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Neutron-induced fission reactions play a crucial role in a variety of fields of fundamental and applied nuclear science. In basic nuclear physics they provide important information on properties of nuclear matter, while in nuclear technology they are at the basis of present and future reactor designs. Finally, there is a renewed interest in fission reactions in nuclear astrophysics due to the multi-messenger observation of neutron star mergers and the important role played by fission recycling in r-process nucleosynthesis. Although studied for several decades, many fundamental questions still remain on fission reactions, while modern applications and the development of more reliable nuclear models require high-accuracy and consistent experimental data on fission cross sections and other fission observables. To address these needs, an extensive fission research programme has been carried out at the n_TOF neutron time-of-flight facility at CERN during the last 18 years, taking advantage of the high energy resolution, high luminosity and wide energy range of the neutron beam, as well as of the detection and data acquisition systems designed for this purpose. While long-lived isotopes are studied on the 185 m long flight-path, the recent construction of a second experimental area at a distance of about 19 m has opened the way to challenging measurements of short-lived actinides. This article provides an overview of the n_TOF experimental programme on neutron-induced fission reactions along with the main characteristics of the facility, the various detection systems and data analysis techniques used. The most important results on several major and minor actinides obtained so far and the future perspectives of fission measurements at n_TOF are presented and discussed. [ABSTRACT FROM AUTHOR]

The U neutron-induced fission cross-section has been measured at incident neutron energies of 452, 550, 651 keV and 7.5, 8.7, 10 MeV using the Li ( p, n) and the H( d, n) reactions, respectively, relative to the U( n, f ) and U( n, f ) reference reactions. The measurement was performed at the neutron beam facility of the National Center for Scientific Research 'Demokritos', using a set-up based on Micromegas detectors. The active mass of the actinide samples and the corresponding impurities were determined via $ \alpha$ -spectroscopy using a surface barrier silicon detector. The neutron spectra intercepted by the actinide samples have been thoroughly studied by coupling the NeuSDesc and MCNP5 codes, taking into account the energy and angular straggling of the primary ion beams in the neutron source targets in addition to contributions from competing reactions ( e.g. deuteron break-up) and neutron scattering in the surrounding materials. Auxiliary Monte Carlo simulations were performed making combined use of the FLUKA and GEF codes, focusing particularly on the determination of the fission fragment detection efficiency. The developed methodology and the final results are presented. [ABSTRACT FROM AUTHOR]

We investigated maternal body size and environmental effects on the oocyte size of the Atlantic sardine, Sardina pilchardus, a marine pelagophil, using a novel, oocyte stage-specific approach which takes into account the spawning lag. In particular, we focused on anatomical constraints imposed by the maternal body cavity to the growth of the ovary and its oocytes during the course of vitellogenesis (VIT) and oocyte maturation (OM). We analyzed variability in oocyte size in VIT and OM ovaries as a factor of maternal size, ambient temperature (SST) and preservation medium (formalin vs. ethanol) using the spawning lag of recent and imminent spawners, respectively, as a covariate. We showed that oocyte size correlates with maternal size in OM ovaries but not in VIT ovaries. More specifically, 10 cm difference in maternal body length corresponds to 0.112 mm (or 12 %) difference in the cross section of fully hydrated oocytes just previous to ovulation. On the other hand there was no inverse relationship between OM oocyte size at spawning and batch fecundity. Ambient SST was not an important determinant of hydrated oocyte size since the same 12 % difference in oocyte size was estimated for the entire SST range of the study. We suggest that these stage-specific differences in the effect of maternal size on oocyte size are due to a functional relationship between the abdominal volume and ovarian size. [ABSTRACT FROM AUTHOR]