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arXiv · 1607.07588

Universality of the ion flux to the JET outer wall

N. R. Walkden·A. Wynn·F. Militello·B. Lipschultz·G. Matthews·C. Guillemaut·J. Harrison·D. Moulton·JET Contributors
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Abstract

Universality in the ion flux to the JET outer-wall is observed in outerwall limiter mounted Langmuir probe (OLP) time-series across a large range of plasma current and line-averaged density during Ohmically heated horizontal target L-mode plasmas. The mean, M, and the standard deviation, sigma, of the ion-saturation current measured by the OLP show systematic variation with plasma current and density. Both increase as either plasma current decreases and/or density increases. Upon renormalization, achieved by subtraction of M and rescaling by sigma, the probability distribution functions (PDFs) of each signal collapse approximately onto a single curve. The shape of the curve deviates from a distribution in the tail of the PDF and is better described by a log-normal distribution. The collapse occurs over 4 decades of the ordinate which, given the wide parameter space over which the data spans, is a strong indication of universality.

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N. R. Walkden, A. Wynn, F. Militello, B. Lipschultz, G. Matthews, C. Guillemaut, J. Harrison, D. Moulton, JET Contributors. 2016-07-26. Universality of the ion flux to the JET outer wall. https://doi.org/10.1088/1741-4326/aa515a

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