Electron Beam Transport in Plasma-Accelerator-Driven Free-Electron Lasers in the Presence of Coherent Synchrotron Radiation and Microbunching Instability

Simone Di Mitri,Giovanni Perosa

doi:10.3390/physics2040029

Simone Di Mitri, Giovanni Perosa

Open Access

https://doi.org/10.3390/physics2040029

Copy DOI

Abstract

Laser- and beam-driven plasma accelerators promise electron beam brightness at the exit of plasma cells suitable for X-ray free-electron lasers. Beam transport from the accelerator to the undulator may include a multi-bend, energy-dispersive switchyard, in which energy collimators can be installed to protect the undulator or to serve multiple photon beamlines. Coherent synchrotron radiation and microbunching instability in the switchyard can seriously degrade the brightness of the accelerated beam, reducing the lasing efficiency. We present a semi-analytical analysis of those collective effects for beam parameters expected at the exit of state-of-the-art plasma accelerators. Prescriptions for the linear optics design used to minimize transverse and longitudinal beam instability are discussed.

Highlights

The rapid development of narrow-bandwidth free-electron lasers (FELs) has drawn the attention of the particle accelerator community to the spectral degradation that originates from the microbunching instability (MBI) [1,2]
MBI is exhibited as broadband density and energy modulation at wavelengths comparable to those involved in the FEL coherent emission
We find that the optics associated with a larger gain, i.e., non-zero R56, show a non-linear trend of σMBI for σE,i < 60 keV, which is a signature of the phase space dominated by the instability

Summary

Introduction

The rapid development of narrow-bandwidth free-electron lasers (FELs) has drawn the attention of the particle accelerator community to the spectral degradation that originates from the microbunching instability (MBI) [1,2]. This instability results from the interplay of the longitudinal space charge (LSC). MBI is exhibited as broadband density and energy modulation at wavelengths comparable to those involved in the FEL coherent emission Such modulations in the beam longitudinal phase space can enlarge the intrinsic FEL bandwidth via sideband instability [6]. The development of FEL projects at short wavelengths has occurred in parallel to the growing interest and rapid progress in laser- and beam-driven, plasma-based accelerators, whereby high-quality electron beams can be accelerated to multi-GeV energy levels in centimeter-scale plasma [8,9,10,11,12,13,14]

Objectives

Results

Discussion

Conclusion