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Title: Density perturbation mode structure of high frequency compressional and global Alfvén eigenmodes in the National Spherical Torus Experiment using a novel reflectometer analysis technique

Abstract

Reflectometry measurements of compressional (CAE) and global (GAE) Alfvén eigenmodes are analyzed to obtain the amplitude and spatial structure of the density perturbations associated with the modes. A novel analysis technique developed for this purpose is presented. The analysis also naturally yields the amplitude and spatial structure of the density contour radial displacement, which is found to be 2–4 times larger than the value estimated directly from the reflectometer measurements using the much simpler ‘mirror approximation’. The modes were driven by beam ions in a high power (6 MW) neutral beam heated H-mode discharge (#141398) in the National Spherical Torus Experiment. The results of the analysis are used to assess the contribution of the modes to core energy transport and ion heating. The total displacement amplitude of the modes, which is shown to be larger than previously estimated (Crocker et al 2013 Nucl. Fusion 53 43017), is compared to the predicted threshold (Gorelenkov et al 2010 Nucl. Fusion 50 84012) for the anomalously high heat diffusion inferred from transport modeling in similar NSTX discharges. The results of the analysis also have strong implications for the energy transport via coupling of CAEs to kinetic Alfvén waves seen in simulations with themore » Hybrid MHD code (Belova et al 2015 Phys. Rev. Lett. 115 15001). Finally, the amplitudes of the observed CAEs fall well below the threshold for causing significant ion heating by stochastic velocity space diffusion (Gates et al 2001 Phys. Rev. Lett. 87 205003).« less

Authors:
; ; ; ; ; ; ; ;
Publication Date:
DOE Contract Number:  
AC02-09CH11466, SC0011810; FG02-99ER54527
Product Type:
Dataset
Research Org.:
Princeton Plasma Physics Lab. (PPPL), Princeton, NJ (United States)
Sponsoring Org.:
U. S. Department of Energy
Keywords:
Reflectometry
OSTI Identifier:
1562041
DOI:
https://doi.org/10.11578/1562041

Citation Formats

Crocker, N A, Kubota, S, Peebles, W A, Rhodes, T L, Fredrickson, E D, Belova, E, Diallo, A, LeBlanc, B P, and Sabbagh, S A. Density perturbation mode structure of high frequency compressional and global Alfvén eigenmodes in the National Spherical Torus Experiment using a novel reflectometer analysis technique. United States: N. p., 2017. Web. doi:10.11578/1562041.
Crocker, N A, Kubota, S, Peebles, W A, Rhodes, T L, Fredrickson, E D, Belova, E, Diallo, A, LeBlanc, B P, & Sabbagh, S A. Density perturbation mode structure of high frequency compressional and global Alfvén eigenmodes in the National Spherical Torus Experiment using a novel reflectometer analysis technique. United States. doi:https://doi.org/10.11578/1562041
Crocker, N A, Kubota, S, Peebles, W A, Rhodes, T L, Fredrickson, E D, Belova, E, Diallo, A, LeBlanc, B P, and Sabbagh, S A. 2017. "Density perturbation mode structure of high frequency compressional and global Alfvén eigenmodes in the National Spherical Torus Experiment using a novel reflectometer analysis technique". United States. doi:https://doi.org/10.11578/1562041. https://www.osti.gov/servlets/purl/1562041. Pub date:Wed Nov 01 00:00:00 EDT 2017
@article{osti_1562041,
title = {Density perturbation mode structure of high frequency compressional and global Alfvén eigenmodes in the National Spherical Torus Experiment using a novel reflectometer analysis technique},
author = {Crocker, N A and Kubota, S and Peebles, W A and Rhodes, T L and Fredrickson, E D and Belova, E and Diallo, A and LeBlanc, B P and Sabbagh, S A},
abstractNote = {Reflectometry measurements of compressional (CAE) and global (GAE) Alfvén eigenmodes are analyzed to obtain the amplitude and spatial structure of the density perturbations associated with the modes. A novel analysis technique developed for this purpose is presented. The analysis also naturally yields the amplitude and spatial structure of the density contour radial displacement, which is found to be 2–4 times larger than the value estimated directly from the reflectometer measurements using the much simpler ‘mirror approximation’. The modes were driven by beam ions in a high power (6 MW) neutral beam heated H-mode discharge (#141398) in the National Spherical Torus Experiment. The results of the analysis are used to assess the contribution of the modes to core energy transport and ion heating. The total displacement amplitude of the modes, which is shown to be larger than previously estimated (Crocker et al 2013 Nucl. Fusion 53 43017), is compared to the predicted threshold (Gorelenkov et al 2010 Nucl. Fusion 50 84012) for the anomalously high heat diffusion inferred from transport modeling in similar NSTX discharges. The results of the analysis also have strong implications for the energy transport via coupling of CAEs to kinetic Alfvén waves seen in simulations with the Hybrid MHD code (Belova et al 2015 Phys. Rev. Lett. 115 15001). Finally, the amplitudes of the observed CAEs fall well below the threshold for causing significant ion heating by stochastic velocity space diffusion (Gates et al 2001 Phys. Rev. Lett. 87 205003).},
doi = {10.11578/1562041},
journal = {},
number = ,
volume = ,
place = {United States},
year = {2017},
month = {11}
}