A5026623418- Magnetic confinement fusion research
- Superconducting Materials and Applications
- Ionosphere and magnetosphere dynamics
- Particle accelerators and beam dynamics
- Fusion materials and technologies
- Plasma Diagnostics and Applications
- Solar and Space Plasma Dynamics
- Laser-Plasma Interactions and Diagnostics
- Nuclear reactor physics and engineering
- Atomic and Subatomic Physics Research
- Geomagnetism and Paleomagnetism Studies
- Spacecraft and Cryogenic Technologies
- Particle Accelerators and Free-Electron Lasers
- Magnetic Field Sensors Techniques
- Laser-induced spectroscopy and plasma
- Real-time simulation and control systems
- Nuclear Physics and Applications
- Astro and Planetary Science
- Semiconductor materials and devices
- Nuclear Materials and Properties
- Magnetic Properties and Applications
- Physics of Superconductivity and Magnetism
- Computational Physics and Python Applications
- Astronomical Observations and Instrumentation
- Engineering Applied Research
Princeton Plasma Physics Laboratory
2015-2024
Princeton University
2009-2023
Institut für Nichtklassische Chemie
2015
Lawrence Livermore National Laboratory
2014
Leipzig University
2011
University of Wisconsin–Madison
2001-2005
Abstract The spherical tokamak (ST) is a leading candidate for Fusion Nuclear Science Facility (FNSF) due to its compact size and modular configuration. National Spherical Torus eXperiment (NSTX) MA-class ST facility in the US actively developing physics basis an ST-based FNSF. In plasma transport research, experiments exhibit strong (nearly inverse) scaling of normalized confinement with collisionality, if this trend holds at low high fusion neutron fluences could be achievable very...
In this Letter we report a clear and unambiguous observation of the out-of-plane quadrupole magnetic field suggested by numerical simulations in reconnecting current sheet reconnection experiment. Measurements show that Hall effect is large collisionless regime becomes small as collisionality increases, indicating plays an important role reconnection.
This article describes the recent findings on two-fluid effects magnetic reconnection in plasmas with variable collisionality experiment (MRX) [M. Yamada et al., Phys. Plasmas 4, 1936 (1997)]. The MRX device has been upgraded to accommodate a variety of operation modes and high energy density experiments by increasing its capacitor bank extending discharge duration. As our experimental regime moved from collisional collision-free, have become more evident. It is observed that two-dimensional...
Reduction or elimination of edge localized modes (ELMs) while maintaining high confinement is essential for future fusion devices, e.g., the ITER. An ELM-free regime was recently obtained in National Spherical Torus Experiment, following lithium (Li) evaporation onto plasma-facing components. Edge stability calculations indicate that pre-Li discharges were unstable to low-$n$ peeling ballooning modes, broader pressure profiles stabilized post-Li discharges. Normalized energy increased by 50%...
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....
Disruption prediction and avoidance is a critical need for next-step tokamaks, such as ITER. Event Characterization Forecasting (DECAF) research fully automates analysis of tokamak data to determine chains events that lead disruptions forecast their evolution allowing sufficient time mitigation or complete the disruption. event related local rotating global magnetohydrodynamic (MHD) modes vertical instability are examined with warnings issued many off-normal physics events, including density...
Experiments in the National Spherical Torus Experiment (NSTX) have shown beneficial effects on performance of divertor plasmas as a result applying lithium coatings graphite and carbon-fiber-composite plasma-facing components. These mostly been applied by pair evaporators mounted at top vacuum vessel which inject collimated streams vapor toward lower divertor. In neutral beam injection (NBI)-heated deuterium H-mode run immediately after application lithium, modifications included decreases...
Liquid metal plasma-facing components (PFCs) have been proposed as a means of solving several problems facing the creation economically viable fusion power reactors. To date, few demonstrations exist this approach in diverted tokamak and we here provide an overview such work on National Spherical Torus Experiment (NSTX). The Lithium Divertor (LLD) was installed operated for 2010 run campaign using evaporated coatings filling method. LLD consisted copper-backed structure with porous...
The low-aspect ratio, low magnetic field and wide range of plasma beta NSTX plasmas provide new insight into the origins effects errors. An extensive array sensors has been used to analyse error fields, measure error-field amplification detect resistive wall modes (RWMs) in real time. measured normalized threshold for onset locked shows a linear scaling with density, weak inverse dependence on toroidal positive shear. These results extrapolate favourable ITER. For these low-beta locked-mode...
A multi-device database of disruption characteristics has been developed under the auspices International Tokamak Physics Activity magneto-hydrodynamics topical group. The purpose this ITPA (IDDB) is to find commonalities between and mitigation in a wide variety tokamaks order elucidate physics underlying tokamak disruptions extrapolate toward much larger devices, such as ITER future burning plasma devices. In contrast previous smaller data collation efforts, IDDB aims provide significant...
