Efficient generation of short and high-power x-ray free-electron-laser pulses based on superradiance with a transversely tilted beam

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Efficient generation of short and high-power x-ray free-electron-laser pulses based on superradiance with a transversely tilted beam

Eduard Prat, Florian Löhl, and Sven Reiche

Phys. Rev. ST Accel. Beams 18, 100701 – Published 12 October 2015

Abstract

X-ray free electron lasers (XFELs) are innovative research tools able to produce high-power and short radiation pulses for multiple scientific applications. We present a new method to produce XFEL radiation with much higher power and shorter pulse lengths than the ones obtained at standard XFEL facilities. This will enable new kinds of experiments in scientific fields such as nonlinear optics and bioimaging. The scheme is based on introducing a transverse tilt to the electron beam, thus limiting the fraction of the bunch able to produce XFEL radiation. In the first part of the undulator beam line only the tail of the electron bunch lases. Then, by properly delaying and correcting the trajectory of the electron beam between some undulator modules, all the electrons can contribute to the amplification of a very short XFEL pulse. Apart from being efficient, our method is flexible since by tuning the tilt amplitude one can obtain shorter or more energetic XFEL pulses. The scheme can readily be applied since, besides the standard components of an XFEL facility, it only needs small chicanes between certain undulator modules. We have confirmed the validity of our proposal with numerical simulations done for the SwissFEL case.

Received 22 July 2015

DOI:https://doi.org/10.1103/PhysRevSTAB.18.100701

This article is available 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

Authors & Affiliations

Eduard Prat^*, Florian Löhl, and Sven Reiche

Paul Scherrer Institut, CH-5232 Villigen PSI, Switzerland

^*eduard.prat@psi.ch

Article Text

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Issue

Vol. 18, Iss. 10 — October 2015

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Images

Figure 1
Layout of the proposed scheme.
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Figure 2
Working principle of the proposed scheme for an example case with three undulator sections. The horizontal axis for all the plots is time in the reference system of the radiation field. The dashed green lines define the GTR outside of which the electron beam cannot significantly amplify the XFEL radiation. In the first undulator section only the tail of the electron beam produces XFEL radiation. After each undulator section the electron beam trajectory is corrected and the bunch is delayed such that all other regions of the electron beam contribute consecutively to enhance the XFEL pulse generated in the first undulator section.
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Figure 3
Trajectory offset (left plots) and angle (right plots) as a function of the longitudinal position of the bunch at the undulator entrance (top plots) and after every other undulator section for the case of an initial tilt amplitude in offset of 50. The blue solid lines indicate the tilt and the red dashed lines show for reference the aligned trajectory. The horizontal axis corresponds to longitudinal position along the bunch in all plots. The trajectory correction at the exit of each section can be performed with the first and last dipole magnets of the magnetic chicane used also to delay the electron beam (see text for more details). The phase advance per undulator module is about 30 degrees.
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Figure 4
XFEL peak power (top), XFEL pulse energy (center), and rms pulse duration (bottom) along the undulator beam line for the two simulated cases: initial tilt amplitude in offset of 50 with ten undulator sections (blue curves) and initial tilt amplitude in offset of 100 with 20 sections (red curves). We note that the rms pulse length is significantly affected by the spontaneous radiation background until $z \approx 30 m$ .
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Figure 5
XFEL peak power at 1 Å along the longitudinal position of the electron bunch after each undulator section for the case with an initial tilt amplitude of 50 in offset. The final XFEL peak power is around 1 TW, the pulse energy is around $500 μ J$ , and the rms pulse duration is around 500 as.
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Figure 6
Relative XFEL peak power (top), XFEL energy (center), and rms pulse duration (bottom) as a function of the initial tilt amplitude in offset. The simulations are done for the SwissFEL parameters with ten undulator sections (total of 15 undulator modules). The reference case (100% relative power, energy and length) corresponds to the optimum case in terms of XFEL power and is indicated by a blue dot.
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