Analytic fluid theory of beam spiraling in high-intensity cyclotrons

Antoine Cerfon, J. P. Freidberg, F. I. Parra, T. A. Antaya

Research output: Contribution to journalArticle

Abstract

Using a two-dimensional fluid description, we investigate the nonlinear radial-longitudinal dynamics of intense beams in isochronous cyclotrons in the nonrelativistic limit. With a multiscale analysis separating the time scale associated with the betatron motion and the slower time scale associated with space-charge effects, we show that the longitudinal-radial vortex motion can be understood in the frame moving with the charged beam as the nonlinear advection of the beam by the E×B velocity field, where E is the electric field due to the space charge and B is the external magnetic field. This interpretation provides simple explanations for the stability of round beams and for the development of spiral halos in elongated beams. By numerically solving the nonlinear advection equation for the beam density, we find that it is also in quantitative agreement with results obtained in particle-in-cell simulations.

Original languageEnglish (US)
Article number024202
JournalPhysical Review Special Topics - Accelerators and Beams
Volume16
Issue number2
DOIs
Publication statusPublished - Feb 26 2013

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ASJC Scopus subject areas

  • Physics and Astronomy (miscellaneous)
  • Surfaces and Interfaces
  • Nuclear and High Energy Physics

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