Dr
Hiroshi Gota
(Tri Alpha Energy, Inc.)
19/10/2016, 08:30
EXS - Magnetic Confinement Experiments: Stability
Poster
The world’s largest compact-toroid device, C-2, has been upgraded to C-2U at Tri Alpha Energy to achieve sustainment of field-reversed configuration (FRC) plasmas by neutral-beam (NB) injection (NBI) and edge biasing [1,2], and the C-2U experiment is characterized by the following key system upgrades: increased total NB input power from ~4 MW (20 keV hydrogen) to 10+ MW (15 keV hydrogen) with...
Prof.
Egemen Kolemen
(Princeton University)
19/10/2016, 08:30
EXS - Magnetic Confinement Experiments: Stability
Poster
A comprehensive adaptive real-time (rt) ELM control system that exploits key properties of ELM physics, Resonant Magnetic Perturbation (RMP) ELM suppression physics, and an extensive set of diagnostic inputs to make rt decisions about the control of multiple actuators to sustain ELM suppression/mitigation is demonstrated at DIII D. The control experiments showed the path dependence and...
Dr
Walter Guttenfelder
(Princeton Plasma Physics Laboratory)
19/10/2016, 08:30
THC - Magnetic Confinement Theory and Modelling: Confinement
Poster
The inward momentum convection or “pinch” observed in many tokamaks can be explained by the Coriolis drift mechanism, with relatively good quantitative agreement found with gyrokinetic predictions of the ion temperature gradient (ITG) instability. Here we attempt to validate this model over a broader range of beta and aspect ratio by extending into the spherical tokamak (ST) plasma regime...
Prof.
Thomas Jarboe
(University of Washington,)
19/10/2016, 08:30
EXS - Magnetic Confinement Experiments: Stability
Poster
Understanding sustainment of stable equilibria with helicity injection in HIT-SI has led to a simple picture of several tokamak features. Perturbations cause a viscous-like force on the current that flattens the j/B profile, which sustains and stabilizes the equilibrium. An explanation of the mechanism is based on the two properties of stable, ideal, two-fluid, magnetized plasma. First, the...
Prof.
Yasuaki Kishimoto
(Kyouto University)
19/10/2016, 08:30
THC - Magnetic Confinement Theory and Modelling: Confinement
Poster
Profile stiffness and intermittent bursts are the basis in understanding L-mode plasmas. However, why and how these different processes coexist and regulate the transport have not been fully clarified. Here, we presented an overall picture of flux-driven ITG turbulent transport which reveals profile stiffness with self-similarity and SOC type intermittent bursts simultaneously using a...
Dr
Christel Fenzi
(CEA)
19/10/2016, 08:30
THC - Magnetic Confinement Theory and Modelling: Confinement
Poster
Lower hybrid (LH) wave effect on toroidal plasma rotation in L-mode Tore Supra plasmas has been analyzed in more than 50 plasma discharges, with LH input power P_LH up to 4.8MW, plasma current Ip up to 1.4MA, line integrated density n_l up to 6 × 10^19m−2, B_T = 3.8T, and a significant ripple amplitude (up to 5% at the plasma boundary) which makes ripple-induced momentum non negligible. At low...
Dr
Alan Costley
(Tokamak Energy Ltd)
19/10/2016, 08:30
EXS - Magnetic Confinement Experiments: Stability
Poster
Tokamak Energy Ltd, UK, is developing spherical tokamaks (STs) using High Temperature Superconductor (HTS) magnets as a route to fusion power based on high gain, small size power plants. The paper presents an overview of the continuing advances in technology and modeling, which, together with key engineering developments, support this concept. The ST achieved recognition as a high beta plasma...
Prof.
Tomohiko Asai
(Nihon University)
19/10/2016, 08:30
EXS - Magnetic Confinement Experiments: Stability
Poster
A repetitively driven compact toroid (CT) injector has been developed for large-sized field-reversed configuration (FRC) facility of the C-2/C-2U primarily for refueling. Pursuit of the FRC as fusion reactor is motivated by highly favorable technological features: extremely high beta (>50%), a natural divertor, and axial mobility allowing separation of start-up and confinement functions....
