Direct observation of the fast beam-ion instability

Abstract

Direct evidence of the fast beam-ion instability (FBII) was obtained in the Pohang Light Source by measuring the bunch-by-bunch parameters from the snapshots of the beam image. With the direct observation, we confirmed the FBII signals and clarified uncertainties of the blowup factors quantitatively: bunch size blowup of similar to 2 sigma(y) and the oscillation amplitude of -0.75 sigma(y). Suppression of the FBII was also demonstrated in the presence of the multiple gases or an extra clearing gap in the bunch train.