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

Knolker, M.; Evans, T. E.; Wingen, A.; Bortolon, A.; Chrystal, C.; Laggner, F.; Moyer, R. A.; Nazikian, R.; Zohm, H.

doi:10.1016/j.nme.2019.01.003

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:

Knolker, M.; Evans, T. E.; Wingen, A.; Bortolon, A.; Chrystal, C.;

; Moyer, R. A.; Nazikian, R.; Zohm, H.

Publication Date:: Tue Jan 01 00:00:00 EST 2019

Research Org.:: General Atomics, San Diego, CA (United States); Univ. of California, San Diego, CA (United States); Princeton Plasma Physics Laboratory (PPPL), Princeton, NJ (United States); Oak Ridge National Laboratory (ORNL), Oak Ridge, TN (United States)

Sponsoring Org.:: USDOE Office of Science (SC), Fusion Energy Sciences (FES)

OSTI Identifier:: 1547897

Alternate Identifier(s):: OSTI ID: 1502366; OSTI ID: 1570890

Grant/Contract Number:: FC02-04ER54698; FG02-07ER54917; FG02-05ER54809; AC05-00OR22725

Resource Type:: Published Article

Journal Name:: Nuclear Materials and Energy

Additional Journal Information:: Journal Name: Nuclear Materials and Energy Journal Volume: 18 Journal Issue: C; Journal ID: ISSN 2352-1791

Publisher:: Elsevier

Country of Publication:: Netherlands

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.  Netherlands: N. p., 2019. 
Web.  doi:10.1016/j.nme.2019.01.003.

Copy to clipboard


                    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.  Netherlands.  https://doi.org/10.1016/j.nme.2019.01.003

Copy to clipboard


                    Knolker, M., Evans, T. E., Wingen, A., Bortolon, A., Chrystal, C., Laggner, F., Moyer, R. A., Nazikian, R., and Zohm, H. Tue .  
"Observation of divertor currents during type-I ELMs on the DIII-D tokamak".  Netherlands.  https://doi.org/10.1016/j.nme.2019.01.003.

Copy to clipboard


                    
@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},

  number       = C,

  volume       = 18,

  place        = {Netherlands},

  year         = {Tue Jan 01 00:00:00 EST 2019},

  month        = {Tue Jan 01 00:00:00 EST 2019}

}

Copy to clipboard

Journal Article:

Free Publicly Available Full Text

Publisher's Version of Record
https://doi.org/10.1016/j.nme.2019.01.003

Other availability

Search WorldCat to find libraries that may hold this journal

Citation Metrics:

Cited by: 4 works

Citation information provided by
Web of Science

Figures / Tables:

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 »

All figures and tables (8 total)

Save / Share:

Export Metadata

Save to My Library

Works referencing / citing this record:

On the possiblity of direct electrical power extraction from scrape-off layer currents in tokamaks
journal, August 2019

Komm, M.; Stockel, J.; Adamek, J.
Plasma Physics and Controlled Fusion, Vol. 61, Issue 9
DOI: 10.1088/1361-6587/ab2739

Figures / Tables found in this record:

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

Similar Records in DOE PAGES and OSTI.GOV collections:

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

Journal Article Knolker, M. ; Evans, T. E. ; Wingen, A. ; ... - Nuclear Fusion

Measurements of divertor currents on DIII-D lead to new insights in nonlinear edge-localized mode (ELM) dynamics and a possible mechanism to explain their explosive growth. 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 is developedmore »« less
Cited by 3
https://doi.org/10.1088/1741-4326/ab3e9a

Full Text Available
Experimental validation of a model for particle recycling and tungsten erosion during ELMs in the DIII-D divertor

Journal Article Abrams, T. ; Unterberg, E. A. ; McLean, A. G. ; ... - Nuclear Materials and Energy

A refined version of the Fundamenksi-Moulton 'free-streaming' model (FSM) for the dynamics of divertor density, particle flux, and heat flux during edge localized modes (ELMs) is presented. This model depends only on inter-ELM pedestal and divertor conditions and, crucially, incorporates particle recycling: a FSM with recycling model, FSRM. The effective particle recycling coefficient, R_eff, is the only empirical fitting parameter in the FSRM. The predictions of the FSRM are systematically tested against a DIII-D database of ELM ion and energy fluence measurements and are shown to be consistent with the model across a wide range of pedestal and divertor conditionsmore »« less
Cited by 18
https://doi.org/10.1016/j.nme.2018.10.011
ELM and inter-ELM heat and particle flux to a secondary divertor in the DIII-D tokamak

Journal Article Perillo, Renato ; Boedo, Jose A. ; Lasnier, Charles ; ... - Nuclear Fusion

DIII-D ELMing discharges with a secondary X-point (XPT) inside the vessel were used to evaluate the power distribution between the primary and secondary divertors. The magnetic balance, defined by the distance between the primary and secondary separatrices at the outer midplane (dRsep), was varied from -5 mm (lower-single-null, LSN) to +16 mm (upper-single-null, USN). In this work, we find that the secondary divertor receives up to 1/3 of the total heat flux (primary + secondary divertors), and it is dominated by the ELM-driven flux. Both the radially-integrated and the peak heat flux to the secondary divertor decay below ~50% ofmore »« less
https://doi.org/10.1088/1741-4326/ac0f38

Full Text Available
Development of Surface Eroding Thermocouples in Small Angle Slot Divertor in DIII-D

Journal Article Ren, J. ; Donovan, D. ; Watkins, J. G. ; ... - IEEE Transactions on Plasma Science

The surface eroding thermocouple (SETC) has proved to be a useful fast local temperature and heat flux diagnostic since its application in DIII-D. The SETC system in DIII-D was upgraded, and seven new SETCs were installed in the small angle slot (SAS) divertor to create a localized poloidal array to provide heat flux profiles with sub-10-ms temporal resolution. In addition, a smaller SETC was developed to increase the spatial resolution and simplify installation in the SAS divertor. The SETC-containing tiles were re-engineered with a double-wide format so that the distance between the SETCs and the tile edges is extended tomore »« less
https://doi.org/10.1109/tps.2019.2943085

Full Text Available
Divertor heat and particle flux due to ELMs in DIII-D and ASDEX-Upgrade

Conference Leonard, A W ; Osborne, T H ; Suttrop, W

The authors characterize the divertor target plate heat and particle fluxes that occur due to Edge-Localized-Modes (ELMs) during H-mode in DIII-D and ASDEX-Upgrade. During steady-state ELMing H-mode the fraction of main plasma stored energy lost with each ELM varies from 6% to 2% as input power increases above the H-mode power threshold. The ELM energy is deposited near the strikepoints on the divertor target plates in a fast time scale of {le} 1 ms. The spatial profile of the ELM heat pulse is flatter and broader, up to about a factor of 2, than that of the heat flux betweenmore »« less
Full Text Available

Similar Records

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

Abstract

Citation Formats

Figures / Tables:

On the possiblity of direct electrical power extraction from scrape-off layer currents in tokamaks journal, August 2019

On the possiblity of direct electrical power extraction from scrape-off layer currents in tokamaks
journal, August 2019