A5085859739- Magnetic confinement fusion research
- Fusion materials and technologies
- Superconducting Materials and Applications
- Particle accelerators and beam dynamics
- Ionosphere and magnetosphere dynamics
- Plasma Diagnostics and Applications
- Laser-Plasma Interactions and Diagnostics
- Semiconductor materials and devices
- Nuclear Physics and Applications
- Laser-induced spectroscopy and plasma
- Nuclear reactor physics and engineering
- Atomic and Molecular Physics
- Solar and Space Plasma Dynamics
- Advanced Data Storage Technologies
- Silicon Carbide Semiconductor Technologies
- Electrostatic Discharge in Electronics
- Advancements in Semiconductor Devices and Circuit Design
- Diamond and Carbon-based Materials Research
- Atomic and Subatomic Physics Research
- GaN-based semiconductor devices and materials
- Thin-Film Transistor Technologies
- Particle Detector Development and Performance
- Quantum, superfluid, helium dynamics
- Metal and Thin Film Mechanics
- Spectroscopy and Laser Applications
Oak Ridge National Laboratory
1999-2021
General Atomics (United States)
2009-2021
University of Surrey
2020
Instituto de Ciencias Agrarias
2020
Lawrence Livermore National Laboratory
1995-2012
Japan Atomic Energy Agency
2003-2007
University of York
2007
Higashihiroshima Medical Center
2006
Hiroshima University
2006
University of California, Irvine
2006
The understanding and predictive capability of transport physics plasma confinement is reviewed from the perspective achieving reactor-scale burning plasmas in ITER tokamak, for both core edge regions. Very considerable progress has been made understanding, controlling predicting tokamak across a wide variety conditions regimes since publication Physics Basis (IPB) document (1999 Nucl. Fusion 39 2137–2664). Major areas considered here follow. (1) Substantial improvement content, reliability...
Significant progress has been made in the area of advanced modes operation that are candidates for achieving steady state conditions a fusion reactor. The corresponding parameters, domain operation, scenarios and integration issues discussed this chapter. A review presently developed scenarios, including discussions on operational space, is given. heating current drive recent years, especially off-axis drive, which essential achievement required profile. actuators necessary to produce...
As part of the ITER Design Review and in response to issues identified by Science Technology Advisory Committee, physics requirements were reviewed as appropriate updated. The focus this paper will be on recent work affecting design with special emphasis topics near-term procurement arrangements. This describe results on: sensitivity studies, poloidal field coil requirements, vertical stability, effect toroidal ripple thermal confinement, material choice heat load for plasma-facing...
Combined theoretical and experimental work has resulted in the creation of a paradigm which allowed semi-quantitative understanding edge confinement improvement that occurs H-mode. Shear E*B flow fluctuations plasma can lead to decorrelation fluctuations, decreased radial correlation lengths reduced turbulent transport. Changes electric field, density transport consistent with shear stabilization turbulence have been seen several tokamaks. The purpose this paper is discuss most recent data...
High-confinement (H-mode) operation is the choice for next-step tokamak devices based either on conventional or advanced physics. This choice, however, comes at a significant cost both and tokamaks because of effects edge localized modes (ELMs). ELMs can produce erosion in divertor affect beta limit reduced core transport regions needed operation. Experimental results from DIII-D [J. L. Luxon et al., Plasma Physics Controlled Nuclear Fusion Research 1986 (International Atomic Energy Agency,...
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 EPED model predicts the H-mode pedestal height and width based upon two fundamental calculable constraints: (1) onset of non-local peeling-ballooning modes at low to intermediate mode number, (2) nearly local kinetic ballooning high number. We present detailed tests in discharges with edge localized (ELMs), employing new resolution measurements, finding good quantitative agreement across a range parameters. is then applied for first time quiescent (QH), similar level between predicted...
Rapid bifurcations in the plasma response to slowly varying $n=2$ magnetic fields are observed as transitions into and out of edge-localized mode (ELM) suppression. The rapid transition ELM suppression is characterized by an increase toroidal rotation a reduction electron pressure gradient at top pedestal that reduces perpendicular flow there near zero. These events occur simultaneously with inner-wall response. observations consistent strong resonant field penetration onset suppression,...
H-mode operation is the choice for next-step tokamak devices based either on conventional or advanced physics. This choice, however, comes at a significant cost both and tokamaks because of effects edge-localized modes (ELMs). ELMs can produce erosion in divertor affect β limit reduced core transport regions needed operation. Recent experimental results from DIII-D have demonstrated new operating regime, quiescent which solves these problems. We achieved ELM-free yet has good density...
Poloidal and toroidal rotation of the main ions (${\mathrm{He}}^{2+}$) impurity (${\mathrm{C}}^{6+}$ ${\mathrm{B}}^{5+}$) in H-mode helium plasmas have been measured via charge exchange recombination spectroscopy DIII-D tokamak. It was discovered that ion poloidal is diamagnetic drift direction while electron direction, qualitative agreement with neoclassical theory. The deduced radial electric field edge same negative-well shape regardless which species used, validating fundamental nature...
The first suppression of the important and deleterious m = 2/n 1 neoclassical tearing mode (NTM) is reported using electron cyclotron current drive (ECCD) to replace 'missing' bootstrap in island O-point. Experiments on DIII-D tokamak verify that maximum shrinkage occurs when ECCD location coincides with q 2 surface. plasma control system put into a 'search suppress' make small changes toroidal field find lock onto optimum position, based real time measurements dBθ/dt, for complete NTM by...
