Cross section of 3He(3He,2p)4He measured over the range of 45 to 26 keV

We have measured the nuclear fusion cross section for ³He(³He, 2p)⁴He near the solar Gamow peak with a compact accelerator facility OCEAN and with an assembly of counter telescopes with a detection efficiency of 10%. The data obtained at E_cm = 45.3 to 31.2 keV improved the existing astrophysical S-factors in statistical and systematic errors. A Monte Carlo simulation program exploiting GEANT3, SRIM and GENBOD computer codes has been developed to estimate the detection efficiency for two proton coincidences with ΔE-E telescopes. The precision of the developed program has been investigated by comparing the simulated results with the experimental values for the cross section of the D(³He,p)α reaction carried out by replacing the target with D gas. It turned out that the present study involves around 3% systematic errors for an estimation of the detection efficiency. The overall systematic errors for these data from 45.3 to 31.2 keV is 3.8%, that is as good as those of the previous experiments. The latest data obtained at 29.1 and 26.9 keV with large statistical and systematic errors show considerable larger S-factors than previous. An enhancement of the astrophysical S-factor might be expected by the existence of a certain resonance as well as by an atomic effect on the screening potential near the solar Gamow energy.