Abstract Details
Abstracts
Author: Jong-Kyu Park
Requested Type: Poster
Submitted: 2022-03-04 13:50:09
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Contact Info:
Princeton Plasma Physics Laboratory
Stellarator Rd, P.O.Box 451
Princeton, NJ 08543
United States
Abstract Text:
A non-axisymmetric magnetic field arising in a tokamak either by external or internal perturbations can induce complex non-ideal MHD responses near their resonant layer surface while remaining ideally evolved outside the layer. This layer response can be characterized in a linear regime only by a single parameter called the layer impedance, which enables outer-layer matching and thereby the prediction of torque balance and field penetration to non-linear islands. Here we follow strictly one of the most comprehensive analytic formulations including two fluids and drift MHD effects [1] but keep the fidelity of the prediction by incorporating a numerical method based on the Riccati transformation [2] into the calculations of the layer impedance. The proposed scheme reproduces not only the predicted responses essentially in all asymptotic regimes but also the response transitions in detail with improved accuracies. In particular, the variations of layer impedance across the inertial regimes with viscous or semi-collisional effects have been further resolved, in comparison with additional analytic solutions. The results show greater shielding of the electromagnetic torque at the layer than expected as the viscous or semi-collisional effects can compete the inertial effects, as well as the intermediate regulations by kinetic Alfven wave resonances as rotation slows down. These are important features that can alter the non-axisymmetric plasma responses including the field penetration by external fields or island seeding process in rotating tokamak plasmas. The application indeed yields realistic predictions of error field threshold scaling, predicting locked-mode thresholds measured in Ohmic plasmas across devices within a factor of 2 and thus demonstrating its utility as a quick and efficient guidance of resonant field penetration.
[1] A. Cole et al., Phys. Plasmas 13, 032503 (2006)
[2] D. Brennen et al., APS DPP (2019)
Work supported by the U.S. DOE #DE-AC02-09CH1
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