A5060108984- Magnetic confinement fusion research
- Fusion materials and technologies
- Superconducting Materials and Applications
- Laser-Plasma Interactions and Diagnostics
- Ionosphere and magnetosphere dynamics
- Nuclear Materials and Properties
- Solar and Space Plasma Dynamics
- Plasma Diagnostics and Applications
- Metal and Thin Film Mechanics
- Astronomy and Astrophysical Research
- Astronomical Observations and Instrumentation
- Particle accelerators and beam dynamics
- Spacecraft and Cryogenic Technologies
- Atomic and Subatomic Physics Research
- Nuclear Physics and Applications
- Semiconductor materials and devices
- Silicon and Solar Cell Technologies
- Quantum, superfluid, helium dynamics
- Nuclear reactor physics and engineering
- Diamond and Carbon-based Materials Research
- Advanced Data Storage Technologies
- Particle Accelerators and Free-Electron Lasers
- Laser-induced spectroscopy and plasma
- Non-Destructive Testing Techniques
- Induction Heating and Inverter Technology
Oak Ridge National Laboratory
2014-2020
Princeton Plasma Physics Laboratory
2016
General Atomics (United States)
2016
Oak Ridge Associated Universities
2016
University of Wisconsin–Madison
2010-2012
Periods of edge localized mode (ELM)-free H-mode with increased pedestal pressure and width were observed in the DIII-D tokamak when density fluctuations to region near separatrix present. Injection a powder 45 µm diameter lithium particles duration enhanced phases up 350 ms, also likelihood transition phase. Lithium injection at level sufficient for triggering extended resulted significant plasma core, but carbon other higher Z impurities as well radiated power levels reduced. Recycling...
The charge exchange recombination spectroscopy diagnostic on the DIII-D tokamak has been upgraded with addition of more high radial resolution view chords near edge plasma (r/a > 0.8). additional views are diagnosed same number spectrometers by placing fiber optics side-by-side at spectrometer entrance a precise separation that avoids wavelength shifted crosstalk without use bandpass filters. new improve measurement impurity parameters in steep gradient, H-mode plasmas many different...
It is important to develop a predictive capability for the tungsten source rate near strike points during H-mode operation in ITER and beyond. deuterium plasma exposures were performed on W-coated graphite molybdenum substrates DIII-D divertor using DiMES. The W-I 400.9 nm spectral line was monitored by fast filtered diagnostics cross calibrated via high-resolution spectrometer resolve inter-ELM W erosion. effective ionization/photon (S/XB) unique method developed based surface analysis....
Tungsten nanostructures (W-fuzz) prepared in the PISCES-A linear device have been found to survive direct exposure divertor plasmas DIII-D. W-fuzz was exposed lower of DIII-D using material evaluation system. Two samples were single null (LSN) deuterium H-mode plasmas. The first sample three discharges terminated by vertical displacement event disruptions, and second two near lowered X-point. More recently, outer strike point predominantly helium LSN In all cases, survived plasma with little...
Abstract A dual-band frequency-modulated reflectometry is employed in the Helically Symmetric eXperiment (HSX) stellarator. This system equips a fast PIN switch to alternate frequency source between two voltage-controlled oscillators (VCOs), providing an operational range from 14.5 GHz 25.5 GHz. monostatic antenna geometry and ellipsoidal mirror are implemented vessel of HSX, where polarization transmitted beam can be switched O- X-mode accommodate magnetic field plasma density. Although...
Electron cyclotron heated plasmas in the Helically Symmetric Experiment (HSX) feature strongly peaked electron temperature profiles; central temperatures are 2.5 keV with 100 kW injected power. These measurements, coupled neoclassical predictions of large “electron root” radial electric fields strong shear, evidence a neoclassically driven thermal transport barrier. Neoclassical quantities calculated using PENTA code [D. A. Spong, Phys. Plasmas 12, 056114 (2005)], which momentum is conserved...
Dedicated DIII-D experiments coupled with modeling reveal that the net erosion rate of high-Z materials, i.e. Mo and W, is strongly affected by carbon concentration in plasma magnetic pre-sheath properties. Different methods such as electrical biasing local gas injection have been investigated to control material erosion. The materials significantly reduced due high re-deposition ratio. ERO shows ratio mainly controlled electric field density within pre-sheath. can be suppressed reducing...
Recent experiments in DIII-D helium plasmas are examined to resolve the role of atomic and molecular physics major discrepancies between experiment modeling dissipative divertor operation. Helium operation removes complicated processes deuterium that a prime candidate for inability standard fluid models reproduce operation, primarily consistent under-prediction radiated power. Modeling these shows full radiation can be accounted for, but only if measures taken ensure model reproduces...
