Effect of resonant magnetic perturbations on three dimensional equilibria in the Madison Symmetric Torus reversed-field pinch

Munaretto, S.; Chapman, B. E.; Nornberg, M. D.; Boguski, J.; DuBois, Ami M.; Almagri, A. F.; Sarff, J. S.

doi:10.1063/1.4943524

Cited by 10 publications

(9 citation statements)

References 58 publications

(68 reference statements)

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“…It is worth mentioning that as the n ¼ 5 mode amplitude grows, eddy-currents in the MST's conducting shell provide a torque which slow and lock the plasma to the wall at a fixed phase. 27 Externally applied resonant magnetic perturbations (RMPs) aid in locking and allow for experimental phase control of the helical core for preferential diagnostic viewing. 28 Of note, no fast ion measurements were found to have any associated phase dependence.…”

Section: Tearing Mode Induced Transportmentioning

confidence: 99%

Fast ion transport in the quasi-single helical reversed-field pinch

et al. 2019

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The reversed-field pinch (RFP) can spontaneously transition from an axisymmetric magnetic topology to a 3D-helical geometry. Investigations on fast ion transport associated with energetic particle driven Alfv en instabilities, tearing mode induced stochasticity, and neoclassical effects have been performed on the Madison Symmetric Torus. STELLGAP produced shear-Alfv en continua seeded with V3FIT 3D-equilibrium reconstructions describe the response of Alfv enic bursting activity as a direct consequence of the equilibrium change on the fast ion resonance. Far infrared interferometry resolved electron density perturbations associated with the bursts provide a spatial measurement of the mode structure and support the reconstructions. The bursts produce no global resonant fast ion transport; however, their disappearance at a high core-resonant amplitude implies other transport mechanisms at play. Neutral particle analysis and neutron signals suggest fast ion losses at sufficient core tearing mode strength, supporting the lack of Alfv enic activity. The guiding-center code ORBIT corroborates rapid fast ion loss times in the helical state largely as a consequence of remnant tearing modes. Additionally, ORBIT simulations demonstrate little neoclassical enhancement of particle transport. While superbanana orbits may exist, the growth in the core-resonant fast ion island and the associated secondary mode overlap govern the largest transport process, leading to robust fast ion losses in the 3D-RFP.

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Section: Tearing Mode Induced Transportmentioning

confidence: 99%

Fast ion transport in the quasi-single helical reversed-field pinch

et al. 2019

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“…This is consistent with the previous research indicating that thermal confinement during QSH is intermittent, in ways not explained by trends in the secondary mode amplitudes as measured at the plasma edge. 14,34 The observation detailed in FIG. 5.…”

Section: Power Balance Transport Estimatementioning

confidence: 99%

Electron thermal confinement in a partially stochastic magnetic structure

et al. 2018

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Using a high-repetition-rate Thomson scattering diagnostic, we observe a peak in electron temperature T e coinciding with the location of a large magnetic island in the Madison Symmetric Torus. Magnetohydrodynamic modeling of this quasi-single helicity plasma indicates that smaller adjacent islands overlap with and destroy the large island flux surfaces. The estimated stochastic electron thermal conductivity (%30 m 2 =s) is consistent with the conductivity inferred from the observed T e gradient and ohmic heating power. Island-shaped T e peaks can result from partially stochastic magnetic islands.

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“…In the past, the stochasticity associated with the secondary modes has been considered the main driver for particle and energy transport in RFPs [11,31,33,37,38]. As a consequence it can be considered contradictory that plasmas with lower resonance amplitude of the secondary modes show higher level of transport.…”

Section: Transport Analyses On Rfx-mod: Comparison Between Dax and Sh...mentioning

confidence: 99%

A novel approach to studying transport in plasmas with magnetic islands

Auriemma¹,

López‐Bruna²,

Lorenzini³

et al. 2018

Nucl. Fusion

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In magnetically confined experiments the presence of rational surfaces modifies the magnetic configuration with one or more islands embedded in the main plasma. The islands strongly modify particle and heat fluxes, hence their role must be included in the study of the transport properties. Two examples of this phenomenology are here presented: a cold pulse propagation in LHD with an RMP (1,1) island highlights a diffusivity reduction inside the island. A second study has been carried out on the RFX-mod reversed field pinch device where the transport on the ITB associated to a spontaneous m = 1 magnetic structure is discussed.To perform these studies a new approach in modeling transport in the presence of islands is presented: this new method, dubbed the multiple domains scheme (MDS), with some simplifying assumptions, is directly applicable to 1.5D transport codes. In the MDS different regions are identified inside the plasma all interfaced by the separatrix that acts as common boundary. In each domain a monotonic radial coordinate can be chosen and the metric elements can be computed accordingly. This scheme is independent of the equilibrium magnetic configuration hence it can be applied to either tokamaks, stellarators or reversed field pinches. The MDS has been implemented in a new numerical tool, dubbed the multiple axis solver .

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Effect of resonant magnetic perturbations on three dimensional equilibria in the Madison Symmetric Torus reversed-field pinch

Cited by 10 publications

References 58 publications

Fast ion transport in the quasi-single helical reversed-field pinch

Fast ion transport in the quasi-single helical reversed-field pinch

Electron thermal confinement in a partially stochastic magnetic structure

A novel approach to studying transport in plasmas with magnetic islands

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