Cooperative accumulation of coherent undulator radiation emitted from periodic electron bunches

Abstract

Cavity build-up of coherent undulator synchrotron radiation emitted by periodic electron bunches is investigated. At the optimal off-grazing resonance, the bunch slippage relative to the radiation pulse introduces an initial transient period during which radiation accumulates cooperatively as if it is emitted by a single bunch. The power growth during the period is quadratic to the number of bunches. The number of cooperative bunches is ∼2 ℓs 2, where ℓs denotes the slippage length in units of the resonant wavelength.

Superradiant and stimulated-superradiant emission of bunched electron beams

“…The main challenge for realizing this concept is the requirement for a high intensity radiation seed "igniter" and a high repetition bunched beam train synchronous with the round trip time of the resonator. Concepts of stimulated superradiant FEL oscillator with uniform wiggler have been considered in [179,180] and in [6,178], where a strategy of buildup in the resonator is considered starting from zero-order superradiance and stimulated superradiance. In this scheme the beam energy is temporally ramped in a process in which the bunched beam eventually gets trapped in the built-up radiation field, and then continues in a steady state saturated superradiant oscillation mode.…”