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Title: Divertor currents during type-I edge-localized modes on the DIII-D tokamak

Abstract

Measurements of divertor currents on DIII-D lead to new insights in nonlinear ELM dynamics and a possible mechanism to explain their explosive growth. Herein rapidly oscillating currents flowing into the divertor before a significant increase in divertor heat flux occurs are measured with an array of shunted tiles and characterized. Extrapolation results in total n=0 currents of 5-10 kA flowing into a concentric circle near the strike point. The detected Fourier harmonics appear consistent with a mix of low-n modes (n<4) with currents up to 4 kA. A heuristic framework for ELM currents (ECF) is developed based on thermoelectric origin of the tile currents with flow through regions inside of the nominal separatrix and found consistent with the current measurements. A current flow through the confined plasma leading to increased stochasticity and transport at the plasma edge, could provide a mechanism for additional nonlinear growth as sought for in computational ELM simulations. Results also imply that ELM currents may open the possibility to manipulate the ELM character by perturbations through non-axisymmetric divertor bias or tile insulation.

Authors:
ORCiD logo [1]; ORCiD logo [2]; ORCiD logo [3]; ORCiD logo [4]; ORCiD logo [4]; ORCiD logo [1]; ORCiD logo [4]; ORCiD logo [5]
  1. Univ. of California, San Diego, CA (United States)
  2. General Atomics, San Diego, CA (United States)
  3. Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)
  4. Princeton Plasma Physics Lab. (PPPL), Princeton, NJ (United States)
  5. Max Planck Inst. for Plasma Physics, Garching (Germany)
Publication Date:
Research Org.:
General Atomics, San Diego, CA (United States); Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States); Princeton Plasma Physics Lab. (PPPL), Princeton, NJ (United States); General Atomics, San Diego, CA (United States). DIII-D National Fusion Facility
Sponsoring Org.:
USDOE Office of Science (SC), Fusion Energy Sciences (FES)
OSTI Identifier:
1571140
Alternate Identifier(s):
OSTI ID: 1608415; OSTI ID: 1651251
Grant/Contract Number:  
FC02-04ER54698; AC05-00OR22725; FG02-05ER54809; FG02-07ER54917; SC0018030
Resource Type:
Accepted Manuscript
Journal Name:
Nuclear Fusion
Additional Journal Information:
Journal Volume: 59; Journal Issue: 12; Journal ID: ISSN 0029-5515
Publisher:
IOP Science
Country of Publication:
United States
Language:
English
Subject:
70 PLASMA PHYSICS AND FUSION TECHNOLOGY; ELM; divertor; current; nonlinear

Citation Formats

Knolker, M., Evans, T. E., Wingen, A., Bortolon, A., Laggner, F. M., Moyer, R. A., Nazikian, R., and Zohm, H. Divertor currents during type-I edge-localized modes on the DIII-D tokamak. United States: N. p., 2019. Web. doi:10.1088/1741-4326/ab3e9a.
Knolker, M., Evans, T. E., Wingen, A., Bortolon, A., Laggner, F. M., Moyer, R. A., Nazikian, R., & Zohm, H. Divertor currents during type-I edge-localized modes on the DIII-D tokamak. United States. doi:10.1088/1741-4326/ab3e9a.
Knolker, M., Evans, T. E., Wingen, A., Bortolon, A., Laggner, F. M., Moyer, R. A., Nazikian, R., and Zohm, H. Fri . "Divertor currents during type-I edge-localized modes on the DIII-D tokamak". United States. doi:10.1088/1741-4326/ab3e9a. https://www.osti.gov/servlets/purl/1571140.
@article{osti_1571140,
title = {Divertor currents during type-I edge-localized modes on the DIII-D tokamak},
author = {Knolker, M. and Evans, T. E. and Wingen, A. and Bortolon, A. and Laggner, F. M. and Moyer, R. A. and Nazikian, R. and Zohm, H.},
abstractNote = {Measurements of divertor currents on DIII-D lead to new insights in nonlinear ELM dynamics and a possible mechanism to explain their explosive growth. Herein rapidly oscillating currents flowing into the divertor before a significant increase in divertor heat flux occurs are measured with an array of shunted tiles and characterized. Extrapolation results in total n=0 currents of 5-10 kA flowing into a concentric circle near the strike point. The detected Fourier harmonics appear consistent with a mix of low-n modes (n<4) with currents up to 4 kA. A heuristic framework for ELM currents (ECF) is developed based on thermoelectric origin of the tile currents with flow through regions inside of the nominal separatrix and found consistent with the current measurements. A current flow through the confined plasma leading to increased stochasticity and transport at the plasma edge, could provide a mechanism for additional nonlinear growth as sought for in computational ELM simulations. Results also imply that ELM currents may open the possibility to manipulate the ELM character by perturbations through non-axisymmetric divertor bias or tile insulation.},
doi = {10.1088/1741-4326/ab3e9a},
journal = {Nuclear Fusion},
number = 12,
volume = 59,
place = {United States},
year = {2019},
month = {10}
}

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