A5053379085- Magnetic confinement fusion research
- Fusion materials and technologies
- Superconducting Materials and Applications
- Ionosphere and magnetosphere dynamics
- Plasma Diagnostics and Applications
- Particle accelerators and beam dynamics
- Laser-Plasma Interactions and Diagnostics
- Nuclear reactor physics and engineering
- Solar and Space Plasma Dynamics
- Semiconductor materials and devices
- Dust and Plasma Wave Phenomena
- Nuclear Physics and Applications
- Physics of Superconductivity and Magnetism
- Metal and Thin Film Mechanics
- Advancements in Semiconductor Devices and Circuit Design
- Electrostatic Discharge in Electronics
- Silicon Carbide Semiconductor Technologies
- Laser-induced spectroscopy and plasma
- Atomic and Subatomic Physics Research
- Diamond and Carbon-based Materials Research
- Magnetic Field Sensors Techniques
- Iterative Learning Control Systems
- Fault Detection and Control Systems
- Advanced Data Storage Technologies
- Acoustic Wave Resonator Technologies
École Polytechnique Fédérale de Lausanne
2015-2024
Laboratoire de Physique des Plasmas
2012-2023
University of California, San Diego
2021
National Agency for New Technologies, Energy and Sustainable Economic Development
2021
Max Planck Institute for Plasma Physics
1997-2015
Max Planck Society
1996-2015
Ludwig-Maximilians-Universität München
2012-2013
Columbia University
2003-2012
General Atomics (United States)
2000-2007
National Center on Addiction and Substance Abuse at Columbia University
2006
A stochastic magnetic boundary, produced by an applied edge resonant perturbation, is used to suppress most large edge-localized modes (ELMs) in high confinement ($H$-mode) plasmas. The resulting $H$ mode displays rapid, small oscillations with a bursty character modulated coherent 130 Hz envelope. transport barrier and core are unaffected the despite threefold drop toroidal rotation. These results demonstrate that boundaries compatible may be attractive for ELM control next-step fusion tokamaks.
We present the first evidence for existence of a neoclassical toroidal rotation driven in direction counter to plasma current by nonaxisymmetric, nonresonant magnetic fields. At high beta and with large injected neutral beam momentum, field torque slows down toward ``offset'' rate. With small is accelerated offset rotation, resulting improvement global energy confinement time. The observed magnitude, direction, radial profile are consistent theory predictions [A. J. Cole et al., Phys. Rev....
The application of static, non-axisymmetric, nonresonant magnetic fields (NRMFs) to high beta DIII-D plasmas has allowed sustained operation with a quiescent H-mode (QH-mode) edge and both toroidal rotation neutral beam injected torque near zero. Previous studies have shown that QH-mode can be accessed only if sufficient radial shear in the plasma flow is produced edge. In past experiments, this was using injection (NBI) provide torque. recent nearly completely replaced by from applied...
Divertor detachment is explored on the TCV tokamak in alternative magnetic geometries. Starting from typical single-null shapes, poloidal flux expansion at outer strikepoint varied by a factor of 10 to investigate X-divertor characteristics, and total 70 study properties super-X divertor. The effect an additional X-point near target investigated divertors. Detachment studied these plasmas during Ohmic density ramps with ion B drift away primary X-point. threshold, depth detachment, stability...
Abstract The tokamak à configuration variable (TCV) continues to leverage its unique shaping capabilities, flexible heating systems and modern control system address critical issues in preparation for ITER a fusion power plant. For the 2019–20 campaign configurational flexibility has been enhanced with installation of removable divertor gas baffles, diagnostic capabilities an extensive set upgrades new dual frequency gyrotrons. baffles reduce coupling between main chamber allow detailed...
Self-consistent full-size turbulent-transport simulations of the divertor and SOL existing tokamaks have recently become feasible. This enables direct comparison turbulence against experimental measurements. In this work, we perform a series diverted Ohmic L-mode discharges on TCV tokamak, building first-of-a-kind dataset for validation edge models. dataset, referred to as TCV-X21, contains measurements from 5 diagnostic systems -- giving total 45 1- 2-D observables in two toroidal magnetic...
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...
Recent DIII-D experiments with reduced neutral beam torque and minimum nonaxisymmetric perturbations of the magnetic field show a significant reduction toroidal plasma rotation required for stabilization resistive-wall mode (RWM) below threshold values observed in that apply fields to slow rotation. A frequency less than 10 krad/s at q=2 surface (measured charge exchange recombination spectroscopy using C VI) corresponding 0.3% inverse Alfvén time is sufficient sustain pressure above ideal...
A set of twelve coils for stability control has recently been installed inside the DIII-D [J. L. Luxon, Nucl. Fusion 42, 614 (2002)] vacuum vessel, offering faster time response and a wider range applied mode spectra than previous external coils. Stabilization n=1 ideal kink is crucial to many high beta, steady-state tokamak scenarios. resistive wall converts slowly growing (RWM). With feedback-controlled error field correction, rotational stabilization RWM sustained more 2.5 s. Using...
Utilizing a capability to vary neutral beam torque injection in the DIII-D [J. L. Luxon, Nucl. Fusion 42, 614 (2002)] tokamak, m∕n=2∕1 neoclassical tearing mode onset thresholds are found fall by about one unit βN, from ∼3 ∼2, ITER-like sawtoothing high-energy confinement modes of plasma operation [R. Aymar, Plasma Phys. Control. B385 (2000)] as “co-injected” and rotation reduced. However, increasing levels counter-direction do not lead corresponding rises βN thresholds. More encouragingly,...
