Speaker
Description
Free-electron lasers (FELs) driven by electron beams generated by laser-plasma-accelerators (LPAs) offer an attractive avenue towards compact, high brightness and short wavelength coherent light sources. The BELLA Center LPA FEL facility at the Lawrence Berkeley National Laboratory delivers few fs-duration, 40-80 pC electron bunches of 100 MeV energy, 4% FWHM energy spread, at a 1Hz repetition rate to the 4-meter long VISA undulator, producing 420-nm radiation via self-amplified spontaneous emission (SASE). Although the 6D electron beam brightness is sufficient for amplification, the percent-level energy spread, and the nonlinear longitudinal phase space structure, degrades FEL lasing and is a key challenge for LPA-driven FELs. A magnetic chicane is used to lengthen the bunch, reduce the slice energy spread and generate an energy chirp. We investigate the impact of slippage and the effect of large energy chirps in the BELLA FEL amplification process using both numerical simulations and theoretical models, and compare their predictions to experimental measurements.
Funding Agency
This work was supported by the U.S. Department of Energy (DOE), Office of Science, the Office of Basic Energy Sciences, and the Office of High Energy Physics, under Contract No. DE-AC02-05CH11231.
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