Release mechanism of dust grains causing fast LHC beam losses
In plain words
Micron-sized dust grains fall from the LHC vacuum chamber walls into the beam and cause sudden losses that can quench magnets; what makes them detach is unclear.
Precise statement
Fast loss events in the LHC (called UFOs, unidentified falling objects) last of order $10^{-3}$ s and are modeled as micron-scale dust grains entering the proton beam, being ionized and repelled; this dust-beam dynamics was analyzed in 2020. Determine the release mechanism (electrostatic detachment driven by beam-induced charging or electron cloud, mechanical vibration, magnetic forces on ferromagnetic grains) and predict the event rate versus beam intensity, bunch spacing and cumulative beam time.
What would settle it
Laboratory release tests on beam-screen surfaces under electron bombardment and electric field that reproduce the measured dependence of the event rate on intensity and conditioning time.
Status in the literature
Dust-beam interaction dynamics were modeled and matched to loss signals in 2020 (Lindstrom et al., https://doi.org/10.1103/PhysRevAccelBeams.23.124501); the release step is not established.
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