Ultrashort electron beam isochronous, achromatic transport line design

Abstract

With the recent development of ultrashort laser pulse generation, many laser facilities around the world can routinely accelerate stable, high-energy electron bunches with a duration in the order of several femtoseconds in a very short distance. Due to the short bunch duration, they are suitable for various femtosecond and sub-picosecond applications. However, one of the less favorable properties of this acceleration is a relatively large electron bunch energy spread which causes the increase in the bunch duration when propagating a long distance in space. Hence, for utilizing them in such applications, they need to be compressed back down to the femtosecond duration. In this work we present a progress in design of the electron beam transport line preserving the femtosecond bunch duration. The transport line including the final focusing system consists of commonly used, standard types of electron optical devices – dipoles, quadrupoles and sextupoles. The design exploits setups in conventional radiofrequency accelerators for beams with low energy spread, including chromaticity correction. Our design focuses on the transport of electron bunches with relatively large energy spread, while maximizing the transport line acceptance for given beam parameters, as energy, relative energy spread and emittance.