Determination of structure tilting in magnetized plasmas - Time delay estimation in two dimensions

TL;DR

This paper develops a mathematical framework for estimating the variance of time delay in plasma turbulence measurements and introduces a method to determine the tilt angle of structures, validated with experimental data from a tokamak.

Contribution

It provides an analytic derivation of the TDE variance in 2D plasma models and a new method to determine structure tilt angles from experimental data.

Findings

Derived explicit variance formula for TDE in 2D plasma turbulence

Introduced a method to determine tilt angles of turbulent structures

Validated the approach with BES measurements at TEXTOR tokamak

Abstract

Time delay estimation (TDE) is a well-known technique to investigate poloidal flows in fusion plasmas. The present work is an extension of the earlier works of A. Bencze and S. Zoletnik 2005 and B. T\'al et al. 2011. From the prospective of the comparison of theory and experiment it seem to be important to estimate the statistical properties of the TDE based on solid mathematical groundings. This paper provides analytic derivation of the variance of the TDE using a two-dimensional model for coherent turbulent structures in the plasma edge and also gives an explicit method for determination of the tilt angle of structures. As a demonstration this method is then applied to the results of a quasi-2D Beam Emission Spectroscopy (BES) measurement performed at the TEXTOR tokamak.