skip to main content
DOE PAGES title logo U.S. Department of Energy
Office of Scientific and Technical Information

Title: Initial development of the DIII–D snowflake divertor control

Abstract

Simultaneous control of two proximate magnetic field nulls in the divertor region is demonstrated on DIII–D to enable plasma operations in an advanced magnetic configuration known as the snowflake divertor (SFD). The SFD is characterized by a second-order poloidal field null, created by merging two first-order nulls of the standard divertor configuration. The snowflake configuration has many magnetic properties, such as high poloidal flux expansion, large plasma-wetted area, and additional strike points, that are advantageous for divertor heat flux management in future fusion reactors. However, the magnetic configuration of the SFD is highly-sensitive to changes in currents within the plasma and external coils and therefore requires complex magnetic control. The first real-time snowflake detection and control system on DIII–D has been implemented in order to stabilize the configuration. The control algorithm calculates the position of the two nulls in real-time by locally-expanding the Grad–Shafranov equation in the divertor region. A linear relation between variations in the poloidal field coil currents and changes in the null locations is then analytically derived. This formulation allows for simultaneous control of multiple coils to achieve a desired SFD configuration. It is shown that the control enabled various snowflake configurations on DIII–D in scenarios suchmore » as the double-null advanced tokamak. The SFD resulted in a 2.5×reduction in the peak heat flux for many energy confinement times (2–3 s) without any adverse effects on core plasma performance.« less

Authors:
 [1];  [1];  [2];  [2];  [3];  [2];  [3];  [3];  [2]; ORCiD logo [3];  [2];  [1];  [1];  [3];  [2]; ORCiD logo [4]
  1. Princeton Univ., NJ (United States)
  2. Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States)
  3. General Atomics, San Diego, CA (United States)
  4. Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)
Publication Date:
Research Org.:
General Atomics, San Diego, CA (United States); Princeton Univ., NJ (United States); Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)
Sponsoring Org.:
USDOE Office of Science (SC), Fusion Energy Sciences (FES)
OSTI Identifier:
1435461
Alternate Identifier(s):
OSTI ID: 1515659
Grant/Contract Number:  
FC02-04ER54698; AC02-09CH11466; AC52-07NA27344; AC05-00OR22725; SC0015480; SC0015878
Resource Type:
Accepted Manuscript
Journal Name:
Nuclear Fusion
Additional Journal Information:
Journal Volume: 58; Journal Issue: 6; Journal ID: ISSN 0029-5515
Publisher:
IOP Science
Country of Publication:
United States
Language:
English
Subject:
70 PLASMA PHYSICS AND FUSION TECHNOLOGY; advanced divertor; divertor; control; snowflake; DIII-D

Citation Formats

Kolemen, Egemen, Vail, P. J., Makowski, M. A., Allen, Steve L., Bray, B. D., Fenstermacher, Max E., Humphreys, David A., Hyatt, Alan W., Lasnier, Charles J., Leonard, Anthony W., McLean, Adam G., Maingi, R., Nazikian, Raffi, Petrie, Thomas W., Soukhanovskii, V. A., and Unterberg, Ezekial A. Initial development of the DIII–D snowflake divertor control. United States: N. p., 2018. Web. https://doi.org/10.1088/1741-4326/aab0d3.
Kolemen, Egemen, Vail, P. J., Makowski, M. A., Allen, Steve L., Bray, B. D., Fenstermacher, Max E., Humphreys, David A., Hyatt, Alan W., Lasnier, Charles J., Leonard, Anthony W., McLean, Adam G., Maingi, R., Nazikian, Raffi, Petrie, Thomas W., Soukhanovskii, V. A., & Unterberg, Ezekial A. Initial development of the DIII–D snowflake divertor control. United States. https://doi.org/10.1088/1741-4326/aab0d3
Kolemen, Egemen, Vail, P. J., Makowski, M. A., Allen, Steve L., Bray, B. D., Fenstermacher, Max E., Humphreys, David A., Hyatt, Alan W., Lasnier, Charles J., Leonard, Anthony W., McLean, Adam G., Maingi, R., Nazikian, Raffi, Petrie, Thomas W., Soukhanovskii, V. A., and Unterberg, Ezekial A. Wed . "Initial development of the DIII–D snowflake divertor control". United States. https://doi.org/10.1088/1741-4326/aab0d3. https://www.osti.gov/servlets/purl/1435461.
@article{osti_1435461,
title = {Initial development of the DIII–D snowflake divertor control},
author = {Kolemen, Egemen and Vail, P. J. and Makowski, M. A. and Allen, Steve L. and Bray, B. D. and Fenstermacher, Max E. and Humphreys, David A. and Hyatt, Alan W. and Lasnier, Charles J. and Leonard, Anthony W. and McLean, Adam G. and Maingi, R. and Nazikian, Raffi and Petrie, Thomas W. and Soukhanovskii, V. A. and Unterberg, Ezekial A.},
abstractNote = {Simultaneous control of two proximate magnetic field nulls in the divertor region is demonstrated on DIII–D to enable plasma operations in an advanced magnetic configuration known as the snowflake divertor (SFD). The SFD is characterized by a second-order poloidal field null, created by merging two first-order nulls of the standard divertor configuration. The snowflake configuration has many magnetic properties, such as high poloidal flux expansion, large plasma-wetted area, and additional strike points, that are advantageous for divertor heat flux management in future fusion reactors. However, the magnetic configuration of the SFD is highly-sensitive to changes in currents within the plasma and external coils and therefore requires complex magnetic control. The first real-time snowflake detection and control system on DIII–D has been implemented in order to stabilize the configuration. The control algorithm calculates the position of the two nulls in real-time by locally-expanding the Grad–Shafranov equation in the divertor region. A linear relation between variations in the poloidal field coil currents and changes in the null locations is then analytically derived. This formulation allows for simultaneous control of multiple coils to achieve a desired SFD configuration. It is shown that the control enabled various snowflake configurations on DIII–D in scenarios such as the double-null advanced tokamak. The SFD resulted in a 2.5×reduction in the peak heat flux for many energy confinement times (2–3 s) without any adverse effects on core plasma performance.},
doi = {10.1088/1741-4326/aab0d3},
journal = {Nuclear Fusion},
number = 6,
volume = 58,
place = {United States},
year = {2018},
month = {4}
}

