A New Measurement of the E1 Component of the $^{12}$C($\alpha,\gamma$)$^{16}$O Reaction

Durin the past few years we have been involved in a measurement of the E1 component of the $^{12}$C($\alpha,\gamma$)$^{16}$O reaction. Using a new approach with a set of high acceptance ionization chambers, we have measured the beta-delayed alpha decay in $^{16}$N. The subthreshold 1$^-$ state, which dominates the S-factor S(E1) at astrophysical energies, produces a small interference peak in the alpha spectrum, whose strength is sensitive to S(E1). The data have been analyzed using extrapolations obtained from R-matrix theory. The results from two independent runs will be presented and compared to previous experiments. The contributions from systematic uncertainties as well as the sensitivity of S(E1) to various R-matrix parameters will be discussed. This work was supported by the US Department of Energy, Nuclear Physics Division, under contract No. W-31-109-ENG-38 and by the NSF Grant No. PHY-02-16783 (Joint Institute for Nuclear Astrophysics).