Spatial-frequency features of radiation produced by a step-wise tapered undulator.

Andrei Trebushinin,Yakov Rakshun,Gianluca Geloni,Svitozar Serkez,Mykola Veremchuk

doi:10.1107/s1600577521001958

Abstract

A scheme to generate wide-bandwidth radiation using a step-wise tapered undulator with a segmented structure is proposed. This magnetic field configuration allows to broaden the undulator harmonic spectrum by two orders of magnitude, providing 1 keV bandwidth with spectral flux density exceeding 1016 photons s-1 mm-2 (0.1% bandwidth)-1 at 5 keV on the sample. Such a magnetic setup is applicable to superconducting devices where magnetic tapering cannot be arranged mechanically. The resulting radiation with broadband spectrum and flat-top shape may be exploited at a multipurpose beamline for scanning over the spectrum at time scales of 10-100 ms. The radiation from a segmented undulator is described analytically and derivations with numerical simulations are verified. In addition, a start-to-end simulation ofan optical beamline is performed and issues related to the longitudinally distributed radiation source and its image upon focusing on the sample are addressed.

Highlights

Synchrotron radiation (SR) serves as a powerful tool for investigating materials with X-rays
Fast monochromators allow to speed up data acquisition, for example for extended X-ray absorption fine structure (EXAFS) spectroscopy resulting in quick-EXAFS (Frahm, 1988)
We found that to effectively generate a wide-bandwidth flat-top spectrum the individual resonances of each segment should be shifted by their full width at half-maximum (FWHM)

Summary

Introduction

Synchrotron radiation (SR) serves as a powerful tool for investigating materials with X-rays. Fast monochromators allow to speed up data acquisition, for example for extended X-ray absorption fine structure (EXAFS) spectroscopy resulting in quick-EXAFS (Frahm, 1988). This requires fast scanning over 1 keV bandwidth at a sub-second time scale with a sufficient photon flux on the sample. We propose an advanced superconducting undulator scheme for the experiments where fast scanning over the spectrum along with micrometre-scale focusing is required We suggest that this source may be installed for future beamlines specialized in micro- and nano-probing, e.g. I18 at DIAMOND (Mosselmans et al, 2009), P06 and P11 at PETRA III (Schroer et al, 2010; Burkhardt et al, 2016) and ID13 at ESRF (Flot et al, 2010)

Objectives

Findings

Discussion

Conclusion