Measurement of the ¹⁴N(p,γ)¹⁵O CNO cycle reaction at CASPAR

The CNO cycle is the dominant energy source for large main sequence stars and significantly contributes to the hydrogen burning in asymptotic giant branch stars. Of the reactions in the CNO cycle, the ¹⁴N(p,γ)¹⁵O reaction is the slowest and therefore it regulates the energy production, lifetime, and abundance distribution of a given star. Measurements of this cross section show some large discrepancies and they are crucially inconsistent in the range of 300-600 keV, which is important for extrapolation to astrophysical energies. To address this problem, we have performed a measurement of this reaction at CASPAR, the first deep underground accelerator facility in the U.S., located on the 4850 ft. level of the Sanford Underground Research Facility in Western South Dakota. A proton beam impinged on TiN and ZrN targets at energies ranged from 270-1070 keV. The resulting cross-section information and its extrapolation to stellar burning energies will be presented.