A5031376131- Magnetic confinement fusion research
- Fusion materials and technologies
- Superconducting Materials and Applications
- Laser-Plasma Interactions and Diagnostics
- Ionosphere and magnetosphere dynamics
- Plasma Diagnostics and Applications
- Particle accelerators and beam dynamics
- Nuclear reactor physics and engineering
- Nuclear Materials and Properties
- Semiconductor materials and devices
- Solar and Space Plasma Dynamics
- Laser-induced spectroscopy and plasma
- Gyrotron and Vacuum Electronics Research
- Nuclear Physics and Applications
- Physics of Superconductivity and Magnetism
- Particle Accelerators and Free-Electron Lasers
- Dust and Plasma Wave Phenomena
- Advanced Data Storage Technologies
- Diamond and Carbon-based Materials Research
- High-Energy Particle Collisions Research
- Advancements in Semiconductor Devices and Circuit Design
- Metal and Thin Film Mechanics
- Thin-Film Transistor Technologies
- Atomic and Molecular Physics
- Metallurgical Processes and Thermodynamics
Lawrence Livermore National Laboratory
2016-2025
General Atomics (United States)
2003-2024
Fusion (United States)
2019-2024
University of California, San Diego
2007-2022
Sandia National Laboratories
2016-2022
University of California, Los Angeles
2004-2019
The University of Texas at Austin
2019
Massachusetts Institute of Technology
2019
Fusion Academy
2019
University of Wisconsin–Madison
2019
A stochastic magnetic boundary, produced by an applied edge resonant perturbation, is used to suppress most large edge-localized modes (ELMs) in high confinement ($H$-mode) plasmas. The resulting $H$ mode displays rapid, small oscillations with a bursty character modulated coherent 130 Hz envelope. transport barrier and core are unaffected the despite threefold drop toroidal rotation. These results demonstrate that boundaries compatible may be attractive for ELM control next-step fusion tokamaks.
Large Type-I edge localized modes (ELMs) are completely eliminated with small n = 3 resonant magnetic perturbations (RMP) in low average triangularity, , plasmas and ITER similar shaped (ISS) plasmas, relevant collisionalities . Significant differences the RMP requirements properties of ELM suppressed found when comparing two triangularities. In ISS current required to suppress ELMs is approximately 25% higher than triangularity plasmas. It also that width q95 window for suppression smaller...
Metallic mirrors will be used in ITER for optical diagnostics working different spectral ranges. Their properties change with time due to erosion, deposition, and particle implantation. First tests of molybdenum were performed the DIII-D divertor under deposition-dominated conditions. Two sets recessed 2cm below floor private flux region exposed a series identical, lower-single-null, ELMing (featuring edge localized modes) H-mode discharges detached plasma conditions both legs. The first set...
Dust production and accumulation present potential safety operational issues for the ITER. diagnostics can be divided into two groups: of dust on surfaces in plasma. Diagnostics from both groups are employed contemporary tokamaks; new suitable ITER also being developed tested. is likely to occur hidden areas, e.g., between tiles under divertor baffles. A novel electrostatic detector monitoring these regions has been tested at PPPL. In DIII-D tokamak include Mie scattering Nd:YAG lasers,...
Large sub-millisecond heat pulses due to Type-I edge localized modes (ELMs) have been eliminated reproducibly in DIII-D for periods approaching nine energy confinement times (τE) with small dc currents driven a simple magnetic perturbation coil. The current required eliminate all but few isolated ELM impulses during coil pulse is less than 0.4% of plasma current. Based on field line modelling, the fields resonate flux surfaces across most pedestal region (0.9 ⩽ ψN 1.0) when q95 = 3.7 ± 0.2,...
The key remaining physics design issue for the ITER tungsten (W) divertor is question of monoblock (MB) front surface shaping in high heat flux target areas actively cooled targets. Engineering tolerance specifications impose a challenging maximum radial step between toroidally adjacent MBs 0.3 mm. Assuming optical projection parallel loads, magnetic shadowing these edges required if quasi-steady state melting to be avoided under certain conditions during burning plasma operation and...
In this paper the manipulation of power deposition on divertor targets at DIII-D by application resonant magnetic perturbations (RMPs) for suppression large type-I edge localized modes (ELMs) is analysed. We discuss modification ELM characteristics RMP applied. It shown that width pattern in ELMy H-mode depends linearly deposited energy, whereas phase discharge those patterns are controlled externally induced perturbation. was also found heat transport due to small, plasma pedestal electron...
A coordinated effort to measure divertor heat flux characteristics in fully attached, similarly shaped H-mode plasmas on C-Mod, DIII-D, and NSTX was carried out 2010 order construct a predictive scaling relation applicable next step devices including ITER, FNSF, DEMO. Few published laws are available those that have been were obtained under widely varying conditions geometries, leading conflicting predictions for this critically important quantity. This study designed overcome these...
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...
Abstract Divertor detachment offers a promising solution to the challenge of plasma-wall interactions for steady-state operation fusion reactors. Here, we demonstrate excellent compatibility actively controlled full divertor with high-performance ( β N ~ 3, H 98 1.5) core plasma, using high-β p (poloidal beta, > 2) scenario characterized by sustained internal transport barrier (ITB) and modest edge (ETB) in DIII-D tokamak. The high- high-confinement facilitates which, turn, promotes...
