  Radiative alpha-capture, ($\alpha,\gamma$), reactions play a critical role in
nucleosynthesis and nuclear energy generation in a variety of astrophysical
environments. The St. George recoil separator at the University of Notre Dame's
Nuclear Science Laboratory was developed to measure ($\alpha,\gamma$) reactions
in inverse kinematics via recoil detection in order to obtain nuclear reaction
cross sections at the low energies of astrophysical interest, while avoiding
the $\gamma$-background that plagues traditional measurement techniques. Due to
the $\gamma$-ray produced by the nuclear reaction at the target location,
recoil nuclei are produced with a variety of energies and angles, all of which
must be accepted by St. George in order to accurately determine the reaction
cross section. We demonstrate the energy acceptance of the St. George recoil
separator using primary beams of helium, hydrogen, neon, and oxygen, spanning
the magnetic and electric rigidity phase space populated by recoils of
anticipated ($\alpha,\gamma$) reaction measurements. We found the performance
of St. George meets the design specifications, demonstrating its suitability
for ($\alpha,\gamma$) reaction measurements of astrophysical interest.
