Jordan, D., Tain, J. L., Algora, A., Agramunt, J., Domingo-Pardo, C., Gomez-Hornillos, M. B., et al. (2013). Measurement of the neutron background at the Canfranc Underground Laboratory LSC. Astropart Phys., 42, 1–6.
Abstract: The energy distribution of the neutron background was measured for the first time at Hall A of the Canfranc Underground Laboratory. For this purpose we used a novel approach based on the combination of the information obtained with six large high-pressure He-3 proportional counters embedded in individual polyethylene blocks of different size. In this way not only the integral value but also the flux distribution as a function of neutron energy was determined in the range from 1 eV to 10 MeV. This information is of importance because different underground experiments show different neutron background energy dependence. The high sensitivity of the setup allowed to measure a neutron flux level which is about four orders of magnitude smaller that the neutron background at sea level. The integral value obtained is Phi(Hall A) = (3.44 +/- 0.35) x 10(-6) cm(-2) s(-1).
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n_TOF Collaboration(Guerrero, C. et al), Domingo-Pardo, C., Giubrone, G., & Tain, J. L. (2013). Performance of the neutron time-of-flight facility n_TOF at CERN. Eur. Phys. J. A, 49(2), 27–15pp.
Abstract: The neutron time-of-flight facility n_TOF features a white neutron source produced by spallation through 20 GeV/c protons impinging on a lead target. The facility, aiming primarily at the measurement of neutron-induced reaction cross sections, was operating at CERN between 2001 and 2004, and then underwent a major upgrade in 2008. This paper presents in detail all the characteristics of the new neutron beam in the currently available configurations, which correspond to two different collimation systems and two choices of neutron moderator. The characteristics discussed include the intensity and energy dependence of the neutron flux, the spatial profile of the beam, the in-beam background components and the energy resolution/broadening. The discussion of these features is based on dedicated measurements and Monte Carlo simulations, and includes estimations of the systematic uncertainties of the mentioned quantities.
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Guastalla, G. et al, Algora, A., & Domingo-Pardo, C. (2013). Coulomb Excitation of Sn-104 and the Strength of the Sn-100 Shell Closure. Phys. Rev. Lett., 110(17), 172501–5pp.
Abstract: A measurement of the reduced transition probability for the excitation of the ground state to the first 2(+) state in Sn-104 has been performed using relativistic Coulomb excitation at GSI. Sn-104 is the lightest isotope in the Sn chain for which this quantity has been measured. The result is a key point in the discussion of the evolution of nuclear structure in the proximity of the doubly magic nucleus Sn-100. The value B(E2; 0(+) -> 2(+)) = 0.10(4) e(2)b(2) is significantly lower than earlier results for Sn-106 and heavier isotopes. The result is well reproduced by shell model predictions and therefore indicates a robust N = Z = 50 shell closure.
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n_TOF Collaboration(Barbagallo, M. et al), Domingo-Pardo, C., Giubrone, G., & Tain, J. L. (2013). High-accuracy determination of the neutron flux at n_TOF. Eur. Phys. J. A, 49(12), 156–11pp.
Abstract: The neutron flux of the nTOF facility at CERN was measured, after installation of the new spallation target, with four different systems based on three neutron-converting reactions, which represent accepted cross sections standards in different energy regions. A careful comparison and combination of the different measurements allowed us to reach an unprecedented accuracy on the energy dependence of the neutron flux in the very wide range (thermal to 1 GeV) that characterizes the nTOF neutron beam. This is a pre-requisite for the high accuracy of cross section measurements at n_TOF. An unexpected anomaly in the neutron-induced fission cross section of U-235 is observed in the energy region between 10 and 30keV, hinting at a possible overestimation of this important cross section, well above currently assigned uncertainties.
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n_TOF Collaboration(Zugec, P. et al), Domingo-Pardo, C., Giubrone, G., & Tain, J. L. (2014). Experimental neutron capture data of Ni-58 from the CERN n_TOF facility. Phys. Rev. C, 89(1), 014605–9pp.
Abstract: The Ni-58(n,gamma) cross section has been measured at the neutron time of flight facility n_TOF at CERN, in the energy range from 27 meV up to 400 keV. In total, 51 resonances have been analyzed up to 122 keV. Maxwellian averaged cross sections (MACS) have been calculated for stellar temperatures of kT = 5-100 keV with uncertainties of less than 6%, showing fair agreement with recent experimental and evaluated data up to kT = 50 keV. The MACS extracted in the present work at 30 keV is 34.2 +/- 0.6(stat) +/- 1.8(sys) mb, in agreement with latest results and evaluations, but 12% lower relative to the recent KADoNIS compilation of astrophysical cross sections. When included in models of the s-process nucleosynthesis in massive stars, this change results in a 60% increase of the abundance of Ni-58, with a negligible propagation on heavier isotopes. The reason is that, using both the old or the new MACS, Ni-58 is efficiently depleted by neutron captures.
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