• Open Access

Three-dimensional time-domain particle-in-cell calculations of impedances and centroid deflections in a linear-accelerator cell

C. Thoma, D. R. Welch, A. M. Russell, R. E. Clark, D. V. Rose, W. A. Stygar, and B. J. Kelsall
Phys. Rev. Accel. Beams 26, 014602 – Published 11 January 2023

Abstract

In linear induction accelerators, high-brightness electron beams are accelerated by voltages applied at gaps at discrete locations along the accelerator. At high currents, the beam itself induces wakefields in the accelerating gaps which can then feedback and distort the beam. The coupling of the gap-cavity modes and the beam can be characterized by frequency-dependent quantities known as the parallel and perpendicular gap impedances. Assessing the effects of instabilities resulting from these interactions requires accurate knowledge of these quantities. In this paper, we describe how a 3D finite-difference time-domain particle-in-cell code can be used to calculate both parallel and perpendicular gap impedances. We also demonstrate good agreement between full particle-in-cell simulations and results from a beam transport code making use of gap impedances to model beam centroid deflections. In practice, ferrite materials are often used in accelerating gaps to dampen cavity modes and reduce the severity of the resulting instabilities. We describe an implicit recursive convolution algorithm used to model the linear response of dispersive ferrite materials.

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  • Received 15 July 2022
  • Accepted 15 December 2022

DOI:https://doi.org/10.1103/PhysRevAccelBeams.26.014602

Published by the American Physical Society under the terms of the Creative Commons Attribution 4.0 International 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)

Accelerators & Beams

Authors & Affiliations

C. Thoma*, D. R. Welch, A. M. Russell, R. E. Clark, and D. V. Rose

  • Voss Scientific, LLC, Albuquerque, New Mexico 87108, USA

W. A. Stygar

  • Lawrence Livermore National Laboratory, Livermore, California 94550, USA

B. J. Kelsall

  • MuEpsln, LLC, Chadds Ford, Pennsylvania 19317, USA

  • *carstent@vosssci.com

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Vol. 26, Iss. 1 — January 2023

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