A. Kleiner

Princeton Plasma Physics Laboratory

Author Statistics

Papers

Citation

H-Index

i-10 index

Research Trends

Author Order

Document Type

Co-Authors

A. Diallo

Princeton Plasma Physics Laboratory

J. P. Graves

École Polytechnique Fédérale de Lausanne

W.A. Cooper

Swiss Federal Office of Energy

N.M. Ferraro

Princeton Plasma Physics Laboratory

W. Guttenfelder

Princeton Plasma Physics Laboratory

C. Clauser

Massachusetts Institute of Technology

J.W. Berkery

Princeton Plasma Physics Laboratory

M. Lampert

Princeton Plasma Physics Laboratory

S. Kaye

Princeton Plasma Physics Laboratory

J. Ménard

Princeton Plasma Physics Laboratory

Cooperative Institutions

General Atomics (United States)

444

Princeton Plasma Physics Laboratory

323

Fusion (United States)

212

Fusion Academy

198

Princeton University

196

Oak Ridge National Laboratory

169

University of California, Los Angeles

148

University of Wisconsin–Madison

147

University of California, San Diego

143

Lawrence Livermore National Laboratory

142

Author Statistics

Papers

Citation

H-Index

i-10 index

Research Field

Kinetic-ballooning-limited pedestals in spherical tokamak plasmas

Nuclear Fusion (2024)

J. F. Parisi W. Guttenfelder A. Nelson Rahul Gaur A. Kleiner

Abstract A theoretical model is presented that for the first time matches experimental measurements of the pedestal width-height Diallo scaling in the low-aspect-ratio high- β tokamak NSTX. Combining linear gyrokinetics with self-consistent pedestal equilibrium variation, kinetic-ballooning, rather than ideal-ballooning plasma instability, is shown to limit achievable confinement in spherical tokamak pedestals. Simulations are used to find the novel Gyrokinetic Critical Pedestal constraint, which determines the steepest pressure profile a pedestal can sustain subject to gyrokinetic instability. Gyrokinetic width-height scaling expressions for NSTX pedestals with varying density and temperature profiles are obtained. These scalings for STs depart significantly from that of conventional aspect ratio tokamaks.

Pedestal

Ballooning

Gyrokinetics

Aspect ratio (aeronautics)

10.1088/1741-4326/ad39fb

Cite

Citations (9)

Kinetic-ballooning-bifurcation in tokamak pedestals across shaping and aspect-ratio

Physics of Plasmas (2024)

J. F. Parisi A. Nelson Rahul Gaur S. Kaye F. I. Parra

We use a new gyrokinetic threshold model to predict a bifurcation in tokamak pedestal width-height scalings that depends strongly on plasma shaping and aspect-ratio. The bifurcation arises from the first and second stability properties of kinetic-ballooning-modes that yields wide and narrow pedestal branches, expanding the space of accessible pedestal widths and heights. The wide branch offers potential for edge-localized-mode-free pedestals with high core pressure. For negative triangularity, low-aspect-ratio configurations are predicted to give steeper pedestals than conventional-aspect-ratio. Both wide and narrow branches have been attained in tokamak experiments.

Pedestal

Aspect ratio (aeronautics)

Ballooning

Gyrokinetics

Bootstrap current

BETA (programming language)

10.1063/5.0190818

Cite

Citations (5)

Neoclassical tearing mode seeding by coupling with infernal modes in low-shear tokamaks

Nuclear Fusion (2016)

A. Kleiner J. P. Graves D. Brunetti W.A. Cooper Federico David Halpern

Abstract A numerical and an analytical study of the triggering of resistive MHD modes in tokamak plasmas with low magnetic shear core is presented. Flat q profiles give rise to fast growing pressure driven MHD modes, such as infernal modes. It has been shown that infernal modes drive fast growing islands on neighbouring rational surfaces. Numerical simulations of such instabilities in a MAST-like configuration are performed with the initial value stability code XTOR-2F in the resistive frame. The evolution of magnetic islands are computed from XTOR-2F simulations and an analytical model is developed based on Rutherford’s theory in combination with a model of resistive infernal modes. The parameter Δ ′ is extended from the linear phase to the non-linear phase. Additionally, the destabilising contribution due to a helically perturbed bootstrap current is considered. Comparing the numerical XTOR-2F simulations to the model, we find that coupling has a strong destabilising effect on (neoclassical) tearing modes and is able to seed 2/1 magnetic islands in situations when the standard NTM theory predicts stability.

Tearing

10.1088/0029-5515/56/9/092007

Cite

Citations (9)

Kinetic-Ballooning-Limited Pedestals in Spherical Tokamak Plasmas

arXiv (Cornell University) (2023)

J. F. Parisi W. Guttenfelder A. Nelson Rahul Gaur A. Kleiner

A theoretical model is presented that for the first time matches experimental measurements of the pedestal width-height Diallo scaling in the low-aspect-ratio high-$\beta$ tokamak NSTX. Combining linear gyrokinetics with self-consistent pedestal equilibrium variation, kinetic-ballooning, rather than ideal-ballooning plasma instability, is shown to limit achievable confinement in spherical tokamak pedestals. Simulations are used to find the novel Gyrokinetic Critical Pedestal constraint, which determines the steepest pressure profile a pedestal can sustain subject to gyrokinetic instability. Gyrokinetic width-height scaling expressions for NSTX pedestals with varying density and temperature profiles are obtained. These scalings for spherical tokamaks depart significantly from that of conventional aspect ratio tokamaks.

