A compact tunable polarized X-ray source based on laser-plasma helical undulators.

J Luo,M Zeng,J Vieira,L O Silva,L L Yu,Z M Sheng,M Chen,D A Jaroszynski,S M Weng,J Zhang

doi:10.1038/srep29101

Abstract

Laser wakefield accelerators have great potential as the basis for next generation compact radiation sources because of their extremely high accelerating gradients. However, X-ray radiation from such devices still lacks tunability, especially of the intensity and polarization distributions. Here we propose a tunable polarized radiation source based on a helical plasma undulator in a plasma channel guided wakefield accelerator. When a laser pulse is initially incident with a skew angle relative to the channel axis, the laser and accelerated electrons experience collective spiral motions, which leads to elliptically polarized synchrotron-like radiation with flexible tunability on radiation intensity, spectra and polarization. We demonstrate that a radiation source with millimeter size and peak brilliance of 2 × 1019 photons/s/mm2/mrad2/0.1% bandwidth can be made with moderate laser and electron beam parameters. This brilliance is comparable with third generation synchrotron radiation facilities running at similar photon energies, suggesting that laser plasma based radiation sources are promising for advanced applications.

Highlights

A plasma channel with a transverse density profile of n(r) = n0 + ∆nr2/r02 can guide the laser for long distances, where r represents the transverse coordinate, n0 is the on-axis electron density, Δnis the channel depth and r0 is the channel width[7,22,23]
We have studied highly tunable soft X-ray radiation from a helical plasma undulator based on laser wakefield accelerator (LWFA) in a plasma channel
The plasma can act as a helical undulator modulating electron motion, such that elliptically polarized synchrotron radiation can be produced

Summary

Introduction

Elliptical polarization with arbitrary ellipticity can be produced by injecting the laser pulse into the channel off axis and at an angle We extend these studies by including the electron beams acceleration process and using three dimensional Particle-in-Cell (3D-PIC) simulations to include the laser propagation, wake acceleration processes and show the tunability of radiation from such a laser plasma based helical plasma undulator for the first time, paving the way to more flexible and controllable X-ray generation. Considering typical laser plasma parameters, currently available in many laboratories, we find that our centimeter scale, plasma-based radiation source is expected to deliver ultra-intense X-rays, with peak brilliance as large as 2 × 1019 photons/s/mm2/mrad2/0.1% bandwidth. Such high quality flexible and compact radiation sources have the potential to benefit a wide variety of applications

Methods

Results

Conclusion