Dr
Francesca Turco
(Columbia University)
19/10/2016, 08:30
EXS - Magnetic Confinement Experiments: Stability
Poster
Analysis of ~180 ITER Baseline Scenario (IBS) demonstration discharges in DIII-D provides insight into the cause of the 2/1 disruptive instabilities that limit the duration of these plasmas. Raw MSE data and detailed equilibrium reconstructions show that a larger current profile gradient in the region of the q=2 surface characterises the unstable cases, providing the drive for the 2/1 tearing...
Dr
David Eldon
(Princeton University)
19/10/2016, 08:30
EXS - Magnetic Confinement Experiments: Stability
Poster
A new control system at DIII-D has stabilized the detached divertor plasma state in close proximity to the threshold for reattachment, thus demonstrating ability to maintain detachment with minimum gas puffing. When the same control system was instead ordered to hold the plasma at the threshold, the resulting T_e profiles separated into two groups with one group consistent with marginal...
Susan Leerink
(Aalto University)
19/10/2016, 08:30
THC - Magnetic Confinement Theory and Modelling: Confinement
Poster
Turbulent transport and flow dynamics in Ohmic FT-2 tokamak plasmas are investigated. Measurements utilize highly localized state-of-the art backscattering while the
turbulence simulations are performed with the global full-f nonlinear code ELMFIRE. The role of the geodesic acoustic mode in regulating turbulent transport is studied. Special emphasis is given to the isotope effect observed in...
Dr
Robert Granetz
(MIT)
19/10/2016, 08:30
EXS - Magnetic Confinement Experiments: Stability
Poster
To address the challenge of disruption prediction, we
have created large disruption warning databases for both
Alcator C-Mod and EAST by compiling values for a number
of proposed disruption-relevant parameters sampled at
many different times throughout all plasma discharges,
disruptive and non-disruptive, during the 2015 campaigns
on the respective machines. The...
Dr
Alexei Beklemishev
(Budker Institute of Nuclear Physics SB RAS)
19/10/2016, 08:30
THC - Magnetic Confinement Theory and Modelling: Confinement
Poster
A new efficient method of magnetic confinement is suggested for use in linear traps with extremely high plasma pressure. While pressure grows, the equilibrium in a linear trap changes in such a way that the effective mirror ratio increases, and, as a result, the axial particle and energy confinement becomes gas-dynamic and improves linearly with mirror ratio. This effect is due to diamagnetic...
Dr
John deGrassie
(General Atomics)
19/10/2016, 08:30
EXS - Magnetic Confinement Experiments: Stability
Poster
A dimensionless empirical scaling for intrinsic toroidal rotation is given; MA~βNρ*, where MA is the toroidal velocity divided by the Alfvén velocity, βN the usual normalized β value, and ρ* is the ion gyroradius divided by the minor radius. This scaling is in agreement with experimental data from DIII-D, and also incorporates some published data from C-Mod and JET. The velocity used in this...
Mr
Daisuke Shirakid
(Oak Ridge National Laboratory)
19/10/2016, 08:30
EXS - Magnetic Confinement Experiments: Stability
Poster
Experiments on the DIII-D and Alcator C-Mod tokamaks show that disruption mitigation by massive gas injection (MGI) and shattered pellet injection (SPI) of high-Z impurities remain effective in the presence of large pre-existing MHD instabilities. Rotating and locked magnetic islands will precede a large fraction of disruptions in ITER, making their impact on disruption mitigation a critical...
Dr
Dan Brunner
(MIT PSFC)
19/10/2016, 08:30
EXS - Magnetic Confinement Experiments: Stability
Poster
The C-Mod team has developed a new tool for control of plasma conditions at the divertor target. It is the first heat flux mitigation system to employ real-time measurements of surface heat flux to control impurity seeding. Control of the conditions at the divertor surface is one of the remaining challenges to tokamak fusion energy. Active cooling technology limits the surface heat flux to ~10...
Prof.
Saskia Mordijck
(The College of William and Mary)
19/10/2016, 08:30
EXS - Magnetic Confinement Experiments: Stability
Poster
In this paper we will show that particle confinement is determined by changes in turbulence characteristic outside mid-radius up to the top of the pedestal in DIII-D H-mode plasmas. We find that the Electron Cyclotron Heating (ECH) density pump-out at low collisionality is the result of an increase in turbulence drive from ρ=0.7-0.9. The frequency of the mode and thus the turbulence type...
