Beam losses and beam halos in accelerators for new energy sources

Jameson, Robert

doi:10.1016/s0920-3796(96)00463-2

Cited by 11 publications

(8 citation statements)

References 8 publications

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“…Beam loss from impingement of halo particles on accelerator hardware is a major concern in, for example, high‐current light‐ion accelerators. Just a tiny impingement, about 1 W/m, could generate radioactivation that precludes routine, hands‐on maintenance 16. Given a 1‐mA, 1‐GeV light‐ion beam, for example, for baseline beam parameters of the spallation neutron source (SNS) presently under construction at Oak Ridge National Laboratory, this criterion translates to just one in 10 6 particles lost per meter, a quantity that scales linearly with average beam current.…”

Section: Chaotic Mixing: Some Salient Featuresmentioning

confidence: 99%

Chaotic Dynamics in Charged‐Particle Beams: Possible Analogs of Galactic Evolution

Bohn¹

2005

Annals of the New York Academy of Sciences

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During the last couple of years of his life, Henry Kandrup became intensely interested in using charged-particle beams as a tool for exploring the dynamics of evolving galaxies. He and I recognized that both galaxies and chargedparticle beams can exhibit collisionless relaxation on surprisingly short time scales, and that this circumstance can be attributed to phase mixing of chaotic orbits. The chaos is often triggered by resonances caused by time dependence in the bulk potential, which acts almost identically for attractive gravitational forces as for repulsive electrostatic forces superposed on external focusing forces. Together we published several papers concerning evolving beams and galaxies, papers that relate to diverse topics such as the physics of chaotic mixing, the applicability of the Vlasov-Poisson formalism, and the production of diffuse halos. We also teamed with people from the University of Maryland to begin designing controlled experiments to be done at the University of Maryland Electron Ring. This paper highlights our collaborative findings as well as plans for future investigations that the findings have motivated.

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Section: Chaotic Mixing: Some Salient Featuresmentioning

confidence: 99%

Chaotic Dynamics in Charged‐Particle Beams: Possible Analogs of Galactic Evolution

Bohn¹

2005

Annals of the New York Academy of Sciences

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“…The importance of this finding lies in the accelerator's extreme sensitivity to beam loss. For example, in a lightion accelerator, beam impingement of just ∼1 W/m at energies exceeding ∼20 MeV will cause enough radioactivation to preclude hands-on machine maintenance [4]. In high-average-current machines, this amounts to just a few particles lost per meter, and large halos are thereby of practical concern, even if their outermost fringe is extremely tenuous.…”

Section: Introductionmentioning

confidence: 99%

Production of enhanced beam halos via collective modes and colored noise

Sideris

Bohn

2004

Phys. Rev. ST Accel. Beams

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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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“…In the design of high intensity linear accelerators substantial differences between transverse and longitudinal temperatures should be avoided [6,7]. In Fig.…”

Section: Unstable Particle Motion Due To Temperature Exchangementioning

confidence: 99%

Halo formation of bunched beams in periodic focusing systems

Letchford¹,

Bongardt

Pabst

Proceedings of the 1999 Particle Accelerator Conference (Cat. No.99CH36366)

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A very critical design issue for high intensity proton linacs is to keep particle loss below 1 W/m at the high energy end and allow unconstrained hand on maintenance. Particle loss is caused by a small number of particles outside the dense beam core, called the beam halo. Halo formation of bunched beams in a periodic focusing channel is driven by mismatch, high space charge and temperature anisotropy. Unstable particles oscillate in all 3 phase space planes. Mode overlap due to large mismatch amplitudes can lead to a halo much larger than seen in uniform focusing systems. Resonance crossing due to acceleration is a possibility for designing high intensity linacs. where ç env is one of the three envelope tunes of the mismatched radii and ç p t;l the single particle tune. SINGLE PARTICLE -ENVELOPE RESONANCE UNSTABLE PARTICLE MOTION IN A PERIODIC FOCUSING CHANNELIn a periodic focusing channel additional resonances and instabilities, which don't exist in an uniform channel, can influence single particle motion. One is the envelope -lattice instability which occurs for a bunched beam if the high mode frequency is nearly 180 o . The instability leads to an increase of the rms beam envelope. Other important resonances can occur between single particles and the periodic

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Beam losses and beam halos in accelerators for new energy sources

Abstract: United States AbstractLarge particle accelerators are proposed as drivers for new ways to produce electricity from nuclear fusion and fission reactions.

Cited by 11 publications

References 8 publications

Chaotic Dynamics in Charged‐Particle Beams: Possible Analogs of Galactic Evolution

Chaotic Dynamics in Charged‐Particle Beams: Possible Analogs of Galactic Evolution

Production of enhanced beam halos via collective modes and colored noise

Halo formation of bunched beams in periodic focusing systems

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