Space-charge transport limits of ion beams in periodic quadrupolefocusing channels Page: 1 of 13
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Space-charge transport limits of ion beams in
periodic quadrupole focusing channels
Steven M. Lund
Lawrence Livermore National Laboratory, Livermore, CA 94550, USA
Sugreev R. Chawla
Lawrence Berkeley National Laboratory, Berkeley, CA 94720, USA
Accepted February, 2006, Nuclear Instruments and Methods A
It has been empirically observed in both experiments and particle-in-cell simula-
tions that space-charge-dominated beams suffer strong growth in statistical phase-
space area (degraded quality) and particle losses in alternating gradient quadrupole
transport channels when the undepressed phase advance o increases beyond about
850 per lattice period. Although this criterion has been used extensively in practical
designs of strong focusing intense beam transport lattices, the origin of the limit
has not been understood. We propose a mechanism for the transport limit resulting
from classes of halo particle resonances near the core of the beam that allow near-
edge particles to rapidly increase in oscillation amplitude when the space-charge
intensity and the flutter of the matched beam envelope are both sufficiently large.
When coupled with a diffuse beam edge and/or perturbations internal to the beam
core that can drive particles outside the edge, this mechanism can result in large
and rapid halo-driven increases in the statistical phase-space area of the beam,
lost particles, and degraded transport. A core-particle model is applied to para-
metrically analyze this process. Extensive self-consistent particle in cell simulations
are employed to better quantify properties of the space-charge limits and to verify
core-particle model predictions.
Key words: intense beam, space charge, emittance growth, simulation
PA CS: 29.27.Bd, 41.75.-i, 52.59.Sa, 52.27.Jt
Email address: SMLund11n1.gov (Steven M. Lund).
Preprint submitted to Elsevier Science
February 23, 2006
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Lund, S. M. & Chawla, S. R. Space-charge transport limits of ion beams in periodic quadrupolefocusing channels, article, February 23, 2006; United States. (digital.library.unt.edu/ark:/67531/metadc887941/m1/1/: accessed November 18, 2018), University of North Texas Libraries, Digital Library, digital.library.unt.edu; crediting UNT Libraries Government Documents Department.