Revision 1

Accepted · first revision · record

Title: Mechanism of sudden beam losses at SuperKEKB
Plain: The SuperKEKB collider in Japan repeatedly loses much of a stored beam within a few turns, together with pressure bursts in the vacuum pipe.
Precise: SuperKEKB, mainly its low-energy positron ring, shows sudden beam loss events in which bunches begin to oscillate and grow within a few revolutions and hit collimators, correlated with local vacuum pressure bursts recorded by bunch-by-bunch monitors. Determine the physical chain from the source to fast blow-up (dust or debris entering the beam, discharge, ion or electron trapping), with timescale and intensity dependence matching monitor data.
Settled by: A model reproducing the measured onset time, bunch pattern and pressure correlation, confirmed by removal of the identified source eliminating the events.
Kind: phenomenon
Answer type: mechanism
References: (empty)
Literature status: partially-resolved
Status note: Terui et al. (Phys. Rev. Accel. Beams 29, 093501, 2026, https://doi.org/10.1103/pyl3-rfjg) traced the events, more than 200 in 2019-2024 and mainly in the low-energy ring, to stains of degraded vacuum sealant whose removal sharply reduced their frequency; the beam-dynamics chain from contaminant to loss within a few turns is not established.
Posed since: (empty)