n_TOF Collaboration(Alcayne, V. et al), Caballero-Ontanaya, L., Domingo-Pardo, C., Ladarescu, I., & Tain, J. L. (2024). Measurement and analysis of the 246Cm and 248Cm neutron capture cross-sections at the EAR2 of the n_TOF facility at CERN. Eur. Phys. J. A, 60(12), 246–20pp.
Abstract: The 246Cm(n,γ) and 248Cm(n,γ) cross-sections have been measured at the Experimental Area 2 (EAR2) of the nTOF facility at CERN with three C6D6 detectors. This measurement is part of a collective effort to improve the capture cross-section data for Minor Actinides (MAs), which are required to estimate the production and transmutation rates of these isotopes in light water reactors and innovative reactor systems. In particular, the neutron capture in 246Cm and 248Cm open the path for the formation of other Cm isotopes and heavier elements such as Bk and Cf and the knowledge of (n,γ) cross-sections of these Cm isotopes plays an important role in the transport, transmutation and storage of the spent nuclear fuel. The reactions 246Cm(n,γ) and 248Cm(n,γ) have been the two first capture measurements analyzed at nTOF EAR2. Until this experiment and two recent measurements performed at J-PARC, there was only one set of data of the capture cross-sections of 246Cm and 248Cm, that was obtained in 1969 in an underground nuclear explosion experiment. In the measurement at n_TOF a total of 13 resonances of 246Cm between 4 and 400 eV and 5 of 248Cm between 7 and 100 eV have been identified and fitted. The radiative kernels obtained for 246Cm are compatible with JENDL-5, but some of them are not with JENDL-4, which has been adopted by JEFF-3.3 and ENDF/B-VIII.0. The radiative kernels obtained for the first three 248Cm resonances are compatible with JENDL-5, however, the other two are not compatible with any other evaluation and are 20% and 60% larger than JENDL-5.
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n_TOF Collaboration(Sosnin, N. V. et al), Babiano-Suarez, V., Caballero-Ontanaya, L., Domingo-Pardo, C., Ladarescu, I., & Tain, J. L. (2024). Measurement of the 78Se(n, γ)79Se cross section up to 600 keV at the n_TOF facility at CERN. Phys. Rev. C, 110(6), 065805–12pp.
Abstract: The Se-78(n, gamma)Se-79 cross section has a high impact on the abundances of Se-78 produced during the slow neutron capture process (s process) in massive stars. A measurement of the Se-78 radiative neutron capture cross section has been performed at the Neutron Time-of-Flight facility at CERN using a set of liquid scintillation detectors that have been optimized for a low sensitivity to neutrons. We present resonance capture kernels up to 70 keV and cross section from 70 to 600 keV. Maxwellian-averaged cross section (MACS) values were calculated for stellar temperatures between kT = 5 and 100 keV, with uncertainties between 4.6% and 5.8%. The new MACS values result in substantial decreases of 20-30% of Se-78 abundances produced in the s process in massive stars and AGB stars. Massive stars are now predicted to produce subsolar Se-78/Se-76 ratios, which is expected since Se-76 is an s-only isotope, while solar Se-78 abundances have also contributions from other nucleosynthesis processes.
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Tolosa-Delgado, A. et al, Tain, J. L., Agramunt, J., Algora, A., Domingo-Pardo, C., Morales, A. I., et al. (2025). Impact of Newly Measured β-Delayed Neutron Emitters around 78Ni on Light Element Nucleosynthesis in the Neutrino Wind Following a Neutron Star Merger. Phys. Rev. Lett., 134(17), 172701–11pp.
Abstract: Neutron emission probabilities and half-lives of 37 /3-delayed neutron emitters from 75Ni to 92Br were measured at the RIKEN Nishina Center in Japan, including 11 one-neutron and 13 two-neutron emission probabilities and six half-lives for the first time that supersede theoretical estimates. These nuclei lie in the path of the weak r process occurring in neutrino-driven winds from the accretion disk formed after the merger of two neutron stars synthesizing elements in the A 80 abundance peak. The presence of such elements dominates the accompanying kilonova emission over the first few days and have been identified in the AT2017gfo event, associated to the gravitational wave detection GW170817. Abundance calculations based on over 17 000 simulated trajectories describing the evolution of matter properties in the merger outflows show that the new data lead to an increase of 50%-70% in the abundance of Y, Zr, Nb, and Mo. This enhancement is large compared to the scatter of relative abundances observed in old very metal poor stars and thus is significant in the comparison with other possible astrophysical processes contributing to the light-element production. These results underline the importance of including experimental decay data for very neutron-rich /3-delayed neutron emitters into r-process models.
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AGATA Collaboration(Akkoyun, S. et al), Algora, A., Barrientos, D., Domingo-Pardo, C., Egea, F. J., Gadea, A., et al. (2012). AGATA-Advanced GAmma Tracking Array. Nucl. Instrum. Methods Phys. Res. A, 668, 26–58.
Abstract: The Advanced GAmma Tracking Array (AGATA) is a European project to develop and operate the next generation gamma-ray spectrometer. AGATA is based on the technique of gamma-ray energy tracking in electrically segmented high-purity germanium crystals. This technique requires the accurate determination of the energy, time and position of every interaction as a gamma ray deposits its energy within the detector volume. Reconstruction of the full interaction path results in a detector with very high efficiency and excellent spectral response. The realisation of gamma-ray tracking and AGATA is a result of many technical advances. These include the development of encapsulated highly segmented germanium detectors assembled in a triple cluster detector cryostat, an electronics system with fast digital sampling and a data acquisition system to process the data at a high rate. The full characterisation of the crystals was measured and compared with detector-response simulations. This enabled pulse-shape analysis algorithms, to extract energy, time and position, to be employed. In addition, tracking algorithms for event reconstruction were developed. The first phase of AGATA is now complete and operational in its first physics campaign. In the future AGATA will be moved between laboratories in Europe and operated in a series of campaigns to take advantage of the different beams and facilities available to maximise its science output. The paper reviews all the achievements made in the AGATA project including all the necessary infrastructure to operate and support the spectrometer.
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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.
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