Stochastic extraction of periodic attosecond bunches from relativistic electron beams.

Intense laser waves can form a time-dependent gate, which transmits or reflects particles depending on their initial phases. When faced by a relativistic electron beam, such a barrier slices it by randomly scattering all but some particles, which nearly conserve their velocity. Subfemtosecond or attosecond periodic electron bunches are then formed downstream and can be used, for example, to generate coherent x rays via Thomson backscattering of the laser light.