D. R. Mikkelsen
A5012314660- Magnetic confinement fusion research
- Ionosphere and magnetosphere dynamics
- Fusion materials and technologies
- Particle accelerators and beam dynamics
- Superconducting Materials and Applications
- Laser-Plasma Interactions and Diagnostics
- Plasma Diagnostics and Applications
- Solar and Space Plasma Dynamics
- Nuclear reactor physics and engineering
- Laser-induced spectroscopy and plasma
- Atomic and Molecular Physics
- Dust and Plasma Wave Phenomena
- Nuclear Physics and Applications
- Astro and Planetary Science
- Stellar, planetary, and galactic studies
- Electromagnetic Launch and Propulsion Technology
- Particle Accelerators and Free-Electron Lasers
- Pulsars and Gravitational Waves Research
- Fluid Dynamics and Turbulent Flows
- Ion-surface interactions and analysis
- Meteorological Phenomena and Simulations
- Diamond and Carbon-based Materials Research
- Metal and Thin Film Mechanics
- Geomagnetism and Paleomagnetism Studies
- Geophysical and Geoelectrical Methods
Princeton Plasma Physics Laboratory
2009-2021
Powerlink Queensland (Australia)
2017-2019
Princeton University
2001-2016
University of California, Los Angeles
1987-2016
Massachusetts Institute of Technology
1994-2016
University of California, San Diego
2006-2016
Max Planck Society
2016
Fusion Academy
1994-2016
Fusion (United States)
1994-2016
Max Planck Institute for Plasma Physics
2016
Numerical results for the three mono-energetic transport coefficients required a complete neoclassical description of stellarator plasmas have been benchmarked within an international collaboration. These are flux-surface-averaged moments solutions to linearized drift kinetic equation which determined using field-line-integration techniques, Monte Carlo simulations, variational method employing Fourier–Legendre test functions and finite-difference scheme. The benchmarking has successfully...
This Letter presents nonlinear gyrokinetic simulations of microtearing mode turbulence. The include collisional and electromagnetic effects use experimental parameters from a high-β discharge in the National Spherical Torus Experiment. predicted electron thermal transport is comparable to that given by analysis, it dominated contribution electrons free-streaming along resulting stochastic magnetic field line trajectories. Experimental values flow shear can significantly reduce transport.
The object of this review is to summarize the achievements research on Alcator C-Mod tokamak [Hutchinson et al., Phys. Plasmas 1, 1511 (1994) and Marmar, Fusion Sci. Technol. 51, 261 (2007)] place that in context quest for practical fusion energy. a compact, high-field tokamak, whose unique design operating parameters have produced wealth new important results since it began operation 1993, contributing data extends tests critical physical models into parameter ranges regimes. Using only...
Compact optimized stellarators offer novel solutions for confining high-β plasmas and developing magnetic confinement fusion. The three-dimensional plasma shape can be designed to enhance the magnetohydrodynamic (MHD) stability without feedback or nearby conducting structures provide drift-orbit similar tokamaks. These configurations possibility of combining steady-state low-recirculating power, external control, disruption resilience previous with low aspect ratio, high β limit, good...
Wall conditioning in the Tokamak Fusion Test Reactor (TFTR) [K. M. McGuire et al., Phys. Plasmas 2, 2176 (1995)] by injection of lithium pellets into plasma has resulted large improvements deuterium–tritium fusion power production (up to 10.7 MW), Lawson triple product 1021 m−3 s keV), and energy confinement time 330 ms). The maximum current for access high-performance supershots been increased from 1.9 2.7 MA, leading stable operation at stored values greater than 5 MJ. amount on limiter...
A transport code (TRANSP) is used to simulate future deuterium-tritium (DT) experiments in TFTR.The simulations are derived from 14 TFTR DD discharges, and the modelling of one supershot discussed detail indicate degree accuracy TRANSP modelling.Fusion energy yields 01 particle parameters calculated, including profiles slowing down time, average energy, AlfvBn speed frequency.Two types simulation discussed.The main emphasis on DT equivalent, where an equal mix D T substituted for initial...
Peak fusion power production of 6.2\ifmmode\pm\else\textpm\fi{}0.4 MW has been achieved in TFTR plasmas heated by deuterium and tritium neutral beams at a total 29.5 MW. These have an inferred central alpha particle density 1.2\ifmmode\times\else\texttimes\fi{}${10}^{17}$ ${\mathrm{m}}^{\mathrm{\ensuremath{-}}3}$ without the appearance either disruptive magnetohydrodynamics events or detectable changes Alfv\'en wave activity. The measured loss rate energetic particles agreed with...
Recent experiments (Synakowski et al 2004 Nucl. Fusion 43 1648, Lloyd Plasma Phys. Control. 46 B477) on the Spherical Tokamak (or Torus, ST) (Peng 2000 Plasmas 7 1681) have discovered robust plasma conditions, easing shaping, stability limits, energy confinement, self-driven current and sustainment. This progress has encouraged an update of conditions engineering a Component Test Facility (CTF), (Cheng 1998 Eng. Des. 38 219) which is very valuable step in development practical fusion energy....
The NSTX operates at low aspect ratio (R/a ∼ 1.3) and high beta (up to 40%), allowing tests of global confinement local transport properties that have been established from higher devices. plasmas are heated by up 7 MW deuterium neutral beams with preferential electron heating as expected for ITER. Confinement scaling studies indicate a strong BT dependence, current dependence is weaker than observed ratio. Dimensionless experiments increase in decreasing collisionality weak degradation...
