Nuclear processes in magnetic fusion reactors with polarized fuel

We consider the processes $d +d \to n +{^3He}$, $d +{^3He} \to p +{^4He}$, $d +{^3H} \to n +{^4He}$, ${^3He} +{^3He}\to p+p +{^4He}$, ${^3H} +{^3He}\to d +{^4He}$, with particular attention for applications in fusion reactors. After a model independent parametrization of the spin structure of the matrix elements for these processes at thermal colliding energies, in terms of partial amplitudes, we study polarization phenomena in the framework of a formalism of helicity amplitudes. The strong angular dependence of the final nuclei and of the polarization observables on the polarizations of the fuel components can be helpful in the design of the reactor shielding, blanket arrangement etc..We analyze also the angular dependence of the neutron polarization for the processes $\vec d +\vec d \to n +{^3He}$ and $\vec d +\vec {^3H} \to n +{^4He}$.Comment: 33 pages 4 figure

No-Core Shell Model Analysis of Light Nuclei

The fundamental description of both structural properties and reactions of light nuclei in terms of constituent protons and neutrons interacting through nucleon-nucleon and three-nucleon forces is a long-sought goal of nuclear theory. I will briefly present a promising technique, built upon the {\em ab initio} no-core shell model, which emerged recently as a candidate to reach such a goal: the no-core shell model/resonating-group method. This approach, capable of describing simultaneously both bound and scattering states in light nuclei, complements a microscopic cluster technique with the use of two-nucleon realistic interactions, and a microscopic and consistent description of the nucleon clusters. I will discuss applications to light nuclei binary scattering processes and fusion reactions that power stars and Earth based fusion facilities, such as the deuterium-$^3$He fusion, and outline the progress toward the inclusion of the three-nucleon force into the formalism and the treatment of three-body clusters.Comment: 8 pages, 6 figures, Proceedings of the 20th International IUPAP Conference on Few-Body Problems in Physics, 20 - 25 August, 2012, Fukuoka, Japa

Ab Initio Theory of Light-ion Reactions

The exact treatment of nuclei starting from the constituent nucleons and the fundamental interactions among them has been a long-standing goal in nuclear physics. Above all nuclear scattering and reactions, which require the solution of the many-body quantum-mechanical problem in the continuum, represent a theoretical and computational challenge for ab initio approaches. After a brief overview of the field, we present a new ab initio many-body approach capable of describing simultaneously both bound and scattering states in light nuclei. By combining the resonating-group method with the ab initio no-core shell model, we complement a microscopic cluster technique with the use of realistic interactions and a microscopic and consistent description of the clusters. We show results for neutron and proton scattering on light nuclei, including p-7Be and n-8He. We also highlight the first results of the d-3He and d-3H fusion calculations obtained within this approach.Comment: To appear in the proceedings of the International Nuclear Physics Conference INPC 2010, Vancouver, Canada, July 4 - 9, 2010, 10 pages, 5 figure

Solar fusion cross sections II: the pp chain and CNO cycles

We summarize and critically evaluate the available data on nuclear fusion cross sections important to energy generation in the Sun and other hydrogen-burning stars and to solar neutrino production. Recommended values and uncertainties are provided for key cross sections, and a recommended spectrum is given for 8B solar neutrinos. We also discuss opportunities for further increasing the precision of key rates, including new facilities, new experimental techniques, and improvements in theory. This review, which summarizes the conclusions of a workshop held at the Institute for Nuclear Theory, Seattle, in January 2009, is intended as a 10-year update and supplement to Reviews of Modern Physics 70 (1998) 1265.Comment: 54 pages, 20 figures, version to be published in Reviews of Modern Physics; various typos corrected and several updates mad

Influence of the Electronic Chaotic Motion on the Fusion Dynamics at Astrophysical Energies

We perform semi-classical molecular dynamics simulations of screening by bound electrons in low energy nuclear reactions. In our simulations quantum effects corresponding to the Pauli and Heisenberg principle are enforced by constraints. In addition to the well known adiabatic and sudden limits, we propose a new "dissipative limit" which is expected to be important not only at high energies but in the extremely low energy region. The dissipative limit is associated with the chaotic behavior of the electronic motion. It affects also the magnitude of the enhancement factor. We discuss also numerical experiments using polarized targets. The derived enhancement factors in our simulation are in agreement with those extracted within the $R$-matrix approach.Comment: 17 pages, 9 figure