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| Title | Distributed Seeding for Narrow-band X-ray Free-Electron Lasers | |||||
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| Abstract | The MaRIE XFEL is the proposed XFEL driven by a 12-GeV electron beam to generate coherent 42-keV photons based on a new seeding technique called distributed seeding (DS). This paper presents details of the distributed seeding technique using Si(111) Bragg crystals as the spectral filters. DS differs from self-seeding in three important aspects. First, DS relies on spectral filtering of the undulator radiation at more than one location early in the exponential gain curve. This leads to an FEL output that is dominated by the coherent seed signal, not SASE noise. Secondly, DS affords the ability to select a wavelength longer than the peak of the SASE gain curve, which leads to improved spectral contrast of the seeded FEL over the SASE background. Lastly, the power growth curves in successive DS stages exhibit the behavior of an FEL amplifier, i.e. a lethargy region followed by the exponential growth region. This behavior results in FEL output pulses that are less spiky than the SASE pulses. Using 3D Genesis simulations, we show that DS with two filters provides a 12X enhancement in spectral brightness relative to SASE and that DS with three filters produces negligible SASE background. The DS FEL spectrum has a relative spectral bandwidth (FWHM) of 8 X 10⁻⁵ with about 9 spectral modes. | |||||
| Funding | We thank Bruce Carlsten, John Lewellen, Steve Russell, and Rich Sheffield (LANL), Craig Ogata and Yuri Shvyd'ko (ANL) for helpful discussion, and the MaRIE project for financial support. | |||||
| Paper | download TUB02.PDF [0.601 MB / 4 pages] | |||||
| Slides | download TUB02_TALK.PDF [1.241 MB] | |||||
| Conference | FEL2015, Daejeon, Republic of Korea | |||||
| Series | International Free Electron Laser Conference (37th) | |||||
| Proceedings | Link to full FEL2015 Proccedings | |||||
| Session | Seeded FELs | |||||
| Date | 25-Aug-15 10:30–12:00 | |||||
| Main Classification | Seeded FELs | |||||
| Keywords | undulator, radiation, electron, FEL, simulation | |||||
| 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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