A5046986353- Magnetic confinement fusion research
- Particle accelerators and beam dynamics
- Ionosphere and magnetosphere dynamics
- Superconducting Materials and Applications
- Plasma Diagnostics and Applications
- Gyrotron and Vacuum Electronics Research
- Laser-Plasma Interactions and Diagnostics
- Fusion materials and technologies
- Advanced Data Storage Technologies
- Electrostatic Discharge in Electronics
- Antenna Design and Analysis
- Semiconductor materials and devices
- Solar and Space Plasma Dynamics
- Acoustic Wave Resonator Technologies
- Microwave Engineering and Waveguides
- Silicon Carbide Semiconductor Technologies
- Physics of Superconductivity and Magnetism
- Dust and Plasma Wave Phenomena
- Particle Accelerators and Free-Electron Lasers
- Semiconductor Lasers and Optical Devices
- Atomic and Subatomic Physics Research
- Radio Frequency Integrated Circuit Design
- Semiconductor Quantum Structures and Devices
- Nuclear Physics and Applications
- Antenna Design and Optimization
General Atomics (United States)
2016-2025
University of California, Los Angeles
1995-2021
University of California, Irvine
2006-2021
Massachusetts Institute of Technology
2006-2020
Princeton Plasma Physics Laboratory
1985-2011
Oak Ridge National Laboratory
2006-2011
Polytechnic University of Turin
2011
Hexcel (United States)
2011
Tech-X Corporation (United States)
2010
Higashihiroshima Medical Center
2006
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...
The authors' data indicate that the L-mode to H-mode transition in DIII-D tokamak is associated with sudden reduction anomalous, fluctuation-connected transport across outer midplane of plasma. In addition edge density and magnetic fluctuations observed at transition, radial electric field becomes more negative after transition. They have determined scaling power threshold various plasma parameters; roughly linear increase toroidal are particularly significant. Control ELM frequency duration...
A new sustained high-performance regime, combining discrete edge and core transport barriers, has been discovered in the DIII-D tokamak. Edge localized modes (ELMs) are replaced by a steady oscillation that increases particle transport, thereby allowing control with no ELM-induced pulsed divertor heat load. The barrier resembles those usually seen low (L) mode edge, without degradation often associated ELMs. barriers separated narrow region of high zero crossing E x B shearing rate.
Combined neutral beam injection and fast wave heating at the fourth fifth cyclotron harmonics accelerate ions in DIII-D tokamak. Measurements with a nine-channel fast-ion D-alpha (FIDA) diagnostic indicate formation of tail above energy. Tail correlates enhancement d–d neutron rate value that is expected absence fast-wave acceleration. FIDA spatial profiles pressure inferred from equilibrium both acceleration near magnetic axis for centrally located resonance layer. The largest 8–10 cm...
Fast waves at frequencies far above the ion cyclotron frequency and approaching lower hybrid (also called 'helicons' or 'whistlers') have application to off-axis current drive in tokamaks with high electron beta. The causes whistler-like behaviour of wave power nearly following field lines, but a small radial component, so spiral slowly towards plasma centre. also contributes strong damping. Modelling predicts robust good efficiency compared alternatives performance discharges DIII-D Fusion...
The scaling of cross-field heat transport with relative gyroradius ρ* was measured in low (L) and high (H) mode tokamak plasmas using the technique dimensionally similar discharges. scalings electron ion thermal diffusivities were determined separately a two-fluid analysis. For L-mode plasmas, diffusivity scaled as χe∝χBρ1.1±0.3* (gyro-Bohm-like) while χi∝χBρ−0.5±0.3* (worse than Bohm-like). results independent method auxiliary heating (radio frequency or neutral beam). Since fluids had...
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...
A new frequency-stepped Doppler backscattering (DBS) system has been integrated into a real-time steerable electron cyclotron heating launcher to simultaneously probe local background turbulence (f < 10 MHz) and high-frequency (20–550 density fluctuations in the DIII-D tokamak. The allows for 2D steering (horizontally vertically) over wide angular ranges optimize location wavenumber response. vertical can be optimized during discharge real time. DBS employs programmable frequency...
