High-repetition-rate few-attosecond high-quality electron beams generated from crystals driven by intense X-ray laser

Zhenfeng Liang,Lingang Zhang,Xiaomei Zhang,Baifei Shen

doi:10.1063/5.0004524

Abstract

Advances in X-ray laser sources have paved the way to relativistic attosecond X-ray laser pulses and opened up the possibility of exploring high-energy-density physics with this technology. With particle-in-cell simulations, we investigate the interaction of realistic metal crystals with relativistic X-ray laser pulses of parameters that will be available in the near future. A wakefield of the order of TV/cm is excited in the crystal and accelerates trapped electrons stably even though the wakefield is locally modulated by the crystal lattice. Electron injection either occurs at the sharp crystal–vacuum boundary or is controlled by coating the crystal with a high-density film. High-repetition-rate attosecond (20 as) monoenergetic electron beams of energy 125 MeV, charge 100 fC, and emittance 1.6 × 10−9 m rad can be produced by shining MHz X-ray laser pulses of energy 2.1 mJ onto coated crystals several micrometers thick. Such a miniature crystal accelerator, which has high reproducibility and allows sufficient control of the parameters of the electron beams, greatly expands the applications of X-ray free electron lasers. For example, it could serve as an ideal electron source for ultrafast electron diffraction and ultrafast electron microscopy to achieve attosecond resolution.

Highlights

Since X-ray laser wakefield acceleration (LWFA) usually occurs in solid-density plasma, a strong wakefield of the order of TV/cm can be excited, whether in scitation.org/journal/mre crystals,35 nanotubes,36 or uniform plasma.36–40 In uniform plasma, when the laser and plasma wavelengths have the same ratio, the electron energy gains via X-ray LWFA are similar to those via optical LWFA over one dephasing length, while the electron emittance in Xray LWFA is of the order of 10−2 mm mrad, almost three orders of magnitude smaller than that of optical LWFA, because the electron emittance is proportional to the wavelength.36 in plasmas with free electrons and a lattice of ions, one-dimensional particle-incell (PIC) simulations have proved that the central wakefield dynamics are not affected by the ionic lattice force, where the wavelength of the X-ray laser is 100 times the ion spacing.38
We investigate the production of attosecond highquality electron beams by the interaction of a realistic metal crystal with relativistic X-ray laser pulses having parameters that will be available in the near future
This miniature crystal accelerator, a simple converter from X-ray laser to energetic electron beam, greatly expands the applications of X-ray free electron lasers (XFELs). It could serve as an ideal electron source for ultrafast electron diffraction and ultrafast electron microscopy to achieve attosecond resolution

Summary

Introduction

Since X-ray LWFA usually occurs in solid-density plasma, a strong wakefield of the order of TV/cm can be excited, whether in scitation.org/journal/mre crystals,35 nanotubes,36 or uniform plasma.36–40 In uniform plasma, when the laser and plasma wavelengths have the same ratio, the electron energy gains via X-ray LWFA are similar to those via optical LWFA over one dephasing length, while the electron emittance in Xray LWFA is of the order of 10−2 mm mrad, almost three orders of magnitude smaller than that of optical LWFA, because the electron emittance is proportional to the wavelength.36 in plasmas with free electrons and a lattice of ions, one-dimensional particle-incell (PIC) simulations have proved that the central wakefield dynamics are not affected by the ionic lattice force, where the wavelength of the X-ray laser is 100 times the ion spacing.38. It is practically possible to use relativistic attosecond X-ray laser pulses to explore high-energy-density physics, such as X-ray LWFA.35–39

Results

Conclusion