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n_TOF Collaboration(Weiss, C. et al), Domingo-Pardo, C., Giubrone, G., & Tain, J. L. (2014). The (n,alpha) Reaction in the s-process Branching Point Ni-59. Nucl. Data Sheets, 120, 208–210.
Abstract: The (n,alpha) reaction in the radioactive Ni-59 is of relevance in nuclear astrophysics as Ni-59 can be considered as the first branching point in the astrophysical s-process. Its relevance in nuclear technology is especially related to material embrittlement in stainless steel. However, there is a discrepancy between available experimental data and the evaluated nuclear data files for this reaction. At the n_TOF facility at CERN, a dedicated system based on sCVD diamond diodes was set up to measure the Ni-59(n,alpha)Fe-56 cross section. The results of this measurement, with special emphasis on the dominant resonance at 203 eV, are presented here.
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n_TOF Collaboration(Weiss, C. et al), Domingo-Pardo, C., Tain, J. L., & Tarifeño-Saldivia, A. (2015). The new vertical neutron beam line at the CERN n_TOF facility design and outlook on the performance. Nucl. Instrum. Methods Phys. Res. A, 799, 90–98.
Abstract: At the neutron Lime-of-flight facility n_TOF at CERN a new vertical beam line was constructed in 2014, in order to extend the experimental possibilities at this facility to an even wider range of challenging cross-section measurements of interest in astrophysics, nuclear technology and medical physics. The design of the beam line and the experimental hall was based on FLUKA Monte Carlo simulations, aiming at maximizing the neutron flux, reducing the beam halo and minimizing the background from neutrons interacting with the collimator or back-scattered in the beam dump. The present paper gives an overview on the design of the beam line and the relevant elements and provides an outlook on the expected performance regarding the neutron beam intensity, shape and energy resolution, as well as the neutron and photon backgrounds.
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Weber, M. et al, & Esperante, D. (2024). DONES EVO: Risk mitigation for the IFMIF-DONES facility. Nucl. Mater. Energy, 38, 101622–5pp.
Abstract: The International Fusion Materials Irradiation Facility- DEMO Oriented Neutron Source (IFMIF-DONES) is a scientific infrastructure aimed to provide an intense neutron source for the qualification of materials to be used in future fusion power reactors. Its implementation is critical for the construction of the fusion DEMOnstration Power Plant (DEMO). IFMIF-DONES is a unique facility requiring a broad set of technologies. Although most of the necessary technologies have already been validated, there are still some aspects that introduce risks in the evolution of the project. In order to mitigate these risks, a consortium of companies, with the support of research centres and the funding of the CDTI (Centre for the Development of Industrial Technology and Innovation), has launched the DONES EVO Programme, which comprises six lines of research: center dot Improvement of signal transmission and integrity (planning and integration risks) center dot Optimisation of RF conditioning processes (planning and reliability risks) center dot Development of a reliable beam extraction device (reliability risks) center dot Development of technologies for the production of medical isotopes (reliability risks) center dot Improvement of critical parts of the lithium purification system (safety and reliability risks) center dot Validation of the manufacture of critical components with special materials (reliability risk). DONES EVO will focus on developing the appropriate response to the risks identified in the IFMIFDONES project through research and prototyping around the associated technologies.
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Watanabe, H., Watanabe, Y. X., Hirayama, Y., Andreyev, A. N., Hashimoto, T., Kondev, F. G., et al. (2021). Beta decay of the axially asymmetric ground state of Re-192. Phys. Lett. B, 814, 136088–6pp.
Abstract: The beta decay of Re-192(75)117, which lies near the boundary between the regions of predicted prolate and oblate deformations, has been investigated using the KEK Isotope Separation System (KISS) in RIKEN Nishina Center. This is the first case in which a low-energy beam of rhenium isotope has been successfully extracted from an argon gas-stopping cell using a laser-ionization technique, following production via multi-nucleon transfer between heavy ions. The ground state of Re-192 has been assigned J(pi) = (0(-)) based on the observed beta feedings and deduced logf t values towards the 0(+) and 2(+) states in Os-192, which is known as a typical gamma-soft nucleus. The shape transition from axial symmetry to axial asymmetry in the Re isotopes is discussed from the viewpoint of single-particle structure using the nuclear Skyrme-Hartree-Fock model.
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Watanabe, H. et al, & Montaner-Piza, A. (2021). Impact of shell evolution on Gamow-Teller beta decay from a high-spin long-lived isomer in Ag-127. Phys. Lett. B, 823, 136766–6pp.
Abstract: The change of the shell structure in atomic nuclei, so-called “nuclear shell evolution”, occurs due to changes of major configurations through particle-hole excitations inside one nucleus, as well as due to variation of the number of constituent protons or neutrons. We have investigated how the shell evolution affects Gamow-Teller (GT) transitions that dominate the beta decay in the region below Sn-132 using the newly obtained experimental data on a long-lived isomer in Ag-127. The T-1/2 = 67.5(9) ms isomer has been identified with a spin and parity of (27/2(+)) at an excitation energy of 1942(-20)(+14) keV, and found to decay via an internal transition of an E3 character, which competes with the dominant beta-decay branches towards the high-spin states in Cd-127. The underlying mechanism of a strong GT transition from the Ag-127 isomer is discussed in terms of configuration-dependent optimization of the effective single-particle energies in the framework of a shell-model approach.