Experiments in L- and H-mode plasmas performed on the DIII-D tokamak explored ion cyclotron emission (ICE) propagation via recently upgraded ICE diagnostic. The distance between plasma outer wall was scanned to alter evanescent region, which seen impact detection of runaway electron-driven whistler modes a comparable frequency range typical harmonics (f≳10fci) [Heidbrink et al., Plasma Phys. Controlled Fusion 61, 014007 (2018)]. In L-mode plasmas, core did not exhibit clear trends as...
A noninductive current drive concept, based on internal pressure-driven currents in a low-aspect-ratio toroidal geometry, has been demonstrated the Current Drive Experiment Upgrade (CDX-U) [Forest et al., Phys. Rev. Lett. 68, 3559 (1992)] and further tested DIII-D [in Plasma Physics Controlled Nuclear Fusion Research, 1986, Proceedings of 11th International Conference, Kyoto (International Atomic Energy Agency, Vienna, 1987), Vol. 1, p. 159]. For both experiments, electron cyclotron power...
This introductory-level tutorial article describes the application of plasma waves in lower hybrid range frequencies (LHRF) for current drive tokamaks. Wave damping mechanisms a nearly collisionless hot magnetized are briefly described, and connections between properties optimal choices wave (mode, frequency, wavelength) explored. The two modes available LHRF described compared. terms applied to these different applications physics elucidated. character ray paths is illustrated slab toroidal...
Abstract Experiments have been performed under the coordination of International Tokamak Physics Activity (ITPA) on several tokamaks, including ASDEX Upgrade (AUG), JET and DIII-D, to characterize increased Ion cyclotron range frequency (ICRF) antenna loading achieved by optimizing position gas injection relative RF antennas. On AUG (with ITER-Like Wall) a 50% increase in was observed when injecting deuterium ELMy H-mode plasmas using mid-plane inlets close powered antennas instead divertor...
The Ion Cyclotron Emission (ICE) diagnostic on the DIII-D tokamak consists of two outboard midplane systems. In first system, straps an ion cyclotron range frequencies antenna are configured as receiving antennas. For second dedicated magnetic probes incorporated into outer wall carbon tiles have recently been restored. These systems collected a large set radio frequency measurements in 2015-2018 experimental campaigns by digitizing signals at 200 MSamples/s for ∼5 s per discharge. Each shot...
Collective ion cyclotron emission (ICE) at the frequency and its harmonics is a potential passive diagnostic of fast-ion distribution in fusion reactors. ICE observed most plasmas DIII-D tokamak strongly excited by fast ions from neutral beam injection. The conventional outboard-edge detected H-mode plasmas. However, weaker centrally-localized measured L-mode plasmas, including those with negative triangularity shapes. Similar spectra are found both diagnostics systems, dedicated magnetic...
The scaling of heat diffusion with relative gyroradius ${\ensuremath{\rho}}_{*}$ is measured on the DIII-D tokamak using dimensionally similar discharges. For first time, a two-fluid transport analysis allows electron and ion fluids to be determined separately. diffusivity found scale like ${\ensuremath{\chi}}_{e}\ensuremath{\propto}{\ensuremath{\chi}}_{B}{\ensuremath{\rho}}_{*}^{1.1\ifmmode\pm\else\textpm\fi{}0.3}$ (gyro-Bohm-like) while...
Significant progress in obtaining high performance discharges lasting many energy confinement times the DIII-D tokamak has been realized recent experimental campaigns. Normalized ~10 sustained for more than 5τE with qmin>1.5. (The normalized is measured by product βN H89, indicating proximity to conventional β limits and quality, respectively.) These H mode have an ELMing edge 1. The global parameters were chosen optimize potential fully non-inductive current sustainment at performance,...
