We describe RAGE, the "Radiation Adaptive Grid Eulerian" radiation-hydrodynamics code, including its data structures, its parallelization strategy and performance, its hydrodynamic algorithm(s), its (gray) radiation diffusion algorithm, and some of the considerable amount of verification and validation efforts. The hydrodynamics is a basic Godunov solver, to which we have made significant improvements to increase the advection algorithm's robustness and to converge stiffnesses in the equation of state. Similarly, the radiation transport is a basic gray diffusion, but our treatment of the radiation-material coupling, wherein we converge nonlinearities in a novel manner to allow larger timesteps and more robust behavior, can be applied to any multi-group transport algorithm.

Mass spectrometric methods have long been suggested as ways of measuring (14)C/(12)C ratios for carbon dating. One problem has been to distinguish between (14)N and (14)C. With negative ions and a tandem electrostatic accelerator, the (14)N background is virtually absent and fewer than three (14)C atoms in 10(16) atoms of (12)C have been easily measured.

The elastic and inelastic scattering of 12C on 12C has been measured in the angular range between 2.8 ~ and 70.4 ~ in the c.m. system at EL, b=300MeV. Optical model calculations have been performed with Woods-Saxon and folded potentials, the ground state and the first 2 § were coupled in the calculations. The large cross sections of the elastic scattering at large angles is related to the nuclear rainbow scattering, which is centered at about 56 ~ This requires a potential depth of 100 MeV at a distance of 3 fm, the fit to the data is sensitive down to this region. The calculations with the folded potential show a better agreement with the data than those with the Woods-Saxon shape. The total reaction cross section of 1,420mb, obtained from the optical model analysis, corresponds to the geometrical value; no transparency is observed.

2014 Dans cette communication on discute d'une expérience où l'on fait une recherche d'ions 14Nen presence d'un faisceau intense de carbone. On utilise une source d'ions Middleton à sputtering. Malgré un champ accélérateur de 1,5 MV/m nous n'avons pas trouvé d'ions azote négatifs avec des intensités détectables. La publication indique aussi les conditions que doivent remplir l'accélérateur si on veut bénéficier pleinement de ce résultat négatif afin de faire des mesures avec des faisceaux très faibles de 14C.Abstract. 2014 The present paper discusses an experiment, using a Middleton sputter ion source, where a sensitive search was made for 14Nions in the presence of an intense carbon beam. It was found that negative nitrogen ions, capable of withstanding acceleration fields of 1.5 MV/m, were not produced in detectable intensities. The paper also points out some design requirements of tandem facilities that must be satisfied if full advantage is to be taken of this negative result to permit the measurement of very weak 14C beams.

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