Experimental investigation of the 30S(α, p) thermonuclear reaction in x-ray bursts

Abstract

We performed the first measurement of 30S+α resonant elastic scattering to experimentally examine the 30S(α, p) stellar reaction rate in type I x-ray bursts. These bursts are the most frequent thermonuclear explosions in the galaxy, resulting from thermonuclear runaway on the surface of accreting neutron star binaries. The 30S(α, p) reaction plays a critical role in burst models, yet very little is known about the compound nucleus 34Ar at these energies nor the reaction rate itself. We performed a measurement of alpha elastic scattering with a radioactive beam of 30S to experimentally probe the entrance channel. Utilizing a gaseous active target system and silicon detector array, we extracted the excitation function from 1.8 to 5.5 MeV near 160° in the center-of-mass frame. The experimental data were analyzed with an R-Matrix calculation, and we discovered several new resonances and extracted their quantum properties (resonance energy, width, spin, and parity). Finally, we calculated the narrow resonant thermonuclear reaction rate of 30S(α, p) for these new resonances.