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,...
The first quantitative comparison of linear ideal magnetohydrodynamic (MHD) theory with external magnetic measurements the nonaxisymmetric plasma perturbation driven by long-wavelength fields in high-temperature tokamak plasmas is presented. yields good (within 20%) agreement for pressures up to ∼75% stability limit calculated without a conducting wall. For higher pressures, MHD model tends overestimate perturbed field indicating increasing importance stabilizing nonideal effects.
The resistive wall mode (RWM) instability in high-beta tokamaks is stabilized by energy dissipation mechanisms that depend on plasma rotation and kinetic effects. Kinetic modification of ideal stability calculated with the “MISK” code [B. Hu et al., Phys. Plasmas 12, 057301 (2005)] outlined. For an advanced scenario ITER [R. Aymar Nucl. Fusion 41, 1301 (2001)] plasma, present calculation finds alpha particles are required for RWM at presently expected levels rotation. stabilization theory...
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...
A detailed cross-device investigation on the role of filamentary dynamics in high-density regimes has been performed within EUROfusion framework, comparing ASDEX Upgrade (AUG) and TCV tokamaks. Both devices run density ramp experiments at different levels plasma current, keeping toroidal field or q95 constant order to disentangle parallel connection length current. During scan a field, both scrape-off layer (SOL) profiles tend develop clear SOL shoulder lower edge whenever current is...
Plasma exhaust has been identified as a major challenge towards the realisation of magnetic confinement fusion. To mitigate risk that single null divertor (SND) with high radiation fraction in scrape-of-layer (SOL) adopted for ITER will not extrapolate to DEMO reactor, EUROfusion consortium is assessing potential benefits and engineering challenges alternative configurations. Alternative configurations could be readily design include X (XD), Super-X (SXD), Snowflake (SFD) double (DND). The...
Future fusion reactors require a safe, steady-state divertor operation. With deep detachment, which is typically induced by impurity seeding, the radiation concentrates in small region at X-point or on closed flux surfaces above X-point. This so-called radiator (XPR) moves further inside confined with increasing seeding and location can be actively controlled. At AUG, parameter space for operation an XPR was significantly extended, using active feedback location. The observed nearly whole...
Abstract The impact of plasma shaping on the properties high density H-mode scrape-off layer (SOL) profiles and transport at outer midplane has been investigated Tokamakà configuration variable. experimental dataset acquired by evolving upper triangularity while keeping other parameters constant. scan comprises <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:msub> <mml:mi>δ</mml:mi> <mml:mrow> <mml:mi mathvariant="normal">u</mml:mi>...
Using resonant magnetic perturbations with toroidal mode number n = 3, we have produced H-mode discharges without edge localized modes (ELMs) which run constant density and radiated power for periods up to about 2550 ms (17 energy confinement times). These ELM suppression results are achieved at pedestal collisionalities close those desired next step burning plasma experiments such as ITER provide a means of eliminating the rapid erosion divertor components in machines could be caused by...
Neoclassical tearing modes are one of the most serious concerns for operation on a next-step tokamak device. The occur present tokamaks at normalized pressure (βN) values comparable to those envisaged baseline scenarios in future devices, such as ITER-FEAT. Further, empirical scalings based data from many machines point much lower thresholds larger However, physics-based models indicate an important role seed island mechanisms, which may fact give rise increased stability devices - i.e. if...
A steady-state, fully noninductive plasma current has been sustained for the first time in a tokamak using electron cyclotron drive only. In this discharge, 123 kA of have entire gyrotron pulse duration 2 s. Careful distribution across minor radius power deposited from three 0. 5-MW gyrotrons was essential reaching steady-state conditions. With central drive, up to 153 replaced transiently 100 ms. The scenario is confirmed by ability recharge Ohmic transformer. dependence efficiency on also...
Dedicated experiments in the DIII-D tokamak [J. L. Luxon, Nucl. Fusion, 42, 614 (2002)], Joint European Torus (JET) [P. H. Rebut, R. J. Bickerton, and B. E. Keen, Fusion 25, 1011 (1985)], National Spherical Experiment (NSTX) [M. Ono, S. M. Kaye, Y.-K. Peng et al., 40, 557 (2000)] reveal commonalities of resistive wall mode (RWM) stabilization by sufficiently fast toroidal plasma rotation devices different size aspect ratio. In each device weakly damped n=1 RWM manifests itself resonant field...
The stability of the resistive-wall mode (RWM) in DIII-D plasmas above conventional pressure limit, where toroidal plasma rotation order a few percent Alfv\'en velocity is sufficient to stabilize $n=1$ RWM, has been probed using technique active MHD spectroscopy at frequencies Hertz. measured frequency spectrum response externally applied rotating resonant magnetic fields well described by single-mode approach and provides an absolute measurement damping rate natural stable RWM.
Internal coils, 'I-Coils', were installed inside the vacuum vessel of DIII–D device to generate non-axisymmetric magnetic fields act directly on plasma. These are predicted stabilize resistive wall mode (RWM) branch long-wavelength external kink with plasma beta close ideal limit. Feedback using these I-Coils was found be more effective as compared coils located outside vessel. Locating allows for a faster response and coil geometry also better coupling helical structure. Initial results...