dorsal/arxiv
View SchemaProduction of Enhanced Beam Halos via Collective Modes and Colored Noise
| Authors | Ioannis V. Sideris, Courtlandt L. Bohn |
|---|---|
| Categories | |
| ArXiv ID | physics/0406086 |
| URL | https://arxiv.org/abs/physics/0406086 |
| DOI | 10.1103/PhysRevSTAB.7.104202 |
| Journal | Phys.Rev.ST Accel.Beams 7 (2004) 104202 |
Abstract
We investigate how collective modes and colored noise conspire to produce a beam halo with much larger amplitude than could be generated by either phenomenon separately. The collective modes are lowest-order radial eigenmodes calculated self-consistently for a configuration corresponding to a direct-current, cylindrically symmetric, warm-fluid Kapchinskij-Vladimirskij equilibrium. The colored noise arises from unavoidable machine errors and influences the internal space-charge force. Its presence quickly launches statistically rare particles to ever-growing amplitudes by continually kicking them back into phase with the collective-mode oscillations. The halo amplitude is essentially the same for purely radial orbits as for orbits that are initially purely azimuthal; orbital angular momentum has no statistically significant impact. Factors that do have an impact include the amplitudes of the collective modes and the strength and autocorrelation time of the colored noise. The underlying dynamics ensues because the noise breaks the Kolmogorov-Arnol'd-Moser tori that otherwise would confine the beam. These tori are fragile; even very weak noise will eventually break them, though the time scale for their disintegration depends on the noise strength. Both collective modes and noise are therefore centrally important to the dynamics of halo formation in real beams.
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"abstract": "We investigate how collective modes and colored noise conspire to produce a\nbeam halo with much larger amplitude than could be generated by either\nphenomenon separately. The collective modes are lowest-order radial eigenmodes\ncalculated self-consistently for a configuration corresponding to a\ndirect-current, cylindrically symmetric, warm-fluid Kapchinskij-Vladimirskij\nequilibrium. The colored noise arises from unavoidable machine errors and\ninfluences the internal space-charge force. Its presence quickly launches\nstatistically rare particles to ever-growing amplitudes by continually kicking\nthem back into phase with the collective-mode oscillations. The halo amplitude\nis essentially the same for purely radial orbits as for orbits that are\ninitially purely azimuthal; orbital angular momentum has no statistically\nsignificant impact. Factors that do have an impact include the amplitudes of\nthe collective modes and the strength and autocorrelation time of the colored\nnoise. The underlying dynamics ensues because the noise breaks the\nKolmogorov-Arnol\u0027d-Moser tori that otherwise would confine the beam. These tori\nare fragile; even very weak noise will eventually break them, though the time\nscale for their disintegration depends on the noise strength. Both collective\nmodes and noise are therefore centrally important to the dynamics of halo\nformation in real beams.",
"arxiv_id": "physics/0406086",
"authors": [
"Ioannis V. Sideris",
"Courtlandt L. Bohn"
],
"categories": [
"physics.acc-ph"
],
"doi": "10.1103/PhysRevSTAB.7.104202",
"journal_ref": "Phys.Rev.ST Accel.Beams 7 (2004) 104202",
"title": "Production of Enhanced Beam Halos via Collective Modes and Colored Noise",
"url": "https://arxiv.org/abs/physics/0406086"
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