The time-scales for sawtooth repetition and heat pulse propagation are much longer (tens of milliseconds) in the large tokamak TFTR than previous, smaller tokamaks. This extended time-scale, coupled with more detailed diagnostics, has led us to revisit analysis as a method determine electron diffusivity χe plasma. A combination analytic computer solutions diffusion equation is used clarify previous work develop new methods determining χe. Direct comparison predicted pulses soft-X-ray ECE...
Because experiment/model comparisons in magnetic confinement fusion have not yet satisfied the requirements for validation as understood broadly, a set of approaches to validating mathematical models and numerical algorithms are recommended good practices. Previously identified procedures, such verification, qualification, analysis error uncertainty, remain important. However, particular challenges intrinsic plasmas physical measurement therein lead identification new or less familiar...
A series of carefully designed experiments on DIII-D have taken advantage a broad set turbulence and profile diagnostics to rigorously test gyrokinetic simulations. In this paper the goals, tools performed in these validation studies are reviewed specific examples presented. It is found that predictions transport fluctuation levels mid-core region (0.4 < ρ 0.75) better agreement with experiment than those outer (ρ ⩾ where edge coupling effects may become increasingly important multiscale...
Nonlinear simulations based on multiple NSTX discharge scenarios have progressed to help differentiate unique instability mechanisms and validate with experimental turbulence transport data. First nonlinear gyrokinetic of microtearing in a high-beta H-mode predict levels electron thermal that are dominated by magnetic flutter increase collisionality, roughly consistent energy confinement times dimensionless collisionality scaling experiments. Electron temperature gradient (ETG) significant...
Momentum confinement was investigated on DIII-D as a function of applied neutral beam torque at constant normalized beta βN, by varying the mix co (parallel to plasma current) and counter beams. Under balanced injection (i.e. zero total plasma), maintains significant rotation in co-direction. This 'intrinsic' can be modeled being due an offset 'anomalous torque'). anomalous appears have magnitude comparable one source. The presence such source must taken into account obtain meaningful...
Charge exchange with neutral hydrogen is examined as a recombination mechanism for multicharged impurity ions present in high-temperature fusion plasmas. At sufficiently low electron densities, fluxes of atomic produced by either the injection heating beams or background 'thermal' neutrals can yield an important even dominant process such ions. Equilibrium results are given selected elements showing altered ionisation balance and radiative cooling rate presence various populations. A notable...
Abstract Nonlinear gyrokinetic simulations of impurity transport are compared to experimental for the first time. The GYRO code (Candy and Waltz 2003 J. Comput. Phys. 186 545) was used perform global, nonlinear a standard Alcator C-Mod, L-mode discharge. laser blow-off technique combined with soft x-ray measurements single charge state calcium provide time-evolving profiles this non-intrinsic, non-recycling over radial range 0.0 ⩽ r / 0.6. Experimental coefficient their uncertainties were...
Thermal energy confinement times in National Spherical Torus Experiment (NSTX) dimensionless parameter scans increase with decreasing collisionality. While ion thermal transport is neoclassical, the source of anomalous electron these discharges remains unclear, leading to considerable uncertainty when extrapolating future spherical tokamak (ST) devices at much lower Linear gyrokinetic simulations find microtearing modes be unstable high collisionality discharges. First non-linear turbulence...
The Tokamak Fusion Test Reactor (TFTR) (R. J. Hawryluk, to be published in Rev. Mod. Phys.) experiments on high-temperature plasmas, that culminated the study of deuterium–tritium D–T plasmas containing significant populations energetic alpha particles, spanned over two decades from conception completion. During design TFTR, key physics issues were magnetohydrodynamic (MHD) equilibrium and stability, plasma energy transport, impurity effects, reactivity. Energetic particle was given less...
AbstractThe mission of the National Spherical Torus Experiment (NSTX) is to prove principles spherical torus physics by producing high-βt plasmas that are noninductively sustained and whose current profiles in steady state. The NSTX will be one first ultralow-aspect-ratio tori (R/a ≤ 1.3) operate at high power (Pinput up 11 MW) produce (25 40%), low-collisionality, high-bootstrap-fraction (≤70%) discharges. Both radio-frequency neutral beam heating drive employed. Built into sufficient...
The Tomamak Fusion Test reactor has performed initial high-power experiments with the plasma fueled nominally equal densities of deuterium and tritium. Compared to pure plasmas, energy stored in electron ions increased by \ensuremath{\sim}20%. These increases indicate improvements confinement associated use tritium possibly heating electrons \ensuremath{\alpha} particles created D-T fusion reactions.
The global confinement and the local transport properties of improved core plasmas in JT-60U were studied connection with Er shear formation. In mode internal barriers (ITBs), these are roughly classified into `parabolic type' ITBs `box ITBs. parabolic type ITB has a reduced thermal diffusivity χ region; however, shear, dEr/dr, is not as strong. box very strong at thin layer decreases to level neoclassical there. estimated E × B shearing rate, ωE B, becomes almost same linear growth rate...
An approximate normal mode analysis of plasma current diffusion in tokamaks is presented. The work based on numerical solutions the equation cylindrical geometry. Eigenvalues and eigenfunctions are shown for a broad range conductivity profile shapes. Three classes considered that correspond to three types tokamak operation. Convenient approximations lowest eigenvalues each class presented, simple formulas relaxation time scales given applied several cases as well noninductive drive....
Recent developments in neutral beam technology prompt us to reconsider the prospects for steady-state tokamak reactors. A mathematical reactor model is developed that includes physics of beam-driven currents and power balance, as well system costs. This used find plasma temperatures minimize cost per unit net electrical output. The optimum are nearly independent ß roughly twice high ignited If beams deuterium atoms with near-optimum energies 1 2 MeV drive current a size International Tokamak...