| Paper |
Title |
Page |
| TUAX03 |
Beam loss, emittance growth and halo formation due to the pinched electron cloud
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84 |
| |
- E. Benedetto, F. Zimmermann
CERN, Geneva
- G. Franchetti
GSI, Darmstadt
- K. Ohmi
KEK, Ibaraki
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Electron cloud can cause beam losses and emittance growth in proton or positron storage rings. If the electron density exceeds a certain threshold value, a strong head-tail instability manifests itself, characterized by a rapid beam-size blow-up with a rise time comparable to the synchrotron period. However, even for densities below the coherent-instability threshold, the electron-cloud can give rise to a significant emittance growth. We identified the mechanism for this incoherent growth as one caused by the combined effect of the beam particles synchrotron motion and the longitudinal variation of the tune shift, which is proportional to the pinched electron-cloud distribution along the bunch. This can give rise to the periodic crossing of a resonance, in analogy to halo formation in space-charge dominated beams, or eventually, if the tune shift is sufficiently large, to the crossing of bunch regions where the single-particle motion is linearly unstable.
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| WEAX01 |
Resonance trapping due to space charge and synchrotron motion, in theory, simulations, and experiments
|
167 |
| |
- G. Franchetti, I. Hofmann
GSI, Darmstadt
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| |
With the development of high intensity accelerator, the role of space charge effect in a nonlinear lattice gained special attention, as in the FAIR project at GSI, where long term storage of high intensity beams is required. The simultaneous presence of space charge and a nonlinear lattice creates an unprecedented challenge for ring designers as well as a new area of studies in beam physics. We present our understanding of the effect of space charge and chromaticity on the nonlinear beam dynamics of a bunched beam.
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| WEBX05 |
Scaling laws for space charge resonances
|
268 |
| |
- I. Hofmann, G. Franchetti
GSI, Darmstadt
- S.-Y. Lee
IUCF, Bloomington, Indiana
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| |
Space charge can be the driving term of nonlinear resonances, like the resonant emittance exchange 2Qx-2Qy=0 ("Montague resonance", in linacs and high-intensity rings), or the fourth-order structure resonance 4Qx=n (high-intensity rings, FFAG's). In this study we present scaling laws to describe the dependence of the expected emittance growth effect on the initial emittances, the tune shift and/or the crossing rate through the resonance.
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| THBW01 |
Code benchmarking on induce space charge particle trapping
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344 |
| |
- G. Franchetti, I. Hofmann
GSI, Darmstadt
- S. Machida
CCLRC/RAL/ASTeC, Chilton, Didcot, Oxon
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Trapping of particles in a high intensity bunch has been studied by using the MICROMAP. The numerical studies were used to interpret the CERN-PS experiments and explore the underlying beam loss/emittance growth mechanisms. We present in this contributed talk the first attempt of code benchmarking in modeling the long term storage of a high intensity bunch. The code benchmarking is initiated between MICROMAP and SIMPSONS.
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