|TUP019||Regime of Multi-Stage Non-Resonant Trapping in Free Electron Lasers||83|
Funding: This work is supported by the RFBR (grants #18-02-40009, #18-02-00765) and by the IAP RAS Project 0035-2019-0001.
We describe three works united by the idea of the non-resonant regime  providing an effective trapping in a beam with a great energy spread. In this regime, the "bucket" corresponding to the resonant electron-wave interaction passes through the electron layer on the energy-phase plane and traps a fraction of electrons. (I) Operability of this regime was demonstrated in the high-efficient 0.8 MeV Ka-band FEM-amplifier . (II) In short-wavelength FELs the multi-stage trapping in several consecutive sections can be organized . In each section a small e-beam fraction is trapped due to a weak electron-wave interaction. However, repetition of this process from section to section involves in the interaction almost the whole e-beam. We describe efficiency enhancement and improving the frequency wave spectrum in multi-stage SASE FELs. (III) The multi-stage amplification of a single-frequency wave signal can provide cooling of the electron bunch. In this regime, tapering of every section is provided such that the "bucket" goes from maximal initial electron energy down to the minimal one and moves down energies of trapped electrons.
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|DOI •||reference for this paper ※ https://doi.org/10.18429/JACoW-FEL2019-TUP019|
|About •||paper received ※ 14 August 2019 paper accepted ※ 27 August 2019 issue date ※ 05 November 2019|
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