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TY - CONF AU - Suetsugu, Y. AU - Fukuma, H. AU - Ohmi, K. AU - Shibata, K. AU - Tobiyama, M. ED - Li, Ying-ying ED - Li, Lu ED - Schaa, Volker RW TI - Study to Mitigate Electron Cloud Effect in SuperKEKB J2 - Proc. of eeFACT2018, Hong Kong, China, 24-27 September 2018 CY - Hong Kong, China T2 - ICFA ABDW on High Luminosity Circular e$^+$e$^-$ Colliders T3 - 62 LA - english AB - During Phase-1 commissioning of the SuperKEKB from February to June 2016, electron cloud effects (ECE) were observed in the positron ring. The electron clouds were considered to exist in the beam pipes in the drift spaces of the ring, where the beam pipes have antechambers and titanium nitride (TiN) coating as countermeasures against ECE. Following this, permanent magnets and solenoids were attached to the beam pipes as additional countermeasures. Consequently, during Phase-2 commissioning from March to July 2018, experiments showed that the threshold beam current for exciting ECE increased by a factor of at least two relative to that during Phase-1 commissioning. While the countermeasures were strengthened, the effectiveness of the antechambers and TiN film coating was re-evaluated. From various simulations and experiments during Phase-2 commissioning, the antechamber was found to be less effective than expected with regard to reducing the number of photoelectrons in the beam channel. The TiN film coating, on the other hand, was considered to have a low secondary electron yield as expected. PB - JACoW Publishing CP - Geneva, Switzerland SP - 95 EP - 102 KW - electron KW - MMI KW - photon KW - simulation KW - solenoid DA - 2019/04 PY - 2019 SN - 978-3-95450-216-5 DO - DOI: 10.18429/JACoW-eeFACT2018-TUYAA04 UR - http://jacow.org/eefact2018/papers/tuyaa04.pdf ER -