A5075969768- Magnetic confinement fusion research
- Fusion materials and technologies
- Superconducting Materials and Applications
- Laser-Plasma Interactions and Diagnostics
- Particle accelerators and beam dynamics
- Carbon Nanotubes in Composites
- Nuclear reactor physics and engineering
- Ionosphere and magnetosphere dynamics
- Semiconductor materials and devices
- Plasma Diagnostics and Applications
- Diamond and Carbon-based Materials Research
- Nuclear Physics and Applications
- Graphene research and applications
- Nuclear Materials and Properties
- Advancements in Semiconductor Devices and Circuit Design
- Digital Holography and Microscopy
- Advanced Data Storage Technologies
- Advancements in Photolithography Techniques
- Ion-surface interactions and analysis
- Solar and Space Plasma Dynamics
- Radiation Effects in Electronics
- Particle Detector Development and Performance
- Electromagnetic Launch and Propulsion Technology
- Laser-induced spectroscopy and plasma
- Metal and Thin Film Mechanics
Oak Ridge National Laboratory
2016-2025
University of Florida
2017-2018
University of California, Los Angeles
2009
Lawrence Livermore National Laboratory
2003
Forschungszentrum Jülich
2002
General Atomics (United States)
1997-2001
Knoxville College
2000
Princeton Plasma Physics Laboratory
1997
Princeton University
1997
CEA Cadarache
1997
Progress in the definition of requirements for edge localized mode (ELM) control and application ELM methods both high fusion performance DT operation non-active low-current ITER is described. Evaluation power fluxes low plasma current H-modes shows that uncontrolled ELMs will not lead to damage tungsten (W) divertor target, unlike high-current which by expected. Despite lack at lower currents, found be required under these conditions prevent an excessive contamination W, could eventually...
Operating ITER in the reference inductive scenario at design values of Ip = 15 MA and QDT 10 requires achievement good H-mode confinement that relies on presence an edge transport barrier whose pedestal pressure height is key to plasma performance. Strong gradients occur such conditions can drive magnetohydrodynamic instabilities resulting localized modes (ELMs), which produce a rapid energy loss from region facing components (PFC). Without appropriate control, heat loads PFCs during ELMs...
Abstract The tritium aspects of the DT fuel cycle embody some most challenging feasibility and attractiveness issues in development fusion systems. review analyses this paper provide important information to understand quantify these challenges define phase space plasma physics technology parameters features that must guide a serious R&D world program. We focus particular on components, necessary satisfy three ‘principal requirements’: (1) achieving self-sufficiency within system, (2)...
High repetition rate injection of deuterium pellets from the low-field side (LFS) DIII-D tokamak is shown to trigger high-frequency edge-localized modes (ELMs) at up $12\ifmmode\times\else\texttimes\fi{}$ low natural ELM frequency in $H$-mode plasmas designed match ITER baseline configuration shape, normalized beta, and input power just above threshold. The pellet size, velocity, location were chosen limit penetration outer 10% plasma. resulting perturbations plasma density energy...
Abstract Shattered pellet injection (SPI) is one of the prime candidates for ITER disruption mitigation system because its deeper penetration and larger particle flux than massive gas (MGI) (Taylor et al 1999 Phys. Plasmas 6 1872) using deuterium (Commaux 2010 Nucl. Fusion 50 112001, Combs IEEE Trans. Plasma Sci . 38 400, Baylor 2009 49 085013). The will likely use mostly high Z species such as neon more effective thermal pumping constraints on maximum amount or helium that could be...
The capability to inject deuterium pellets from the magnetic high field side (HFS) has been added DIII-D tokamak [J. L. Luxon and G. Davis, Fusion Technol. 8, 441 (1985)]. It is observed that injected HFS lead deeper mass deposition than identical outside midplane, in spite of a factor 4 lower pellet speed. have used generate peaked density profile plasmas [peaking (ne(0)/〈ne〉) excess 3] develop internal transport barriers when centrally heated with neutral beam injection. are formed...
A severe consequence of a disruption on large tokamaks such as ITER could be the generation multi-megaelectronvolt electron beams that damage vacuum vessel and structures machine if they hit wall unmitigated. The mitigation runaway is thus key requirement for reliable operation ITER. In order to achieve mitigation, new fast shutdown technique has been developed: injection shattered cryogenic pellet in plasma, which expected increase density up levels where beam processes are mitigated by...
Injection of large shattered pellets composed variable quantities the main ion species (deuterium) and high-Z impurities (neon) in DIII-D tokamak demonstrates control thermal quench (TQ) current (CQ) properties mitigated disruptions. As pellet composition is varied, TQ radiation fractions increase continuously with quantity radiating impurity pellet, a corresponding decrease divertor heating. Post-TQ plasma resistivities as result higher fraction, allowing decay timescales based on...
Recent experimental results in the Large Helical Device have indicated that a large pressure gradient can be formed beyond stability criterion for Mercier (high-n) mode. While against an interchange mode is violated inward-shifted configuration due to enhancement of magnetic hill, neoclassical transport and confinement high-energy particle are, contrast, improved by this inward shift. Mitigation unfavourable effects MHD instability has led significant extension operational regime....
