A5067313238- Magnetic confinement fusion research
- Ionosphere and magnetosphere dynamics
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- Fluid Dynamics and Turbulent Flows
- Cold Fusion and Nuclear Reactions
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Fusion Academy
2014-2025
Fusion (United States)
2014-2025
The University of Texas at Austin
2015-2025
Bellevue Hospital Center
2025
General Atomics (United States)
1997-2022
Columbia University
2022
Ain Shams University
2022
Oak Ridge National Laboratory
2022
Princeton Plasma Physics Laboratory
2016-2022
Princeton University
2022
Collisionless electron-temperature-gradient-driven (ETG) turbulence in toroidal geometry is studied via nonlinear numerical simulations. To this aim, two massively parallel, fully gyrokinetic Vlasov codes are used, both including electromagnetic effects. Somewhat surprisingly, and unlike the analogous case of ion-temperature-gradient-driven (ITG) turbulence, we find that turbulent electron heat flux significantly underpredicted by simple mixing length estimates a certain parameter regime...
The predictions of gyrokinetic and gyrofluid simulations ion-temperature-gradient (ITG) instability turbulence in tokamak plasmas as well some plasma thermal transport models, which have been widely used for predicting the performance proposed International Thermonuclear Experimental Reactor (ITER) [Plasma Physics Controlled Nuclear Fusion Research, 1996 (International Atomic Energy Agency, Vienna, 1997), Vol. 1, p. 3], are compared. These comparisons provide information on effects...
The first toroidal, gyrokinetic, electromagnetic simulations of small scale plasma turbulence are presented. considered is driven by gradients in the electron temperature. It found that temperature gradient (ETG) can induce experimentally relevant thermal losses magnetic confinement fusion devices. For typical tokamak parameters, transport essentially electrostatic character. simulation results qualitatively consistent with a model balances linear and secondary mode growth rates. Significant...
A physically comprehensive and theoretically based transport model tuned to three-dimensional (3-D) ballooning mode gyrokinetic instabilities gyrofluid nonlinear turbulence simulations is formulated with global local magnetic shear stabilization E×B rotational stabilization. Taking no fit coefficients from experiment, the tested against a large profile database good agreement. This capable of describing enhanced core confinement barriers in negative central discharges on The used make...
A kinetic theory for the nonlinear evolution of a magnetic island in collisionless plasma confined toroidal system is presented. An asymptotic analysis Grad–Shafranov equation including neoclassical effects such as bootstrap current defines an time dependence width. Initially, strongly influences evolution. As surpasses certain critical width effect diminishes and grows at Rutherford rate. For profiles that Δ′<0 saturates island.
We address the mechanisms underlying zonal flow generation and stability in turbulent systems driven by electrostatic ion-temperature-gradient (ITG) mode. In case of stability, we show poloidal flows typical numerical simulations become unstable when they exceed a critical level. Near marginal linear ITG mode, system can generate that are sufficiently weak to remain stable strong suppress This region corresponds parameter regime nonlinear Dimits up-shift.
The Super-X Divertor (SXD), a robust axisymmetric redesign of the divertor magnetic geometry that can allow fivefold increase in core power density toroidal fusion devices, is presented. With small changes poloidal coils and currents for standard divertors, SXD allows largest plate radius inside field coils. This increases plasma-wetted area by 2–3 times over all flux-expansion-only methods (e.g., near main X point, tilting, divertor, snowflake), decreases parallel heat flux hence plasma...
A generalization of reduced magnetohydrodynamics is constructed from moments the Fokker–Planck equation. The new model uses familiar aspect-ratio approximations but allows for (i) evolution as slow diamagnetic drift frequency, thereby including certain finite Larmor radius effects, (ii) pressure gradient terms in a generalized Ohm’s law, thus making accessible adiabatic electron limit, and (iii) plasma compressibility, divergence both parallel perpendicular flows. system isothermal...
Abstract A fusion nuclear science facility (FNSF) could play an important role in the development of energy by providing environment needed to develop materials and components. The spherical torus/tokamak (ST) is a leading candidate for FNSF due its potentially high neutron wall loading modular configuration. key consideration choice configuration range achievable missions as function device size. Possible include: fluence, demonstrating tritium self-sufficiency, electrical self-sufficiency....
Abstract The first nonlinear gyrokinetic turbulence simulations that quantitatively reproduce experimental transport levels in an H-mode pedestal are reported. In the JET-ILW (ITER-like wall) pedestal, bulk of steep gradient region is caused by driven microtearing mode (MTM). Kinetic ballooning modes found to be a second-stability regime. With contributions from neoclassical and electron temperature transport, MTM mechanism reproduces, quantitatively, power balance across most pedestal.
Curvature and finite pressure are known to have a dramatic influence on linear magnetic tearing stability. An analytic theory of the nonlinear resistive growth islands in tokamaks that includes interchange driving term presented here. A Grad-Shafranov equation describe magnetohydrodynamic (MHD) equilibrium thin is derived. The evolution these then obtained. Interchange effects found become progressively less important with increasing island width.
