MHD Equilibrium Reconstruction in the DIII-D Tokamak

Lao, L. L.; John, H.E. St.; Peng, Qian; Ferron, J. R.; Strait, E.J.; Taylor, T.S.; Meyer, William H.; Zhang, C.; You, K.-I.

doi:10.13182/fst48-968

Cited by 255 publications

(222 citation statements)

References 34 publications

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“…The axisymmetric equilibrium reconstruction, a so-called "kinetic EFIT" analysis, 62 was completed for each timeslice to calculate the q profile consistent with the measured pressure profile and the effects of the edge bootstrap current. This was important to do because the island overlap width is sensitive to the q-shear in the plasma edge.…”

Section: Resultsmentioning

confidence: 99%

Effect of island overlap on edge localized mode suppression by resonant magnetic perturbations in DIII-D

Fenstermacher¹,

Evans²,

Osborne³

et al. 2008

Physics of Plasmas

149

229

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Recent DIII-D [J. L. Luxon et al., Nucl. Fusion 43, 1813 (2003)] experiments show a correlation between the extent of overlap of magnetic islands induced in the edge plasma by perturbation coils and complete suppression of Type-I edge localized modes (ELMs) in plasmas with ITER-like electron pedestal collisionality νe*∼0.1, flux surface shape and low edge safety factor (q95≈3.6). With fixed amplitude n=3 resonant magnetic perturbation (RMP), ELM suppression is obtained only in a finite window in the edge safety factor (q95) consistent with maximizing the resonant component of the applied helical field. ELM suppression is obtained over an increasing range of q95 by either increasing the n=3 RMP strength, or by adding n=1 perturbations to “fill in” gaps between islands across the edge plasma. The suppression of Type-I ELMs correlates with a minimum width of the edge region having magnetic islands with Chirikov parameter >1.0, based on vacuum calculations of RMP mode components excluding the plasma response or rotational shielding. The fraction of vacuum magnetic field lines that are lost from the plasma, with connection length to the divertor targets comparable to an electron-ion collisional mean free path, increases throughout the island overlap region in the ELM suppressed case compared with the ELMing case.

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Section: Resultsmentioning

confidence: 99%

Effect of island overlap on edge localized mode suppression by resonant magnetic perturbations in DIII-D

Fenstermacher¹,

Evans²,

Osborne³

et al. 2008

Physics of Plasmas

149

229

View full text Add to dashboard Cite

show abstract

“…However, the corresponding EP pressure moment profiles computed from the EP density and fixed EP effective temperature profiles can be compared directly with experimental EP pressure profiles. When the EP beta fraction is high (>50% as in the case here), NBI fast ion pressure profile from MHD equilibrium EFIT [9,10] reconstruction (using magnetics, motional Stark effect, thermal pressure data, etc.) is the most robust experimental EP profile data.…”

Section: Introductionmentioning

confidence: 88%

Development and validation of a critical gradient energetic particle driven Alfven eigenmode transport model for DIII-D tilted neutral beam experiments

et al. 2015

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Recent experiments with the DIII-D tilted neutral beam injection (NBI) varying the beam energetic particle (EP) source profiles have provided strong evidence that unstable Alfven eigenmodes (AE) drive stiff EP transport at a critical EP density gradient [Heidbrink et al 2013 Nucl. Fusion 53 093006]. Here the critical gradient is identified by the local AE growth rate being equal to the local ITG/TEM growth rate at the same low toroidal mode number. The growth rates are taken from the gyrokinetic code GYRO. Simulation show that the slowing down beam-like EP distribution has a slightly lower critical gradient than the Maxwellian. The ALPHA EP density transport code [Waltz and Bass 2014 Nucl. Fusion 54 104006], used to validate the model, combines the low-n stiff EP critical density gradient AE mid-core transport with the Angioni et al (2009 Nucl. Fusion 49 055013) energy independent high-n ITG/TEM density transport model controling the central core EP density profile. For the on-axis NBI heated DIII-D shot 146102, while the net loss to the edge is small, about half the birth fast ions are transported from the central core r/a < 0.5 and the central density is about half the slowing down density. These results are in good agreement with experimental fast ion pressure profiles inferred from MSE constrained EFIT equilibria.

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“…A third loop executes a Grad-Shafranov solver that additionally fits ten spatially localized measurements from the Motional Stark Effect diagnostic [45]. The accuracy of the q profile is improved by the measurements of the polarization angle, γ m which is related to the viewing geometry [46]:…”

Section: Mse Constraintsmentioning

confidence: 99%

A data acquisition system for real-time magnetic equilibrium reconstruction on ASDEX Upgrade and its application to NTM stabilization experiments

Giannone

Reich

Maraschek

et al. 2013

Fusion Engineering and Design

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The pre-emptive stabilization of a neoclassical tearing mode, NTM, requires the calculation of the tokamak magnetic equilibrium in real-time. A launcher mirror is positioned to deposit electron cyclotron current drive on the rational surface where the NTM should appear. A real-time Grad-Shafranov solver using constraints from magnetic probe, flux loop and Motional Stark Effect measurements has been developed to locate these rational surfaces and deliver this information to the mirror controller in real-time. A novel algorithm significantly reduces the number of operations required in the first and second step of the solver. Contour integrals are carried out to calculate the q profile as a function of normalized radius and the rational surfaces are found by spline interpolation. A cycle time of 0.6 ms for calculating two tokamak equilibria in parallel using four current basis functions with magnetic constraints only and using six current basis functions with magnetic and MSE constraints has been achieved. Using these tools, pre-emptive stabilization

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MHD Equilibrium Reconstruction in the DIII-D Tokamak

Cited by 255 publications

References 34 publications

Effect of island overlap on edge localized mode suppression by resonant magnetic perturbations in DIII-D

Effect of island overlap on edge localized mode suppression by resonant magnetic perturbations in DIII-D

Development and validation of a critical gradient energetic particle driven Alfven eigenmode transport model for DIII-D tilted neutral beam experiments

A data acquisition system for real-time magnetic equilibrium reconstruction on ASDEX Upgrade and its application to NTM stabilization experiments

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