Universality of the ion flux to the JET outer wall

Universality of the ion flux to the JET outer wall

Universality of the ion flux to the JET outer wall 150 150 UKAEA Opendata

Statistical analysis of the ion flux to the JET outer-wall is conducted in outer-wall limiter mounted Langmuir probe (OLP) time-series across a wide range of plasma current and line-averaged density during Ohmically heated horizontal target L-mode plasmas. The mean, _, and the standard deviation, _, 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 _ and rescaling by _, 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 invariance in the shape of the PDF, which occurs over approximately four decades of the ordinate, is shown to be the result of a balance between the duration time of the average burst wave-form, _d and the waiting time between bursts, _w. This implies that the intermittency parameter, _d=_w, can be considered constant at the JET outer wall during horizontal target Ohmic L-mode operation. This result may be important both for model validation and prediction.

Collection:
Journals
Journal:
Nuclear Fusion
Publisher:
IOP
Published date:
01/01/2017