Stable two-plane focusing for emittance-dominated sheet-beam transport

Two-plane focusing of sheet electron beams will be an essential technology for an emerging class of high-power, 100 to 300 GHz rf sources [Carlsten et al., IEEE Trans. Plasma Sci. 33, 85 (2005)]. In these devices, the beam has a unique asymmetry in which the transport is emittance dominated in the s...

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Bibliographic Details
Published in:Physical review special topics. PRST-AB. Accelerators and beams 2005-06, Vol.8 (6), p.062002, Article 062002
Main Authors: Carlsten, B. E., Earley, L. M., Krawczyk, F. L., Russell, S. J., Potter, J. M., Ferguson, P., Humphries, S.
Format: Article
Language:English
Subjects:
Electron beams
Emittance
Focusing
Permanent magnets
Quadrupoles
Scalloping
Stability
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Summary:Two-plane focusing of sheet electron beams will be an essential technology for an emerging class of high-power, 100 to 300 GHz rf sources [Carlsten et al., IEEE Trans. Plasma Sci. 33, 85 (2005)]. In these devices, the beam has a unique asymmetry in which the transport is emittance dominated in the sheet’s thin dimension and space-charge dominated in the sheet’s wide dimension. Previous work has studied the stability of the transport of beams in the emittance-dominated regime for both wiggler and periodic permanent magnet (PPM) configurations with single-plane focusing, and has found that bigger envelope scalloping occurs for equilibrium transport, as compared to space-charge dominated beams [Carlsten et al., this issue, Phys. Rev. ST Accel. Beams 8, 062001 (2005)]. In this paper, we describe the differences in transport stability when two-plane focusing is included. Two-plane wiggler focusing degrades the transport stability slightly, whereas two-plane PPM focusing greatly compromises the transport. On the other hand, single-plane PPM focusing can be augmented with external quadrupole fields to provide weak focusing in the sheet’s wide dimension, which has stability comparable to two-plane wiggler transport.
ISSN:1098-4402
1098-4402
2469-9888
DOI:10.1103/PhysRevSTAB.8.062002