A5015224972- Magnetic confinement fusion research
- Superconducting Materials and Applications
- Ionosphere and magnetosphere dynamics
- Particle accelerators and beam dynamics
- Fusion materials and technologies
- Plasma Diagnostics and Applications
- Laser-Plasma Interactions and Diagnostics
- Nuclear reactor physics and engineering
- Advanced Data Storage Technologies
- Electrostatic Discharge in Electronics
- Physics of Superconductivity and Magnetism
- Solar and Space Plasma Dynamics
- Atomic and Subatomic Physics Research
- Semiconductor materials and devices
- Magnetic Field Sensors Techniques
- Integrated Circuits and Semiconductor Failure Analysis
- Semiconductor Quantum Structures and Devices
- Silicon and Solar Cell Technologies
- Plasma and Flow Control in Aerodynamics
- Target Tracking and Data Fusion in Sensor Networks
- High voltage insulation and dielectric phenomena
- Nuclear Materials and Properties
- Gyrotron and Vacuum Electronics Research
- Dust and Plasma Wave Phenomena
- Iterative Learning Control Systems
Columbia University
2015-2025
Technical University of Darmstadt
2023
Max Planck Society
2018
Max Planck Institute for Plasma Physics
2018
Oak Ridge Associated Universities
2011-2017
University of California, San Diego
2017
Princeton Plasma Physics Laboratory
2015-2017
William & Mary
2017
Williams (United States)
2017
University of California, Los Angeles
2017
Abstract The tokamak approach, utilizing a toroidal magnetic field configuration to confine hot plasma, is one of the most promising designs for developing reactors that can exploit nuclear fusion generate electrical energy 1,2 . To reach goal an economical reactor, reactor 3–10 simultaneously require reaching plasma line-averaged density above empirical limit—the so-called Greenwald 11 —and attaining confinement quality better than standard high-confinement mode 12,13 However, such...
Density pumpout and edge-localized mode (ELM) suppression by applied $n=2$ magnetic fields in low-collisionality DIII-D plasmas are shown to be correlated with the magnitude of plasma response driven on high-field side (HFS) axis but not low-field (LFS) midplane. These distinct responses a direct measurement multimodal response, each structure preferentially excited different spectrum detected LFS or HFS. Ideal resistive magneto-hydrodynamic (MHD) calculations find that is primarily...
Recent EAST/DIII-D joint experiments on the high poloidal beta tokamak regime in DIII-D have demonstrated fully noninductive operation with an internal transport barrier (ITB) at large minor radius, normalized fusion performance increased by ≥30% relative to earlier work (Politzer et al 2005 Nucl. Fusion 45 417). The advancement was enabled improved understanding of 'relaxation oscillations', previously attributed repetitive ITB collapses, and fast ion behavior this regime. It found that...
Using data-driven methodology, we exploit the time series of relevant plasma parameters for a large set disrupted and non-disrupted discharges to develop classification algorithm detecting disruptive phases in shots that eventually disrupt. Comparing same methodology on different devices is crucial order have information portability developed possible extrapolation ITER. Therefore, use data from two very tokamaks, DIII-D Alcator C-Mod. We focus subset disruption predictors, most which are...
A detailed experiment-theory comparison reveals that linear ideal MHD theory is in quantitative agreement with external magnetic and internal soft x-ray measurements of the plasma response to externally applied non-axisymmetric fields over a broad range beta rotation. This result represents significant step toward goal advancing understanding three-dimensional tokamak equilibria. Both show driven perturbation increases linearly perturbation, suggesting relevance models. The are made at...
The DIII-D tokamak magnetic diagnostic system [E. J. Strait, Rev. Sci. Instrum. 77, 023502 (2006)] has been upgraded to significantly expand the measurement of plasma response intrinsic and applied non-axisymmetric “3D” fields. placement design 101 additional sensors allow resolution toroidal mode numbers 1 ≤ n 3, poloidal wavelengths smaller than MARS-F, IPEC, VMEC magnetohydrodynamic model predictions. Small 3D perturbations, relative equilibrium field (10−5 < δB/B0 10−4), require...
