Statistical theory of a self-seeded free electron laser with noise pedestal growth

Abstract

We study the impact of a spectral noise pedestal on the statistical properties of a self-seeded free electron laser (FEL). The broad pedestal is assumed to come from self amplified spontaneous emission (SASE) in the second stage of the self-seeding system and is uncorrelated with the narrowband amplified seed. An analytic description is developed based on the statistical theory of a one-dimensional FEL in the high gain linear regime. The theory shows good agreement with experimental data, which show that the presence of a SASE background can have a strong impact on the statistical behavior of self-seeding systems.

Quantum state features of the FEL radiation from the occupation number statistics

“…The natural relative spectral bandwidth can be as low as 10 −4 [37,38]. Thus, micronscale modulations of the electron energy distribution, accumulated during the acceleration process, can add a statistically significant pedestal to the FEL spectrum [39][40][41][42].…”

Statistical analysis of a self-seeded x-ray free-electron laser in the presence of the microbunching instability

“…II B below). Third, SASE radiation is produced in the downstream postmonochromator undulators that is uncorrelated with the monochromatized SASE radiation from the upstream undulators [19]. This occurs because the magnetic chicane that bridges the upstream and downstream undulator sections resets the shot noise in the electron beam that is assumed to be uncorrelated with the initial shot noise.…”

Atomic, molecular and optical physics applications of longitudinally coherent and narrow bandwidth Free-Electron Lasers

“…This method of self-seeding has the drawback that a "pedestal" is created, that is, there is a broad background of other wavelengths. For experiments where only the monochromatic beam produces signal this is not problematic, but for experiments where the other wavelengths produce background signal, this is an issue (Marcus et al, 2019;Hemsing et al, 2019Hemsing et al, , 2020.…”