Neutron-upscattering enhancement of the triple-alpha process
J. Bishop, C. E. Parker, G. V. Rogachev, S. Ahn, E. Koshchiy, K. Brandenburg, C. R. Brune, R. J. Charity, J. Derkin, N. Dronchi, G. Hamad, Y. Jones-Alberty, Tz. Kokalova, T. N. Massey, Z. Meisel, E. V. Ohstrom, S. N. Paneru, E. C. Pollacco, M. Saxena, Nisha Singh, R. Smith, L. G. Sobotka, D. Soltesz, S. K. Subedi, A. Voinov, J. Warren, C. Wheldon
Abstract
Abstract The neutron inelastic scattering of carbon-12, populating the Hoyle state, is a reaction of interest for the triple-alpha process. The inverse process (neutron upscattering) can enhance the Hoyle state’s decay rate to the bound states of 12 C, effectively increasing the overall triple-alpha reaction rate. The cross section of this reaction is impossible to measure experimentally but has been determined here at astrophysically-relevant energies using detailed balance. Using a highly-collimated monoenergetic beam, here we measure neutrons incident on the Texas Active Target Time Projection Chamber (TexAT TPC) filled with CO 2 gas, we measure the 3 α -particles (arising from the decay of the Hoyle state following inelastic scattering) and a cross section is extracted. Here we show the neutron-upscattering enhancement is observed to be much smaller than previously expected. The importance of the neutron-upscattering enhancement may therefore not be significant aside from in very particular astrophysical sites (e.g. neutron star mergers).