| Paper | Title | Page |
|---|---|---|
| WEPC45 | Numerical Performance Studies on the new Sliced-Beam-Parameter Measurement Section for FLASH | 599 |
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The free-electron laser (FEL) user facility FLASH at DESY operates a high-gain FEL and provides radiation in the vacuum-ultraviolet and soft X-ray regime. In order to improve the capability and performance of the facility, FLASH will be upgraded with a third-harmonic (3.9 GHz) RF system to linearise the longitudinal phase space in front of the bunch compressors. For the study of the phase space linearisation, a new diagnostic and matching section located directly in front of the undulators which are used for the generation of SASE (self-amplified spontaneous emission) was designed. This section makes it possible to determine sliced beam parameters with high longitudinal resolution. In this paper, we describe the design considerations for this diagnostic section and demonstrate the expected performance by means of particle tracking simulations. |
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| 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. |