Measurement of escaping ions in the Fermilab antiproton accumulator

Positively charged ions trapped in the negatively charged beam of the Fermilab antiproton accumulator pose a limit to beam stability and density. To better understand the dynamics and the consequences of the beam-ion interaction, we have built and installed a low energy ion detector and energy analyser in the Fermilab accumulator. This analyser is capable of energy analysis of the escaping ions using a probe with energy retarding grids and may also be scanned in the pitch angle of the escaping ions. Measurements have been made in both longitudinal and transverse planes under a variety of machine operating conditions. The experimental measurement results will be presented together with attempts to model the ion dynamics and explain observations