A5077990009- Magnetic confinement fusion research
- Fusion materials and technologies
- Plasma Diagnostics and Applications
- Particle accelerators and beam dynamics
- Ionosphere and magnetosphere dynamics
- Laser-Plasma Interactions and Diagnostics
- Laser-induced spectroscopy and plasma
- Atomic and Molecular Physics
- Superconducting Materials and Applications
- Nuclear reactor physics and engineering
- Nuclear Physics and Applications
- Atomic and Subatomic Physics Research
- Solar and Space Plasma Dynamics
- Nuclear Materials and Properties
- Mass Spectrometry Techniques and Applications
- Metal and Thin Film Mechanics
- Spectroscopy and Laser Applications
- Semiconductor materials and devices
- Dust and Plasma Wave Phenomena
- Advanced Chemical Physics Studies
- Electromagnetic Compatibility and Measurements
- Quantum, superfluid, helium dynamics
- Atmospheric Ozone and Climate
- Diamond and Carbon-based Materials Research
- Particle Accelerators and Free-Electron Lasers
Oak Ridge National Laboratory
2008-2018
University of Tennessee at Knoxville
2016
Commissariat à l'Énergie Atomique et aux Énergies Alternatives
2015
CEA Cadarache
2015
General Atomics (United States)
1978-2001
Lawrence Livermore National Laboratory
1997-2000
Princeton Plasma Physics Laboratory
1992-1995
Princeton University
1990-1995
Fusion Academy
1986-1995
Fusion (United States)
1986-1995
Charge-exchange spectroscopy in fusion plasmas entails the use of optical transitions that follow electron transfer from a neutral atom into an excited state impurity ion. In most applications, sources particles are high-energy beams employed either for heating or specific purpose active plasma diagnosis. The following charge exchange particularly useful determining densities fully stripped low-Z ions and measuring ion temperatures rotation, although they have also been exploited other...
Impurities continue to be a concern for future fusion devices, and ongoing efforts are made study their generation, confinement, control. Techniques analysis of concentrations, power losses, confinement impurities surveyed, experimental examples illustrating typical observations in tokamak plasmas presented. The use diagnosing plasma properties is outlined briefly.
Several lines of O viii have been investigated during the injection hydrogen atoms at energies 10, 15, and 30 keV into Oak Ridge tokamak (ORMAK). The Lyman-$\ensuremath{\alpha}$, -$\ensuremath{\beta}$, -$\ensuremath{\gamma}$ Balmer-$\ensuremath{\beta}$ line exhibit slowly increasing signals, but intensity Balmer-$\ensuremath{\alpha}$ increases sharply as soon begins. This prompt signal is interpreted to be direct result charge transfer from ${\mathrm{O}}^{7+}$ ions in excited states.
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...
Recent calculations have shown that when external momentum sources and plasma rotation are included in the neoclassical theory, standard results for impurity transport can be strongly altered. Under appropriate conditions, inward convection is reduced by co-injection enhanced counter-injection. In order to examine theoretical predictions, several observations of been made ISX-B tokamak during neutral-beam injection comparison with seen Ohmic heating alone. Both intrinsic contaminants...
Plasma potentials have been measured for the first time in neutral-beam-heated tokamak discharges, with a heavy-ion beam probe. Radial profiles of these are presented coinjection, counterinjection, and balanced injection, plasmas having only Ohmic heating. They found to be very dependent on direction rotation respect plasma current. also qualitatively consistent those inferred from radial momentum balance use toroidal velocity.
Confinement studies on the Impurity Study Experiment (ISX-B) in beam-heated plasmas contaminated with small quantities of low-Z impurities are reported. Experimental results correlation particle and energy confinement presented. A linear relationship plasma density is observed. As increased further, this effect saturates becomes independent electron density. The experiments have been extended to higher beam power, resulting an expansion ISX-B operating space. Impurities other than neon...
Linear plasma generators are cost effective facilities to simulate divertor conditions of present and future fusion reactors. They used address important R&D gaps in the science material interactions towards viable facing components for Next generation have be able access expected on targets ITER devices. The steady-state linear device MPEX will this regime with electron temperatures 1–10 eV densities . resulting heat fluxes about 10 MW is designed deliver those a novel Radio Frequency...
The first encouraging experiments demonstrating direct, explicit control of the ${\mathrm{He}}^{2+}$ density in a tokamak plasma have been performed TEXTOR with Advanced Limiter Test-II pump limiter. Helium is injected short gas puff from outside plasma, observed to reach core, and then readily removed plasma. An exhaust efficiency \ensuremath{\sim}8% obtained. Active charge-exchange spectroscopy used study transport within evolution modeled diffusive-convective code.
Pre-ionization experiments have been performed on a tokamak by injecting about 80 kW of microwave power at 35 GHz for up to 15 ms. Microwave absorption occurs the electron cyclotron and upper hybrid resonance frequencies as predicted theory. causes substantial (40%) reductions in loop voltage during initial phase shot. Flux (volt-second) savings with pre-ionization are 30% first 2 ms or 2% total flux expenditure The plasma current begins 200 μs earlier rises 1.4 times more rapidly...
