Measurement of Low Energy Resonances in $^{31}$P(p,$\alpha$)$^{28}$Si

The (p,$\alpha$) reactions on T=1/2 nuclei like $^{23}$Na, $^{27}$Al, $^{31}$P, and $^{35}$Cl, and the competing (p,$\gamma$) reactions are important for understanding the reaction flow to heavier elements in the rp-process. Previous rate calculations of the $^{31}$P(p,$\alpha$)$^{28}$Si reaction were based on indirect information gained from studies of the $^{31}$P($^{3}$He,d)$^{28}$S reaction [1]. At ORNL, we measured the energy and strength of the 371 and 599 keV resonances in $^{31}$P(p,$\alpha$)$^{28}$Si using a technique previously employed for an $^{17}$O(p,$\alpha$)$^{14}$N study[2]. A beam of $^{31}$P bombarded hydrogen gas which filled a large, differentially pumped scattering chamber at a pressure of 3 Torr. The alpha particle and $^{28}$Si recoil were detected in coincidence and the reaction vertex was determined using the relative kinematics of the reaction products. The experimental setup and preliminary results will be presented. [1] Ross $\it et$ $\it al$., Phys. Rev C 52, 1681 (1995) [2] B. H. Moazen $\it et$ $\it al$., Phys. Rev. C 75, 065801 (2006) ORNL is managed by UT-Battelle for the US DOE