Pedestal

Ballooning

BETA (programming language)

Aspect ratio (aeronautics)

Gyrokinetics

10.48550/arxiv.2308.05238

Cite

Citations (1)

Free boundary 3D ideal MHD equilibrium calculations for non-linearly saturated current driven external kink modes in tokamaks

Nuclear Fusion (2018)

A. Kleiner J. P. Graves W.A. Cooper T Nicolas C Wahlberg

It is shown that free boundary 3D equilibrium calculations in tokamak geometry are capable of capturing the physics of non-linearly saturated external kink modes for monotonic current and q profiles typical of standard (baseline) plasma scenarios. The VMEC ideal MHD equilibrium model exhibits strong flux surface corrugations of the plasma vacuum boundary, driven by the core current profile. A method is presented which conveniently extracts the amplitude of the corrugation in terms of Fourier components in straight field line coordinates. The Fourier spectrum, and condition for non-linear corrugation agrees well with linear simulations, and the saturated amplitude agrees well with non-linear analytic calculations.

Kink instability

10.1088/1741-4326/aac607

Cite

Citations (9)

Importance of resistivity on edge-localized mode onset in spherical tokamaks

Nuclear Fusion (2021)

A. Kleiner N.M. Ferraro A. Diallo G.P. Canal

Abstract We explore the impact of realistic plasma resistivity on the linear stability of peeling-ballooning (PB) modes in tokamak discharges with low-aspect ratio. For this study we consider discharges that are subject to edge-localized modes (ELMs) in the National Spherical Torus Experiment (NSTX). Employing the state of the art extended-magnetohydrodynamic (MHD) code M3D-C1 it is demonstrated that non-ideal effects can significantly affect PB stability thresholds in NSTX discharges. In particular, robust resistive PB modes are found to exist well before the ideal PB stability threshold is met. These novel results can explain why ideal-MHD theory often does not accurately describe ELM onset in spherical torus configurations, and also present a valuable basis for the development of a predictive model for ELMs in low-aspect ratio tokamaks.

Spherical tokamak

Ballooning

Aspect ratio (aeronautics)

BETA (programming language)

Resistive touchscreen

Safety factor

Edge-localized mode

10.1088/1741-4326/abf416

Cite

Citations (14)

Data for "NSTX-U research advancing the physics of spherical tokamaks"

OSTI OAI (U.S. Department of Energy Office of Scientific and Technical Information) (2024)

Jack Berkery Promise Adebayo-Ige Hassan Al Khawaldeh G. Avdeeva S. G. Baek

Spherical tokamak

10.34770/2brb-2f62

Cite

Citations (0)

Stability properties and fast ion confinement of hybrid tokamak plasma configurations

APS (2015)

J. P. Graves D. Brunetti David Pfefferlé J. Faustin W.A. Cooper

Plasma confinement

Source

Cite

Citations (0)

Stability and transport of gyrokinetic critical pedestals

Nuclear Fusion (2024)

J. F. Parisi A. Nelson W. Guttenfelder Rahul Gaur J.W. Berkery

Abstract A gyrokinetic threshold model for pedestal width–height scaling prediction is applied to multiple devices. A shaping and aspect ratio scan is performed on National Spherical Torus Experiment (NSTX) equilibria, finding Δ ped = 0.92 A 1.04 κ − 1.24 0.38 δ β θ , ped 1.05 for the wide-pedestal branch with pedestal width Δ ped , aspect ratio A , elongation κ , triangularity δ , and normalized pedestal height β θ , ped . The width–transport scaling is found to vary significantly if the pedestal height is varied either with a fixed density or fixed temperature, showing how fueling and heating sources affect the pedestal density and temperature profiles for the kinetic-ballooning-mode (KBM) limited profiles. For an NSTX equilibrium, at fixed density, the wide branch is Δ ped = 0.028 ( q e / Γ e − 1.7 ) 1.5 ∼ η e 1.5 and at fixed temperature Δ ped = 0.31 ( q e / Γ e − 4.7 ) 0.85 ∼ η e 0.85 , where q e and Γ e are turbulent electron heat and particle fluxes and η e = ∇ ln ⁡ T e / ∇ ln ⁡ n e for an electron temperature T e and density n e . Pedestals close to the KBM limit are shown to have modified turbulent transport coefficients compared to the strongly driven KBMs. The role of flow shear is studied as a width–height scaling constraint and pedestal saturation mechanism for a standard and lithiated wide pedestal discharge. Finally, the stability, transport, and flow shear constraints are combined and examined for an NSTX experiment.

10.1088/1741-4326/ad4d02

Cite

Citations (6)

Conceptual design of ELM control coils for the TCABR tokamak

Fusion Engineering and Design (2025)

Felipe Machado Salvador André S. Bouzan Roberto Ramos Y.P. Asnis A. Kleiner

Conceptual design

10.1016/j.fusengdes.2024.114788

Cite

Citations (0)