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Watanabe, H. et al, & Montaner-Piza, A. (2014). Monopole-Driven Shell Evolution below the Doubly Magic Nucleus Sn-132 Explored with the Long-Lived Isomer in Pd-126. Phys. Rev. Lett., 113(4), 042502–6pp.
Abstract: A new isomer with a half-life of 23.0(8) ms has been identified at 2406 keV in Pd-126 and is proposed to have a spin and parity of 10(+) with a maximally aligned configuration comprising two neutron holes in the 1h(11/2) orbit. In addition to an internal-decay branch through a hindered electric octupole transition, beta decay from the long-lived isomer was observed to populate excited states at high spins in Ag-126. The smaller energy difference between the 10(+) and 7(-) isomers in Pd-126 than in the heavier N = 80 isotones can be interpreted as being ascribed to the monopole shift of the 1h(11/2) neutron orbit. The effects of the monopole interaction on the evolution of single-neutron energies below Sn-132 are discussed in terms of the central and tensor forces.
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Watanabe, H. et al, & Montaner-Piza, A. (2019). New isomers in (125)Pd(79)( )and Pd-127(81): Competing proton and neutron excitations in neutron-rich palladium nuclides towards the N=82 shell closure. Phys. Lett. B, 792, 263–268.
Abstract: The neutron-rich isotopes of palladium have attracted considerable interest in terms of the evolution of the N = 82 neutron shell closure and its influence on the r-process nucleosynthesis. In this Letter, we present the first spectroscopic information on the excited states in Pd-125(79) and Pd-127(81) studied using the EURICA gamma-ray spectrometer, following production via in-flight fission of a high-intensity U-238 beam at the RIBF facility. New isomeric states with half-lives of 144(4) ns and 39(6) μs have been assigned spins and parities of (23/2(+)) and (19/2(+)) in Pd-125 and Pd-127, respectively. The observed level properties are compared to a shell-model calculation, suggesting the competition between proton excitations and neutron excitations in the proton-hole and neutron-hole systems in the vicinity of the doubly magic nucleus Sn-132.
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Watanabe, H. et al, & Montaner-Piza, A. (2013). Isomers in Pd-128 and Pd-126: Evidence for a Robust Shell Closure at the Neutron Magic Number 82 in Exotic Palladium Isotopes. Phys. Rev. Lett., 111(15), 152501–5pp.
Abstract: The level structures of the very neutron-rich nuclei Pd-128 and Pd-126 have been investigated for the first time. In the r-process waiting-point nucleus Pd-128, a new isomer with a half-life of 5.8(8) μs is proposed to have a spin and parity of 8(+) and is associated with a maximally aligned configuration arising from the g(9/2) proton subshell with seniority v = 2. For Pd-126, two new isomers have been identified with half-lives of 0.33(4) and 0.44(3) μs. The yrast 2(+) energy is much higher in Pd-128 than in Pd-126, while the level sequence below the 8(+) isomer in Pd-128 is similar to that in the N = 82 isotone Cd-130. The electric quadrupole transition that depopulates the 8(+) isomer in Pd-128 is more hindered than the corresponding transition in Cd-130, as expected in the seniority scheme for a semimagic, spherical nucleus. These experimental findings indicate that the shell closure at the neutron number N = 82 is fairly robust in the neutron-rich Pd isotopes.
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Wasilewska, B. et al, & Gaudilla, V. (2022). gamma decay to the ground state from the excitations above the neutron threshold in the Pb-208(p, p ' gamma) reaction at 85 MeV. Phys. Rev. C, 105(1), 014310–7pp.
Abstract: A new measurement of gamma decay from the states above the neutron threshold in Pb-208 has been performed at Cyclotron Centre Bronowice in Krakow, Poland. The main goal of the experiment was to observe the gamma decay to the ground state from the isoscalar giant quadrupole resonance (ISGQR). To this day, the only published observation of this phenomenon dates back to the late 1980s, where gamma decay to the ground state branching ratio was reported. At variance with the existing measurement using inelastic scattering of O-17, here proton inelastic scattering is employed. In particular, data were obtained for Pb-208(p, p'gamma) at 85 MeV beam energy, where gamma rays were measured for proton scattering angles 8.9 degrees, 10.7 degrees, 12.5 degrees, and 14.3 degrees. By applying a similar analysis method as in the previous experiment, the branching ratio of ISGQR gamma decay to the ground state was extracted from the data.
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Warnecke, S., Sevryuk, M. B., Ceperley, D. M., Toennies, J. P., Guardiola, R., & Navarro, J. (2010). The structure of para-hydrogen clusters. Eur. Phys. J. D, 56(3), 353–358.
Abstract: The path integral Monte Carlo calculated radial distributions of para-hydrogen clusters (p-H-2) N consisting of N = 4-40 molecules interacting via a Lennard-Jones potential at T = 1.5 K show evidence for additional peaks compared to radial distributions calculated by diffusion Monte Carlo (T = 0 K) and path integral Monte Carlo at T <= 0.5 K. The difference in structures is attributed to quantum delocalization at the lowest temperature. The new structures at finite temperatures appear to be consistent with classical structures calculated for an effective Morse potential, which in order to account for the large zero point energy, is substantially softer than the Lennard-Jones potential.
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