Energy confinement comparable with tokamak quality is achieved in the Madison Symmetric Torus (MST) reversed field pinch (RFP) at a high beta and low toroidal magnetic field. Magnetic fluctuations normally present RFP are reduced via parallel current drive outer region of plasma. In response, electron temperature nearly triples doubles. The time increases ten-fold (to ∼10 ms), which L- H-mode scaling values for same plasma current, density, heating power, size shape. Runaway evidenced by...
The major objective of the National Spherical Torus Experiment (NSTX) is to understand basic toroidal confinement physics at low aspect ratio and high βT in order advance spherical torus (ST) concept. In do this, NSTX utilizes up 7.5 MW neutral beam injection, 6 harmonic fast waves (HHFWs), it operates with plasma currents 1.5 MA elongations 2.6 a field 0.45 T. New facility, diagnostic modelling capabilities developed over past two years have enabled research team make significant progress...
The DIII-D Advanced Tokamak (AT) program in the tokamak [J. L. Luxon, Plasma Physics and Controlled Fusion Research, 1986, Vol. I (International Atomic Energy Agency, Vienna, 1987), p. 159] is aimed at developing a scientific basis for steady-state, high-performance operation future devices. This requires simultaneously achieving 100% noninductive with high self-driven bootstrap current fraction toroidal beta. Recent progress this area includes demonstration of conditions beta, βT=3.6%,...
Abstract Sawtooth control using electron cyclotron current drive (ECCD) has been demonstrated in ITER-like plasmas with a large fast ion fraction, wide q = 1 radius and long uncontrolled sawtooth period DIII-D. The is minimized when the ECCD resonance just inside surface. destabilization driven avoids triggering of performance-degrading neoclassical tearing modes (NTMs), even at much higher pressure than required ITER baseline scenario. Operation β N 3 without 3/2 or 2/1 NTMs achieved...
Helicon waves have been recently proposed as an off-axis current drive actuator for DIII-D, FNSF, and DEMO tokamaks. Previous ray tracing modeling using GENRAY predicts strong single pass absorption in the mid-radius region on DIII-D high beta tokamak discharges. The full wave code AORSA, which is valid to all order of Larmor radius can resolve arbitrary ion cyclotron harmonics, has used validate technique. If scrape-off-layer (SOL) ignored modeling, AORSA agrees with both amplitude location...
To prepare for steady-state operation of future fusion reactors (e.g. the International Thermonuclear Experimental Reactor and China Fusion Engineering Test (CFETR)), experiments on DIII-D have extended high poloidal beta (βP) scenario to reactor-relevant edge safety factor q95 ∼ 6.0, while maintaining a large-radius internal transport barrier (ITB) using negative magnetic shear. Excellent energy confinement quality (H98y2 > 1.5) is sustained at normalized (βN 3.5). This high-performance ITB...
The article reports results of experiments to further determine the underlying physics behind formation and development internal transport barriers (ITBs) in DIII-D tokamak. initial ITB occurs when neutral beam heating power exceeds a threshold value during early stages current ramp low density discharges. This region reduced transport, made accessible by suppression long wavelength turbulence sheared flows, is most evident ion temperature impurity rotation profiles. In some cases, also...
Coupling structures for lower hybrid current drive experiments have, until now, been smaller than a free space wavelength and have had correspondingly broad wavenumber spectrum. The paper reports the results of on PLT tokamak using 16-waveguide grill (2.2 wavelengths) which produces very narrow n∥ = k∥c/ω Experimental from are compared with three other grills less sharply defined n1 spectra. figure merit, , is approximately 40% higher coupler previously reported PLT, in spite larger...
New processes have been discovered in the interaction of 3D fields with tearing mode stability at low torque and modest β on DIII-D NSTX. These are thought to arise from plasma response resonant surface, which theoretically is expected depend strongly rotation underlying intrinsic stability. This leads sensitivities additional those previously identified density where more readily stopped, or high N ideal MHD responses amplify (where divided by ratio current minor radius multiplied toroidal...