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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: The low frequency edge oscillation in alcator C-Mod and ASDEX upgrade I-mode
The low frequency edge oscillation in alcator C-Mod and ASDEX upgrade I-mode Open
The low frequency edge oscillation (LFEO) is a low frequency fluctuation in many plasma quantities in the pedestal region of the I-Mode confinement regime. It is observed on Alcator C-Mod between 10–30 kHz and on ASDEX Upgrade between 5–10…
View article: EDA H-mode in ASDEX Upgrade: scans of heating power, fueling, and plasma current
EDA H-mode in ASDEX Upgrade: scans of heating power, fueling, and plasma current Open
Electron cyclotron resonance heating (ECRH) staircase discharges in strongly shaped plasmas were performed at the full-tungsten ASDEX Upgrade tokamak to investigate the enhanced D α (EDA) H-mode, a high-confinement regime without edge loca…
Pedestal properties of negative triangularity discharges in ASDEX Upgrade Open
In this work, we explore the pedestal properties of negative triangularity discharges with upper triangularity of and with both ion drift directions. In all cases, the discharges undergo a transition to H-mode with accompanying edge-locali…
The multi-faced nature of the quasicoherent mode in EDA H-mode Open
In order to extend the enhanced D-Alpha H-mode to future devices, it is crucial to understand the properties of the main signature of this regime, the quasicoherent mode (QCM), that likely clamps the pressure gradient below the ideal magne…
View article: Negative triangularity scenarios: from TCV and AUG experiments to DTT predictions
Negative triangularity scenarios: from TCV and AUG experiments to DTT predictions Open
Experiments, gyrokinetic simulations and transport predictions were performed to investigate if a negative triangularity (NT) L-mode option for the Divertor Tokamak Test (DTT) full-power scenario would perform similarly to the positive tri…
View article: From L-mode to the L–H transition, experiments on ASDEX upgrade and related gyrokinetic simulations
From L-mode to the L–H transition, experiments on ASDEX upgrade and related gyrokinetic simulations Open
This work combines experimental observations from the ASDEX Upgrade tokamak with related gyrokinetic simulations of the turbulence moving from L-mode toward, and beyond, the L–H transition. Dedicated experiments have been performed with sl…
View article: Experiments and modelling of negative triangularity ASDEX Upgrade plasmas in view of DTT scenarios
Experiments and modelling of negative triangularity ASDEX Upgrade plasmas in view of DTT scenarios Open
The paper presents experimental and modelling results of a comparison of negative (NT) and positive (PT) triangularity ASDEX Upgrade (AUG) discharges using the plasma shapes presently foreseen in the DTT tokamak, under construction in Ital…
Experimental evidence for the drift wave nature of the weakly coherent mode in ASDEX Upgrade I-mode plasmas Open
The improved energy confinement mode (I-mode) is a potential candidate for future fusion power plants, as it combines ELM-free operation with good confinement. The unusual edge transport and turbulence in this regime is still not fully und…
View article: Reduced model for H-mode sustainment in unfavorable <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:mrow> <mml:mi>∇</mml:mi> <mml:mtext>B</mml:mtext> </mml:mrow> </mml:math> drift configuration in ASDEX Upgrade
Reduced model for H-mode sustainment in unfavorable drift configuration in ASDEX Upgrade Open
A recently developed reduced model of H-mode sustainment based on interchange-drift-Alfvén turbulence description in the vicinity of the separatrix matching experimental observations in ASDEX Upgrade has been extended to experiments with t…
View article: The radial localization of the transition from low to high confinement mode in the ASDEX Upgrade tokamak
The radial localization of the transition from low to high confinement mode in the ASDEX Upgrade tokamak Open
A novel experimental method is applied to localize the initial suppression of turbulence, in the form of density fluctuations, at the transition from the low (L-) to the high (H-) confinement mode in toroidal magnetic fusion plasmas. The h…
View article: Reduced model for H-mode sustainment in unfavorable $\mathbf{ \nabla B}$ drift configuration in ASDEX Upgrade
Reduced model for H-mode sustainment in unfavorable $\mathbf{ \nabla B}$ drift configuration in ASDEX Upgrade Open
A recently developed reduced model of H-mode sustainment based on interchange-drift-Alfvén turbulence description in the vicinity of the separatrix matching experimental observations in ASDEX Upgrade has been extended to experiments with t…
W-band tunable, multi-channel, frequency comb Doppler backscattering diagnostic in the ASDEX-Upgrade tokamak Open
This article presents the design, implementation, and first data of a uniquely flexible, multi-channel, frequency comb Doppler backscattering diagnostic recently made operational in the ASDEX-Upgrade tokamak [A. Gruber and O. Gruber, Fusio…
View article: Pellet-fueled I-mode plasmas in ASDEX Upgrade
Pellet-fueled I-mode plasmas in ASDEX Upgrade Open
This letter reports on the efforts carried out at the ASDEX Upgrade tokamak to integrate I-mode plasmas with pellet fueling and to increase the I-mode Greenwald fraction , two important requirements for any DEMO operational scenario. For t…
