Beam contaminants reduction for experiments with St. George*

The St. George recoil mass separator at the University of Notre Dame was designed to study radiative capture reactions relevant for stellar burning. St. George is coupled to the 5U accelerator at the Nuclear Science Laboratory.  A benchmark reaction, ²⁰Ne(α, γ) ²⁴Mg, was studied in November 2019. While showing results consistent with literature, 5U accelerator beam contaminants, which have indistinguishable mass and momentum from recoils, have limited the ability to extend the measurements to lower energies. A Wien filter was installed on the 5U transport line earlier this year with the goal of rejecting the beam contaminants before they enter St. George. The significant background reduction measured in a recent experimental test will be presented.