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Title: Observation of divertor currents during type-I ELMs on the DIII-D tokamak

Abstract

In DIII-D, large currents flowing into the divertor floor during edge-localized modes (ELMs) have been measured by an array of shunt current resistors before an increase of heat flux is measured by IR thermography. The diagnostic consists of 40 tiles distributed in five concentric circles in the lower divertor with sampling rates range between 50 and 500 kHz. Typically, the current measured by a single tile during an ELM can reach 500 A. This amounts to 5–25 kA flowing in the divertor tiles. The temporal evolution of the ELM currents shows a first phase with large amplitude oscillations, occurring before the heat flux increase measured by infrared thermography at the same location, lasting between 0.05 ms and 0.3 ms. A second phase follows where the time evolution of the divertor current mimics the evolution of the divertor heat flux. These currents could affect the plasma edge stability in the nonlinear ELM phase and provide a mechanism leading to explosive growth of edge stochasticity, the need of which and existence is predicted in contemporary nonlinear ELM simulations.

Authors:
 [1];  [2];  [3];  [4];  [2]; ORCiD logo [4];  [5];  [4];  [6]
  1. Ludwig Maximilian Univ., Munich (Germany)
  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. Univ. of California, San Diego, CA (United States)
  6. Max Planck Inst. for Plasma Physics, Garching (Germany)
Publication Date:
Research Org.:
General Atomics, San Diego, CA (United States); Univ. of California, San Diego, CA (United States); Princeton Plasma Physics Lab. (PPPL), Princeton, NJ (United States)
Sponsoring Org.:
USDOE Office of Science (SC), Fusion Energy Sciences (FES) (SC-24)
OSTI Identifier:
1547897
Alternate Identifier(s):
OSTI ID: 1502366
Grant/Contract Number:  
FC02-04ER54698; FG02-07ER54917; FG02-05ER54809
Resource Type:
Journal Article: Published Article
Journal Name:
Nuclear Materials and Energy
Additional Journal Information:
Journal Volume: 18; Journal ID: ISSN 2352-1791
Publisher:
Elsevier
Country of Publication:
United States
Language:
English
Subject:
70 PLASMA PHYSICS AND FUSION TECHNOLOGY

Citation Formats

Knolker, M., Evans, T. E., Wingen, A., Bortolon, A., Chrystal, C., Laggner, F., Moyer, R. A., Nazikian, R., and Zohm, H. Observation of divertor currents during type-I ELMs on the DIII-D tokamak. United States: N. p., 2019. Web. doi:10.1016/j.nme.2019.01.003.
Knolker, M., Evans, T. E., Wingen, A., Bortolon, A., Chrystal, C., Laggner, F., Moyer, R. A., Nazikian, R., & Zohm, H. Observation of divertor currents during type-I ELMs on the DIII-D tokamak. United States. doi:10.1016/j.nme.2019.01.003.
Knolker, M., Evans, T. E., Wingen, A., Bortolon, A., Chrystal, C., Laggner, F., Moyer, R. A., Nazikian, R., and Zohm, H. Wed . "Observation of divertor currents during type-I ELMs on the DIII-D tokamak". United States. doi:10.1016/j.nme.2019.01.003.
@article{osti_1547897,
title = {Observation of divertor currents during type-I ELMs on the DIII-D tokamak},
author = {Knolker, M. and Evans, T. E. and Wingen, A. and Bortolon, A. and Chrystal, C. and Laggner, F. and Moyer, R. A. and Nazikian, R. and Zohm, H.},
abstractNote = {In DIII-D, large currents flowing into the divertor floor during edge-localized modes (ELMs) have been measured by an array of shunt current resistors before an increase of heat flux is measured by IR thermography. The diagnostic consists of 40 tiles distributed in five concentric circles in the lower divertor with sampling rates range between 50 and 500 kHz. Typically, the current measured by a single tile during an ELM can reach 500 A. This amounts to 5–25 kA flowing in the divertor tiles. The temporal evolution of the ELM currents shows a first phase with large amplitude oscillations, occurring before the heat flux increase measured by infrared thermography at the same location, lasting between 0.05 ms and 0.3 ms. A second phase follows where the time evolution of the divertor current mimics the evolution of the divertor heat flux. These currents could affect the plasma edge stability in the nonlinear ELM phase and provide a mechanism leading to explosive growth of edge stochasticity, the need of which and existence is predicted in contemporary nonlinear ELM simulations.},
doi = {10.1016/j.nme.2019.01.003},
journal = {Nuclear Materials and Energy},
issn = {2352-1791},
number = ,
volume = 18,
place = {United States},
year = {2019},
month = {1}
}

Journal Article:
Free Publicly Available Full Text
Publisher's Version of Record at 10.1016/j.nme.2019.01.003

Figures / Tables:

Figure 1 Figure 1: Discharge evolution of 119,434: (a) Stored energy, (b) ELM filterscope, (c) pedestal (red) and line-averaged (black) density (red), (d) NBI power (blue), (e) pedestal electron pressure. The dashed lines mark the H-mode time window most analysis presented here is focused on. (For interpretation of the references to colormore » in this figure legend, the reader is referred to the web version of this article.)« less

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Figures/Tables have been extracted from DOE-funded journal article accepted manuscripts.