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@inproceedings{terui:ipac2022-wepotk050, author = {S. Terui and H. Fukuma and Y. Funakoshi and T. Ishibashi and T. Nakamura and K. Ohmi and Y. Ohnishi and M. Tobiyama and R. Ueki}, % author = {S. Terui and H. Fukuma and Y. Funakoshi and T. Ishibashi and T. Nakamura and K. Ohmi and others}, % author = {S. Terui and others}, title = {{The Report of Machine Studies Related to the Vertical Beam Size Blow-Up in SuperKEKB LER}}, booktitle = {Proc. IPAC'22}, % booktitle = {Proc. 13th International Particle Accelerator Conference (IPAC'22)}, pages = {2169--2172}, eid = {WEPOTK050}, language = {english}, keywords = {experiment, emittance, luminosity, beam-beam-effects, coupling}, venue = {Bangkok, Thailand}, series = {International Particle Accelerator Conference}, number = {13}, publisher = {JACoW Publishing, Geneva, Switzerland}, month = {07}, year = {2022}, issn = {2673-5490}, isbn = {978-3-95450-227-1}, doi = {10.18429/JACoW-IPAC2022-WEPOTK050}, url = {https://jacow.org/ipac2022/papers/wepotk050.pdf}, abstract = {{In the Low Energy Ring (LER) for positrons in the SuperKEKB, a vertical beam size blow-up was observed when the bunch current was approximately 1 mA. If a beam size blow-up occurs, the design luminosity cannot be achieved. Therefore, beam size blow-ups must be pre-vented. According to calculations, the bunch current threshold of the Transverse Mode Coupling instability (TMCI) is 2 mA or more, and the observed value is 50% or smaller. This vertical beam size blow-up cannot be explained by ordinary TMCI. This paper shows that by analyzing factors such as beam oscillation, the cause of the vertical beam size blow-up was determined. The study results showed that the vertical beam size blow-up in the LER was caused by the oscillations of the -1 mode.}}, }