Abstract Negative triangularity (NT) is a potentially transformative configuration for tokamak-based fusion energy with its high-performance core, edge localized mode (ELM)-free edge, and low-field-side divertors that could readily scale to an integrated reactor solution. Previous NT work on the TCV DIII-D tokamaks motivated installation of graphite-tile armor lower outer wall DIII-D. A dedicated multiple-week experimental campaign was conducted qualify scenario future reactors. During...
Small non-axisymmetric perturbations of poloidally diverted tokamaks create edge stochastic magnetic field lines that connect to material surfaces such as those in the divertors. Separatrix structure calculations show distribution on vessel walls is closely related topology homoclinic tangles formed perturbed system. Since these prescribe how fields are organized, they significant practical interest tokamak experiments. Experimental measurements heat and particle distributions plasma facing...
High-pressure gas-jet injection of neon and argon is shown to be a simple robust method mitigate the deleterious effects disruptions on DIII-D tokamak. The gas jet penetrates central plasma at its sonic velocity. deposited species dissipates >95% by radiation substantially reduces mechanical stresses vessel caused poloidal halo currents. species-charge distribution can include >50% fraction neutral which inhibits runaway electrons. favorable scaling this technique burning fusion plasmas discussed.
Fusion power has been increased by a factor of 3 in DIII-D tailoring the pressure profile to avoid kink instability $H$-mode plasmas. The resulting plasmas are found have neoclassical ion confinement. This reduction transport losses beam-heated with negative central shear is correlated dramatic density fluctuations. Improved magnetohydrodynamic stability achieved controlling plasma width. In deuterium highest gain $Q$ (the ratio fusion input power), was 0.0015, corresponding an equivalent...
Far Scrape-Off Layer (SOL) and near-wall plasma parameters in DIII-D depend strongly on the discharge confinement regime. In L-mode discharges cross-field transport increases with average density flattens far SOL profiles, thus increasing contact low field side (LFS) main chamber wall. H-mode between edge localized modes (ELMs) plasma–wall is weaker than L-mode. During ELM fluxes of particles heat to LFS wall increase transiently above values. Depending conditions, ELMs are responsible for...
A study of three-dimensional (3D) perturbed magnetic field structures and transport for edge localized mode control experiments with resonant perturbations at DIII-D is presented. We focus on ITER-Similar Shape plasmas ITER relevant electron pedestal collisionalities . This performed in comparison results from TEXTOR-Dynamic Ergodic Divertor circular limiter plasmas. For both the structure analyzed vacuum paradigm—superimposing external RMP unperturbed equilibrium. TEXTOR L-mode this...
Plasmas with a negative triangularity shape have been created on the DIII-D tokamak that, despite maintaining standard L-mode edge radial profiles, reach volume averaged pressure levels typical of H-mode scenarios. Within auxiliary power available for these experiments, plasmas exhibit near-zero degradation while sustaining βN = 2.7 and H98,y2 1.2 several energy confinement times. Detailed comparison matched discharges at positive indicates that Trapped Electron Modes are weakened...
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...
Multimachine empirical scaling predicts an extremely narrow heat exhaust layer in future high magnetic field tokamaks, producing power densities that require mitigation. In the experiments presented, width of this is nearly doubled using actuators to increase turbulent transport plasma edge. This achieved low collisionality, confinement edge pedestals with their gradients limited by instead large-scale, coherent instabilities. The flux profile and divertor leg diffusive spreading both double...
Abstract Experiments performed during strongly-shaped high-power diverted negative triangularity (NT) experiments in DIII-D achieved detached divertor conditions and a transient-free edge, showcasing the potential for application of NT to core-edge integrated reactor-like scenario providing first characterization parametric dependencies detachment onset. Detached will be required future devices mitigate heat fluxes. Access dissipative was investigated via an increase upstream density....
Using resonant magnetic perturbations with toroidal mode number n = 3, we have produced H-mode discharges without edge localized modes (ELMs) which run constant density and radiated power for periods up to about 2550 ms (17 energy confinement times). These ELM suppression results are achieved at pedestal collisionalities close those desired next step burning plasma experiments such as ITER provide a means of eliminating the rapid erosion divertor components in machines could be caused by...
ELM-free H-mode plasmas with stationary plasma density and radiation level are obtained in the ASDEX Upgrade tokamak large clearance between last closed flux surface wall, neutral beam injection a toroidal direction opposite to that of current. This behaviour is accompanied by characteristic narrow-band magnetohydrodynamic (MHD) oscillation clear harmonics up n = 11 visible. mode localized edge region. Conditions properties phases MHD closely resemble `quiescent H-mode' `edge harmonic...
The energy lost from the pedestal region due to an average ELM in DIII-D is determined changes electron density and temperature profiles as measured by Thomson scattering. loss of associated with conduction found decrease increasing density. density, or convective transport, remains constant a function scaling two transport channels, convection, are examined terms parallel processes scrape-off-layer divertor.