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| WG113 |
Seeding of the microbunching instability in a storage ring
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- J. M. Byrd, Z. Hao, M. C. Martin, D. Robin, F. Sannibale, R. W. Schoenlein, A. Zholents, M. S. Zolotorev
LBNL, Berkeley, California
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Funding: This work was supported by the Director, Office of Science, Office of High Energy Physics and Basic Energy Sciences, of the U. S. Department of Energy under Contract No. DE-AC02-05CH11231.
We report observations of laser seeding of the storage ring microbunching instability (MBI). Above a threshold bunch current, the interaction of the beam and its radiation results in a coherent instability, observed as a series of stochastic bursts of coherent synchrotron radiation (CSR) at THz frequencies initiated by fluctuations in the beam density. We have observed that this effect can be seeded by imprinting an initial density modulation on the beam by means of laser ‘slicing'. In such a situation, random bursts of Terahertz CSR become synchronous with the pulses of the modulating laser and their average intensity scales exponentially with the current per bunch. We present detailed experimental observations of the seeding effect and a model of the phenomenon. Control of this instability also creates potential applications as a high power source of CSR at Terahertz frequencies.
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Slides
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| WG313 |
Beam Physics Highlights of the FERMI@ELETTRA Project
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27 |
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- S. Di Mitri, M. Cornacchia, P. Craievich, G. Penco, M. Trovo
ELETTRA, Basovizza, Trieste
- P. Emma, Z. Huang, J. Wu
SLAC, Menlo Park, California
- D. Wang
MIT, Middleton, Massachusetts
- A. Zholents
LBNL, Berkeley, California
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The electron beam dynamics in the Fermi Linac has been studied in the framework of the design of a single-pass free electron laser (fel) based on a seeded harmonic cascade. The wakefields of some accelerating sections represent a challenge for the preservation of a small beam emittance and for achieving a small final energy spread. Various analytical techniques and tracking codes have been employed in order to minimize the quadratic and the cubic energy chirps in the longitudinal phase space, since they may cause a degradation of the fel bandwidth. As for the transverse motion, the beam breakup (bbu) instability has been recognized as the main source of emittance dilution; the simulations show the validity of local and non-local correction methods in order to counteract the typical “banana” shape distortion of the beam caused by the instability.
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Slides
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