Measurement of 19F(γ,α)15N with a bubble chamber and a bremsstrahlung beam

We have devised a new technique for determining thermonuclear reaction rates of astrophysical importance. By measuring (γ,α) cross sections we will determine (α,γ) reaction rates of processes such as 15N(α,γ)19F and 12C(α,γ)16O with a considerable improvement in sensitivity from previous experiments. Adopting ideas from dark matter search experiments with bubble detectors, we have found that a superheated liquid is sensitive to α-particle and heavy ion recoils produced from a γ ray beam impinging on the nuclei in the liquid. The main advantage of the new target-detector system is a density factor of 4-6 orders of magnitude higher than conventional gas targets. Also, the detector is virtually insensitive to the γ-ray beam itself, thus allowing us to detect only the products of the nuclear reaction of interest. This proposal requests 100 hours of beam time for measuring the 15N(α,γ)19F reaction. With this new method data can be recorded directly in the Gamow window. Only one other case of this is known. Depending on the success of the experiment, we will submit a separate proposal for the measurement of the key astrophysical reaction 12C(α,γ)16O.