Solid-state effects in d+d fusion reactions

Abstract

The nuclear fusion reactions 2 H( d, p) 3 H and 2 H( d, n) 3 He have been measured at projectile energies between 5 and 60 keV using deuteron-implanted solid targets (C, Al, Zr and Ta). An exponential-like enhancement of the reaction cross-section compared to the bare nuclei fusion could be observed for energies below 20 keV. This effect may be interpreted as a result of the electron screening of the Coulomb barrier between reacting deuterons and described by a screening energy U e. The experimentally determined U e values show a clear target-material dependence and reach for heavier materials values being one order of magnitude larger than the value achieved in a gas target experiment and significantly larger than the theoretical predictions. Specific solid-state contributions to the enhancement of the fusion cross-sections arising from the channeling of projectiles in the crystal lattice and some other related effects will be discussed.