R. J. Groebner
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View article: Progress in pedestal and edge physics: Chapter 3 of the special issue: on the path to tokamak burning plasma operation
Progress in pedestal and edge physics: Chapter 3 of the special issue: on the path to tokamak burning plasma operation Open
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 …
View article: Pedestal formation via different trajectories in the stability space in response to the timing scan of neutral beam heating in DIII-D
Pedestal formation via different trajectories in the stability space in response to the timing scan of neutral beam heating in DIII-D Open
The frequency of type-I ELMs decreases as the initiation of the neutral beam injection (NBI) heating is delayed with respect to the time when plasma current (Ip) reaches flat-top in the ITER Baseline Scenario discharges in DIII-D. Hencefor…
View article: ELM-free enhanced D<b> <i>α</i> </b> H-mode with near zero NBI torque injection in DIII-D tokamak
ELM-free enhanced D<b> <i>α</i> </b> H-mode with near zero NBI torque injection in DIII-D tokamak Open
Enhanced Dα H-mode (EDA H-mode), an ELM-free H-mode regime, and the concomitant quasi-coherent mode (QCM) are explored in neutral beam heated, lower single null plasmas with near zero external torque injection. This regime exhibits good en…
View article: The role of ion-scale micro-turbulence in pedestal width of the DIII-D wide-pedestal QH mode
The role of ion-scale micro-turbulence in pedestal width of the DIII-D wide-pedestal QH mode Open
The low-edge rotation, intrinsically ELM-free, and improved confinement wide-pedestal quiescent H-mode (QH-mode), discovered in DIII-D tokamak, has pedestal widths exceeding the EPED-kinetic-ballooning mode (KBM) model scaling typically by…
View article: Manipulating density pedestal structure to improve core–edge integration towards low collisionality
Manipulating density pedestal structure to improve core–edge integration towards low collisionality Open
DIII-D experiments have achieved promising core–edge integrated plasma scenarios which combine a high-temperature low-collisionality pedestal (pedestal top temperature T e ,ped > 0.8 keV and collisionality ν * ped < 1) with a partially det…
View article: Turbulence link to L-mode, I-mode, and H-mode confinement in the DIII-D tokamak
Turbulence link to L-mode, I-mode, and H-mode confinement in the DIII-D tokamak Open
Understanding the physics of low-confinement (L-), improved-confinement (I-), and high-confinement (H-) modes is critical for fusion reactors. The finding herein reports observations of two types of turbulence coexisting near the L-mode ed…
View article: Inter-ELM pedestal turbulence dynamics dependence on q<sub>95</sub> and temperature gradient
Inter-ELM pedestal turbulence dynamics dependence on q<sub>95</sub> and temperature gradient Open
A series of dedicated experiments from the DIII-D tokamak provide spatially and temporally resolved measurements of electron density and temperature, and multiscale and multichannel fluctuations over a wide range of conditions. Measurement…
View article: Decoupling of peeling and ballooning thresholds for pedestal stability and reduction in ELM frequency via enhanced turbulence with edge electron cyclotron heating in DIII-D
Decoupling of peeling and ballooning thresholds for pedestal stability and reduction in ELM frequency via enhanced turbulence with edge electron cyclotron heating in DIII-D Open
The edge localized mode (ELM) frequency ( f ELM ) decreased by 63% when electron cyclotron heating (ECH) deposition location is shifted from ρ = 0.4 to ρ = 0.8 in DIII-D discharges where the power ratio between neutral beam injection (NBI)…
View article: Modeling electron temperature profiles in the pedestal with simple formulas for ETG transport
Modeling electron temperature profiles in the pedestal with simple formulas for ETG transport Open
This paper reports on the refinement (building on (Hatch D.R. et al 2022 Phys. Plasmas 29 062501)) and application of simple formulas for electron heat transport from electron temperature gradient (ETG) driven turbulence in the pedestal. T…
View article: ELM-free Enhanced Dα H-mode with Near Zero NBI Torque Injection in DIII-D Tokamak
ELM-free Enhanced Dα H-mode with Near Zero NBI Torque Injection in DIII-D Tokamak Open
