On the statistics of edge fluctuations: comparative study between various fusion devices

TL;DR

This study compares edge fluctuation statistics across four fusion devices using GPI diagnostics, revealing parabolic trends in skewness and kurtosis and proposing a phenomenological model to explain observed deviations.

Contribution

It provides a comparative statistical analysis of edge fluctuations in multiple fusion devices and introduces a phenomenological model to interpret the data.

Findings

Data align along parabolic curves with device-dependent variations.

Statistical moments show consistent trends across different machines.

A phenomenological model is proposed to explain the statistical behavior.

Abstract

In this paper we present a statistical study of edge fluctuations taken with the Gas Puffing Imaging (GPI) diagnostics. We carry out a comparison of GPI signal from an extensive database including four devices (two Tokamaks and two Reversed Field Pinches). The data are analyzed in terms of their statistical moments Skewness and Kurtosis, as done in [B. Labit, et al, Phys. Rev. Lett. \textbf{98}, 255002 (2007)]. The data align along parabolic curves, although different from machine to machine, with some spread around the best-fitting curve. A discussion about the meaning of the parabolic trend as well as the departure of real data from it is provided. A phenomenological model is finally provided, attempting to accomodate experimental evidence.