Sustained stabilization of the n=1 kink mode by plasma rotation at beta approaching twice stability limit calculated without a wall has been achieved in DIII-D combination error field reduction and sufficient drive. Previous experiments have transiently exceeded no-wall limit. However, demonstration sustained rotational remained elusive because found to decay whenever is stabilized. Recent theory [Boozer, Phys. Rev. Lett. 86, 5059 (2001)] predicts resonant response fields marginal low-n...
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...
The noninductive part of the measured current profile has been determined for DIII-D plasmas. A technique determining flux surface average quantity $\mathbf{E}\ifmmode\cdot\else\textperiodcentered\fi{}\mathbf{B}$ and a model resistivity separates into inductive portions. Analysis shows directly that neoclassical is adequate to explain experimental observations, while Spitzer not, large exists in plasmas which neutral beam drive pressure driven bootstrap currents are expected.
Recent QH-mode research on DIII-D [J. L. Luxon et al., Plasma Physics and Controlled Nuclear Fusion Research 1996 (International Atomic Energy Agency, Vienna, 1987), Vol. I, p. 159] has used the peeling-ballooning modes model of edge magnetohydrodynamic stability as a working hypothesis to organize data; several predictions this theory are consistent with experimental results. Current ramping results indicate that QH operate near current limit set by peeling modes. This operating point...
A low amplitude (δbr∕BT=1 part in 5000) edge resonant magnetic field perturbation with toroidal mode number n=3 and poloidal numbers between 8 15 has been used to suppress most large type I localized modes (ELMs) without degrading core plasma confinement. ELMs have suppressed for periods of up 8.6 energy confinement times when the safety factor q95 is 3.5 4. The are replaced by packets events (possibly II ELMs) small amplitude, narrow radial extent, a higher level density fluctuations,...
We report the results of first experiments on DIII-D tokamak to examine dependence transport and stability characteristics ITER hybrid scenario plasmas toroidal flow (or rotation) plasma. With new capability independently vary neutral beam torque power, central rotation has been reduced by as much a factor 4.6 compared with discharges unidirectional beams. Although energy confinement decreases m/n = 3/2 NTM amplitude increases for low speed, fusion performance figure merit, , still exceeds...
Abstract Recent experiments on DIII-D have increased confidence in the ability to suppress edge-localized modes (ELMs) using edge-resonant magnetic perturbations (RMPs) ITER, including an improved physics basis for edge response RMPs as well expansion of RMP ELM suppression more ITER-like conditions. Complete has been achieved utilizing n = 3 ITER baseline scenario. In addition, expanded include plasmas with helium concentrations near 25% and use 2 RMPs. Analysis kinetic profile suggests...
Long-wavelength turbulence increases dramatically in the outer regions of DIII-D plasmas with application resonant magnetic field perturbations (RMPs) that suppress edge-localized modes (ELMs). Correspondingly, transport and global energy confinement decreases these low-collisionality RMP-ELM suppressed discharges. The core pedestal density are sharply reduced, while ion electron temperatures may change only slightly. Low wavenumber (k⊥ρi < 1) range 60–300 kHz, measured beam emission...
The observation of internal transport barriers (ITBs) in which ion thermal diffusivity is reduced to a neoclassical level has been made for the first time tokamak plasmas fueled with deuterium and tritium ions using broad current density profile. heating profiles required obtain an ITB are similar D-T D-D plasmas. Central temperatures 40 keV plasma pressure gradients ${10}^{6}\mathrm{Pa}/\mathrm{m}$ were observed plasma, leading fusion triple product...
The characteristics of the H-mode are studied in discharges with varying triangularity and squareness. pressure at top pedestal increases strongly triangularity, primarily due to an increase margin by which edge gradient exceeds ideal ballooning mode first stability limit. Two models considered for how may exceed In one model, access second stable regime allows associated bootstrap current continue until localized, low toroidal number, kink is destabilized. finite width transport barrier...
Plasma turbulence characteristics, including radial correlation lengths, decorrelation times, amplitude profile and flow velocity, have been measured during a ρ* scan on DIII-D while all other transport relevant dimensionless quantities (e.g., β, ν*, κ, q, Te/Ti) are held nearly constant. The is by examining the properties of local long wavelength (k⊥ρi ≤ 1) density fluctuations, with beam emission spectroscopy. length Lc,r shown to scale ion gyroradius, ≈ 5ρi, times acoustic velocity as...
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&gt;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...
Discharges which can satisfy the high gain goals of burning plasma experiments have been demonstrated in DIII-D tokamak under stationary conditions at relatively low current (q95>4). A figure merit for fusion (βNH89/q952) has maintained values corresponding to Q = 10 operation a >6 s or 36τE and 2τR. The key element is relaxation profile state with qmin>1. In absence sawteeth fishbones, stable achieved up estimated no-wall β limit. Feedback control energy content particle inventory allow...
A potential new standard in stationary tokamak performance is emerging from experiments on DIII-D. These have demonstrated the ability to operate near free boundary, n = 1 stability limit with good confinement quality under conditions. The normalized fusion at or above that projected for Qfus 10 operation International Thermonuclear Experimental Reactor (ITER) design over a wide operating range both edge safety factor (2.8–4.7) and plasma density (35–70% of Greenwald density). Projections...