THE EFFECTS OF ELECTRON SCREENING AND RESONANCES IN (P,ALPHA) REACTIONS ON B-10 AND B-11 AT THERMAL ENERGIES

The fusion reactions B-10(p, alpha) Be-7 and B-11(p, alpha) Be-8 have been studied over the c.m. energy range E = 17 to 134 keV using intens e proton beams and thick solid targets. In the case of B-11(p, alpha) Be-8 the low-energy data in terms of the astrophysical S(E) factor sho w an exponential enhancement (up to a factor of 1.9) due to the effect s of electron screening, where the deduced screening potential is larg er than expected. In the case of B-10(p, alpha) Be-7 the low-energy da ta exhibit an enhancement by more than a factor of 200, which cannot b e explained by the effects of electron screening. The enhancement aris es here from the high-energy tail of an expected s-wave resonance at E (R) = 10 keV The results offer an improved prospect for this reaction as advanced fuel in future fusion reactors than previously envisioned.