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n_TOF Collaboration(Zugec, P. et al), Domingo-Pardo, C., Giubrone, G., & Tain, J. L. (2016). Integral measurement of the C-12(n, p)B-12 reaction up to 10 GeV. Eur. Phys. J. A, 52(4), 101–13pp.
Abstract: The integral measurement of the C-12(n, p)B-12 reaction was performed at the neutron time-of-flight facility nTOF at CERN. The total number of B-12 nuclei produced per neutron pulse of the nTOF beam was determined using the activation technique in combination with a time-of-flight technique. The cross section is integrated over the n_TOF neutron energy spectrum from reaction threshold at 13.6 MeV to 10 GeV. Having been measured up to 1 GeV on basis of the U-235(n, f) reaction, the neutron energy spectrum above 200 MeV has been re-evaluated due to the recent extension of the cross section reference for this particular reaction, which is otherwise considered a standard up to 200 MeV. The results from the dedicated GEANT4 simulations have been used to evaluate the neutron flux from 1 GeV up to 10 GeV. The experimental results related to the C-12(n, p)B-12 reaction are compared with the evaluated cross sections from major libraries and with the predictions of different GEANT4 models, which mostly underestimate the B-12 production. On the contrary, a good reproduction of the integral cross section derived from measurements is obtained with TALYS-1.6 calculations, with optimized parameters.
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Jordan, D., Algora, A., & Tain, J. L. (2016). An event generator for simulations of complex beta-decay experiments. Nucl. Instrum. Methods Phys. Res. A, 828, 52–57.
Abstract: This article describes a Monte Carlo event generator for the design, optimization and performance characterization of beta decay spectroscopy experimental set-ups. The event generator has been developed within the Geant4 simulation architecture and provides new features and greater flexibility in comparison with the current available decay generator.
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Caballero-Folch, R. et al, Domingo-Pardo, C., Agramunt, J., Algora, A., Rubio, B., & Tain, J. L. (2016). First Measurement of Several beta-Delayed Neutron Emitting Isotopes Beyond N=126. Phys. Rev. Lett., 117(1), 012501–6pp.
Abstract: The beta-delayed neutron emission probabilities of neutron rich Hg and Tl nuclei have been measured together with beta-decay half-lives for 20 isotopes of Au, Hg, Tl, Pb, and Bi in the mass region N greater than or similar to 126. These are the heaviest species where neutron emission has been observed so far. These measurements provide key information to evaluate the performance of nuclear microscopic and phenomenological models in reproducing the high-energy part of the beta-decay strength distribution. This provides important constraints on global theoretical models currently used in r-process nucleosynthesis.
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Mach, H., Lindroth, A., Ruchowska, E., Kvasil, J., Fogelberg, B., Gulda, K., et al. (2016). On the enhanced E1 transitions in the K=3/2 parity doublet band in Ra-223. Eur. Phys. J. A, 52(6), 172–10pp.
Abstract: We have applied the fast timing beta gamma gamma(t) technique to remeasure lifetimes of selected states in Ra-223 populated in the beta(-) decay of Fr-223. T-1/2 = 587(12) ps and 210(13) ps have been obtained for the 3/2(-) and 5/2(-) states at 50.1 and 79.7 keV, that are more accurate than the previous values of 630(70) ps and 166(55) ps, respectively. Our vertical bar D0 vertical bar value of 0.155(10) e.fm obtained for the K = 3/2 configuration together with the available values of vertical bar D0 vertical bar for the K = 1/2 and K = 5/2 parity doublet bands establish the configuration dependence of vertical bar D0 vertical bar at low spins in this nucleus. Results of theoretical calculations performed for Ra-223, using the quasiparticle-phonon model (QPM) with inclusion of the Coriolis coupling, reasonably well reproduce octupole correlations in this nucleus.
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n_TOF Collaboration(Cosentino, L. et al), Domingo-Pardo, C., Tain, J. L., & Tarifeño-Saldivia, A. (2016). Experimental setup and procedure for the measurement of the Be-7(n,alpha)alpha reaction at n_TOF. Nucl. Instrum. Methods Phys. Res. A, 830, 197–205.
Abstract: The newly built second experimental area EAR2 of then n_ToF spallation neutron source at CERN allows to perform (n, charged particles) experiments on short-lived highly radioactive targets. This paper describes a detection apparatus and the experimental procedure for the determination of the cross-section of the Be-7(n,alpha)alpha reaction, which represents one of the focal points toward the solution of the cosmological Lithium abundance problem, and whose only measurement, at thermal energy, dates back to 1963. The apparently unsurmountable experimental difficulties stemming from the huge Be-7 gamma-activity, along with the lack of a suitable neutron beam facility, had so far prevented further measurements. The detection system is subject to considerable radiation damage, but is capable of disentangling the rare reaction signals from the very high background. This newly developed setup could likely be useful also to study other challenging reactions requiring the detectors to be installed directly in the neutron beam.
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