution of the neutron shell structure beyond N = 82 and thus allows for a crucial test of shellmodel calculations in this region. The experimental findings are in full agreement with calculations performed employing microscopic effective two-body interactions derived from CD-Bonn and N3LO nucleon-nucleon potentials, which do not predict a pronounced subshell gap at neutron number N=90. The occurrence of such a gap in Sn-140, i.e., when the 1f(7/2) orbital is completely filled, had been proposed in the past, in analogy to the magicity of Ca-48, featuring a completely filled 0f(7/2) orbital one harmonic oscillator shell below.
|
|
|
|
Yue, Z. et al, Algora, A., & Nacher, E. (2024). Magnetic moments of thallium isotopes in the vicinity of magic N=126. Phys. Lett. B, 849, 138452–7pp.
Abstract: The magnetic dipole moments (mu) of Tl-209(g)(N =128) and Tl-207(m)(N = 126) have been measured for the first time using the in -source laser resonance -ionization spectroscopy technique with the Laser Ion Source and Trap (LIST) at ISOLDE (CERN). The application of the LIST suppresses the usually overwhelming background of the isobaric francium isotopes and allows access to heavy thallium isotopes with >207. The self -consistent theory of finite Fermi systems based on the energy density functional by Fayans et al. well describes the N dependence of μfor 1/2(+) thallium ground states, as well as μfor the 11/2(-) isomeric states in europium, gold and thallium isotopes. The inclusion of particle-vibration coupling leads to a better agreement between the theory and experiment for mu(Tl-g , I-pi = 1/2(+)). It is shown that beyond mean-field contributions tocannot be neglected at least for thallium isotopes with I-pi = 1/2(+).
|
|
|
|
Algora, A., Ganioglu, E., Sarriguren, P., Guadilla, V., Fraile, L. M., Nacher, E., et al. (2021). Total absorption gamma-ray spectroscopy study of the beta-decay of Hg-186. Phys. Lett. B, 819, 136438–7pp.
Abstract: The Gamow-Teller strength distribution of the decay of Hg-186 into Au-186 has been determined for the first time using the total absorption gamma spectroscopy technique and has been compared with theoretical QRPA calculations using the SLy4 Skyrme force. The measured Gamow-Teller strength distribution and the half-life are described by mixing oblate and prolate configurations independently in the parent and daughter nuclei. In this theoretical framework the best description of the experimental beta strength is obtained with dominantly prolate components for both parent Hg-186 and daughter Au-186. The approach also allowed us to determine an upper limit of the oblate component in the parent state. The complexity of the analysis required the development of a new approach in the analysis of the X-ray gated total absorption spectrum.
|
|
|
|
R3B Collaboration(Benlliure, J. et al), Cortina-Gil, D., & Nacher, E. (2025). Fission studies using quasi-free NN scattering reactions in inverse kinematics. Nucl. Phys. A, 1063, 123173–5pp.
Abstract: The combined use of the inverse kinematics technique and the advanced detection setup R3B (Reactions with Relativistic Radioactive Beams) at GSI/FAIR provides unique opportunities to study the fission process. This approach provides access to the complete isotopic identification of the two fission fragments, the precise determination of their velocities and the measurement of the neutrons and gammas emitted in coincidence, for a wide range of unstable fissile nuclei. In addition, quasi-free NN scattering represents a surrogate reaction to induce fission, allowing the complete identification of the fissioning system in terms of isotopic composition and excitation energy. The manuscript describes the technical realisation of these experiments as well as the physics programme and some preliminary results.
|
|
