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Title: Magnetic Polarization Measurements of the Multi-modal Plasma Response to 3D fields in the EAST Tokamak

Abstract

A multi-modal plasma response to applied non-axisymmetric fields has been found in EAST tokamak plasmas. Here, multi-modal means the radial and poloidal structure of an individually driven toroidal harmonic is not fixed. The signature of such a multi-modal response is the magnetic polarization (ratio of radial and poloidal components) of the plasma response field measured on the low field side device mid-plane. A difference in the 3D coil phasing (the relative phase of two coil arrays) dependencies between the two responses is observed in response to n=2 fields in the same plasma for which the n=1 responses are well synchronized. Neither the maximum radial nor the maximum poloidal field response to n=2 fields agrees with the best applied phasing for mitigating edge localized modes, suggesting that the edge plasma response is not a dominant component of either polarization. GPEC modeling reproduces the discrepant phasing dependences of the experimental measurements, and confirms the edge resonances are maximized by the coil phasing that mitigates ELMs in the experiments. The model confirms the measured plasma response is not dominated by resonant current drive from the external field. Instead, non-resonant contributions play a large role in the diagnostic signal for both toroidal harmonics n=1more » and n=2. The analysis in this paper demonstrates the ability of 3D modeling to connect external magnetic sensor measurements to the internal plasma physics and accurately predict optimal applied 3D field configurations in multi-modal plasmas.« less

Authors:
 [1];  [1];  [2]; ORCiD logo [2];  [2]; ORCiD logo [2];  [1];  [3]
  1. Princeton Plasma Physics Lab. (PPPL), Princeton, NJ (United States)
  2. Chinese Academy of Sciences, Anhui (China)
  3. General Atomics, San Diego, CA (United States)
Publication Date:
Research Org.:
Princeton Plasma Physics Lab. (PPPL), Princeton, NJ (United States)
Sponsoring Org.:
USDOE
OSTI Identifier:
1436768
Grant/Contract Number:  
AC02-09CH11466; 11475224
Resource Type:
Accepted Manuscript
Journal Name:
Nuclear Fusion
Additional Journal Information:
Journal Volume: 58; Journal Issue: 7; Journal ID: ISSN 0029-5515
Publisher:
IOP Science
Country of Publication:
United States
Language:
English
Subject:
70 PLASMA PHYSICS AND FUSION TECHNOLOGY; Tokamak; Resonant Magnetic Perturbations; Edge Localized Modes; Reluctance; GPEC

Citation Formats

Logan, Nikolas, Cui, L., Wang, Hui -Hui, Sun, Youwen, Gu, Shuai, Li, Guoqiang, Nazikian, Raffi, and Paz-Soldan, Carlos. Magnetic Polarization Measurements of the Multi-modal Plasma Response to 3D fields in the EAST Tokamak. United States: N. p., 2018. Web. doi:10.1088/1741-4326/aac129.
Logan, Nikolas, Cui, L., Wang, Hui -Hui, Sun, Youwen, Gu, Shuai, Li, Guoqiang, Nazikian, Raffi, & Paz-Soldan, Carlos. Magnetic Polarization Measurements of the Multi-modal Plasma Response to 3D fields in the EAST Tokamak. United States. doi:10.1088/1741-4326/aac129.
Logan, Nikolas, Cui, L., Wang, Hui -Hui, Sun, Youwen, Gu, Shuai, Li, Guoqiang, Nazikian, Raffi, and Paz-Soldan, Carlos. Mon . "Magnetic Polarization Measurements of the Multi-modal Plasma Response to 3D fields in the EAST Tokamak". United States. doi:10.1088/1741-4326/aac129. https://www.osti.gov/servlets/purl/1436768.
@article{osti_1436768,
title = {Magnetic Polarization Measurements of the Multi-modal Plasma Response to 3D fields in the EAST Tokamak},
author = {Logan, Nikolas and Cui, L. and Wang, Hui -Hui and Sun, Youwen and Gu, Shuai and Li, Guoqiang and Nazikian, Raffi and Paz-Soldan, Carlos},
abstractNote = {A multi-modal plasma response to applied non-axisymmetric fields has been found in EAST tokamak plasmas. Here, multi-modal means the radial and poloidal structure of an individually driven toroidal harmonic is not fixed. The signature of such a multi-modal response is the magnetic polarization (ratio of radial and poloidal components) of the plasma response field measured on the low field side device mid-plane. A difference in the 3D coil phasing (the relative phase of two coil arrays) dependencies between the two responses is observed in response to n=2 fields in the same plasma for which the n=1 responses are well synchronized. Neither the maximum radial nor the maximum poloidal field response to n=2 fields agrees with the best applied phasing for mitigating edge localized modes, suggesting that the edge plasma response is not a dominant component of either polarization. GPEC modeling reproduces the discrepant phasing dependences of the experimental measurements, and confirms the edge resonances are maximized by the coil phasing that mitigates ELMs in the experiments. The model confirms the measured plasma response is not dominated by resonant current drive from the external field. Instead, non-resonant contributions play a large role in the diagnostic signal for both toroidal harmonics n=1 and n=2. The analysis in this paper demonstrates the ability of 3D modeling to connect external magnetic sensor measurements to the internal plasma physics and accurately predict optimal applied 3D field configurations in multi-modal plasmas.},
doi = {10.1088/1741-4326/aac129},
journal = {Nuclear Fusion},
number = 7,
volume = 58,
place = {United States},
year = {2018},
month = {4}
}

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