Neutron-upscattering enhancement of the triple-alpha process
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 12C, 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 CO2 gas, we measure the 3α-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).
Bishop, J.; Parker, C. E.; Rogachev, G. V.; Ahn, S.; Koshchiy, E.; Brandenburg, K.; Brune, C. R.; Charity, R. J.; Derkin, J.; Dronchi, N.; Hamad, G.; Jones-Alberty, Y.; Kokalova, Tz; Massey, T. N.; Meisel, Z.; Ohstrom, E. V.; Paneru, S. N.; Pollacco, E. C.; Saxena, M.; Singh, N.; Smith, R.; Sobotka, L. G.; Soltesz, D.; Subedi, S. K.; Voinov, A. V.; Warren, J.; and Wheldon, C., "Neutron-upscattering enhancement of the triple-alpha process" (2022). Physics & Astronomy Open Access Publications. 172.