Dr
John Omotani
(Department of Physics, Chalmers University of Technology)
19/10/2016, 08:30
THC - Magnetic Confinement Theory and Modelling: Confinement
Poster
The accessibility and performance of the H-mode are critical to tokamak fusion reactors. While the physics of the pedestal is complicated and far from fully understood, it is clear that flow shear plays an important role. One of the mechanisms that may regulate flow velocity in the plasma edge is momentum transport by neutrals. Due to their high cross-field mobility they may be the most...
Dr
Thomas W. Petrie
(General Atomics)
19/10/2016, 08:30
EXS - Magnetic Confinement Experiments: Stability
Poster
We identify major challenges to reducing divertor heat flux in high power, high performance near-double null DIII-D plasmas, while still maintaining sufficiently low
density to allow for application of RF heating. The plasmas discussed here are characterized by: β_N ≅ 3–4, H_98 ≅ 1.5–1.7, dR_SEP ≅ -5 mm, and P_IN up to 20 MW. The scaling of the peak heat flux (q⊥p) at the outer target of the...
Mr
Chan-Yong An
(Soongsil University)
19/10/2016, 08:30
THC - Magnetic Confinement Theory and Modelling: Confinement
Poster
Turbulent plasma transport is an important issue in the confinement of the fusion plasmas. E×B nonlinear flux plays a deciding role in redistributing the energy and the momentum. In the case of the isothermal plasma the particle flux Γ is the fundamental measure of the turbulent transport. In the fusion plasma where the particle collisions are relatively rare the plasma is near the adiabatic...
Dr
Rajaraman Ganesh
(Institute for Plasma Researh, Bhat Village, Gandhinagar 382428, Gujarat, INDIA)
19/10/2016, 08:30
THC - Magnetic Confinement Theory and Modelling: Confinement
Poster
Turbulent transport of energy, particles and momentum is
one of the important limiting factors for long time
plasma confinement. Modern kinetic study using
gyrokinetic formalism and simulation has progressed
to identify several microinstabilities that cause ion
and electron thermal transport. Typically, these have
been ballooning parity modes such as the ITG, KBM and
ETG modes...
Dr
Silvana Nowak
(IFP-CNR)
19/10/2016, 08:30
THC - Magnetic Confinement Theory and Modelling: Confinement
Poster
The modification of low toroidal plasma rotation under application of central EC power injection with possible onset of neoclassical tearing modes (NTM) is an important issue for plasma confinement and for future devices (ITER will be characterized by a low rotation). In low collisionality regime and PEC/Poh >1 TCV experiments central co-ECCD was observed to modify the toroidal plasma rotation...
Dr
Thawatchai Onjun
(Sirindhorn International Institute of Technology)
19/10/2016, 08:30
THC - Magnetic Confinement Theory and Modelling: Confinement
Poster
This work aims to investigate the effects of perturbations of heat and particle sources on the formations of edge transport barrier (ETB) and on the hysteresis properties at the L-H-L transitions in the framework of bifurcation concept. The formation of transport barriers is studied via the combination of thermal and particle transport equations, which also includes neoclassical and anomalous...
Dr
JaeChun Seol
(National Fusion Research Institute)
19/10/2016, 08:30
THC - Magnetic Confinement Theory and Modelling: Confinement
Poster
KSTAR provides a great environment to carry out the NTV study in that the intrinsic error fields and the toroidal field ripples are very small in magnitude, and asymmetric magnetic fields can be added by the in-vessel coil current on demand. In this paper, we report both theoretical and experimental studies on NTV in KSTAR. It is shown that the radial transport of the toroidal angular...
Dr
John Rice
(MIT PSFC)
19/10/2016, 08:30
EXS - Magnetic Confinement Experiments: Stability
Poster
In future magnetic fusion devices, external momentum input from neutral beam injection will be low, and to reap the benefits of rotation, such as stabilization of deleterious MHD modes and shear suppression of turbulence, utilizing radio frequency drive and understanding self-generated flow would be prudent. Changes in the core toroidal rotation profiles following injection of lower hybrid...
