Motional Stark effect diagnostic expansion on DIII-D for enhanced current and Er profile measurements

Holcomb, C. T.; Makowski, M. A.; Jayakumar, R. J.; Allen, Susan; Ellis, R. J.; Geer, R.; Behne, D.; Morris, Kevin L.; Seppala, Lynn G.; Moller, J.M.

doi:10.1063/1.2235812

Cited by 48 publications

(36 citation statements)

References 9 publications

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“…The flux surface averaged toroidal current density in the core plasma is determined from motional Stark effect (MSE) [39] measurements, while in the pedestal region, it is derived from the sum of the parallel bootstrap current given by the Sauter expression [40,41], the neutral beam driven current computed using NUBEAM and the Ohmic current density. The Ohmic current density is determined from the neoclassical expression for the resistivity with a loop voltage, which is assumed spatially constant and adjusted to give a net plasma current matching the measured total plasma current.…”

Section: Profile Data and Equilibrium Inputs For The Analysismentioning

confidence: 99%

E × Bflow shear drive of the linear low-nmodes of EHO in the QH-mode regime

Wan

Wang

et al. 2017

Nucl. Fusion

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A new model for the edge harmonic oscillations (EHOs) in the quiescent H-mode regime has been developed, which successfully reproduces the recent observations in the DIII-D tokamak. In particular, at high E × B flow shear only a few low-n kink modes remain unstable at the plasma edge, consistent with the EHO behavior, while at low E × B flow shear, the unstable mode spectrum is significantly broadened, consistent with the low-n broadband electromagnetic turbulence behavior. The model is based on a new mechanism for destabilizing low-n kink/peeling modes by the E × B flow shear, which underlies the EHOs, separately from the previously found Kelvin-Helmholtz drive. We find that the differential advection of mode vorticity by sheared E × B flows modifies the 2D pattern of mode electrostatic potential perpendicular to the magnetic field lines, which in turn causes a radial expansion of the mode structure, an increase of field line bending away from the mode rational surface, and a reduction of inertial stabilization. This enhances the kink drive as the parallel wavenumber increases significantly away from the rational surface at the plasma edge where the magnetic shear is also strong. This destabilization is also shown to be independent of the sign of the flow shear, as observed experimentally, and has not been taken into account in previous pedestal linear stability analyses. Verification of the veracity of this EHO mechanism will require analysis of the nonlinear evolution of low-n kink/peeling modes so destabilized in the linear regime.

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Section: Profile Data and Equilibrium Inputs For The Analysismentioning

confidence: 99%

E × Bflow shear drive of the linear low-nmodes of EHO in the QH-mode regime

Wan

Wang

et al. 2017

Nucl. Fusion

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“…These will enhance our ability to perform in-depth AT physics, transport studies, and ITER-relevant studies. The new counterbeam MSE system will provide improved equilibrium analysis and current profile measurement [13]. The new counter-beam CER system allows more accurate measurement of low rotation velocities.…”

Section: Plasma Control System and Diagnostic Upgradesmentioning

confidence: 99%

“…The PCS now incorporates the new counter-beam CER system and computes both ion temperature and ion rotation velocity in real-time (638 s per channel), thus enabling the real-time control of plasma rotation. The new counter viewing motional Stark effect (MSE) system [13] was added with all 24 channels available for use in the realtime EFIT. Although not fully implemented, the new processors will permit the increase in the EFIT computational grid size from 33 × 33 to a 65 × 65 grid.…”

Section: Plasma Control System and Diagnostic Upgradesmentioning

confidence: 99%

System upgrades to the DIII–D facility

Kellman

2007

Fusion Engineering and Design

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“…A magnetic equilibrium calculated by EFIT [16] is shown in figure 2. This equilibrium is constrained by magnetic pitch angle measurements from a motional Stark effect system [17]. The fast wave system is set to an injection frequency of f = 90 MHz in this discharge, and the resulting deuterium ion cyclotron harmonics are plotted in figure 2 as nearly vertical lines.…”

Section: Methodsmentioning

confidence: 99%

Scrape-off layer ion acceleration during fast wave injection in the DIII-D tokamak

Pace¹,

Pinsker²,

Heidbrink³

et al. 2012

Nucl. Fusion

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Fast wave injection is employed on the DIII-D tokamak as a current drive and electron heating method. Bursts of energetic ions with energy E o > 20 keV are observed immediately following fast wave injection in experiments featuring the 8th ion cyclotron harmonic near the antenna. Using the energy and pitch angle of the energetic ion burst as measured by a fast-ion loss detector, it is possible to trace the origin of these ions to a particular antenna. The ion trajectories exist entirely within the scrape-off layer. These observations are consistent with the presence of parametric decay instabilities near the antenna strap. It is suggested that the phase space capabilities of the loss detector diagnostic can improve studies of wave injection coupling and efficiency in tokamaks by directly measuring the effects of parametric decay thresholds.

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Motional Stark effect diagnostic expansion on DIII-D for enhanced current and Er profile measurements

Cited by 48 publications

References 9 publications

E × Bflow shear drive of the linear low-nmodes of EHO in the QH-mode regime

E × Bflow shear drive of the linear low-nmodes of EHO in the QH-mode regime

System upgrades to the DIII–D facility

Scrape-off layer ion acceleration during fast wave injection in the DIII-D tokamak

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