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Design of an ECHO-seeded FEL at nm wavelength. D. Xiang March-17-2011. Introductions. External seeding to improve temporal coherence of FEL output. Success of ECHO relies on preservation of long-term memory of phase space correlations. ECHO-7 to verify basic physics.
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Design of an ECHO-seeded FEL at nm wavelength D. Xiang March-17-2011
Introductions • External seeding to improve temporal coherence of FEL output • Success of ECHO relies on preservation of long-term memory of phase space correlations • ECHO-7 to verify basic physics • Before applying the ECHO technique to a user facility at ultrahigh harmonic number (100~200), it should be tested at a moderate harmonic number (25~50) to prove technologies and identify possible risks. • SLAC provides an excellent base and offer much of the required infrastructure for the R&D • Topic is to design a ~2 GeV ECHO-seeded FEL at SLAC
Time tables • 03-2011, Fix basic beam parameters (energy, current, energy spread) and laser parameters • 05-2011, Design of the photoinjector, linac, bunch compressors, undulators • 07-2011, S2E simulation from cathode to undulator • 09-2011, Time-dependent simulation for the ECHO-seeded FEL at nm wavelength • Deliverables: a design report should be documented for SLAC-PUB.
Tentative parameters • Seed laser wavelength: 258 nm (tripled from a Ti:Sapphire laser, the same as LCLS cathode laser) • Target FEL wavelength: 10.32 nm (25th) / 5.16 nm (50th) • Undulator period: 3 cm (LCLS-I) • Beam energy: 1.64 GeV • If we start from a 774 nm seed laser, the harmonic number is 75th and 150th accordingly
Open questions • Coherent radiation, or FEL lasing? • How many BCs? At what energy? • 20 pC, 250 pC, 1 nC? • Laser heater? • Where to put the ECHO beam line? • Compatible to FAULT? • High harmonic number or short wavelength?