A5003884937- Magnetic confinement fusion research
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Fusion Academy
1983-2023
Fusion (United States)
1983-2022
University of Washington
2010-2016
American Institute of Aeronautics and Astronautics
2010-2014
Princeton Plasma Physics Laboratory
1975-2011
Princeton University
1974-2011
École Polytechnique Fédérale de Lausanne
2011
Voss Scientific (United States)
2011
Los Alamos National Laboratory
2001-2010
North Carolina State University
2002
Previous work by Johnson and Greene on resistive instabilities is extended to finite-pressure configurations. The Mercier criterion for the stability of ideal magnetohydrodynamic interchange mode rederived, generalization earlier obtained, a relation between two noted. Conditions tearing instability are recovered with growth rate scaling resistivity in more complicated manner than η3/5. Nyquist techniques used show that favorable average curvature can convert into an overstable often stabilize it.
A WKB formalism for constructing normal modes of short-wavelength ideal hydromagnetic, pressure-driven instabilities (ballooning modes) in general toroidal magnetic containment devices with sheared fields is developed. No incompressibility approximation made. dispersion relation obtained from the eigenvalues a fourth-order system ordinary differential equations to be solved by integrating along line force. Higher-order calculations are performed find amplitude equation and phase change at...
Application of resistive instability theory shows that toroidal effects can stabilize the tearing mode in devices like Princeton Large Torus. Contraction current channel is destabilizing. Finite fluid compressibility crucial to this phenomenon.
A nominally axisymmetric plasma configuration, such as a tokamak or spherical torus, is highly sensitive to nonaxisymmetric magnetic perturbations due currents outside of the plasma. The high sensitivity means that primary interest in response very small perturbations, i.e., ∣b⃗∕B⃗∣≈10−2 10−4, which can be calculated using theory perturbed equilibria. ideal equilibrium code (IPEC) described and applied study torus external perturbations.
We studied ballooning instabilities in tokamaks of arbitrary cross section and finite shear. These azimuthally localized, ideal magnetohydrodynamic modes have large toroidal-mode numbers, but variation along the field across flux surfaces. Stability is determined by solving a second-order ordinary differential equation on each surface, subject to proper boundary conditions. Qualitative agreement achieved with Princeton pest stability code.
Research in NSTX has been conducted to establish spherical torus plasmas be used for high β, auxiliary heated experiments. This device a major radius R0 = 0.86 m and midplane halfwidth of 0.7 m. It operated with toroidal magnetic field B0 ⩽ 0.3 T Ip 1.0 MA. The evolution the plasma equilibrium is analysed between discharges an automated version EFIT code. Limiter, double null lower single diverted configurations have sustained several energy confinement times. stored reached 92 kJ (βt 17.8%)...
The National Spherical Torus Experiment (NSTX) has demonstrated the advantages of low aspect ratio geometry in accessing high toroidal and normalized plasma beta, βN ≡ 108⟨βt⟩ aB0/Ip. Experiments have reached βt = 39% 7.2 through boundary profile optimization. High plasmas can exceed ideal no-wall stability limit, βNno−wall, for periods much greater than wall eddy current decay time. Resistive mode (RWM) physics is studied to understand stabilization these plasmas. spectrum unstable RWMs...
Research on the National Spherical Torus Experiment, NSTX, targets physics understanding needed for extrapolation to a steady-state ST Fusion Nuclear Science Facility, pilot plant, or DEMO. The unique operational space is leveraged test theories next-step tokamak operation, including ITER. Present research also examines implications coming device upgrade, NSTX-U. An energy confinement time, τE, scaling unified varied wall conditions exhibits strong improvement of BTτE with decreased electron...
A method is presented for determining the ideal magnetohydrodynamic stability of an axisymmetric toroidal plasma, based on a generalization developed by Newcomb fixed-boundary modes in cylindrical plasma. For mode number n≠0, problem reduced to numerical integration high-order complex system ordinary differential equations, Euler-Lagrange equation extremizing potential energy, coupled amplitudes poloidal harmonics m as function radial coordinate ψ straight-fieldline flux system. Unlike case,...
NIMROD is a code development project designed to study long-wavelength, low-frequency, nonlinear phenomena in toroidal plasmas with realistic geometry and dynamics. The numerical challenges of solving the fluid equations for fusion plasma are discussed our discretization scheme presented. Simulations resistive tearing mode show that time steps much greater than Alfven possible without loss accuracy. Validation tests interchange shaped equilibrium, ballooning activity reversed-field pinches described.
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Optimized current profiles are shown to be capable of providing simultaneous stability against all resistive kink modes in the tokamak.Received 24 September 1976DOI:https://doi.org/10.1103/PhysRevLett.38.234©1977 American Physical Society
The ’’ballooning mode formalism,’’ previously developed for the ideal magnetohydrodynamic problem, is applied to kinetic problem in tokamaks. general two-dimensional equation governing drift and trapped-electron eigenmodes reduces a one-dimensional integral along lines of force with radial structure determined by WKB procedure. Comparisons made between present code previous embodying identical physical assumptions indicate reasonable agreement. This correspondence holds both field line...
