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Title: Impact of plasma response on plasma displacements in DIII-D during application of external 3D perturbations

Journal Article · · Nuclear Fusion
 [1];  [2];  [3];  [1];  [2];  [1];  [2]
  1. ORNL
  2. General Atomics, San Diego
  3. Oak Ridge National Laboratory (ORNL)
+ Show Author Affiliations

The effects of applied 3D resonant magnetic perturbations are modelled with and without self-consistent plasma response. The plasma response is calculated using a linear two-fluid model. A synthetic diagnostic is used to simulate soft x-ray (SXR) emission within the steep gradient region of the pedestal, 0.98 > > 0.94. Two methods for simulating the SXR emission given the perturbed fields are considered. In the first method, the emission is assumed to be constant on magnetic field lines, with the emission on each line determined by the penetration depth into the plasma. In the second method, the emission is taken to be a function of the perturbed electron temperature and density calculated by the two-fluid model. It is shown that the latter method is more accurate within the plasma, but is inadequate in the scrape-off layer due to the breakdown of the linearized temperature equation in the two-fluid model. The resulting synthetic emission is compared to measured SXR data, which show helical m = 11 1 displacements around the 11/3 rational surface of sizes up to 5 cm, depending on the poloidal angle. The helical displacements around the 11/3 surface are identified to be directly related to the kink response, caused by amplification of non-resonant components of the magnetic field due to plasma response. The role of different plasma parameters is investigated, but it appears that the electron rotation plays a key role in the formation of screening and resonant amplification, while the kinking appears to be sensitive to the edge current density. It is also hypothesized that the plasma response affects the edge-localized-mode (ELM) stability, i.e. the discharge s operational point relative to the peeling ballooning stability boundary.

Research Organization:
Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)
Sponsoring Organization:
USDOE Office of Science (SC)
DOE Contract Number:
DE-AC05-00OR22725
OSTI ID:
1154868
Journal Information:
Nuclear Fusion, Vol. 54, Issue 6; ISSN 0029-5515
Country of Publication:
United States
Language:
English

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Cited By (8)

Advances in the physics understanding of ELM suppression using resonant magnetic perturbations in DIII-D journal January 2015
Equilibrium drives of the low and high field side n   =  2 plasma response and impact on global confinement journal April 2016
Dynamics of ideal modes and subsequent ELM crashes in 3D tokamak geometry from external magnetic perturbations journal November 2018
Assessment of equilibrium field coil misalignments on the divertor footprints in NSTX-U journal June 2019
Optimizing multi-modal, non-axisymmetric plasma response metrics with additional coil rows on DIII-D journal July 2019
Divertor currents during type-I edge-localized modes on the DIII-D tokamak journal October 2019
Nonlinear modeling of the effect of n   =  2 resonant magnetic field perturbation on peeling-ballooning modes in KSTAR journal January 2020
Observation of a Multimode Plasma Response and its Relationship to Density Pumpout and Edge-Localized Mode Suppression journal March 2015

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