Generation of a few femtosecond keV x-ray pulse via interaction of a tightly focused laser copropagating with a relativistic electron bunch

Abstract

It is demonstrated in a numerical simulation that an intense fs keV x-ray pulse can be generated by the interaction of a tightly focused femtosecond laser copropagating with an electron bunch. In general, the interaction of a loosely focused (focal spot similar to 100 mu m in diameter) laser with a copropagating electron is rather weak so that the radiation is not only weak but also produced in the vicinity of laser wavelength. However, in the case of tight focus (focal spot on the order of wavelength), the radiation characteristics turn out to be drastically different so that a keV x-ray pulse can be produced at high flux. This is due to the nonparaxial fields induced in a tight-focus regime. The radiation characteristics are discussed for different beam waists and electron beam energies. This simulation suggests that the interaction of a tightly focused laser with a copropagating electron bunch can be a unique source for an x-ray pulse of the photon energy from 10 to 100 keV that lasts a few femtoseconds.