# Characterization of mesoscopic turbulent transport events with long-radial-range correlation in DIII-D H-mode plasmas

## TL;DR

This study investigates mesoscopic turbulent transport events with long-radial-range correlation in DIII-D H-mode plasmas, revealing their characteristics, driving mechanisms, and impact on plasma confinement at high collisionality.

## Contribution

It provides detailed measurements and analysis of LRRC turbulence, linking it to electron-temperature-gradient modes and confinement degradation in H-mode plasmas.

## Key findings

- LRRC turbulence develops in high-collisionality discharges.
- LRRC transport events are intermittent with a specific power spectrum.
- Decreased flow shear increases the magnitude and scale of LRRC structures.

## Abstract

A dimensionless collisionality scan has been performed in H-mode plasmas on DIII-D tokamak, with detailed measurements of intermediate-to-high wavenumber turbulence using Doppler backscattering systems. It is found that the shorter wavelength turbulence develops into spatially asymmetric turbulent structures with a long-radial-range correlation (LRRC) in the mid-radius region of high-collisionality discharges. Linear \textsc{cgyro} simulations indicate that the underlying turbulence is likely driven by the electron-temperature-gradient (ETG) mode. The LRRC transport events are highly intermittent and show a power spectrum of \(S_{\tilde{n}}(k_\perp) \propto k^{-1}_\perp\) for density fluctuations, which is often associated with self-organized criticality. The magnitude and the radial scale of those turbulent structures increase significantly when the $E_{r}\times B$ mean flow shearing rate decreases. The enhanced LRRC transport events appear to be correlated with the degraded energy confinement time. The emergence of such LRRC transport events may serve as a candidate explanation for the degrading nature of \emph{H}-mode core plasma confinement at high collisionality.