Verification of Recoil Separator Properties through Direct Reaction Measurements

The St. George recoil separator is designed to measure (α,γ) cross sections of astrophysical interest in inverse kinematics. The design of the separator allows for a large energy (±7.5% ∆E/E) and angular (±40 mrad) acceptance that must be verified across a wide range of electric and magnetic rigidities before primary experi- mental work can begin. The beam rejection properties of the separator system must be determined to ensure that the direct incident beam is adequately rejected such that the produced recoils can be confidently measured. The procedures used during the commissioning work to experimentally verify these properties will be discussed.

Utilization of the separator for measuring cross sections of astrophysical interest that were not considered during the design phase is an additional benefit of the commissioning work and expands the potential domain of study for the separator. The first such experiment to measure two strong resonances in the 27Al(p,α)24Mg cross section has been completed. This reaction study is additionally a test of the separator’s energy and angular acceptances in situ as a precursor to studying (α,γ) reactions. The results of this measurement in relation to the properties of St. George will be discussed. An analysis package and pipeline were developed to support the study of the reaction in question and any future experiments using St. George.