Edge turbulence measurements in L-mode and I-mode at ASDEX Upgrade
Name
5.0088062.pdf
Description
Published version
Size
6.41 MB
Format
Adobe PDF
Checksum (MD5)
7856fb8a2c3cf6997eebfc604d2cbabc
Author(s)
Bielajew, R
Conway, GD
Griener, M
Happel, T
Höfler, K
Howard, NT
Hubbard, AE
McCarthy, W
Molina Cabrera, PA
Nishizawa, T
Date Issued
May 2022
Journal
Physics of Plasmas
Publisher
AIP Publishing
Citation
Bielajew, R, Conway, GD, Griener, M, Happel, T, Höfler, K et al. 2022. "Edge turbulence measurements in L-mode and I-mode at ASDEX Upgrade." Physics of Plasmas, 29 (5).
Version
Final published version
Abstract
The I-mode confinement regime is promising for future reactor operation due to high energy confinement without high particle confinement. However, the role of edge turbulence in creating I-mode's beneficial transport properties is still unknown. New measurements of edge turbulence ([Formula: see text]) in L-modes and I-modes at low and high densities at ASDEX Upgrade are presented in this paper. A high radial resolution correlation electron cyclotron emission radiometer measures the broadband turbulence throughout the L-mode and I-mode edge and pedestal. The weakly coherent mode (WCM) is measured in both L-mode and I-mode near the last closed flux surface with Te fluctuation levels of 2.3%–4.2%, with a frequency shift between the two phases related to a deeper Er well in I-mode. An [Formula: see text] phase diagnostic captures a change of the WCM [Formula: see text] phase between L-mode and I-mode from [Formula: see text] to [Formula: see text]. The thermal He beam diagnostic measures a WCM wavenumber range of −0.5 to −1.0 cm−1. A low-frequency edge oscillation (LFEO) appears in the I-mode phase of these discharges and displays coupling to the WCM, but the LFEO does not appear in the L-mode phase. Linear gyrokinetic simulations of the outer core and pedestal top turbulence indicate that while the dominant turbulent modes in the outer core are ion directed and electrostatic, the turbulence becomes increasingly electron directed and electromagnetic with increasing radius. Collisionality is not found to impact characteristics of the L-mode and I-mode edge turbulence with respect to the presence of the WCM; however, the quality of global confinement decreases with collisionality.
MIT Department
Massachusetts Institute of Technology. Plasma Science and Fusion Center
Massachusetts Institute of Technology. Department of Physics
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Creative Commons Attribution 4.0 International license
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DOI of Published Version
https://doi.org/10.1063/5.0088062
