dorsal/arxiv
View SchemaSpace-charge transport limits of ion beams in periodic quadrupole focusing channels
| Authors | Steven M. Lund, Sugreev R. Chawla |
|---|---|
| Categories | |
| ArXiv ID | physics/0602177 |
| URL | https://arxiv.org/abs/physics/0602177 |
| DOI | 10.1016/j.nima.2006.02.195 |
Abstract
It has been empirically observed in both experiments and particle-in-cell simulations 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 sigma_0 increases beyond about 85 degrees 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 parametrically analyze this process. Extensive self-consistent particle in cell simulations are employed to better quantify space-charge limit and verify core-particle model predictions.
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"abstract": "It has been empirically observed in both experiments and particle-in-cell\nsimulations that space-charge-dominated beams suffer strong growth in\nstatistical phase-space area (degraded quality) and particle losses in\nalternating gradient quadrupole transport channels when the undepressed phase\nadvance sigma_0 increases beyond about 85 degrees per lattice period. Although\nthis criterion has been used extensively in practical designs of strong\nfocusing intense beam transport lattices, the origin of the limit has not been\nunderstood. We propose a mechanism for the transport limit resulting from\nclasses of halo particle resonances near the core of the beam that allow\nnear-edge particles to rapidly increase in oscillation amplitude when the\nspace-charge intensity and the flutter of the matched beam envelope are both\nsufficiently large. When coupled with a diffuse beam edge and/or perturbations\ninternal to the beam core that can drive particles outside the edge, this\nmechanism can result in large and rapid halo-driven increases in the\nstatistical phase-space area of the beam, lost particles, and degraded\ntransport. A core-particle model is applied to parametrically analyze this\nprocess. Extensive self-consistent particle in cell simulations are employed to\nbetter quantify space-charge limit and verify core-particle model predictions.",
"arxiv_id": "physics/0602177",
"authors": [
"Steven M. Lund",
"Sugreev R. Chawla"
],
"categories": [
"physics.acc-ph"
],
"doi": "10.1016/j.nima.2006.02.195",
"title": "Space-charge transport limits of ion beams in periodic quadrupole focusing channels",
"url": "https://arxiv.org/abs/physics/0602177"
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