Fluctuations do matter: large noise-enhanced halos in charged-particle beams.
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.
Bohn
Courtlandt L
CL
Northern Illinois University, DeKalb, Illinois 60115, USA and Fermilab, Batavia, Illinois 60115, USA.
Sideris
Ioannis V
IV