Hidetoshi Yamaguchi

Direct measurement of 12C+4He→16O+γ total cross section at Ecm=1.2 MeV

A fusion reaction of 12C+4He→16O+γ is one of the main reactions in He-burning of stars and important for nucleosynthesis. The fusion cross section at stellar energy of Ecm=0.3 MeV has not been determined precisely yet in spite of efforts for about 40 years. We plan to measure directly the total fusion cross section down to 0.7 MeV at Kyushu University Tandem accelerator Laboratory and to estimate the cross section at 0.3MeV by extrapolation. We have already measured the cross sections at 2.4 MeV and 1.5 MeV. The measurement at Ecm=1.2 MeV is in progress.

Direct measurement of the 4He(12C,16 O)γ cross section in inverse kinematics

K. Fujita ∗ K. Sagara, T. Teranishi, M. Iwasaki, D. Kodama, S. Matsuda, T. Mitsuzumi, M.T. Rosary and H. Yamaguchi Department of Physics, Kyushu University E-mail: kfujita@phys.kyushu-u.ac.jp sagara@phys.kyushu-u.ac.jp , teranishi@phys.kyushu-u.ac.jp , goto@phys.kyushu-u.ac.jp , iwa@phys.kyushu-u.ac.jp , sayaka@phys.kyushu-u.ac.jp , oba@phys.kyushu-u.ac.jp , taniguchi@phys.kyushu-u.ac.jp , h-yamaguchi@phys.kyushu-u.ac.jp

Direct measurement of 4He(12C,16O)γ reaction at KUTL

A 12 C + 4 He → 16 O +γ is regarded as the very important reaction to know the evolution of heavy stars. The cross section is, however, still unknown in spite of more than 40 years experiment in the world because of an existence of a resonance state of 16 O at sub‐threshold region. A cross section measurement with the direct detection of the produced 16 O from E cm = 2.4 downto 0.7 MeV have been planned at Kyushu University Tandem Laboratory(KUTL). Detection of the 16 O is the most possible method at low energy, since a detection efficiency of the 16 O is very high. The new windowless blow‐in gas target was developed to achieve the pressure of 24 Torr. Many movable slit were installed in a recoil mass separator, so that the backgrounds generated by the 12 C beam was eliminated effectively. The results of recent experiments at E cm = 2.4 and 1.5 MeV are reported.

Direct measurement of 4He(12C, 16O)γ reaction near stellar energy

A cross section measurement with a direct 16O detection method for the reaction energy from Ecm = 2.4 down to 0.7 MeV is planned at Kyushu University Tandem Laboratory (KUTL). To perform the experiment successfully and to get the quantitative information of the cross section within the 10% error, we have newly developed several instruments in 2009, such as a blow‐in type windowless gas target and movable slit system placed in the recoil mass separator. By using the windowless blow‐in gas target, a pressure of 24 Torr was achieved. The effective thickness along the beam axis was measured by p+4He scattering. Thanks to the movable slits installed in a recoil mass separator and the trajectory analysis, we found effective reduction of background conditions from the 12C beam.