Upper Limit on the molecular resonance strengths in the 12{}^{12}C+12{}^{12}C fusion reaction

Carbon burning is a crucial process for a number of important astrophysical scenarios. The lowest measured energy is around E$_{\rm c.m.}$=2.1 MeV, only partially overlapping with the energy range of astrophysical interest. The currently adopted reaction rates are based on an extrapolation which is highly uncertain because of potential resonances existing in the unmeasured energy range and the complication of the effective nuclear potential. By comparing the cross sections of the three carbon isotope fusion reactions, ${}^{12}$C+${}^{12}$C, ${}^{12}$C+${}^{13}$C and ${}^{13}$C+${}^{13}$C, we have established an upper limit on the molecular resonance strengths in ${}^{12}$C+${}^{12}$C fusion reaction. The preliminary results are presented and the impact on nuclear astrophysics is discussed.Comment: 4 pages, 3 figures, FUSION11 conference proceedin

Heavy ion beam measurement of the hydration of cementitious materials

The setting and development of strength of Portland cement concrete depends upon the reaction of water with various phases in the Portland cement. Nuclear resonance reaction analysis (NRRA) involving the 1H(15N,α,γ)12C reaction has been applied to measure the hydrogen depth profile in the few 100 nm thick surface layer that controls the early stage of the reaction. Specific topics that have been investigated include the reactivity of individual cementitious phases and the effects of accelerators and retarders

Experimental investigations of the sub-Coulomb 12C+12C and 12C+16O reactions

Cluster resonances in light heavy-ion systems like 12C+12C and 12C+16O may have a major impact on astrophysics stellar scenarios. Resonant radiative capture reactions have been studied for these systems at energies at and slightly below their Coulomb barriers to investigate the possible 12C-12C and 12C-16O molecular origin of the resonances. Spins have been attributed to the resonances and specificities of their γ-decay have been identified. At deep sub-barrier energies, a fusion cross section measurement using the particle-γ coincidence technique is discussed for the 12C+12C system. A new project is presented to possibly extend the 12C+12C S low-energy S factor study

Measurement of the C 12 (C 12,p) Na 23 cross section near the Gamow energy

The fusion reaction C12(C12,p)Na23 has been studied from E=2.00 to 4.00 MeV by particle spectroscopy. The data reveal broad resonances above E=3.00 MeV and are compatible with previously reported resonance structure around E=2.1 MeV. The data were limited at low energies by low count rates as well as possible background contributions. This experiment extends the previously achieved low-energy measurement by charged particle spectroscopy to 2 MeV, which corresponds to the high-energy side of the astrophysically relevant temperature. Present knowledge of level structures and nonresonant contribution cannot explain the results of the present experiment, which may change the C12+C12 reaction rate significantly. Despite the progress decreasing the low-energy limit, any extrapolation into the astrophysical energy range remains highly uncertain based on available experimental data

Measurement of the C 12 (C 12,p) Na 23 cross section near the Gamow energy

The fusion reaction C12(C12,p)Na23 has been studied from E=2.00 to 4.00 MeV by particle spectroscopy. The data reveal broad resonances above E=3.00 MeV and are compatible with previously reported resonance structure around E=2.1 MeV. The data were limited at low energies by low count rates as well as possible background contributions. This experiment extends the previously achieved low-energy measurement by charged particle spectroscopy to 2 MeV, which corresponds to the high-energy side of the astrophysically relevant temperature. Present knowledge of level structures and nonresonant contribution cannot explain the results of the present experiment, which may change the C12+C12 reaction rate significantly. Despite the progress decreasing the low-energy limit, any extrapolation into the astrophysical energy range remains highly uncertain based on available experimental data