In DIII-D [J. L. Luxon and G. Davis, Fusion Technol. 8, 441 (1985)] tokamak plasmas with an internal transport barrier (ITB), the comparison of gyrokinetic linear stability (GKS) predictions experiments in both low strong negative magnetic shear provide improved understanding for electron thermal within plasma. Within a limited region just inside ITB, temperature gradient (ETG) modes appear to control and, consequently, transport. The increase temperaturegradient more strongly is consistent...
Spatially and temporally resolved toroidal rotation measurements have been made in DIII-D [J. L. Luxon, Nucl. Fusion 42, 614 (2002)] discharges with no externally applied torque. The velocity are using the charge exchange recombination (CER) technique viewing emission from intrinsic carbon impurity deuterium discharges. Three cases studied: L mode H Ohmic heating electron cyclotron (ECH). ECH has counter-rotation center of plasma, co-rotation outside, where co- counter- relative to direction...
Despite the importance of rotation in fusion plasmas, our present understanding momentum transport is inadequate. The lack part related to difficulty performing accurate measurements, especially for poloidal rotation. Recently, measurements impurity ions (Z>1) have been obtained core DIII-D [J. L. Luxon, Nucl. Fusion 42, 6114 (2002)] plasmas using charge exchange recombination spectroscopy. inferred based on careful consideration effective energy-dependent cross section and gyromotion...
New rapid shutdown strategies have been recently tested in the DIII-D tokamak to mitigate runaway electrons (REs). Disruptions ITER are predicted generate multi-MeV REs that could damage machine. The RE population large tokamaks is expected be dominated by avalanche amplification which can mitigated at high density levels collisional drag. Particle injection schemes for suppression of developed and ITER-relevant scenarios: massive gas injection, shattered pellet (SPI) shell injection....
Plasma fuelling with pellet injection, pacing of edge localized modes (ELMs) by small frequent pellets and disruption mitigation gas jets or injected solid material are some the most important technological capabilities needed for successful operation ITER. Tools being developed at Oak Ridge National Laboratory that can be employed on ITER to provide necessary core ELMs disruptions. Here we present progress development technology reliable high throughput inner wall fuelling, ELM frequency...
Abstract A newly installed Lithium Granule Injector (LGI) was used to pace edge localized modes (ELM) in DIII-D. ELM pacing efficiency studied injecting lithium granules of nominal diameter 0.3–0.9 mm, speed 50–120 m s −1 and average injection rates up 100 Hz for 0.9 mm 700 0.3 granules. The triggering found depend strongly on size the injected granules, with close 100% obtained lower smaller sizes, weakly depending granule velocity. Robust demonstrated ITER-like plasmas entire shot length,...
High-speed injection of solid fuel was first proposed in 1954 as a possible solution to the problem transporting fresh across confining magnetic fields into plasma fusion reactor. While it took few decades, use cryogenic pellets (typically H2 and D2) on experiments became common place; most tokamaks stellarators are now equipped with pellet injector(s). These devices operate at low temperatures (~10 20 K) often simple light gas gun accelerate macroscopic-size (~0.4- 6-mm diameter) speeds...
Abstract Precise values for radiated energy in tokamak disruption experiments are needed to validate mitigation techniques burning plasma tokamaks like ITER and SPARC. Control room analysis of power ( P rad ) on JET assumes axisymmetry, since fitting 3D radiation structures with limited bolometry coverage is an under-determined problem. In mitigated disruptions, toroidally asymmetric 3D, due fast-growing MHD modes localized impurity sources. To address this problem, Emis3D adopts a physics...
During pellet injection in tokamaks, a rapid movement of ablation substance towards the low-field or outward major radius R direction is observed, favoring from high-field side order to promote deeper fuel penetration. The motion has been attributed vertical curvature and ∇B drift current induced inside ionized ablated material by 1/R toroidal field variation. uncompensated weakly diamagnetic (β<0.1) cloud will cause charge separation at boundary. resulting electrostatic induces E×B...
We report on the operation of an integrated gated cathode device using a single vertically aligned carbon nanofiber as field emission element. This is capable in moderate vacuum for extended periods time without experiencing degradation performance. Less than 1% total emitted current collected by gate electrode, indicating that electron beam highly collimated. As consequence, this ideal applications require well-focused from microscale structure.
The contents are described of an international pellet ablation database (IPADBASE) that has been assembled to enable studies theories used describe the physics ablating fuel in a tokamak plasma. represents effort assemble data from several tokamaks different magnetic configurations and auxiliary heating methods. In initial configuration, JET, Tore Supra, DIII-D, FTU, TFTR, ASDEX Upgrade, JIPP T-IIU, RTP T-10 have included. contains details measurements deuterium hydrogen ablation, including...
Experiments have been performed in the DIII-D tokamak [J. L. Luxon, Nucl. Fusion 42, 614 (2002)] toward understanding runaway electron formation and amplification during rapid discharge shutdown, as well achieving complete collisional suppression of these electrons via massive delivery impurities. Runaway acceleration appear to be explained using zero-dimensional (0D) current quench toroidal electric field. 0D or even one-dimensional modeling a Dreicer seed term, however, appears too small...
The amplitude and frequency of modes driven in the edge region tokamak high mode (H-mode) discharges [type I edge-localized (ELMs)] are shown to depend on discharge shape. measured pressure gradient threshold for instability its scaling with shape compared predictions from ideal magnetohydrodynamic theory low toroidal number (n) instabilities by current density good agreement is found. Reductions observed shapes either squareness or triangularity where stability predicted be reduced most...