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Title: Pedestal Bifurcation and Resonant Field Penetration at the Threshold of Edge-Localized Mode Suppression in the DIII-D Tokamak

Abstract

Rapid bifurcations in the plasma response to slowly varying n=2 magnetic fields are observed as the plasma transitions into and out of edge localized mode (ELM) suppression. The rapid transition to ELM suppression is characterized by an increase in the toroidal rotation and a reduction in the electron pressure gradient at the top of the pedestal which reduces the perpendicular electron flow to near zero. These events occur simultaneously with an increase in the inner wall magnetic response. These observations are consistent strong resonant field penetration of n=2 fields at the onset of ELM suppression, based on extended MHD simulations using measured plasma profiles. Spontaneous transitions into (and out of) ELM suppression with a static applied n=2 field indicate competing mechanisms of screening and penetration of resonant fields near threshold conditions. Magnetic measurements reveal evidence for the unlocking and rotation of tearing-like structures as the plasma transitions out of ELM suppression.

Authors:
 [1];  [2];  [3];  [2];  [4];  [2];  [2];  [1];  [2];  [5];  [3];  [2];  [1];  [3];  [4];  [1];  [4];  [2];  [1];  [6] more »;  [7];  [2];  [1];  [2];  [2] « less
  1. Princeton Plasma Physics Lab. (PPPL), Princeton, NJ (United States)
  2. General Atomics, San Diego, CA (United States)
  3. Univ. of Wisconsin, Madison, WI (United States)
  4. Univ. of California, San Diego, CA (United States)
  5. Australian National Univ., Canberra, ACT (Australia). Plasma Research Lab.
  6. Univ. of California, Los Angeles, CA (United States)
  7. Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)
Publication Date:
Research Org.:
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)
Sponsoring Org.:
USDOE Office of Science (SC)
OSTI Identifier:
1295123
Alternate Identifier(s):
OSTI ID: 1180277; OSTI ID: 1260730; OSTI ID: 1371744
Grant/Contract Number:  
AC05-00OR22725; FC02-04ER54698; AC02-09CH11466; FG02-07ER54917; FG02-89ER53296; FG02-08ER54999; FG02-08ER54984; FG02-86ER53218; FG02- 92ER54139
Resource Type:
Accepted Manuscript
Journal Name:
Physical Review Letters
Additional Journal Information:
Journal Volume: 114; Journal Issue: 10; Journal ID: ISSN 0031-9007
Publisher:
American Physical Society (APS)
Country of Publication:
United States
Language:
English
Subject:
70 PLASMA PHYSICS AND FUSION TECHNOLOGY

Citation Formats

Nazikian, R., Paz-Soldan, C., Callen, J. D., deGrassie, J. S., Eldon, D., Evans, T. E., Ferraro, N. M., Grierson, B. A., Groebner, R. J., Haskey, S. R., Hegna, C. C., King, J. D., Logan, N. C., McKee, G. R., Moyer, R. A., Okabayashi, M., Orlov, D. M., Osborne, T. H., Park, J-K., Rhodes, T. L., Shafer, M. W., Snyder, P. B., Solomon, W. M., Strait, E. J., and Wade, M. R. Pedestal Bifurcation and Resonant Field Penetration at the Threshold of Edge-Localized Mode Suppression in the DIII-D Tokamak. United States: N. p., 2015. Web. doi:10.1103/PhysRevLett.114.105002.
Nazikian, R., Paz-Soldan, C., Callen, J. D., deGrassie, J. S., Eldon, D., Evans, T. E., Ferraro, N. M., Grierson, B. A., Groebner, R. J., Haskey, S. R., Hegna, C. C., King, J. D., Logan, N. C., McKee, G. R., Moyer, R. A., Okabayashi, M., Orlov, D. M., Osborne, T. H., Park, J-K., Rhodes, T. L., Shafer, M. W., Snyder, P. B., Solomon, W. M., Strait, E. J., & Wade, M. R. Pedestal Bifurcation and Resonant Field Penetration at the Threshold of Edge-Localized Mode Suppression in the DIII-D Tokamak. United States. https://doi.org/10.1103/PhysRevLett.114.105002
Nazikian, R., Paz-Soldan, C., Callen, J. D., deGrassie, J. S., Eldon, D., Evans, T. E., Ferraro, N. M., Grierson, B. A., Groebner, R. J., Haskey, S. R., Hegna, C. C., King, J. D., Logan, N. C., McKee, G. R., Moyer, R. A., Okabayashi, M., Orlov, D. M., Osborne, T. H., Park, J-K., Rhodes, T. L., Shafer, M. W., Snyder, P. B., Solomon, W. M., Strait, E. J., and Wade, M. R. Thu . "Pedestal Bifurcation and Resonant Field Penetration at the Threshold of Edge-Localized Mode Suppression in the DIII-D Tokamak". United States. https://doi.org/10.1103/PhysRevLett.114.105002. https://www.osti.gov/servlets/purl/1295123.
@article{osti_1295123,
title = {Pedestal Bifurcation and Resonant Field Penetration at the Threshold of Edge-Localized Mode Suppression in the DIII-D Tokamak},
author = {Nazikian, R. and Paz-Soldan, C. and Callen, J. D. and deGrassie, J. S. and Eldon, D. and Evans, T. E. and Ferraro, N. M. and Grierson, B. A. and Groebner, R. J. and Haskey, S. R. and Hegna, C. C. and King, J. D. and Logan, N. C. and McKee, G. R. and Moyer, R. A. and Okabayashi, M. and Orlov, D. M. and Osborne, T. H. and Park, J-K. and Rhodes, T. L. and Shafer, M. W. and Snyder, P. B. and Solomon, W. M. and Strait, E. J. and Wade, M. R.},
abstractNote = {Rapid bifurcations in the plasma response to slowly varying n=2 magnetic fields are observed as the plasma transitions into and out of edge localized mode (ELM) suppression. The rapid transition to ELM suppression is characterized by an increase in the toroidal rotation and a reduction in the electron pressure gradient at the top of the pedestal which reduces the perpendicular electron flow to near zero. These events occur simultaneously with an increase in the inner wall magnetic response. These observations are consistent strong resonant field penetration of n=2 fields at the onset of ELM suppression, based on extended MHD simulations using measured plasma profiles. Spontaneous transitions into (and out of) ELM suppression with a static applied n=2 field indicate competing mechanisms of screening and penetration of resonant fields near threshold conditions. Magnetic measurements reveal evidence for the unlocking and rotation of tearing-like structures as the plasma transitions out of ELM suppression.},
doi = {10.1103/PhysRevLett.114.105002},
journal = {Physical Review Letters},
number = 10,
volume = 114,
place = {United States},
year = {Thu Mar 12 00:00:00 EDT 2015},
month = {Thu Mar 12 00:00:00 EDT 2015}
}

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