Journal Article:
Free Publicly Available Full Text
Publisher's Version of Record

Citation Metrics:
Cited by: 1 work
Citation information provided by
Web of Science

Save / Share:

Works referenced in this record:

Geometrical properties of a “snowflake” divertor
journal, June 2007


Feedback for physicists: A tutorial essay on control
journal, August 2005


Snowflake divertor configuration studies in National Spherical Torus Experiment
journal, August 2012

  • Soukhanovskii, V. A.; Bell, R. E.; Diallo, A.
  • Physics of Plasmas, Vol. 19, Issue 8
  • DOI: 10.1063/1.4737117

The ‘churning mode’ of plasma convection in the tokamak divertor region
journal, July 2014


Snowflake divertor plasmas on TCV
journal, March 2009


High density operation for reactor-relevant power exhaust
journal, August 2015


Magnetic geometry and physics of advanced divertors: The X-divertor and the snowflake
journal, October 2013

  • Kotschenreuther, Mike; Valanju, Prashant; Covele, Brent
  • Physics of Plasmas, Vol. 20, Issue 10
  • DOI: 10.1063/1.4824735

Radiative snowflake divertor studies in DIII-D
journal, August 2015


Super-X divertors and high power density fusion devices
journal, May 2009

  • Valanju, P. M.; Kotschenreuther, M.; Mahajan, S. M.
  • Physics of Plasmas, Vol. 16, Issue 5
  • DOI: 10.1063/1.3110984

Investigation of Advanced Divertor Magnetic Configuration for DEMO Tokamak Reactor
journal, May 2013

  • Asakura, Nobuyuki; Shinya, Kichiro; Tobita, Kenji
  • Fusion Science and Technology, Vol. 63, Issue 1T
  • DOI: 10.13182/fst13-a16876

Progress in the ITER Physics Basis
journal, June 2007


The snowflake divertor
journal, November 2015

  • Ryutov, D. D.; Soukhanovskii, V. A.
  • Physics of Plasmas, Vol. 22, Issue 11
  • DOI: 10.1063/1.4935115

Local properties of the magnetic field in a snowflake divertor
journal, August 2010


Application of the radiating divertor approach to innovative tokamak divertor concepts
journal, August 2015


Real time equilibrium reconstruction for tokamak discharge control
journal, July 1998


Strike point control for the National Spherical Torus Experiment (NSTX)
journal, September 2010


Control of plasma poloidal shape and position in the DIII-D tokamak
conference, January 1997

  • Walker, M. L.; Humphreys, D. A.; Ferron, J. R.
  • Proceedings of the 36th IEEE Conference on Decision and Control
  • DOI: 10.1109/cdc.1997.652432

Plasma modelling results and shape control improvements for NSTX
journal, November 2011


Progress in the physics basis of a Fusion Nuclear Science Facility based on the Advanced Tokamak concept
journal, May 2014


On the physics guidelines for a tokamak DEMO
journal, June 2013


EAST alternative magnetic configurations: modelling and first experiments
journal, June 2015


Plasma boundary shape control and real-time equilibrium reconstruction on NSTX-U
journal, January 2018


Progress in the ITER Physics Basis
journal, June 2007


Investigation of Advanced Divertor Magnetic Configuration for DEMO Tokamak Reactor
journal, May 2013

  • Asakura, Nobuyuki; Shinya, Kichiro; Tobita, Kenji
  • Fusion Science and Technology, Vol. 63, Issue 1T
  • DOI: 10.13182/FST13-A16876

Control of plasma poloidal shape and position in the DIII-D tokamak
conference, January 1997

  • Walker, M. L.; Humphreys, D. A.; Ferron, J. R.
  • Proceedings of the 36th IEEE Conference on Decision and Control
  • DOI: 10.1109/CDC.1997.652432

Feedback for physicists: A tutorial essay on control
journal, August 2005


    Works referencing / citing this record:

    Design and simulation of the snowflake divertor control for NSTX–U
    journal, January 2019

    • Vail, P. J.; Boyer, M. D.; Welander, A. S.
    • Plasma Physics and Controlled Fusion, Vol. 61, Issue 3
    • DOI: 10.1088/1361-6587/aaf94a

    Real time magnetic control of the snowflake plasma configuration in the TCV tokamak
    journal, October 2019