Recent emphasis of tungsten (W) plasma-material interaction experiments on DIII-D has made it essential to enhance the W I and II measurement capabilities its spectroscopy diagnostic suite acquire sourcing measurements with high temporal, spatial, wavelength resolution. To this end, four new viewing chords for multichordal divertor spectrometer filterscope systems were installed, leading a 7× increase in blue-light sensitivity. low-Z impurity line identifications performed 3995-4030 Å...
Simulations using the multi-fluid code UEDGE indicates that, in low confinement (L-mode) plasmas DIII-D, poloidal projection of ionization driven flows dominate particle divertor near plates, whereas E × B drift radial flows. In contrast, high (H-mode) conditions both and vicinity strong gradient region separatrix. that toroidal C2+ flow velocities are mainly entrained within 30% to background deuterium L- H-mode plasma where CIII 465 nm emission is measured. Therefore, Doppler Coherence...
Abstract A major challenge facing the design and operation of next-step high-power steady-state fusion devices is to develop a viable divertor solution with order-of-magnitude increases in power handling capability relative present experience, while having acceptable target plate erosion being compatible maintaining good core plasma confinement. new initiative has been launched on DIII-D scientific basis for design, installation, an advanced evaluate boundary solutions applicable next step...
Tungsten button samples were exposed to He ELMing H-mode plasma in DIII-D using 2.3 MW of electron cyclotron heating power. Prior the exposures, W buttons either He, or D, PISCES-A for 2000 s at surface temperatures 225–850 °C create a variety surfaces (surface blisters, subsurface nano-bubbles, fuzz). Erosion was spectroscopically measured from each DiMES sample, with exception fuzzy which showed almost undetectable WI emission. Post-exposure grazing incidence small angle x-ray scattering...
Intrinsic flow velocities of up to ∼20 km s−1 have been measured using charge exchange recombination spectroscopy (CHERS) in the quasi-helically symmetric HSX stellarator and are compared with neoclassical values calculated an updated version (Lore 2010 Measurement Transport Modeling Momentum Conservation Electron Internal Barrier (Madison, WI: University Wisconsin); Lore et al Phys. Plasmas 17 056101) PENTA code (Spong 2005 Plasmas. 12 056114). uses monoenergetic transport coefficients by...
The 3D fluid-plasma edge transport code EMC3-EIRENE is used to test several magnetic field models with and without plasma response against DIII-D experimental data for even odd-parity n = 3 perturbations. include ideal extended MHD equilibria, the vacuum approximation. Plasma required reduce stochasticity in pedestal region even-parity fields, however too much screening suppresses measured splitting of downstream Te profile. Odd-parity perturbations result weak tearing only small additional...
The effects of changes in core density on divertor electron temperature, and heat flux when resonant magnetic perturbations (RMPs) are applied presented, notably a reduction RMP induced secondary radial peaks the temperature profile at target plate is observed increased, which consistent with modeling. RMPs used here to indicate non-axisymmetric field perturbations, created using in-vessel control coils, have least one but typically many resonances rotational transform plasma (Evans et al...
Abstract A Charge Exchange Recombination Spectroscopy (ChERS) system has been used to measure the velocity, density, and temperature profiles of fully stripped carbon impurities in Helically Symmetric eXperiment (HSX). Velocity measurements have obtained by reversing magnetic field between sets shots order reverse plasma flow velocity. This essentially doubles Doppler shift measured photons. It also eliminates need accurately determine exact wavelength unshifted emission line which can...
Two-dimensional imaging of parallel ion velocities is compared to fluid modeling simulations understand the role ions in determining divertor conditions and benchmark UEDGE code. Pure helium discharges are used so that spectroscopic He+ measurements represent main-ion population at small electron temperatures. Electron temperatures densities match simulated values within about 20%–30%, establishing experiment/model as being least good those normally obtained more regularly deuterium plasmas....
Effective helium confinement time, τp*,He, and its ratio with energy τp*,He/τE, are key metrics quantifying the suitability of fusion plasmas for a continuous burn. Comparisons in DIII-D tokamak discharges suppression edge localized modes (ELMs) by resonant magnetic field perturbations (RMPs) to corresponding unperturbed ELMy found that both these were strongly reduced, factor approximately 2, after application RMPs. This reduction τp*,He during RMP ELM was observed plasma core, edge,...
Broadband turbulent density fluctuations are explored in the helically symmetric stellarator experiment (HSX) by investigating changes related to plasma heating power and location. No fluctuation response is observed occur with large electron temperature its gradient, thereby eliminating gradient as a driving mechanism. Instead, measurements reveal that turbulence varies inversely scale length. This consistent drive one might expect for trapped mode (TEM) turbulence. In general, stored...