Research on the stability of spherical torus plasmas at and above no-wall beta limit is being addressed National Spherical Torus Experiment [M. Ono et al., Nucl. Fusion 40, 557 (2000)], that has produced low aspect ratio plasmas, R/a∼1.27 plasma current exceeding 1.4 MA with high energy confinement (TauE/TauE_ITER89P>2). Toroidal normalized have exceeded 25% 4.3, respectively, in q∼7 plasmas. The observed to increase then saturate increasing li. factor βN/li reached 6, limited by...
Odd-parity rotating magnetic fields (${\mathrm{RMF}}_{o}$) applied to mirror-configuration plasmas have produced average electron energies exceeding 200 eV at line-averaged densities of $\ensuremath{\sim}{10}^{12}\text{ }\text{ }{\mathrm{cm}}^{\ensuremath{-}3}$. These plasmas, sustained for over ${10}^{3}{\ensuremath{\tau}}_{\mathrm{Alfven}}$, low Coulomb collisionality, ${v}_{c}^{*}\ensuremath{\equiv}L/{\ensuremath{\lambda}}_{C}\ensuremath{\sim}{10}^{\ensuremath{-}3}$, where...
The mission of the National Spherical Torus Experiment (NSTX) is demonstration physics basis required to extrapolate next steps for spherical torus (ST), such as a plasma facing component test facility (NHTX) or an ST based (ST-CTF), and support ITER. Key issues are transport, steady state high β operation. To better understand electron new high- k scattering diagnostic was used extensively investigate gyro-scale fluctuations with varying temperature gradient scale length. Results from n = 3...
This is a large and important work by one of the leading Russian contributors to this subject. It covers topics central importance magnetic fusion energy research with breadth, depth clarity not found elsewhere. intended as reference book guide original literature for serious practitioners field. The divided into 8 parts, listed below, further subdivided 31 chapters.
Feedback stabilization of the resistive wall mode (RWM) a plasma in general feedback configuration is formulated terms normal modes plasma-resistive system. The growth/damping rates and eigenfunctions are determined by an extended energy principle for during its open (feedback) loop operation. A set equations derived time evolution these with currents coils. dynamics system completed prescription logic. feasibility evaluated using Nyquist diagram method or solving characteristic equations....
One of the goals National Spherical Torus Experiment (NSTX) is to investigate physics global mode stabilization in a low aspect ratio device. NSTX has major radius R0 = 0.86 m, midplane half-width 0.7 and an on-axis vacuum toroidal field B0 ⩽ 0.6 T reached plasma current Ip 1.5 MA. Experiments have established wall-stabilized MHD operating space machine. The maximum βt βN 35% 6.5%, respectively, with reaching 9.5li. Collapses rotation been correlated violation n 1 ideal beta limit, no−wall,...
Steady-state operation of the advanced tokamak reactor relies on maintaining plasma stability with respect to resistive wall mode (RWM). Active magnetic feedback and rotation are two methods proposed demonstrated for this purpose. A comprehensive modeling effort including both is needed understanding physical mechanisms stabilization project future devices. For low rotation, a complete solution issue obtained by assuming obeys ideal magnetohydrodynamics (MHDs) utilizing normal approach (NMA)...
The National Spherical Torus Experiment (NSTX) offers an operational space characterized by high-beta (β t = 39%, β N > 7, ) and low aspect ratio ( A 1.27) to leverage the plasma parameter dependences of RWM stabilization rotation damping physics giving greater confidence for extrapolation ITER. Significant new capability research has been added device with commissioning a set six non-axisymmetric magnetic field coils, allowing generation fields dominant toroidal mode number, n , 1–3....
We present a method for determining the linear resistive magnetohydrodynamic (MHD) stability of an axisymmetric toroidal plasma, based on matched asymptotic expansions. The plasma is partitioned into set ideal MHD outer regions, connected through inner regions about singular layers where q=m/n, with m and n mode numbers, respectively, q safety factor. satisfy equations zero-frequency, which are identical to Euler-Lagrange minimizing potential energy δW. solutions these go infinity at...
A major research goal of the national spherical torus experiment is establishing long-pulse, high beta, confinement operation and its physics basis. This has been enabled by facility capabilities developed during 2001 2002, including neutral beam (up to 7 MW) harmonic fast wave (HHFW) heating 6 MW), toroidal fields up kG, plasma currents 1.5 MA, flexible shape control, wall preparation techniques. These have generation plasmas with 35%. Normalized beta values often exceed no-wall limit,...
The resistive wall mode (RWM) poses a limit to the maximum β that can be sustained in magnetic fusion experiments. RWM stabilization physics at low aspect ratio is studied high-β National Spherical Torus Experiment (NSTX) [M. Ono, S. M. Kaye, Y.-K. Peng et al., Nucl. Fusion 40, 557 (2000)] plasmas (βt up 39%; βN 6.8) understand and alleviate this constraint. Plasmas with increased q NSTX have been maintained above computed ideal no-wall for more than 20 times no signs of growth cases where...