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| TUODAB01 |
Variations of Betatron Tune Spectrum due to Electron Cloud Observed in KEKB
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825 |
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- T. Ieiri
- H. Fukuma, Y. Ohnishi, M. Tobiyama
KEK, Ibaraki
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In order to investigate the characteristics of electron clouds, the wake effects were measured at KEKB using a test bunch placed behind a bunch-train, where there was a rapid decay in the electron cloud density. The current-dependent tune-shift of the test bunch exhibited nonlinear behaviour in the vertical plane [1]. By observing the tune spectrum, we found that the spectrum width expanded and this was accompanied with a large negative tune slope at a low cloud density and at a low bunch current. However, as the cloud density increased, the spectrum width shrunk and this was accompanied with a positive tune slope. These experimental results suggested that a high electron cloud density caused an anti-damping effect in the tune spectrum. We believe that the variations in the tune slope and spectrum width might be related to the wake field in the resonator model, where the wavelength is comparable to the bunch length.
[1] T. Ieiri et al., Proc. of EPAC06, Edinburgh, Scotland, 2101 (2006).
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Slides
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| TUODAB02 |
Electron Cloud Generation and Trapping in a Quadrupole Magnet at the LANL PSR
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828 |
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- R. J. Macek, M. J. Borden, A. A. Browman, R. J. Macek, R. C. McCrady, J. F. O'Hara, L. Rybarcyk, T. Spickermann, T. Zaugg
LANL, Los Alamos, New Mexico
- J. E. Ledford
TechSource, Santa Fe, New Mexico
- M. T.F. Pivi
SLAC, Menlo Park, California
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Funding: Work supported by DOE SBIR Grant No. DE-FG02-04ER84105 and CRADA No. LA05C10535 between TechSource, Inc. and the Los Alamos National Laboratory.
Recent beam physics studies on the two-stream e-p instability at LANL proton storage ring (PSR) have focused on the role of the electron cloud generated in quadrupole magnets where electrons, which seed beam-induced multipacting, are expected to be largest due to grazing angle losses from the beam halo. A new diagnostic to measure electron cloud formation and trapping in a quadrupole magnet has been developed, installed, and successfully tested at PSR. Experimental results will be presented on various characteristics of electron cloud obtain from experiments using this diagnostic and compared with simulations. Results include data on flux and energy spectra of electrons striking the vacuum chamber, the line density and lifetime of electrons trapped in the quadrupole after the beam has been extracted as well as evidence regarding electrons ejected from the magnet during passage of the proton beam.
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Slides
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