Several spectral lines produced by charge transfer of neutral-beam hydrogen atoms with completely ionized oxygen have been detected in the impurity studies experiment $B$ ($\mathrm{I}\mathrm{S}\mathrm{X}\ensuremath{-}B$) tokamak, and used to compute absolute concentrations ${\mathrm{O}}^{8+}$. charge-exchange recombination is found a minor effect on total radiative losses, but enhanced transport during injection appears raise radiation from interior discharges factors 3 5. This result may...
The central toroidal rotation velocities of tokamak plasmas have been measured from the Doppler shifts spectral lines that are excited by charge transfer neutral hydrogen heating beams with fully ionized oxygen.
Optical studies of spectral lines produced in collisions ${\mathrm{He}}^{+}$ + ${\mathrm{H}}_{2}$ have been made at energies below 700 eV. Lines atomic hydrogen and helium are the only features observed. Emission cross sections measured for Lyman-$\ensuremath{\beta}$, Balmer-$\ensuremath{\alpha}$, Balmer-$\ensuremath{\beta}$, following He i lines: $5876 \AA{} (3^{3}D\ensuremath{\rightarrow}2^{3}P)$, $6678 (3^{1}D\ensuremath{\rightarrow}2^{1}P)$, $4471 (4^{3}D\ensuremath{\rightarrow}2^{3}P)$....
Auroral spectra have been obtained in the wavelength region 1050–1550 A over altitude range 90–160 km an Aerobee rocket at Fort Churchill, Manitoba. Spectral lines of atomic hydrogen, nitrogen and oxygen, eighteen bands Lyman-Birge-Hopfield system molecular were identified. The primary electron flux 3914-A emission N2+ also measured throughout flight. Altitude profiles for several spectral features are given, correlations among various observations discussed. hydrogen-Lyman-α radiation 1216...
Plasma-facing materials in the divertor of a magnetic fusion reactor have to tolerate steady state plasma heat fluxes range 10 MW/m2 for ∼107 s, addition neutron fluences, which can damage plasma-facing high displacements per atom (dpa) ∼50 dpa. Materials solutions needed components are yet be developed and tested. The material exposure experiment (MPEX) is newly proposed linear device designed deliver necessary flux target testing, including capability expose priori neutron-damaged samples...
Application of Ion Bernstein Wave Heating (IBWH) into the Princeton Beta Experiment-Modification (PBX-M) [Phys. Fluids B 2, 1271 (1990)] tokamak stabilizes sawtooth oscillations and generates peaked density profiles. A transport barrier, spatially correlated with IBWH power deposition profile, is observed in core IBWH-assisted neutral beam injection (NBI) discharges. precursor to fully developed barrier seen soft x-ray data during edge localized mode (ELM) activity. Sustained operation...
Radiative losses along a fixed view into the divertor chamber of DIII-D tokamak [Plasma Physics Controlled Nuclear Fusion Research 1986 (International Atomic Energy Agency, Vienna, 1987), Vol I, p. 159] have been characterized for attached and partially detached discharges by analyzing line-integrated vacuum ultraviolet (VUV) signals. Essentially all emission can be ascribed to carbon deuterium. Because majority most intense lines, which lie at wavelengths above 1100 Å, are not accessible...
Thomson scattering measurements performed in the divertor of DIII-D tokamak [Plasma Physics Controlled Nuclear Fusion Research, 1986 (International Atomic Energy Agency, Vienna, 1987), Vol. I, p. 159] during detached operation show that electron temperatures are typically between 0.8 and 2.0 eV throughout a region which may extend several centimeters above target plate. At such low excitation recycling deuterium atoms or impurities should be weak. Nevertheless, significant radiation is...
Gross-energy-confinement times (${\ensuremath{\tau}}_{E}$) in the ISX-$A$ (Impurity Study Experiment) tokamak exceeded predictions of usual empirical scaling relations. We attribute this performance to reductions impurity radiation and magnetohydrodynamically driven loss channels. The value ${\ensuremath{\tau}}_{E}$ reached a limit as function plasma density. suggest that is due transition from electron- ion-dominated regimes. Maximum attainable values increased with discharge current,...
Access to the MHD second stability regime has been achieved in ATF torsatron. Experimental \ensuremath{\beta} values (${\ensuremath{\beta}}_{0}$\ensuremath{\le}3%, with fast ions contributing \ensuremath{\approxeq}(1/3 of pressure at high \ensuremath{\beta}) are well above theoretical transition value (${\ensuremath{\beta}}_{c}$\ensuremath{\approxeq}1.3% for ideal modes) required reach this regime. The relatively low ${\ensuremath{\beta}}_{c}$ results from operation peaked profiles. measured...
Detailed studies of spectra from the ISX-$A$ (Impurity Study Experiment) tokamak at Oak Ridge National Laboratory have shown that certain oxygen-ion lines appear too anomalously intense to been excited solely by electron collisions. These results are interpreted as being due charge transfer and suggest necessity incorporating this mechanism into analyses plasmas.
Large relativistic runaway electron currents (0.1–0.5 MA) persisting for ∼100 ms are created in the DIII-D tokamak during rapid discharge shut down caused by argon pellet injection. Slow upward and downward ramps were found response to externally applied loop voltages. Comparison between observed current growth/decay rate expected from knock-on avalanche mechanism suggests that classical collisional dissipation of runaways alone cannot account measured growth/damping rates. It appears a...