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Title: Wall-touching kink mode calculations with the M3D code

Abstract

This paper seeks to address a controversy regarding the applicability of the 3D nonlinear extended MHD code M3D [W. Park et al., Phys. Plasmas 6, 1796 (1999)] and similar codes to calculations of the electromagnetic interaction of a disrupting tokamak plasma with the surrounding vessel structures. M3D is applied to a simple test problem involving an external kink mode in an ideal cylindrical plasma, used also by the Disruption Simulation Code (DSC) as a model case for illustrating the nature of transient vessel currents during a major disruption. While comparison of the results with those of the DSC is complicated by effects arising from the higher dimensionality and complexity of M3D, we verify that M3D is capable of reproducing both the correct saturation behavior of the free boundary kink and the “Hiro” currents arising when the kink interacts with a conducting tile surface interior to the ideal wall.

Authors:
;  [1]
  1. Princeton Plasma Physics Laboratory, Princeton, New Jersey 08542 (United States)
Publication Date:
OSTI Identifier:
22489993
Resource Type:
Journal Article
Resource Relation:
Journal Name: Physics of Plasmas; Journal Volume: 22; Journal Issue: 6; Other Information: (c) 2015 AIP Publishing LLC; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
70 PLASMA PHYSICS AND FUSION TECHNOLOGY; CALORIMETRY; COMPUTERIZED SIMULATION; CONTAINERS; CYLINDRICAL CONFIGURATION; ELECTROMAGNETIC INTERACTIONS; MAGNETOHYDRODYNAMICS; NONLINEAR PROBLEMS; PLASMA; SURFACES; THREE-DIMENSIONAL CALCULATIONS; TOKAMAK DEVICES

Citation Formats

Breslau, J. A., E-mail: jbreslau@pppl.gov, and Bhattacharjee, A.. Wall-touching kink mode calculations with the M3D code. United States: N. p., 2015. Web. doi:10.1063/1.4922760.
Breslau, J. A., E-mail: jbreslau@pppl.gov, & Bhattacharjee, A.. Wall-touching kink mode calculations with the M3D code. United States. doi:10.1063/1.4922760.
Breslau, J. A., E-mail: jbreslau@pppl.gov, and Bhattacharjee, A.. Mon . "Wall-touching kink mode calculations with the M3D code". United States. doi:10.1063/1.4922760.
@article{osti_22489993,
title = {Wall-touching kink mode calculations with the M3D code},
author = {Breslau, J. A., E-mail: jbreslau@pppl.gov and Bhattacharjee, A.},
abstractNote = {This paper seeks to address a controversy regarding the applicability of the 3D nonlinear extended MHD code M3D [W. Park et al., Phys. Plasmas 6, 1796 (1999)] and similar codes to calculations of the electromagnetic interaction of a disrupting tokamak plasma with the surrounding vessel structures. M3D is applied to a simple test problem involving an external kink mode in an ideal cylindrical plasma, used also by the Disruption Simulation Code (DSC) as a model case for illustrating the nature of transient vessel currents during a major disruption. While comparison of the results with those of the DSC is complicated by effects arising from the higher dimensionality and complexity of M3D, we verify that M3D is capable of reproducing both the correct saturation behavior of the free boundary kink and the “Hiro” currents arising when the kink interacts with a conducting tile surface interior to the ideal wall.},
doi = {10.1063/1.4922760},
journal = {Physics of Plasmas},
number = 6,
volume = 22,
place = {United States},
year = {Mon Jun 15 00:00:00 EDT 2015},
month = {Mon Jun 15 00:00:00 EDT 2015}
}
  • Cited by 2
  • One promising approach to maintaining stability of high beta tokamak plasmas is the use of a conducting wall near the plasma to stabilize low-{ital n} ideal magnetohydrodynamic instabilities. However, with a resistive wall, either plasma rotation or active feedback control is required to stabilize the more slowly growing resistive wall modes (RWMs). Previous experiments have demonstrated that plasmas with a nearby conducting wall can remain stable to the n=1 ideal external kink above the beta limit predicted with the wall at infinity. Recently, extension of the wall stabilized lifetime {tau}{sub L} to more than 30 times the resistive wall timemore » constant {tau}{sub w} and detailed, reproducible observation of the n=1 RWM have been possible in DIII-D [Plasma Physics and Controlled Fusion Research (International Atomic Energy Agency, Vienna, 1986), p. 159] plasmas above the no-wall beta limit. The DIII-D measurements confirm characteristics common to several RWM theories. The mode is destabilized as the plasma rotation at the q=3 surface decreases below a critical frequency of 1{endash}7 kHz ({approximately}1{percent} of the toroidal Alfv{acute e}n frequency). The measured mode growth times of 2{endash}8 ms agree with measurements and numerical calculations of the dominant DIII-D vessel eigenmode time constant {tau}{sub w}. From its onset, the RWM has little or no toroidal rotation ({omega}{sub mode}{le}{tau}{sub w}{sup {minus}1}{lt}{omega}{sub plasma}), and rapidly reduces the plasma rotation to zero. These slowly growing RWMs can in principle be destabilized using external coils controlled by a feedback loop. In this paper, the encouraging results from the first open loop experimental tests of active control of the RWM, conducted in DIII-D, are reported. {copyright} {ital 1999 American Institute of Physics.}« less
  • High-resolution active and passive kink mode studies are conducted in a tokamak with an adjustable ferromagnetic wall near the plasma surface. Ferritic tiles made from 5.6 mm thick Hiperco{sup ®} 50 alloy have been mounted on the plasma-facing side of half of the in-vessel movable wall segments in the High Beta Tokamak-Extended Pulse device [D. A. Maurer et al., Plasma Phys. Controlled Fusion 53, 074016 (2011)] in order to explore ferritic resistive wall mode stability. Low-activation ferritic steels are a candidate for structural components of a fusion reactor, and these experiments examine MHD stability of plasmas with nearby ferromagnetic material. Plasma-wallmore » separation for alternating ferritic and non-ferritic wall segments is adjusted between discharges without opening the vacuum vessel. Amplification of applied resonant magnetic perturbations and plasma disruptivity are observed to increase when the ferromagnetic wall is close to plasma surface instead of the standard stainless steel wall. Rapidly rotating m/n=3/1 external kink modes have higher growth rates with the nearby ferritic wall. Feedback suppression of kinks is still as effective as before the installation of ferritic material in vessel, in spite of increased mode growth rates.« less