Spectral Gap of Shear Alfv\'{e}n Waves in a Periodic Array of Magnetic Mirrors

POSTER

Abstract

A multiple magnetic mirror array is formed at the LArge Plasma Device (LAPD), to study axial periodicity-influenced Alfv\'{e}n spectra. Shear Alfv\'{e}n Waves (SAW) are launched by antennas inserted in the LAPD plasma. From radial wave field scans with B-dot probes at many axial locations, SAW standing-wave formation and wave refraction in mirror cell(s) are observed. Alfv\'{e}n wave spectral gaps and continua are formed similar to wave propagation in other periodic media due to the Bragg effect. The width of the propagation gap scales with the modulation amplitude according to the solutions of Mathieu's equation. A 2-D finite-difference code modeling SAW in a mirror array configuration shows similar spectral features. Machine end-reflection conditions and damping mechanisms including electron-ion Coulomb collision and electron Landau damping are important for simulation.

*Work supported by DOE DE-FG02-03ER54720

Authors

  • Roger McWilliams

    • UC Irvine
    • University of California, Irvine

  • Yang Zhang

    • University of California, Irvine
    • UC Irvine

  • William Heidbrink

    • UC Irvine

  • Heinz Boehmer

    • UC Irvine

  • Guangye Chen

    • UT Austin

  • Boris Breizman

    • Institute for Fusion Studies, The University of Texas at Austin
    • UT Austin

  • Stephen Vincena

    • UCLA

  • T.A. Carter

    • UCLA
    • University of California, Los Angeles

  • David Leneman

    • UCLA

  • Walter Gekelman

    • UCLA

  • Brian Brugman

    • UCLA