Tokamaks are sensitive to deviations from axisymmetry as small δB/B0∼10−4. These nonaxisymmetric perturbations greatly modify plasma confinement and performance by either destroying magnetic surfaces with subsequent locking or deforming associated nonambipolar transport. The Ideal Perturbed Equilibrium Code (IPEC) calculates ideal perturbed equilibria provides important basis for understanding the sensitivity of tokamak plasmas perturbations. IPEC calculations indicate that response,...
Reducing plasma flow clearly decreases the stability of tearing modes in multiple regimes (sawtooth, hybrid) both high- and low-aspect-ratio tokamaks (DIII-D [J. L. Luxon, Nucl. Fusion 42, 614 (2002)], Joint European Torus [M. Keilhacker JET Team, Plasma Phys. Controlled 41, 301 (1999)], National Spherical Experiment Ono, S. M. Kaye, Y.-K. Peng, 40, 557 (2000)], each with distinct means lessening rotation). Further, reducing makes pre-existing “saturated” islands larger at same beta (β)....
Detailed comparisons are reported between laboratory observations of electron‐scale dissipation layers near a reconnecting X‐line and direct two‐dimensional full‐particle simulations. Many experimental features the electron layers, such as insensitivity to ion mass, reproduced by simulations; layer thickness, however, is about 3–5 times larger than predictions. Consequently, leading candidate 2D mechanism based on collisionless nongyrotropic pressure insufficient explain observed...
The application of nonaxisymmetric magnetic fields is shown to destabilize edge-localized modes (ELMs) during otherwise ELM-free periods discharges in the National Spherical Torus Experiment (NSTX). Profile analysis shows applied increased temperature and pressure gradients, decreasing edge stability. This robust effect was exploited for a new form ELM control: triggering ELMs at will high performance H mode plasmas enabled by lithium conditioning, yielding time-averaged energy confinement...
Understanding the dependence of confinement on collisionality in tokamaks is important for design next-step devices, which will operate at collisionalities least one order magnitude lower than present generation. A wide range has been obtained National Spherical Torus Experiment (NSTX) by employing two different wall conditioning techniques, with boronization and between-shot helium glow discharge (HeGDC+B), using lithium evaporation (Li EVAP). Previous studies HeGDC+B plasmas indicated a...
A significant fraction of high-harmonic fast-wave (HHFW) power applied to NSTX can be lost the scrape-off layer (SOL) and deposited in bright hot spirals on divertor rather than core plasma. We show that HHFW flows these along magnetic field lines passing through SOL front antenna, implying couples across entire width mostly at antenna face. This result will help guide future efforts understand minimize edge losses order maximize heating current drive.
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...
We report the first identification of electron-diffusion region, where demagnetized electrons are accelerated to super-Alfv\'enic speed, in a reconnecting laboratory plasma. The width region scales with electron skin depth [$\ensuremath{\sim}(5.5--7.5)c/{\ensuremath{\omega}}_{pe}$] and peak outflow velocity Alfv\'en [$\ensuremath{\sim}(0.12--0.16){V}_{eA}$], independent ion mass.
The onset conditions for the m / n = 2/1 neoclassical tearing mode are studied in terms of drive, triggering instabilities, and toroidal rotation or shear, spherical torus NSTX (Ono M. et al 2000 Nucl. Fusion 40 557 ). There three typical these modes, given order increasing drive required onset: by energetic particle edge localized modes cases where appear to grow without a trigger. In all cases, increases with implying stabilizing effect from shear.
This paper explores a range of high-performance equilibrium scenarios achievable with neutral beam heating in the NSTX-Upgrade device (Menard J.E. 2012 Nucl. Fusion 52 083015). is substantial upgrade to existing NSTX (Ono M. et al 2000 40 557), significantly higher toroidal field and solenoid capabilities, three additional sources larger current-drive efficiency. Equilibria are computed free-boundary TRANSP, allowing self-consistent calculation non-inductive sources, plasma poloidal-field...
The engineering limits of plasma-facing components (PFCs) constrain the allowable operational space tokamaks. Poorly managed heat fluxes that push PFCs beyond their not only degrade core plasma performance via elevated impurities, but can also result in PFC failure due to thermal stresses or melting. Simple axisymmetric assumptions fail capture complex interaction between three-dimensional (3-D) geometry and two-dimensional 3-D plasmas. This results fusion systems must either operate with...
Improved confinement has been achieved in the MST through control of poloidal electric field, but it is now known that improvement limited by bursts an edge-resonant instability. Through refined field control, plus toroidal we have suppressed these bursts. This led to a total beta 15% and reversed-field-pinch-record estimated energy time 10 ms, tenfold increase over standard value which for first substantially exceeds scaling characterized most reversed-field-pinch plasmas.
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...