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arXiv · 1202.3204

Ideal MHD theory of low-frequency Alfven waves in the H-1 Heliac

Jason Bertram·Boyd Blackwell·Matthew Hole
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Abstract

A part analytical, part numerical ideal MHD analysis of low-frequency Alfven wave physics in the H-1 stellarator is given. The three-dimensional, compressible ideal spectrum for H-1 is presented and it is found that despite the low beta (approx. 10^-4) of H-1 plasmas, significant Alfven-acoustic interactions occur at low frequencies. Several quasi-discrete modes are found with the three-dimensional linearised ideal MHD eigenmode solver CAS3D, including beta-induced Alfven eigenmode (BAE)- type modes in beta-induced gaps. The strongly shaped, low-aspect ratio magnetic geometry of H-1 causes CAS3D convergence difficulties requiring the inclusion of many Fourier harmonics for the parallel component of the fluid displacement eigenvector even for shear wave motions. The highest beta-induced gap reproduces large parts of the observed configurational frequency dependencies in the presence of hollow temperature profiles.

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Jason Bertram, Boyd Blackwell, Matthew Hole. 2012-02-15. Ideal MHD theory of low-frequency Alfven waves in the H-1 Heliac. https://doi.org/10.1088/0741-3335%2F54%2F5%2F055009

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