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TY - UNPB AU - MacArthur, J.P. AU - Huang, Z. AU - Krzywiński, J. AU - Lutman, A.A. ED - Boland, Mark ED - Tanaka, Hitoshi ED - Button, David ED - Dowd, Rohan ED - Schaa, Volker RW ED - Tan, Eugene TI - Microbunch Rotation and Coherent Undulator Radiation From a Kicked Electron Beam J2 - Proc. of IPAC2019, Melbourne, Australia, 19-24 May 2019 CY - Melbourne, Australia T2 - International Particle Accelerator Conference T3 - 10 LA - english AB - Most X-ray Free Electron Lasers (FELs) emit linearly polarized X-ray pulses. Recently, a device called the Delta undulator has been installed at the Linac Coherent Light Source (LCLS) to provide tuneable polarization. The electron beam is first microbunched by the LCLS normal undulators, then the microbunched beam is kicked prior to the Delta undulator, and an intense circularly polarized X-ray pulse is generated in the Delta undulator towards the kicked direction and is spatially separation from the linearly polarized radiation from upstream undulators. Coherent off-axis radiation is usually strongly suppressed because the microbunches themselves cannot rotate. The talk will show that microbunches can in fact rotate towards the new direction of travel if the kick is applied in a quadrupole focusing channel and also will clarify characteristics of the coherent undulator radiation from a tilted microbunch in the far-field and will compare simulations with experiments. This microbunch rotation can explain the unexpectedly large amount of off-axis radiation that was observed during Delta undulator experiments at LCLS and may have other applications to the advanced X-ray manipulations. PB - JACoW Publishing CP - Geneva, Switzerland ER -