Key plasma physics and real-time control elements needed for robustly stable operation of high fusion power discharges in ITER have been demonstrated recent research worldwide.Recent analysis has identified the current density profile as main drive disruptive instabilities simulating ITER's baseline scenario with low external torque.Ongoing development model-based active magnetohydrodynamic is improving stability multiple scenarios.Significant advances made toward physicsbased prediction...
Diverted discharges at negative triangularity on the DIII-D tokamak sustain normalized confinement and pressure levels typical of standard H-mode scenarios (H98y2 ≃ 1, βN 3) without developing an edge pedestal, despite auxiliary power far exceeding L → H threshold expected from conventional scaling laws. The degradation is substantially weaker than ITER-89P scaling, resulting in a factor that improves with increasing power. absence pedestal beneficial several ways, such as eliminating need...
Abstract The achievement of high gain, stationary conditions in a tokamak scenario aimed at producing fusion energy the ITER Project is crucial to demonstration that this form can be used future reactors provide cheap and clean globally. Disruptions are challenge for field, particular ‘ITER Baseline Scenario’ (IBS), as reproduced DIII-D tokamak. This work shows solution has been found m = 2/ n 1 tearing modes have consistently caused disruptions IBS: stable operation down zero input torque...
Experiments have been executed in the DIII-D tokamak to extend suppression of Edge Localized Modes (ELMs) with Resonant Magnetic Perturbations (RMPs) ITER-relevant levels beam torque. The results support hypothesis for RMP ELM based on transition from an ideal screened response a tearing at resonant surface that prevents expansion pedestal unstable width [Snyder et al., Nucl. Fusion 51, 103016 (2011) and Wade 55, 023002 (2015)]. In ITER baseline plasmas I/aB = 1.4 ν* ∼ 0.15, ELMs are readily...
Measurements show fast ion losses correlated with applied three-dimensional (3D) fields in a variety of plasmas ranging from L-mode to resonant magnetic perturbation (RMP) edge localized mode (ELM) suppressed H-mode discharges. In DIII-D discharges slowly rotating perturbation, scintillator detector loss signals synchronized the are observed decay within one poloidal transit time after beam turn-off indicating they arise predominantly prompt orbits. Full orbit following using M3D-C1...
Type-I edge-localized modes (ELMs) have been suppressed in DIII-D (Luxon et al 2003 Nucl. Fusion 43 1813) H-mode discharges with a H98Y2 confinement factor near 1.0 using magnetic perturbations (MPs) dominant toroidal mode number n = 2. This expands access to the ELM-suppressed regime, which was previously attainable only 3 fields. ELM suppression is obtained two rows of internal coils for 1.8 s normalized beta 1.9 and average triangularity 0.53, corresponding scaled version ITER scenario 2...
Experimental optimum error field correction (EFC) currents found in a wide breadth of dedicated experiments on DIII-D are shown to be consistent with the required null poloidal harmonics vacuum which drive kink mode near plasma edge. This allows identification empirical metrics predict optimal EFC accuracy comparable that first-principles modelling includes ideal response. While further metric refinements desirable, this work suggests can effectively fed-forward based purely knowledge and...
An extensive examination of the plasma response to dominantly n = 2 non-axisymmetric magnetic perturbations (MPs) on DIII-D tokamak shows potential control 3D field interactions by varying poloidal spectrum radial field.The is calculated as a function applied structure and parameters, using linear magnetohydrodynamic code MARS-F (Liu et al 2000 Phys.Plasmas 7 3681).The ideal, single fluid decomposed into two main components: local pitch-resonant occurring at rational flux surfaces, global...
Abstract Imaging beam emission spectroscopy has been used to study the displacement of plasma boundary in ELMing H-mode discharges with a 10 Hz rotating n = 2 external magnetic field perturbation DIII-D. The creates helical profile ∼2 cm on low-field-side (LFS) midplane which rotates applied resonant perturbation. This shift is due primarily electron density profile, independently measured be 1.9 LFS midplane. These displacements exceed calculations for stable and unstable manifolds formed...
For the first time, DIII-D experiments have achieved stationary quiescent H-mode (QH-mode) operation for many energy confinement times at simultaneous ITER-relevant values of beta, confinement, and safety factor, in an ITER-like shape. QH-mode provides excellent even very low plasma rotation, while operating without edge localized modes (ELMs) with strong impurity transport via benign harmonic oscillation (EHO). By tailoring shape to improve stability, space has also been extended densities...
