A5078986856- Magnetic confinement fusion research
- Solar and Space Plasma Dynamics
- Ionosphere and magnetosphere dynamics
- Geomagnetism and Paleomagnetism Studies
- Superconducting Materials and Applications
- Plasma Diagnostics and Applications
- Astrophysics and Star Formation Studies
- Astro and Planetary Science
- Particle accelerators and beam dynamics
- Fluid Dynamics and Turbulent Flows
- Fusion materials and technologies
- Laser-Plasma Interactions and Diagnostics
- Stellar, planetary, and galactic studies
- Characterization and Applications of Magnetic Nanoparticles
- Nuclear reactor physics and engineering
- Laser-induced spectroscopy and plasma
- Gas Dynamics and Kinetic Theory
- Advanced Thermodynamics and Statistical Mechanics
- Nuclear Physics and Applications
- Atomic and Molecular Physics
- Magnetic and Electromagnetic Effects
- Advanced Thermodynamic Systems and Engines
- Magnetic Properties and Applications
- Calibration and Measurement Techniques
- Quantum, superfluid, helium dynamics
Princeton Plasma Physics Laboratory
2014-2025
Princeton University
2015-2025
Amirkabir University of Technology
1998-2022
University of Wisconsin–Madison
2004-2014
University of New Hampshire
2011-2014
University of Washington
2013-2014
Lawrence Livermore National Laboratory
2013-2014
Shahid Beheshti University
2006-2011
KTH Royal Institute of Technology
1998
The National Spherical Torus Experiment (NSTX) has undergone a major upgrade, and the NSTX Upgrade (NSTX-U) Project was completed in summer of 2015.NSTX-U first plasma subsequently achieved, diagnostic control systems have been commissioned, H-mode accessed, magnetic error fields identified mitigated, physics research campaign carried out.During ten run weeks operation, NSTX-U surpassed record pulse-durations toroidal (TF), high-performance ~1 MA plasmas comparable to best sustained near...
We report the first direct evidence for axisymmetric standard magnetorotational instability (SMRI) from a combined experimental and numerical study of magnetized liquid-metal shear flow in Taylor-Couette cell with independently rotating electrically conducting end caps. When uniform vertical magnetic field B_{i} is applied along rotation axis, measured radial B_{r} on inner cylinder increases linearly small Reynolds number Rm due to magnetization residue Ekman circulation. Onset SMRI...
Abstract Throughout the 2023 DIII-D negative triangularity (NT) campaign, unexpected magnetic fluctuations indicative of an edge localized instability were observed in majority strongly shaped ( <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mrow> <mml:mo>−</mml:mo> <mml:mn>0.55</mml:mn> <mml:mtext>⩽</mml:mtext> <mml:mi>δ</mml:mi> <mml:mn>0.45</mml:mn> </mml:mrow> </mml:math> ) discharges. Moreover, these same found to be absent weaker NT plasma shapes....
Global stability of differentially rotating plasma is investigated using a generalized effective potential. We first, for current-free system, obtain general form an potential in terms the free energies global curvature and gradients rotation non-axisymmetric disturbances. then examine disks several profiles present associated onset these instabilities MHD regime. In particular, results axisymmetric magnetorotational instability as well local modes are presented. The latter constitute two...
The formation of an elongated Sweet-Parker current sheet and a transition to plasmoid instability has for the first time been predicted by simulations in large-scale toroidal fusion plasma absence any preexisting instability. Plasmoid is demonstrated through resistive MHD transient coaxial helicity injection experiments National Spherical Torus Experiment (NSTX). Consistent with theory, fundamental characteristics instability, including fast reconnection rate, have observed these realistic...
We investigate numerically the Princeton magnetorotational instability (MRI) experiment and effect of conducting axial boundaries or endcaps. MRI is identified found to reach a much higher saturation than for insulating This probably due stronger driving base flow by magnetically rather viscously coupled boundaries. Although computations are necessarily limited lower Reynolds numbers (Re) their experimental counterparts, it appears that level becomes independent Re when sufficiently large,...
Energy confinement comparable with tokamak quality is achieved in the Madison Symmetric Torus (MST) reversed field pinch (RFP) at a high beta and low toroidal magnetic field. Magnetic fluctuations normally present RFP are reduced via parallel current drive outer region of plasma. In response, electron temperature nearly triples doubles. The time increases ten-fold (to ∼10 ms), which L- H-mode scaling values for same plasma current, density, heating power, size shape. Runaway evidenced by...
The standard magnetorotational instability (SMRI) is a promising mechanism for turbulence and rapid accretion in astrophysical disks. It magnetohydrodynamic (MHD) that destabilizes otherwise hydrodynamically stable disk flow. Due to its microscopic nature at astronomical distances stringent requirements laboratory experiments, SMRI has remained unconfirmed since proposal, despite importance. Here we report nonaxisymmetric MHD modified Taylor-Couette experiment. To search SMRI, uniform...
