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Fluctuations do matter: large noise-enhanced halos in charged-particle beams
Courtlandt L Bohn1, Ioannis V Sideris
1Northern Illinois University, DeKalb, Illinois 60115, USA and Fermilab, Batavia, Illinois 60115, USA.
Abstract:
The formation of beam halos has customarily been described in terms of a particle-core model in which the space-charge field of the oscillating core drives particles to large amplitudes. This model involves parametric resonance and predicts a hard upper bound to the orbital amplitude of the halo particles. We show that the presence of colored noise due to space-charge fluctuations and/or machine imperfections can eject particles to much larger amplitudes than would be inferred from parametric resonance alone.
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