Water-Window X-Ray Pulses from a Laser-Plasma Driven Undulator

A R Maier,B Zeitler,E M Gullikson,N Delbos,J Schmidt,S Karsch,I Dornmair,C Werle,A Guggenmos,F Krausz,U Schramm,U Kleineberg,J Wenz,F Grüner,N Kajumba

doi:10.1038/s41598-020-62401-4

Abstract

Femtosecond (fs) x-ray pulses are a key tool to study the structure and dynamics of matter on its natural length and time scale. To complement radio-frequency accelerator-based large-scale facilities, novel laser-based mechanisms hold promise for compact laboratory-scale x-ray sources. Laser-plasma driven undulator radiation in particular offers high peak-brightness, optically synchronized few-fs pulses reaching into the few-nanometer (nm) regime. To date, however, few experiments have successfully demonstrated plasma-driven undulator radiation. Those that have, typically operated at single and comparably long wavelengths. Here we demonstrate plasma-driven undulator radiation with octave-spanning tuneability at discrete wavelengths reaching from 13 nm to 4 nm. Studying spontaneous undulator radiation is an important step towards a plasma-driven free-electron laser. Our specific setup creates a photon pulse, which closely resembles the plasma electron bunch length and charge profile and thus might enable novel methods to characterize the longitudinal electron phase space.

Highlights

Since they match the intrinsic length and time scales of matter, femtosecond x-ray pulses are ubiquitously applied as an important tool in many scientific disciplines for solving previously unknown structures[1,2,3] and accessing atomic and molecular dynamics[4,5]
The field gradients supported by the plasma wave are orders of magnitude stronger than in a conventional radio-frequency (RF) driven cavity and as a result, the acceleration distance required for typical GeV-level electron beams can be as short as a few centimetres[34,35,36,37]
The laser is focused into a variable-length hydrogen-filled plasma cell[40,48,49], where it drives a plasma wave to generate electron beams in the self-injection regime

Summary

Introduction

Since they match the intrinsic length and time scales of matter, femtosecond (fs) x-ray pulses are ubiquitously applied as an important tool in many scientific disciplines for solving previously unknown structures[1,2,3] and accessing atomic and molecular dynamics[4,5]. The required high-brightness x-ray beams are provided to the user community almost exclusively by large-scale synchrotron[6,7] and free-electron laser facilities[8,9,10,11], which represent mature and highly developed technologies, delivering well-characterized photon beams with exceptional availability and reproducibility Due to their size and cost, access to these important resources is very limited. The field gradients supported by the plasma wave are orders of magnitude stronger than in a conventional radio-frequency (RF) driven cavity and as a result, the acceleration distance required for typical GeV-level electron beams can be as short as a few centimetres[34,35,36,37] In this process, the plasma wavelength, which is typically on the order of 10 microns, determines the characteristic time and length scale. Since an undulator effectively acts as a brightness converter, this electron beam quality is imprinted on the generated photon pulses

Methods

Results

Conclusion