The Study Of Low Energy D-D Nuclear Fusion Reactions In Metals

The reaction rates of low energy nuclear reactions play one of the most importantroles in nuclear synthesis in stellar environments.Measurements for the cross sectionof the light nuclear reactions at very low energies have shown a significantenhancement over the values extrapolated from the cross section measured at higherenergies.The enhancement was considered to be due to a large screening potential.However,the deduced values of the screening potential exceed theoretically predictedones for many reactions.The experimental and theoretical studies of the screeningeffects in charged-particle induced reactions at energies of astrophysical interest aresystematically reviewed.Moreover,extraordinary large screening is required to consider for D-D reactionsin various metal environments.The origin of the large screening effect has not beenunderstood,yet.Thus,investigations of low energy reactions in various conditions ofsurroundings are very important.In order to investigate the interaction between nuclei and their surroundings,deuteron induced fusion reactions in metallic environments have been studied at verylow energies using a low-energy high-current ion beam generator at the Laboratory ofNuclear Science of Tohoku University.The screening potentials of D (d,p) T reactionin Sm,Al,Dy,Ag,Be,Rh,Yb and Zr metals in energy region 10～20 keV weremeasured,considering the effect of the deuteron density distribution in the metalsurface.The deduced screening potentials are extraordinary large,which cannot besimply interpreted by the electron screening.So an improved theory is highly desired.The excitation functions of the D (d,p) T reaction in such low energy region indifferent metals were deduced.Moreover,the screening potentials of the D (d,p) Treaction in special materials Pd,PdO,Pd-Re-Pd and Pd-SWCNT in energy region 5～10 keV were studies.In addition,the kinematic measurements of D (d,p) T reactionin different metals were performed.The yield ratios of protons to tritons in D (d.p) Treaction were measured at a fixed angle.The ratio is equal to the ratio of solid angle ratio of protons to tritons,and depends only on the emitting angle with respect to thedeuteron direction as well as the collision energy.A deviation of the ratio from asimple kinematical calculation was examined in detail by including the multiplescattering effects.These measurements showed that low energy nuclear reactions arestrongly affected by the metallic environment and huge amounts of energy in thecondensed matter scale might be converted to the colliding two-body system.MonteCarlo simulations,which include an electronic energy loss process together withnuclear energy loss and scattering processes,have been carried out.The standardcalculation which using a universal potential between a deuteron and a host metalatom reduced the ratio significantly.But the observed deviations cannot be fullyexplained.In order to reduce the ratio,a strongly screened potential as deduced for theD-D reaction in metal was examined.