Electron cloud effects in SuperKEKB commissioning
DOI:
https://doi.org/10.23732/CYRCP-2020-007.179Abstract
A vertical emittance growth (beam size blow-up) due to electron cloud has been observed in the positron low energy ring (LER) in Phase-I commissioning (2016) of SuperKEKB. The emittance growth is caused by fast head-tail instability due to wake force induced by electron cloud. The emittance growth was suppressed by weak permanent magnets generating longitudinal field, which cover the drift space of the ring in Phase-II (2018). The emittance growth has been studied during the commissioning with measuring electron cloud density in the beam chamber. We discuss threshold of the electron density for the instability.
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