Impact of the turbulence wavenumber spectrum and probing beam geometry on Doppler reflectometry perpendicular velocity measurements Open
The perpendicular propagation velocity of turbulent density fluctuations is an important parameter in fusion plasmas, since sheared plasma flows are crucial for reducing turbulence, and thus an essential input parameter for turbulent trans…
Experimental study of the edge radial electric field in different drift configurations and its role in the access to H-mode at ASDEX Upgrade Open
The formation of the equilibrium radial electric field (Er) has been studied experimentally at ASDEX Upgrade (AUG) in L-modes of “favorable” (ion ∇ B-drift toward primary X-point) and “unfavorable” (ion ∇ B-drift away from primary X-point)…
View article: First measurements of a scintillator-based fast-ion loss detector in reversed Ip/Bt at the ASDEX Upgrade tokamak
First measurements of a scintillator-based fast-ion loss detector in reversed Ip/Bt at the ASDEX Upgrade tokamak Open
Fast-α losses in future fusion power plants are expected to follow the co- and counter-current directions due to the isotropy of the fusion reaction. At the ASDEX Upgrade tokamak, the co-current direction (achieved with positive plasma cur…
View article: Turbulence characterization during the suppression of edge-localized modes by magnetic perturbations on ASDEX Upgrade
Turbulence characterization during the suppression of edge-localized modes by magnetic perturbations on ASDEX Upgrade Open
We study localized edge turbulence in the ASDEX Upgrade tokamak that appears if resonant magnetic perturbations (RMP) are applied to suppress edge localized modes (ELMs) in the high confinement mode. The concomitant density fluctuations ar…
View article: Electron temperature fluctuation measurements with Correlation Electron Cyclotron Emission in L-mode and I-mode plasmas at ASDEX Upgrade
Electron temperature fluctuation measurements with Correlation Electron Cyclotron Emission in L-mode and I-mode plasmas at ASDEX Upgrade Open
The Correlation Electron Cyclotron Emission (CECE) diagnostic at ASDEX Upgrade (AUG) is used to investigate the features of outer core and pedestal ( ρ pol = 0.85-1.0) turbulence across confinement regime transitions. The I-mode confinemen…
Overview of initial negative triangularity plasma studies on the ASDEX Upgrade tokamak Open
An overview of results of negative triangularity (NT) studies from the ASDEX Upgrade tokamak (AUG) is given. Moderate values of the triangularity in the range of δ average ≈ −0.2 have been obtained. Results from both unfavorable and favora…
View article: Edge turbulence measurements in L-mode and I-mode at ASDEX Upgrade
Edge turbulence measurements in L-mode and I-mode at ASDEX Upgrade Open
The I-mode confinement regime is promising for future reactor operation due to high energy confinement without high particle confinement. However, the role of edge turbulence in creating I-mode's beneficial transport properties is still un…
View article: Overview of the TCV tokamak experimental programme
Overview of the TCV tokamak experimental programme Open
The tokamak à configuration variable (TCV) continues to leverage its unique shaping capabilities, flexible heating systems and modern control system to address critical issues in preparation for ITER and a fusion power plant. For the 2019–…
I-mode pedestal relaxation events in the Alcator C-Mod and ASDEX Upgrade tokamaks Open
In some conditions, I-mode plasmas can feature pedestal relaxation events (PREs) that transiently enhance the energy reaching the divertor target plates. To shed light on their appearance, characteristics and energy reaching the divertor t…
Gyrofluid simulation of an I-mode pedestal relaxation event Open
The I-mode is an edge-localized mode (ELM)-free confinement regime showing enhanced heat confinement. Nevertheless, also in I-mode, events similar to ELMs—albeit less harmful to the divertor—can occur, relaxing the pedestal gradients. A gl…
Advances in turbulence measurements using new Correlation ECE and nT-phase diagnostics at ASDEX Upgrade Open
Guided by predictions from nonlinear gyrokinetic simulations, two new turbulence diagnostics were designed and installed at ASDEX Upgrade (AUG) to probe the fundamentals of ion-scale turbulent electron heat transport. The first, a 30-chann…
I-mode in non-deuterium plasmas in ASDEX Upgrade Open
The I-mode confinement regime in non-deuterium plasmas has been investigated in the ASDEX Upgrade tokamak. We report the first experimental observations on the existence and the main characteristics of this regime in hydrogen and helium pl…
Poloidally resolved measurements of the perpendicular propagation velocity of density fluctuations in ASDEX Upgrade L-mode plasmas Open
Poloidal asymmetries of the propagation velocity of density fluctuations perpendicular to the magnetic field measured with Doppler reflectometry have been reported in several magnetic confinement plasma devices. Careful analysis of a large…
Approaching detachment in I-mode—response of core confinement and the edge pedestal in the ASDEX Upgrade tokamak Open
Experiments on nitrogen assisted divertor detachment in the improved energy confinement mode (I-mode) are reported from the ASDEX Upgrade tokamak. When nitrogen is introduced into the divertor and radiation losses cool the divertor plasma …