The constraint imposed by magnetic helicity conservation on the $\ensuremath{\alpha}$ effect is considered for both magnetically and flow dominated self-organizing plasmas. Direct numerical simulations are presented a dominant contribution to effect, which can be cast in functional form of total divergence an averaged flux, called helicity-flux-driven ($\mathrm{H}\ensuremath{\alpha}$) effect. $\mathrm{H}\ensuremath{\alpha}$ two examples---the toroidal plasma unstable tearing modes,...
The National Spherical Torus Experiment (NSTX) is currently being upgraded to operate at twice the toroidal field and plasma current (up 1 T 2 MA), with a second, more tangentially aimed neutral beam (NB) for rotation control, allowing pulse lengths up 5 s. Recent NSTX physics analyses have addressed topics that will allow NSTX-Upgrade achieve research goals critical Fusion Nuclear Science Facility. These include producing stable, 100% non-inductive operation in high-performance plasmas,...
We study the dynamo generation (exponential growth) of large-scale (planar averaged) fields in unstratified shearing box simulations magnetorotational instability (MRI). In contrast to previous studies restricted horizontal (x–y) averaging, we also demonstrate presence when vertical (y–z) averaging is employed instead. By computing space–time planar averaged and power spectra, find action early MRI growth phase – a previously unidentified feature. Non-axisymmetric linear modes with low...
Whitepaper #192 in the Decadal Survey for Solar and Space Physics (Heliophysics) 2024-2033. Main topics: basic research; infrastructure/workforce/other programmatic. Additional ground-based missions/projects; state of profession; laboratory space plasma physics; […]
The dominant finite-Larmour-radius (FLR) stabilization effects on interchange instability can be retained by taking into account the ion gyroviscosity or generalized Ohm's law in an extended MHD model. However, recent simulations and theoretical calculations indicate that complete FLR of mode may not attainable two-fluid effect alone framework MHD. For a class plasma equilibria certain finite-$\ensuremath{\beta}$ nonisentropic regimes, critical wave number for tends toward infinity.
The physics of magnetic reconnection and fast flux closure in transient coaxial helicity injection experiments NSTX is examined using resistive MHD simulations. These simulations have been performed the NIMROD code with fixed boundary (including poloidal coil currents) experimental geometry. Simulations show that an X point formed injector region, followed by formation closed surfaces within 0.5 ms after driven voltage current begin to rapidly decrease. As turned off, field lines tend...
Nonlinear edge localized modes in a tokamak are examined using global three-dimensional resistive magnetohydrodynamics simulations. Coherent current-carrying filament (ribbon-like) structures wrapped around the torus nonlinearly formed due to nonaxisymmetric reconnecting current sheet instabilities, so called peeling-like modes. These fast growing saturate by breaking axisymmetric layers isolated near plasma and go through repetitive relaxation cycles expelling radially outward relaxing it...
The multi-region relaxed magnetohydrodynamics (MRxMHD) has been successful in the construction of equilibria three-dimensional (3D) configurations. In MRxMHD, plasma is sliced into sub-volumes separated by ideal interfaces, each undergoing relaxation, allowing formation islands and chaos. resulting equilibrium a stepped pressure profile across sub-volumes. code (SPEC) (S R Hudson et al, Phys. Plasmas 19, 112502 (2012)) was developed to calculate MRxMHD numerically. this work, we have...
Abstract The mission of the low aspect ratio spherical tokamak NSTX-U is to advance physics basis and technical solutions required for optimizing configuration next-step steady-state fusion devices. will ultimately operate at up 2 MA plasma current 1 T toroidal field on axis 5 s, has available 15 MW neutral beam injection power different tangency radii 6 high harmonic fast wave heating. With these capabilities develop understanding control tools ramp-up sustain performance fully...
We have increased substantially the electron and ion temperatures, density, total beta in plasmas with improved energy confinement Madison Symmetric Torus (MST). The is achieved a well-established current profile control technique for reduction of magnetic tearing reconnection. A sustained temperature >1 keV intensified reconnection-based heating followed immediately by control. In same plasmas, reaches 2 keV, thermal diffusivity drops to about m s −1 . global time 12 ms. This reported...
Axisymmetric current-carrying plasmoids are formed in the presence of nonaxisymmetric fluctuations during nonlinear three-dimensional resistive MHD simulations a global toroidal geometry. We utilize helicity injection technique to form an initial poloidal flux guide field. As is injected, two types current sheets from (1) oppositely directed field lines injector region (primary reconnecting sheet), and (2) compression near plasma edge (edge sheet). first find that arising current-sheet...
Abstract A large-volume flux closure during transient coaxial helicity injection (CHI) in NSTX-U is demonstrated through resistive magnetohydrodynamics (MHD) simulations. Several major improvements, including the improved positioning of divertor poloidal field coils, are projected to improve CHI start-up phase NSTX-U. Simulations configuration with constant time coil currents show that strong shaping injected open lines (injector flux) rapidly reconnect and form large volume closed surfaces....
The cause for sudden reconnection in reversed field pinch plasmas is determined experimentally two cases: large events (the sawtooth crash) and small during improved confinement. We measure the term MHD equations which represents driving (or damping) of edge tearing modes due to axisymmetric magnetic field. negative are stable, implying that may be driven by nonlinear coupling other modes) positive (modes unstable, spontaneous).