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Title: Determination of the non-ideal response of a high temperature tokamak plasma to a static external magnetic perturbation via asymptotic matching

Authors:
ORCiD logo [1]
  1. Department of Physics, Institute for Fusion Studies, University of Texas at Austin, Austin, Texas 78712, USA
Publication Date:
Sponsoring Org.:
USDOE
OSTI Identifier:
1368415
Grant/Contract Number:
FG02-04ER-54742
Resource Type:
Journal Article: Publisher's Accepted Manuscript
Journal Name:
Physics of Plasmas
Additional Journal Information:
Journal Volume: 24; Journal Issue: 7; Related Information: CHORUS Timestamp: 2018-02-15 00:28:30; Journal ID: ISSN 1070-664X
Publisher:
American Institute of Physics
Country of Publication:
United States
Language:
English

Citation Formats

Fitzpatrick, Richard. Determination of the non-ideal response of a high temperature tokamak plasma to a static external magnetic perturbation via asymptotic matching. United States: N. p., 2017. Web. doi:10.1063/1.4990701.
Fitzpatrick, Richard. Determination of the non-ideal response of a high temperature tokamak plasma to a static external magnetic perturbation via asymptotic matching. United States. doi:10.1063/1.4990701.
Fitzpatrick, Richard. Sat . "Determination of the non-ideal response of a high temperature tokamak plasma to a static external magnetic perturbation via asymptotic matching". United States. doi:10.1063/1.4990701.
@article{osti_1368415,
title = {Determination of the non-ideal response of a high temperature tokamak plasma to a static external magnetic perturbation via asymptotic matching},
author = {Fitzpatrick, Richard},
abstractNote = {},
doi = {10.1063/1.4990701},
journal = {Physics of Plasmas},
number = 7,
volume = 24,
place = {United States},
year = {Sat Jul 01 00:00:00 EDT 2017},
month = {Sat Jul 01 00:00:00 EDT 2017}
}

Journal Article:
Free Publicly Available Full Text
Publisher's Version of Record at 10.1063/1.4990701

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  • Experimental comparison of the m = 2, n = 1 mode and plasma rotation velocities at q = 2 magnetic surface in a wide range of the mode amplitudes is presented. Phase velocity of the mode rotation is measured with a set of poloidal magnetic field sensors located at the inner side of the vacuum vessel wall. Plasma rotation velocity at the q = 2 magnetic surface in the direction of the mode phase velocity is measured with the heavy ion beam probe diagnostics. In the presence of a static Resonant Magnetic Perturbation (RMP), the rotation is irregular that appears as cyclical variations of the mode and plasmamore » instantaneous velocities. The period of these variations is equal to the period of the mode oscillations. In the case of high mode amplitude, the rotation irregularity of the mode is consistent with the rotation irregularity of the resonant plasma layer. On the contrary, the observed rise of the mode rotation irregularity in the case of low mode amplitude occurs without an increase of the rotation irregularity of the resonant plasma layer. The experimental results are simulated and analyzed with the TEAR code based on the two-fluid MHD approximation. Calculated irregularities of the mode and plasma rotation depend on the mode amplitude similar to the experimental data. For large islands, the rotation irregularity is attributed to oscillations of the electromagnetic torque applied to the resonant plasma layer. For small islands, the deviation of the mode rotation velocity from the plasma velocity occurs due to the effect of finite plasma resistivity.« less
  • Ideal plasma shielding and amplification of resonant magnetic perturbations in non-axisymmetric tokamak is presented by field line tracing simulation with full ideal plasma response, compared to measurements of divertor lobe structures. Magnetic field line tracing simulations in NSTX with toroidal non-axisymmetry indicate the ideal plasma response can significantly shield/amplify and phase shift the vacuum resonant magnetic perturbations. Ideal plasma shielding for n = 3 mode is found to prevent magnetic islands from opening as consistently shown in the field line connection length profile and magnetic footprints on the divertor target. It is also found that the ideal plasma shielding modifiesmore » the degree of stochasticity but does not change the overall helical lobe structures of the vacuum field for n = 3. Furthermore, amplification of vacuum fields by the ideal plasma response is predicted for low toroidal mode n = 1, better reproducing measurements of strong striation of the field lines on the divertor plate in NSTX.« less
  • Ideal plasma shielding and ampli cation of the resonant magnetic perturbations in non-axisymmetric tokamak is presented with full ideal plasma response calculations. Magnetic field line tracing simulations in NSTX with toroidal non-axisymmetry indicate the ideal plasma response can significantly shield/amplify and phase shift the vacuum resonant magnetic perturbations. Ideal plasma shielding for n = 3 mode is found to prevent magnetic islands from opening as consistently shown in the field line connection length pro le and magnetic footprints on the divertor target. It is also found that the ideal plasma shielding modifies the degree of stochasticity but does not changemore » the overall helical lobe structures of the vacuum field. Amplification of vacuum fields by the ideal plasma response is predicted for low toroidal mode n = 1, better reproducing measurements of strong striation of the field lines on the divertor plate in NSTX.« less
  • A numerical study is carried out, based on a simple toroidal tokamak equilibrium, to demonstrate the radial re-distribution of the electromagnetic torque density, as a result of a rotating resistive plasma (linear) response to a static resonant magnetic perturbation field. The computed electromagnetic torque peaks at several radial locations even in the presence of a single rational surface, due to resonances between the rotating response, in the plasma frame, and both Alfven and sound continuum waves. These peaks tend to merge together to form a rather global torque distribution, when the plasma resistivity is large. The continuum resonance induced netmore » electromagnetic torque remains finite even in the limit of an ideal plasma.« less