DIII-D experiments using new detailed magnetic diagnostics show that linear, ideal magnetohydrodynamics (MHD) theory quantitatively describes the structure (as measured externally) of three-dimensional (3D) equilibria resulting from applied fields with toroidal mode number n = 1, while a nonlinear solution to MHD force balance, VMEC code, requires inclusion ≥ 1 achieve similar agreement. These tests are carried out near ITER baseline parameters, providing validated basis on which exploit 3D...
The three-dimensional plasma boundary displacements induced by applied non-axisymmetric magnetic perturbations have been measured in ASDEX Upgrade, DIII-D, JET, MAST and NSTX. arising from resonant (RMPs) are up to ±5% of the minor radius present-day machines. Good agreement can be found between different experimental measurements a range models—be it vacuum field line tracing, ideal MHD equilibrium modelling, or nonlinear amplification. various with predictions these models is presented,...
Optimal error field correction (EFC) is thought to be achieved when coupling the least-stable “dominant” mode of plasma nulled at each toroidal number (n). The limit this picture tested in DIII-D tokamak by applying superpositions in- and ex-vessel coil set n = 1 fields calculated fully orthogonal dominant mode. In co-rotating H-mode low-density Ohmic scenarios, found be, respectively, 7× 20× less sensitive as compared in-vessel field. For scenarios investigated, any geometry EFC can thus...
Active measurements of the plasma stability in tokamak plasmas reveal importance kinetic resonances for resistive wall mode stability. The rotation dependence magnetic response to externally applied quasistatic $n=1$ fields clearly shows signatures an interaction between and precession bounce motions trapped thermal ions, as predicted by a perturbative model including effects. identification stabilization mechanism is essential step towards quantitative predictions prospects ``passive''...
Energy and pitch angle resolved measurements of escaping neutral beam ions (E ≈ 80 keV) have been made during DIII-D L-mode discharges with applied, slowly rotating, n = 2 magnetic perturbations.Data from separate scintillator detectors (FILDs) near well below the plasma midplane show fast-ion losses correlated internal coil (I-coil) fields.The dominant loss signals are observed to decay within one poloidal transit time after turn-off indicating they primarily prompt orbits.Also, application...
Experimental and modeling investigations on the DIII-D EAST tokamaks show attractive transport stability properties of fully noninductive, high poloidal-beta (βP) plasmas, their suitability for steady-state operating scenarios in ITER CFETR. A key feature high-βP regime is large-radius (ρ > 0.6) internal barrier (ITB), often observed all channels (ne, Te, Ti, rotation), responsible both excellent energy confinement quality properties. Experiments have shown that, with a ITB, very βN βP...
Analysis of the evolving current density (J), pedestal and rotation profiles in a database 200 ITER Baseline Scenario (IBS) demonstration discharges DIII-D tokamak identifies profile as key determinant disruptive instability limiting both high low torque operation these q95 = 3 plasmas. The m 2/n 1 tearing modes, occurring after several pressure-relaxation times, are linked to shape outer region plasma. q 2 surface is located at ρ ~ 0.78, near minimum J. A steeper 'well' around correlated...
Abstract Negative triangularity (NT) experiments in DIII-D point to an emergent reactor scenario free of sawteeth, endowed with benign, nondisruptive n = 2 tearing modes, which experience q min <?CDATA $ \geqslant $?> <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mo>⩾</mml:mo> </mml:math> 1 similar the positive hybrid scenario. Plasmas exhibiting this behavior attain ${\beta _{\text{N}}} > 3$?> <mml:mrow> <mml:msub> <mml:mi>β</mml:mi>...
Recent high-poloidal-beta (high-βP) experiments on DIII-D and EAST have made coordinated breakthroughs for high confinement quality at density near the Greenwald limit. Density gradient amplification of turbulence suppression βP can explain both these achievements. Experiments achieved fraction (fGr = line-averaged density/Greenwald density) above 1 simultaneously with normalized energy (H98y2) around 1.5, as required in fusion reactor designs but never before verified tokamak divertor...