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.