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| Title | Real-World Considerations for Crossed-Polarized Undulator Radiation Conversion | |||||
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| Abstract | Cross-polarized (X-POL) configurations are a means to produce circularly-polarized radiation output from purely planar-polarized undulators. Recent polarization results from both the FERMI FEL-1 [1] at XUV wavelengths and Shanghai DUV FEL [2] at visible wavelengths have confirmed that such configurations do work for single pass FELs. However, analysis of both FERMI and SINAP results indicate that the quantitative degree of planar to circular conversion can be significantly affected by several experimental details. Full conversion requires not only equal intensity of the two cross-polarized beams but also perfect overlap in space and time of their far-field amplitude and phase patterns. From both simple theoretical analysis and more detailed simulation modeling, we examine a number of possible factors that can degrade the net linear to circular conversion efficiency. In addition to the previous suggestions by Ferrari et al. of problems with unbalanced powers and transverse phase variation arising from different effective emission z locations for the two cross-polarized radiation pulses, we also consider separate degradation effects of imperfect downstream overlap of the two linearly-polarized beams arising from different emission tilt angles and mode sizes. We also discuss optimizing the conversion efficiency by aperturing the radiation pulses downstream of the undulators. | |||||
| Footnotes & References | [1] E. Ferrari et al., Paper THA02, Proc. FEL2013 (2013). [2] H. Deng et al., Phys. Rev. ST Accel. Beams 17, 020704 (2014). |
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| Paper | download TUP053.PDF [0.500 MB / 4 pages] | |||||
| Conference | FEL2015, Daejeon, Republic of Korea | |||||
| Series | International Free Electron Laser Conference (37th) | |||||
| Proceedings | Link to full FEL2015 Proccedings | |||||
| Session | Poster Session | |||||
| Date | 25-Aug-15 15:00–17:00 | |||||
| Main Classification | FEL Technology and HW: Undulator, Magnets, Photon Diagnostics, and Beamlines | |||||
| Keywords | polarization, FEL, undulator, radiation, diagnostics | |||||
| Publisher | JACoW, Geneva, Switzerland | |||||
| Editors | Heung-Sik Kang (PAL, Pohang, Republic of Korea); Dong Eon Kim (PAL, Pohang, Republic of Korea); Volker RW Schaa (GSI, Darmstadt, Germany); | |||||
| ISBN | 978-3-95450-134-2 | |||||
| Published | December 2015 | |||||
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