Mechanism of sudden beam losses at SuperKEKB
In plain words
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 statement
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.
What would settle it
A model reproducing the measured onset time, bunch pattern and pressure correlation, confirmed by removal of the identified source eliminating the events.
Status in the literature
Unverified 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.