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Observation of Longitudinal Quadrupole-mode Oscillations of a Bunch which were Induced by RF Phase Modulation in the Electron Storage Ring

2001; Institute of Physics; Volume: 40; Issue: 4R Linguagem: Inglês

10.1143/jjap.40.2465

1347-4065

S. Sakanaka, T. Obina,

Advanced X-ray Imaging Techniques

It has been reported that the beam lifetime in electron storage rings can be improved by applying a small phase modulation on the rf accelerating voltage at a frequency of two-times the synchrotron oscillation frequency. This effect can be explained as being due to the improved Touschek lifetime that is caused by an excited bunch-shape oscillation in the stored bunches. In order to understand this phenomenon further, we investigated the induced bunch-shape oscillation in the 2.5-GeV Photon Factory storage ring at High Energy Accelerator Research Organization (KEK). Using both a streak camera and a spectrum analyzer, we observed the quadrupole-mode oscillations of a stored single bunch very clearly. It showed a splitting of a single bunch into three or two bunchlets, which depended on the modulation frequency. We report on these experimental results, and discuss them using computer simulations and an analytical formalism.