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The rapid neutron capture process (r process) is believed to be responsible for about half of the production of the elements heavier than iron and contributes to abundances of some lighter nuclides as well. A universal pattern of r -process element abundances is observed in some metal-poor stars of the Galactic halo. This suggests that a well-regulated combination of astrophysical conditions and nuclear physics conspires to produce such a universal abundance pattern. The search for the astrophysical site for r -process nucleosynthesis has stimulated interdisciplinary research for more than six decades. There is currently much enthusiasm surrounding evidence for r -process nucleosynthesis in binary neutron star mergers in the multi-wavelength follow-up observations of kilonova/gravitational-wave GRB170807A/GW170817. Nevertheless, there remain questions as to the contribution over the history of the Galaxy to the current solar-system r -process abundances from other sites such as neutrino-driven winds or magnetohydrodynamical ejection of material from core-collapse supernovae. In this review we highlight some current issues surrounding the nuclear physics input, astronomical observations, galactic chemical evolution, and theoretical simulations of r -process astrophysical environments with the goal of outlining a path toward resolving the remaining mysteries of the r process. [ABSTRACT FROM AUTHOR]

The High-Altitude Water Cherenkov (HAWC) observatory is a second-generation continuously operated, wide field-of-view, TeV gamma-ray observatory. The HAWC observatory and its analysis techniques build on experience of the Milagro experiment in using ground-based water Cherenkov detectors for gamma-ray astronomy. HAWC is located on the Sierra Negra volcano in México at an elevation of 4100 meters above sea level. The completed HAWC observatory principal detector (HAWC) consists of 300 closely spaced water Cherenkov detectors, each equipped with four photomultiplier tubes to provide timing and charge information to reconstruct the extensive air shower energy and arrival direction. The HAWC observatory has been optimized to observe transient and steady emission from sources of gamma rays within an energy range from several hundred GeV to several hundred TeV. However, most of the air showers detected are initiated by cosmic rays, allowing studies of cosmic rays also to be performed. This paper describes the characteristics of the HAWC main array and its hardware. [ABSTRACT FROM AUTHOR]

Nuclear masses are the most fundamental of all nuclear properties, yet they can provide a wealth of knowledge, including information on astrophysical sites, constraints on existing theory, and fundamental symmetries. In nearly all applications, it is necessary to measure nuclear masses with very high precision. As mass measurements push to more short-lived and more massive nuclei, the practical constraints on mass measurement techniques become more exacting. Various techniques used to measure nuclear masses, including their advantages and disadvantages are described. Descriptions of some of the world facilities at which the nuclear mass measurements are performed are given, and brief summaries of planned facilities are presented. Future directions are mentioned, and conclusions are presented which provide a possible outlook and emphasis on upcoming plans for nuclear mass measurements at existing facilities, those under construction, and those being planned. [ABSTRACT FROM AUTHOR]

Abstract: The HELIOS irradiation experiment is the latest of a series of experiments on americium transmutation, and has been carried out in the framework of EURATOM’s 6th Framework Programme (FP6) project EUROTRANS, which was completed in March 2010. The transmutation of Minor Actinide (MA) is a fundamental step in order to be able to close the cycle of the nuclear fuel. Past experimental activities in the field of transmutation and testing of innovative nuclear fuel containing Am has proved that the release or trapping of helium is a key issue for the design of such kind of fuel or targets. Therefore, the main objective of the HELIOS experiment is the study of the in-pile behaviour of U-free fuels, such as (Pu,Am,Zr,Y)O2 or (Am,Zr,Y)O2, CERCER (Am2Zr2O7+MgO), CERMET ((Pu,Am)O2+Mo) or ((Am,Zr,Y)O2+Mo), to gain knowledge on the role of the fuel microstructure and of the operating temperature on gas release and fuel swelling. The HELIOS irradiation experiment started in the HFR (High Flux Reactor) in Petten (The Netherlands) on the 29th of April 2010 and finished on the 19th of February after 9 reactor cycles (∼241 full power days). Although the Post-Irradiation Examination (not performed yet) conducted on the CERCER and CERMET target fuel tested during the HELIOS irradiation experiment will determine the performance of the fuel, the behaviour of such targets during the irradiation did not show any difficulties. It is possible to conclude that from an operational point of view, these kinds of fuel targets which have been developed mainly having in mind the possibility to burn MA in a in a subcritical nuclear system, did not show significant issues. This paper summarises the main experimental data obtained during the 9 cycle irradiation of the HELIOS experiment in the HFR. [Copyright &y& Elsevier]