• Open Access

Modified reverse tapering method to prevent frequency shift of the radiation in the planar undulator

Chi Hyun Shim, In Soo Ko, and Yong Woon Parc
Phys. Rev. Accel. Beams 20, 030703 – Published 13 March 2017

Abstract

This paper presents a modified reverse tapering method to generate a polarized soft x ray in x-ray free-electron lasers (XFELs) with a higher photon power and a shorter undulator length than the simple linear reverse tapering method. In the proposed method, a few untapered planar undulators are added before the simple linear reverse tapering section of the undulator line. This simple modification prevents the frequency shift of the radiation that occurs when the simple linear reverse tapering method is applied to planar undulators. In the proposed method, the total length of planar undulators decreased in spite of the additional untapered undulators. When the modified reverse tapering method is used with four untapered planar undulators, the total length of the planar undulators is 64.6 m. On the other hand, the required length of the planar undulators is 94.6 m when the simple linear reverse tapering method is used. The proposed method gives us a way to generate a soft x-ray pulse (1.24 keV) with a high degree of polarization (>0.99) and radiation power (>30GW) at the new undulator line with a 10-GeV electron beam in the Pohang Accelerator Laboratory X-ray Free-Electron Laser. This method can be applied in the existing XFELs in the world without any change in the undulator lines.

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  • Received 24 July 2016

DOI:https://doi.org/10.1103/PhysRevAccelBeams.20.030703

Published by the American Physical Society under the terms of the Creative Commons Attribution 3.0 License. Further distribution of this work must maintain attribution to the author(s) and the published article’s title, journal citation, and DOI.

Published by the American Physical Society

Physics Subject Headings (PhySH)

  1. Physical Systems
Accelerators & Beams

Authors & Affiliations

Chi Hyun Shim1, In Soo Ko1, and Yong Woon Parc2,*

  • 1Department of Physics, Pohang University of Science and Technology, Pohang 37673, Korea
  • 2Pohang Accelerator Laboratory, Pohang University of Science and Technology, Pohang 37673, Korea

  • *young1@postech.ac.kr

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Vol. 20, Iss. 3 — March 2017

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