Enhanced $D_α$ H-mode (EDA H-mode), an ELM-free H-mode regime, is explored in neutral beam heated, lower single null plasmas with near zero torque injection. This regime exhibits a good energy confinement ($\mathrm{H}_{\mathrm{98y2}}$ $\si…
View article: A Gaussian process guide for signal regression in magnetic fusion
A Gaussian process guide for signal regression in magnetic fusion Open
Extracting reliable information from diagnostic data in tokamaks is critical for understanding, analyzing, and controlling the behavior of fusion plasmas and validating models describing that behavior. Recent interest within the fusion com…
View article: DIII-D's role as a national user facility in enabling the commercialization of fusion energy
DIII-D's role as a national user facility in enabling the commercialization of fusion energy Open
The path to fusion in the United States requires partnership between public and private sector. While the private sector provides the vigor to take some of the major steps necessary, there is a depth of expertise and capability in the publ…
View article: Modeling electron temperature profiles in the pedestal with simple formulas for ETG transport
Modeling electron temperature profiles in the pedestal with simple formulas for ETG transport Open
This paper reports on the refinement (building on Ref.~\cite{hatch_22}) and application of simple formulas for electron heat transport from electron temperature gradient (ETG) driven turbulence in the pedestal. The formulas are improved by…
View article: Elements of H-mode pedestal structure
Elements of H-mode pedestal structure Open
This paper reviews current understanding of key physics elements that control the H-mode pedestal structure, which exists at the boundary of magnetically confined plasmas. The structure of interest is the width, height and gradient of temp…
View article: Micro-tearing mode dominated electron heat transport in DIII-D H-mode pedestal
Micro-tearing mode dominated electron heat transport in DIII-D H-mode pedestal Open
A new, comprehensive set of evidence reveals that Micro-Tearing Modes (MTMs) dominate pedestal electron heat transport in an H-mode experiment in the DIII-D tokamak. The experiment investigates the role of MTMs by scanning pedestal collisi…
View article: Gyrokinetic analysis of inter-edge localized mode transport mechanisms in a DIII-D pedestal
Gyrokinetic analysis of inter-edge localized mode transport mechanisms in a DIII-D pedestal Open
In this study, gyrokinetic simulations are used to study pedestal fluctuations for DIII-D discharge 174082 using the GENE code. Nonlinear local simulations indicate that electron heat flux has contributions from electron temperature gradie…
View article: Gyrokinetic simulations compared with magnetic fluctuations diagnosed with a Faraday-effect radial interferometer-polarimeter in the DIII-D pedestal
Gyrokinetic simulations compared with magnetic fluctuations diagnosed with a Faraday-effect radial interferometer-polarimeter in the DIII-D pedestal Open
Experimental data on electromagnetic fluctuations in DIII-D, made available by the Faraday-effect radial interferometer-polarimeter (RIP) diagnostic Chen (2016 Rev. Sci. Instrum. 87 11E108), is examined in comparison with detailed gyrokine…
View article: A survey of pedestal magnetic fluctuations using gyrokinetics and a global reduced model for microtearing stability
A survey of pedestal magnetic fluctuations using gyrokinetics and a global reduced model for microtearing stability Open
This article presents a global reduced model for slab-like microtearing modes (MTMs) in the H-mode pedestal, which reproduces distinctive features of experimentally observed magnetic fluctuations, such as chirping and discrete frequency ba…
View article: Ion thermal transport in the H-mode edge transport barrier on DIII-D
Ion thermal transport in the H-mode edge transport barrier on DIII-D Open
The power balance ion heat flux in the pedestal region on DIII-D increases and becomes increasingly anomalous (above conventional neoclassical) in experiments with higher temperature and lower density pedestals where the ion collisionality…
View article: Comparison of thermal and angular momentum transport in neutral beam-heated hot-ion H- and L-mode discharges in DIII-D
Comparison of thermal and angular momentum transport in neutral beam-heated hot-ion H- and L-mode discharges in DIII-D Open
