Internal kink mode dynamics in high-β NSTX plasmas

Ménard, J.; Bell, R. E.; Fredrickson, E. D.; Gates, D.; Kaye, S. M.; LeBlanc, B.; Maingi, R.; Medley, S. S.; Park, W.; Sabbagh, S.A.; Sontag, A. C.; Stutman, D.; Tritz, K.; Zhu, W.

doi:10.1088/0029-5515/45/7/001

Cited by 91 publications

(109 citation statements)

References 67 publications

(85 reference statements)

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“…This source is generated using a single helicity island model [14,15]. This model generates a helical perturbation where the island width and phase are inputs for a given m and n. A series of toroidal slices can be generated with the island perturbation, which is represented as a flat region in ψ n .…”

Section: Diii-d Sxris Plan and Synthetic Modelmentioning

confidence: 99%

Soft X-Ray Imaging Design and Analysis Methods on DIII-D

Shafer

Battaglia

Unterberg

et al. 2011

Plasma and Fusion Research

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A new tangential 2D Soft X-Ray Imaging System (SXRIS) is being designed to examine the edge magnetic island structure in the lower X-point region of DIII-D. A synthetic diagnostic calculation coupled to 3D emissivity estimates is used to generate phantom images. Phillips-Tikhonov regularization is used to invert the phantom images for comparison to the original emissivity model. Noise level, island size, and equilibrium accuracy are scanned to assess the feasibility of detecting edge island structures. Models of typical DIII-D discharges indicate integration times > 1 ms with accurate equilibrium reconstruction are needed for small island (< 3 cm) detection.

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Section: Diii-d Sxris Plan and Synthetic Modelmentioning

confidence: 99%

Soft X-Ray Imaging Design and Analysis Methods on DIII-D

Shafer

Battaglia

Unterberg

et al. 2011

Plasma and Fusion Research

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“…The first large study of n=1 core kink modes was published in Ref. [103]. It was shown there that these modes can cause severe rotation damping and degrade fast ion confinement.…”

Section: Section 42: Continuous Coupled N=1 Modesmentioning

confidence: 99%

“…The mode eigenfunction in this calculation is composed of both a core m/n=1/1 kink and a 2/1 magnetic island. The 2/1 island is modeled via the method described in reference [103]: the helical flux is computed, a perturbation resonant with the 2/1 surface is imposed, and the island structure is computed. The radius of the island chain is determined by the location of the q=2 surface, and the width of the islands is set by adjusting the amplitude of the helical flux to match the observed USXR emission contours.…”

Section: Appendix 1: Modeling Of the Usxr Emission From Coupled Kink-mentioning

confidence: 99%

Calculation of the Non-Inductive Current Profile in High-Performance NSTX Plasmas

Gerhardt¹,

Gates²,

Kaye³

et al. 2011

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“…β N ∼ 5(%m T MA −1 ) is maintained for 3-4τ CR , and the plasma current flat-top is 1.6 s, an ST record at this current level. Previously long pulse discharges at high-β were limited by a slow degradation of rotation in the plasma core with the eventual onset of either a saturated internal kink mode [30] or an RWM [31]. The measured plasma rotation at various radii plotted versus time during a discharge that utilized combined n = 3 EF correction and n = 1 RFA suppression.…”

Section: Efs and Resonant Field Amplification/resistive Wall Mode (Rfmentioning

confidence: 99%

Overview of results from the National Spherical Torus Experiment (NSTX)

Gates¹,

Ahn²,

Allain³

et al. 2009

Nucl. Fusion

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The mission of the National Spherical Torus Experiment (NSTX) is the demonstration of the physics basis required to extrapolate to the next steps for the spherical torus (ST), such as a plasma facing component test facility (NHTX) or an ST based component test facility (ST-CTF), and to support ITER. Key issues for the ST are transport, and steady state high β operation. To better understand electron transport, a new high-k scattering diagnostic was used extensively to investigate electron gyro-scale fluctuations with varying electron temperature gradient scale length. Results from n = 3 braking studies are consistent with the flow shear dependence of ion transport. New results from electron Bernstein wave emission measurements from plasmas with lithium wall coating applied indicate transmission efficiencies near 70% in H-mode as a result of reduced collisionality. Improved coupling of high harmonic fast-waves has been achieved by reducing the edge density relative to the critical density for surface wave coupling. In order to achieve high bootstrap current fraction, future ST designs envision running at very high elongation. Plasmas have been maintained on NSTX at very low internal inductance l i ∼ 0.4 with strong shaping (κ ∼ 2.7, δ ∼ 0.8) with β N approaching the with-wall β-limit for several energy confinement times. By operating at lower collisionality in this regime, NSTX has achieved record non-inductive current drive fraction f NI ∼ 71%. Instabilities driven by super-Alfvénic ions will be an important issue for all burning plasmas, including ITER. Fast ions from NBI on NSTX are super-Alfvénic. Linear toroidal Alfvén eigenmode thresholds and appreciable fast ion loss during multi-mode bursts are measured and these results are compared with theory. The impact of n > 1 error fields on stability is an important result for ITER. Resistive wall mode/resonant field amplification feedback combined with n = 3 error field control was used on NSTX to maintain plasma rotation with β above the no-wall limit. Other highlights are results of lithium coating experiments, momentum confinement studies, scrape-off layer width scaling, demonstration of divertor heat load mitigation in strongly shaped plasmas and coupling of coaxial helicity injection plasmas to ohmic heating ramp-up. These results advance the ST towards next step fusion energy devices such as NHTX and ST-CTF.

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Internal kink mode dynamics in high-β NSTX plasmas

Cited by 91 publications

References 67 publications

Soft X-Ray Imaging Design and Analysis Methods on DIII-D

Soft X-Ray Imaging Design and Analysis Methods on DIII-D

Calculation of the Non-Inductive Current Profile in High-Performance NSTX Plasmas

Overview of results from the National Spherical Torus Experiment (NSTX)

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