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Title: Origin of the spectral pedestal in self-seeded hard X-ray FELs
Plain: Self-seeding is supposed to make X-ray pulses of one clean color, but a broad background of extra colors remains. Its source has not been fully identified.
Precise: Hard X-ray self-seeded FELs show a broadband pedestal around the seeded line containing a sizable fraction of the energy. Determine the fractions due to residual SASE noise, sideband instability, electron-beam microbunching from the accelerator, and seed-crystal effects, and the minimum achievable pedestal fraction.
Settled by: Spectral measurements with controlled microbunching and undulator taper, compared with 3D FEL simulations using measured electron phase space.
Kind: phenomenon
Answer type: mechanism
References: (empty)
Literature status: open
Status note: (empty)
Posed since: (empty)