Externally applied magnetic fields are used on the Texas Experimental Tokamak (TEXT) to study possibility of controlling particle, impurity and heat fluxes at plasma edge. Fields with toroidal mode number n = 2 or 3 multiple poloidal numbers m (dominantly 7) used, a poloidally toroidally averaged ratio radial field components 〈|br/Bø〉 ≅0. 1%. Calculations show that it is possible produce mixed islands stochastic regions edge (r/a ≥ 0.8) without affecting interior. The expected structure...
The MIT Plasma Science and Fusion Center collaborators are proposing a high-performance Advanced Divertor RF tokamak eXperiment (ADX)-a specifically designed to address critical gaps in the world fusion research programme on pathway next-step devices: nuclear science facility (FNSF), pilot plant (FPP) and/or demonstration power (DEMO). This high-field (>= 6.5 T, 1.5 MA), high density (P/S similar MW m(-2)) will test innovative divertor ideas, including an 'X-point target divertor' concept,...
JET has been unable to recover historical confinement levels when operating with an ITER-like wall (ILW) due largely the inaccessibility of high pedestal temperatures. Finding a path overcome this challenge is utmost importance for both prospective DT campaign and future ITER operation. Gyrokinetic simulations (using Gene code) quantitatively capture experimental transport representative discharge qualitatively major trends. Microtearing turbulence mechanisms low-temperature pedestals...
This paper compares the gyrokinetic instabilities and transport in two representative JET pedestals, one (pulse 78697) from configuration with a carbon wall (C) another 92432) after installation of JET's ITER-like Wall (ILW).The discharges were selected for comparison JET-ILW JET-C good confinement at high current (3 MA, corresponding also to low ρ * ) retain distinguishing features JET-ILW, notably, decreased pedestal top temperature JET-ILW.A profiles heating power reveals stark...
The flux coordinates with dual-region safety factor (q) in the poloidal direction are developed this work. X-point effects on ideal MHD modes tokamaks then analyzed using coordinate system. Since mainly affect edge region, localized at tokamak particularly examined. Two types of studied. first is related to conventional peeling or peeling-ballooning modes. mode existence aligned local magnetic field poloidally core region as observed experimentally confirmed. X points shown contribute a...
Recent high-poloidal-beta (high-βP) experiments on DIII-D and EAST have made coordinated breakthroughs for high confinement quality at density near the Greenwald limit. Density gradient amplification of turbulence suppression βP can explain both these achievements. Experiments achieved fraction (fGr = line-averaged density/Greenwald density) above 1 simultaneously with normalized energy (H98y2) around 1.5, as required in fusion reactor designs but never before verified tokamak divertor...
Advanced divertors are magnetic geometries where a second X-point is added in the divertor region to address serious challenges of burning plasma power exhaust. Invoking physical arguments, numerical work, and detailed model field analysis, we investigate structure advanced physically relevant for exhaust—the scrape-off layer. A primary result our analysis emergence “metric,” Divertor Index DI, which quantifies flux expansion increase as one goes from main strike point. It clearly separates...
The first high fidelity gyrokinetic simulations of the energy losses in transport barriers large tokamaks pursuit fusion gain are presented. These calculate turbulent with an extensive treatment relevant physical effects—fully kinetic, non-linear, electromagnetic—inclusive all major plasma species, and equilibria shape local bootstrap current for fusion-relevant cases. We find that plasmas a small normalized gyroradius lie unexpected regime enhanced can prevent projected gain. Our...
Fusion performance in tokamaks hinges critically on the efficacy of edge transport barrier (ETB) suppressing energy losses.The new concept 'fingerprints' is introduced to identify instabilities that cause losses ETBs many today's experiments, from among widely posited candidates.Analysis gyrokinetic-Maxwell equations and gyrokinetic simulations experiments reveals each mode type produces characteristic ratios various channels: density, heat, impurities.This, together with experimental...
This paper reports on the development of reduced models for electron temperature gradient (ETG) driven transport in pedestal. Model is enabled by a set 61 nonlinear gyrokinetic simulations with input parameters taken from pedestals broad range experimental scenarios. The simulation data has been consolidated new database data, Multiscale Gyrokinetic Database (MGKDB), facilitating analysis. modeling approach may be considered generalization standard quasilinear mixing length procedure....
It is shown here that microturbulence can be stabilized in the presence of steep temperature and density profiles. Indeed high β plasmas, pressure profile gradients are associated with |β′|=−∂β/∂ρ, where β=P/(B2/2μ0) ρ square root toroidal flux normalized to its edge value. values |β′| have a stabilizing influence on drift modes. This may form basis for positive feedback loop which core beta lead improved confinement, further increase β. A gyrokinetic electromagnetic tube code, GS2 [M....
Externally applied resonant magnetic fields have been used on TEXT to modify the particle flux and radial electric field near plasma edge. Magnetic with primary mode numbers m/n = 7/3 7/2, an average amplitude ⟨|br|/Bϕ⟩ ≃ 0.1% employed. This perturbation produces mixed islands stochastic regions at edge (r/a ≥ 0.8) without affecting interior. Working transport is shown be increased by typically 30% only in presence of (computed) islands. The effect diminished high perturbing strength when...