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Title: ELM suppression in helium plasmas with 3D magnetic fields

Abstract

Experiments in DIII-D, using non-axisymmetric magnetic perturbation fields in high-purity low toroidal rotation, 4He plasmas have resulted in Type-I edge localized mode (ELM) suppression and mitigation. Suppression is obtained in plasmas with zero net input torque near the L–H power threshold using either electron cyclotron resonant heating (ECRH) or balanced co- and counter-I p neutral beam injection (NBI) resulting in conditions equivalent to those expected in ITER's non-active operating phase. In low-power ECRH H-modes, periods with uncontrolled density and impurity radiation excursions are prevented by applying n = 3 non-axisymmetric magnetic perturbation fields. ELM suppression results from a reduction and an outward shift of the electron pressure gradient peak compared to that in the high-power ELMing phase. Here, the change in the electron pressure gradient peak is primarily due to a drop in the pedestal temperature rather than the pedestal density.

Authors:
 [1];  [2];  [3];  [4];  [5];  [6];  [4];  [1];  [1];  [3];  [4];  [1];  [7]
  1. General Atomics, San Diego, CA (United States)
  2. ITER Organization, St. Paul lez Durance (France)
  3. Univ. of California San Diego, La Jolla, CA (United States)
  4. Princeton Plasma Physics Lab. (PPPL), Princeton, NJ (United States)
  5. Ludwig Maximilian Univ., Munich (Germany)
  6. General Atomics, San Diego, CA (United States); Oak Ridge Institute for Science Education, Oak Ridge, TN (United States)
  7. Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)
Publication Date:
Research Org.:
Princeton Plasma Physics Lab. (PPPL), Princeton, NJ (United States); General Atomics, San Diego, CA (United States)
Sponsoring Org.:
USDOE
OSTI Identifier:
1373695
Grant/Contract Number:
FC02-04ER54698
Resource Type:
Journal Article: Accepted Manuscript
Journal Name:
Nuclear Fusion
Additional Journal Information:
Journal Volume: 57; Journal Issue: 8; Journal ID: ISSN 0029-5515
Publisher:
IOP Science
Country of Publication:
United States
Language:
English
Subject:
70 PLASMA PHYSICS AND FUSION TECHNOLOGY; ELM suppression; Helium plasmas; resonant magnetic perturbations; DIII-D; ITER

Citation Formats

Evans, T. E., Loarte, A., Orlov, D. M., Grierson, B. A., Knolker, M. M., Lyons, B. C., Cui, L., Gohil, P., Groebner, R. J., Moyer, R. A., Nazikian, R., Osborne, T. H., and Unterberg, E. A. ELM suppression in helium plasmas with 3D magnetic fields. United States: N. p., 2017. Web. doi:10.1088/1741-4326/aa7530.
Evans, T. E., Loarte, A., Orlov, D. M., Grierson, B. A., Knolker, M. M., Lyons, B. C., Cui, L., Gohil, P., Groebner, R. J., Moyer, R. A., Nazikian, R., Osborne, T. H., & Unterberg, E. A. ELM suppression in helium plasmas with 3D magnetic fields. United States. doi:10.1088/1741-4326/aa7530.
Evans, T. E., Loarte, A., Orlov, D. M., Grierson, B. A., Knolker, M. M., Lyons, B. C., Cui, L., Gohil, P., Groebner, R. J., Moyer, R. A., Nazikian, R., Osborne, T. H., and Unterberg, E. A. 2017. "ELM suppression in helium plasmas with 3D magnetic fields". United States. doi:10.1088/1741-4326/aa7530.
@article{osti_1373695,
title = {ELM suppression in helium plasmas with 3D magnetic fields},
author = {Evans, T. E. and Loarte, A. and Orlov, D. M. and Grierson, B. A. and Knolker, M. M. and Lyons, B. C. and Cui, L. and Gohil, P. and Groebner, R. J. and Moyer, R. A. and Nazikian, R. and Osborne, T. H. and Unterberg, E. A.},
abstractNote = {Experiments in DIII-D, using non-axisymmetric magnetic perturbation fields in high-purity low toroidal rotation, 4He plasmas have resulted in Type-I edge localized mode (ELM) suppression and mitigation. Suppression is obtained in plasmas with zero net input torque near the L–H power threshold using either electron cyclotron resonant heating (ECRH) or balanced co- and counter-I p neutral beam injection (NBI) resulting in conditions equivalent to those expected in ITER's non-active operating phase. In low-power ECRH H-modes, periods with uncontrolled density and impurity radiation excursions are prevented by applying n = 3 non-axisymmetric magnetic perturbation fields. ELM suppression results from a reduction and an outward shift of the electron pressure gradient peak compared to that in the high-power ELMing phase. Here, the change in the electron pressure gradient peak is primarily due to a drop in the pedestal temperature rather than the pedestal density.},
doi = {10.1088/1741-4326/aa7530},
journal = {Nuclear Fusion},
number = 8,
volume = 57,
place = {United States},
year = 2017,
month = 6
}

Journal Article:
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  • Experiments in DIII-D, using non-axisymmetric magnetic perturbation fields in high-purity low toroidal rotation, 4He plasmas have resulted in Type-I Edge Localized Mode (ELM) suppression and mitigation. Suppression is obtained in plasmas with zero net input torque near the L-H power threshold using either Electron Cyclotron Resonant Heating (ECRH) or balanced co- and counter-Ip Neutral Beam Injection (NBI) resulting in conditions equivalent to those expected in ITER’s non-active operating phase. In low-power ECRH Hmodes, periods with uncontrolled density and impurity radiation excursions are prevented by applying n=3 non-axisymmetric magnetic perturbation fields. ELM suppression results from a reduction and an outward shiftmore » of the electron pressure gradient peak compared to that in the high-power ELMing phase. The change in the electron pressure gradient peak is primarily due to a drop in the pedestal temperature rather than the pedestal density.« less
  • This is a study of the effect of an energetic ion population injected from a neutral beam source on the nonlinear stability of magnetic islands. A kinetic theory is used to obtain the island current, which includes previously known modifications resulting from bootstrap currents and resistive interchanges. The island current thus obtained is used in an asymptotic treatment of the perturbed Ampere's law, which yields an evolution equation for the island width. It is shown that the island width saturates at a very small amplitude in tokamaks (with {Delta}{prime}{gt}0) when the energetic ion density profile peaks just outside the rationalmore » surface. Energetic ions can also be used to modify the island width in three-dimensional equilibria. It is found that in stellarator equilibria with large vacuum islands, energetic ions can be injected to reduce the widths of equilibrium islands.« less
  • The method of resonant magnetic perturbation (RMP) has been shown to suppress edge-localized modes (ELMs) in the high-performance, stationary (or 'hybrid') scenario in the DIII-D tokamak. Calculations of stability to peeling-ballooning (P-B) modes are shown to be consistent with the observed suppression of type-I ELMs, while the ELM suppression, dependence on edge safety factor and density pump-out are similar for hybrids and standard H-mode discharges. However, other small ELMs can appear when the edge safety factor is outside the resonance window or when the H-mode pedestal is perturbed, which are not related to P-B stability. The role of the edgemore » bootstrap current in determining stochastic heat transport during RMP is discussed.« less