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Stellar Helium Burning Studied with an Optical Readout TPC (O-TPC) at HIγS
Ist Teil von
Journal of physics. Conference series, 2011-09, Vol.316 (1), p.012033-6
Ort / Verlag
Bristol: IOP Publishing
Erscheinungsjahr
2011
Quelle
EZB Electronic Journals Library
Beschreibungen/Notizen
An Optical Readout Time Projection Chamber (O-TPC) operating with the gas mixture of CO2(80%) + N2(20%) at 100 torr with gamma beams from the HIγS facility of TUNL at Duke University were used to study the formation of carbon and oxygen during helium burning. Measurements were carried out with circularly polarized gamma-ray beams at energies: Eγ 9.08, 9.38, 9.58, 9.78, 10.08, 10.38 and 10.68 MeV. We have begun the process of extracting complete angular distributions for the 16O(γ,α)12C reaction and the 12C(γ,3α) reaction (eventually with energy bins of approximately 100 keV) in order to determine the values of SE1, SE2 and the mixing phase φ12 of the 16O(γ, α)12C reaction. The rate of carbon formation at high temperatures (T > 3 GK) was suggested to increase due to contributions from a higher lying 2+ state. We have measured an angular distribution of (essentially) pure E2 transition at Eγ 9.78 MeV of the 12C(γ, 3α) reaction, providing conclusive evidence for the elusive 2+2 state in 12C.