| Paper | Title | Page |
|---|---|---|
| WEPC50 | Observation of Coherent Optical Transition Radiation and Evidence for Microbunching in Magnetic Chicanes | 619 |
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The observation of coherent optical transition radiation (COTR) has recently attracted a lot of attention because of its detrimental influence on OTR based diagnostic techniques, and also as evidence for a microbunching instability in magnetic bunch compressors. At FLASH, we have observed coherent visible and infrared radiation from bunches having passed the magnetic bunch compressor chicanes. The spectral distribution was measured from 400 nm to 1600 nm with high resolution for various settings of the magnet currents in the chicanes. Remarkably, the coherent visible radiation was found to be stronger for uncompressed bunches than for the compressed bunches needed for FEL operation. Additionally, images of the bunches using narrow band filters from 950 nm to 1650 nm have been recorded. |