Installation,commissioning, and acceptance measurements of EMMA

Synopsis

The ElectroMagnetic Mass Analyzer EMMA is a vacuum mode, recoil mass spectrometer. It horizontally disperses recoiling ions according to their mass/charge ratio in the focal plane. These recoils are detected via two consecutive gas-filled proportional counters, one that measures position and the other that measures the residual energy as a function of distance in the gas volume. Thus, the recoils may be uniquely identified. EMMA was designed to exhibit excellent beam suppression so that reaction channels that are weakly populated may be extracted from the unreacted beam and high-yield background channels. EMMA has undergone several commissioning tests to measure its performance compared to its design specifications. This work covers a subset of the commissioning tests, which used a radioactive alpha source and ion beam backscattering to determine its energy/charge, mass/charge, and angular acceptances as well as its mass/charge dispersion.