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| THBAU05 |
COTR and SASE Generated by Compressed Electron Beams
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501 |
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- A. H. Lumpkin
Fermilab, Batavia, Illinois
- R. J. Dejus, N. Sereno
ANL, Argonne, Illinois
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Observations of strongly enhanced optical transition radiation (OTR) following significant bunch compression by a chicane of photoinjector beams have been reported during the commissioning of the Linac Coherent Light Source (LCLS) accelerator and at the Advanced Photon Source (APS) linac. These localized transverse spatial features involve signal enhancements of nearly a factor of ten in the APS case at the 150-MeV and 375-MeV OTR stations. They are consistent with a coherent process seeded by noise and may be evidence of a longitudinal microbunching instability which leads to coherent OTR (COTR) emissions. Additionally, we suggest that localized transverse structure in the previous self-amplified spontaneous emission (SASE) free-electron laser (FEL) data at APS in the visible-UV regime as reported at FEL02 may be attributed to such beam structure entering the FEL undulators and seeding the SASE. In one specific case, the SASE process enhanced separate beam structures 120 microns apart in x and 2.9 nm apart in wavelength. The details of these observations and operational parameters will be presented.
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Slides
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