The fusion reactions 6Li (p, cQ3He, 6Li(d,~)4He, and 7Li(p, c~)4He have been studied over the c.m. energy range E = 10 to 1450 keV. Each reaction involved the use of hydrogen projectiles and LiF solid targets as well as Li projectiles and hydrogen molecular gas targets. In all cases the effects of electron screening on the low-energy fusion cross sections (exponential enhancement) have been observed; the effects are somewhat stronger in the case of atomic p or d projectiles compared to the case of molecular H 2 or D2 gas targets. If isotopic effects on electron screening are negligible, all three reactions should exhibit the same enhancements for each set of experimental techniques. The measurements confirmed this expectation to a large extent.

Abstract. The fusion reactions l~ ~) 7Be and liB(p, ~) 8Be have been studied over the c.m. energy range E = 17 to 134 keV using intense proton beams and thick solid targets. In the case of liB(p, 0~) 8Be the low-energy data in terms of the astrophysical S (E) factor show an exponential enhancement (up to a factor of 1.9) due to the effects of electron screening, where the deduced screening potential is larger than expected. In the case of l~ c 0 7Be the low-energy data exhibit an enhancement by more than a factor of 200, which cannot be explained by the effects of electron screening. The enhancement arises here from the high-energy tail of an expected s-wave resonance at ER = 10 keV. The results offer an improved prospect for this reaction as advanced fuel in future fusion reactors than previously envisioned.

No abstract