|THP069||Observations on Microbunching of Electrons in Laser-Driven Plasma Accelerators and Free-Electron Lasers||722|
Funding: This manuscript has been authored by Fermi Research Alliance, LLC under Contract No. DE-AC02-07CH11359 with the U.S. Department of Energy, Office of Science, Office of High Energy Physics.
The periodic longitudinal density modulation of relativistic electrons at the resonant wavelength (microbunching) is a fundamental aspect of free-electron lasers (FELs). In one case, microbunching fractions reached 20% at saturation of a self-amplified spontaneous emission (SASE) FEL resulting in gains of 1 million at 530 nm . In that experiment the z-dependent gain of coherent optical transition radiation (COTR) was also measured. In laser-driven plasma accelerators (LPAs), microbunching at visible wavelengths has also been recently reported as evidenced by significant COTR enhancements measured in near-field and far-field images on a single shot for the first time . An analytical model for COTR interferometry (COTRI) addresses both cases. In the FEL, one identified microbunched transverse cores of 25-100 microns while in the LPA the reported transverse sizes at the exit of the LPA were a few microns. In the latter case, signal enhancements of nearly 100, 000 and extensive fringes out to 30 mrad in angle space were recorded. The broadband microbunching observed in the LPA case could act as a seed for a SASE FEL experiment with tunability in principle over the visible regime.
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 A.H. Lumpkin, M. LaBerge, D.W. Rule et al., Proceedings of AAC18, (IEEE), (2019).
|DOI •||reference for this paper ※ https://doi.org/10.18429/JACoW-FEL2019-THP069|
|About •||paper received ※ 20 August 2019 paper accepted ※ 28 August 2019 issue date ※ 05 November 2019|
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