Vacuum ultraviolet coherent undulator radiation from attosecond electron bunches

Abstract

Attosecond duration relativistic electron bunches travelling through an undulator can generate brilliant coherent radiation in the visible to vacuum ultraviolet spectral range. We present comprehensive numerical simulations to study the properties of coherent emission for a wide range of electron energies and bunch durations, including space-charge effects. These demonstrate that electron bunches with r.m.s. duration of 50 as, nominal charge of 0.1 pC and energy range of 100–250 MeV produce $$10^9$$ 10 9 coherent photons per pulse in the 100–600 nm wavelength range. We show that this can be enhanced substantially by self-compressing negatively chirped 100 pC bunches in the undulator to produce $$10^{14}$$ 10 14 coherent photons with pulse duration of 0.5–3 fs.

A beamline to control longitudinal phase space whilst transporting laser wakefield accelerated electrons to an undulator

“…This technique to shorten the bunches by compensating for their initial chirp is most effective with longer initial bunch lengths, which have an increased potential for shortening. Shortening a bunch can promote coherent radiation at wavelengths longer than the bunch length, which for a 1 fs bunch (bunch length 300 nm) would be in the ultraviolet range 58 and for a 34 fs bunch (10,000 nm) would be in the infrared range. Shortening a chirped bunch also increases the peak current of the bunch, which is beneficial for the production of free-electron laser (FEL) radiation.…”