Publications
Showing 72 results for Author: Robert S. Wilcox
Aug, 2025
Journal
Unified ELM suppression on KSTAR and DIII-D via adaptive feedback control strategies
This paper reports on the extension of our amplitude-based resonant magnetic perturbation (RMP) edge localized mode (ELM) controller to support phasing control (relative toroidal phases of RMP waveforms between rows of coils), multiple toroidal mode numbers, and new ‘jump’ and ‘probing’ strategies, all deployed on KSTAR and DIII-D. By treating the control algorithm as devi…
Jul, 2025
Journal
Progress in pedestal and edge physics: Chapter 3 of the special issue: on the path to tokamak burning plasma operation
This paper describes the extensive progress that has been made in the understanding of tokamak pedestal physics since the 2007 publication of ‘Progress in the ITER Physics Basis’ (Ikeda 2007 Nucl. Fusion 47 E01–S500). It serves as Chapter 3 of the 2025 Nuclear Fusion Special Issue titled ‘On the Path to Tokamak Burning Plasma Operation’ (Campbell et al 2025 Nucl. Fusion).…
Feb, 2025
Journal
The effect of divertor closure on the impurity stagnation point in detached L-mode discharges on DIII-D
This paper presents experimental measurements of the location of the impurity flow stagnation point in the scrape-off-layer (SOL) of a tokamak plasma. Coherence imaging of carbon-2+ emission (465 nm) is used to track the main-chamber impurity velocity of DIII-D L-mode plasmas with 𝐵 × ∇𝐵 out of the divertor. The 𝐶2+ flow stagnates near the top or crown of the plasma when a…
Feb, 2025
Journal
Tungsten erosion during L-mode discharges in the DIII-D SAS-VW divertor
A series of L-mode plasma discharges was performed in the DIII-D tokamak to assess the impact of outer strike point (OSP) position and toroidal magnetic field direction on erosion and core contamination potential of the recently-installed, tungsten-coated Small Angle Slot (SAS-VW) divertor. In one discharge, in-slot emission spectroscopy measured an < 48 % increase in the…
Jan, 2025
Journal
Enhanced pedestal transport driven by edge collisionality on Alcator C-Mod and its role in regulating H-mode pedestal gradients
Experimental measurements of plasma and neutral profiles across the pedestal are used in conjunction with 2D edge modeling to examine pedestal stiffness in Alcator C-Mod H-mode plasmas. Enhanced Dα experiments on Alcator C-Mod observed pedestal degradation and loss in confinement below a critical value of net power crossing the separatrix, Pnet = P crit/net ≈ 2.3MW, in the…
Dec, 2024
Journal
Simulations of divertor designs that spatially separate power and particle exhaust using mid-leg divertor particle pumping
Predictive design modeling of a Dissipation-Focused Divertor for future operation in DIII-D reveals that increasing the poloidal distance of the pump duct entrance from the target surface along the low-field side divertor baffle increases neutral compression and modifies the spatial distribution of power dissipation. With a divertor pump located mid-leg between the target…
Nov, 2024
Journal
Modeling a divertor with mid-leg pumping for high-power H-mode scenarios in DIII-D considering E x B drift flows
Edge-plasma simulations of a baffled, long-legged divertor in DIII-D, performed using the multi-fluid code UEDGE, indicate that the position of the detachment front is constrained to the location of the pump duct along the low-field side (LFS) baffle. Simulations including magnetic and E x B drifts were performed for 12.5 MW deuterium plasmas including intrinsic carbon and…
Sep, 2024
Journal
Understanding the L-H isotope effect at the DIII-D tokamak and advancements in synthetic turbulence diagnostics
It is determined that while heat flux differences between hydrogen and deuterium isotope experiments result from natural differences in carbon impurity content at DIII-D, it is not the origin of the low to high confinement mode (L-H) transition isotope effect. More specifically, a two times larger edge radial electric field in hydrogen compared to deuterium is uncovered an…