We have carried out experiments using the hot-ion mode of operation to compare the bulk transport in L-mode and H-mode discharges. These experiments have demonstrated that the confinement improvement in the bulk of the plasma in DIII-D is …
View article: New understanding of inter-ELM pedestal turbulence, transport, and gradient behavior in the DIII-D tokamak
New understanding of inter-ELM pedestal turbulence, transport, and gradient behavior in the DIII-D tokamak Open
New observations of pedestal localized turbulence in the inter-ELM period of H-mode plasmas in DIII-D show that ion temperature gradient mode scale (ITG-scale) density fluctuation (ñ) increases immediately after each ELM crash and is quick…
View article: Implications of Wall Recycling and Carbon Source Locations on Core Plasma Fueling and Impurity Content in DIII-D
Implications of Wall Recycling and Carbon Source Locations on Core Plasma Fueling and Impurity Content in DIII-D Open
Measurement and modeling of the 2-D poloidal D{alpha} intensity distribution in DIII-D low and medium density L-mode and ELMy H-mode plasmas indicate that hydrogen neutrals predominantly fuel the core from the divertor X-point region. The …
View article: Edge Currents and Stability in DIII-D
Edge Currents and Stability in DIII-D Open
Understanding the stability physics of the H-mode pedestal in tokamak devices requires an accurate measurement of plasma current in the pedestal region with good spatial resolution. Theoretically, the high pressure gradients achieved in th…
View article: Testing predictions of electron scale turbulent pedestal transport in two DIII-D ELMy H-modes
Testing predictions of electron scale turbulent pedestal transport in two DIII-D ELMy H-modes Open
In this paper, we present linear and nonlinear gyrokinetic analyses in the pedestal region of two DIII-D ELMy H-mode discharges using the CGYRO code. The otherwise matched discharges employ different divertor configurations to investigate …
View article: Evolution of ELMs, pedestal profiles and fluctuations in the inter-ELM period in NBI- and ECH-dominated discharges in DIII-D
Evolution of ELMs, pedestal profiles and fluctuations in the inter-ELM period in NBI- and ECH-dominated discharges in DIII-D Open
In DIII-D, it has been observed that ELM frequency decreases by 40% and ELM spacing becomes more regular in time when heating is changed from pure neutral beam injection (NBI) to predominantly electron cyclotron heating (ECH) in ITER simil…
View article: Towards validated MHD modeling of edge harmonic oscillation in DIII-D QH-mode discharges
Towards validated MHD modeling of edge harmonic oscillation in DIII-D QH-mode discharges Open
The extended-MHD NIMROD code (Sovinec C.R. and King J.R. 2010 J. Comput. Phys. 229 5803) is used to simulate the dynamics of an edge harmonic oscillation (EHO) in quiescent H-mode (QH-mode) DIII-D (Luxon J.L. 2002 Nucl. Fusion 42 614) disc…
View article: FY19 FES Theory Performance Target (Final Report)
FY19 FES Theory Performance Target (Final Report) Open
Understanding the relevant turbulent transport mechanisms at the edge of a high-performance tokamak is essential for predicting and optimizing the H-mode pedestal structure in future burning plasma devices. Global electromagnetic gyrokinet…
View article: H-mode pedestal improvements with neon injection in DIII-D
H-mode pedestal improvements with neon injection in DIII-D Open
Improvements in the H-mode pedestal pressure and global energy confinement were determined on DIII-D with both 3 and 6 MW of neutral beam (NBI) heating with neon injection. The pedestal pressure increased, primarily associated with a signi…
View article: Setting the H-mode pedestal structure: variations of particle source location using gas puff and pellet fueling
Setting the H-mode pedestal structure: variations of particle source location using gas puff and pellet fueling Open
Experiments in DIII-D show that a particle source location inside the top of the H-mode pedestal (pellets) maintains a higher pedestal pressure than an edge source (gas fueling) through a widening of the electron temperature pedestal with …
View article: High fusion performance in Super H-mode experiments on Alcator C-Mod and DIII-D
High fusion performance in Super H-mode experiments on Alcator C-Mod and DIII-D Open
The ‘Super H-Mode’ regime is predicted to enable pedestal height and fusion performance substantially higher than standard H-Mode operation. This regime exists due to a bifurcation of the pedestal pressure, as a function of density, that i…