Dr
Michael Van Zeeland
(General Atomics)
19/10/2016, 08:30
EXS - Magnetic Confinement Experiments: Stability
Poster
Localized electron cyclotron heating (ECH) can have a dramatic impact on neutral beam driven Alfvén eigenmode (AE) activity in DIII-D plasmas. The most common effect, which is explained here for the first time, is a shift in the dominant observed modes from a mix of reversed shear Alfvén eigenmodes (RSAEs) and toroidicity induced Alfvén eigenmodes (TAEs) to a spectrum of weaker TAEs when ECH...
Prof.
Taik Soo Hahm
(Seoul National University)
19/10/2016, 08:30
THC - Magnetic Confinement Theory and Modelling: Confinement
Poster
Starting from the modern bounce-kinetic formalism, [1] a two-point equation which properly describes turbulent eddies associated with trapped electrons is systematically derived in general tokamak geometry. Trapped electron precession shear, as well as ExB shear, is naturally included in the derivation. Our two-point analysis, using moments of separation between the two points, reveals that...
Dr
John Wright
(MIT - PSFC)
19/10/2016, 08:30
EXS - Magnetic Confinement Experiments: Stability
Poster
Recent experiments on Alcator C-Mod using a small fraction of 3He added to a H(D) plasma have demonstrated efficient ion cyclotron radio frequency (ICRF) heating and indications of MeV 3He tail temperatures. For high toroidal magnetic field B0=8 T discharges with D majority, 3He minority absorption is typically used and has low single pass absorption compared to the H minority absorption...
Dr
Robert Pinsker
(General Atomics)
19/10/2016, 08:30
EXS - Magnetic Confinement Experiments: Stability
Poster
Experiments have begun in DIII-D to evaluate non-inductive current drive by the Landau absorption of a toroidally-directive spectrum of helicon waves (also known as 'very high harmonic fast waves', 'fast waves in the lower hybrid range of frequencies', or 'whistlers'). Modeling has shown [1] that non-inductive current drive at mid-radius (ρ~0.5) should be achievable in DIII-D with fast waves...
Dr
Jeffrey Levesque
(Columbia University)
19/10/2016, 08:30
EXS - Magnetic Confinement Experiments: Stability
Poster
The HBT-EP research program aims to: (i) quantify wall-stabilized kink mode dynamics and multimode response to applied magnetic perturbations, (ii) understand the relationship between control coil configuration, conducting and ferromagnetic wall effects, and active feedback control, and (iii) explore advanced feedback algorithms. We present an overview of planned research activities for the...
Dr
Yasuhiro Idomura
(Japan Atomic Energy Agency)
19/10/2016, 08:30
THC - Magnetic Confinement Theory and Modelling: Confinement
Poster
A new hybrid kinetic trapped electron model [Y. Idomura, J. Comput. Phys. 313, 511 (2016)] is developed for electrostatic full-f gyrokinetic simulations. The model is verified by computing the ion and electron neoclassical transport and the linear ion temperature gradient driven trapped electron mode (ITG-TEM) stability, in which collisional TEM stabilization shows an isotope effect. An impact...
Dr
Seikichi Matsuoka
(Japan Atomic Energy Agency)
19/10/2016, 08:30
THC - Magnetic Confinement Theory and Modelling: Confinement
Poster
The neoclassical toroidal viscosity (NTV) caused by a non-axisymmetric magnetic field perturbation is one of the key issues for the prediction and control of the plasma performance and/or stabilities, since it can play an important role in a momentum balance which determines a plasma rotation. However, there remains a severe discrepancy with regard to the NTV prediction; the so-called...
Dr
Lei Qi
(National Fusion Research Institute, Daejeon, Korea)
19/10/2016, 08:30
THC - Magnetic Confinement Theory and Modelling: Confinement
Poster
Nonlinear bounce-averaged kinetic theory[B.H. Fong and T.S. Hahm, Phys. Plasmas 6, 188 (1999)] is used for magnetically trapped electrons for the purpose of achieving efficient gyrokinetic simulations of Trapped Electron Mode (TEM) and Ion Temperature Gradient mode with trapped electrons (ITG-TEM) in shaped tokamak plasmas. Bounce-averaged kinetic equations are explicitly extended to shaped...
Dr
Michael Leconte
(National Fusion Research Institute)
19/10/2016, 08:30
THC - Magnetic Confinement Theory and Modelling: Confinement
Poster
Controlling Edge Localized Modes (ELMs) is very important for ITER, and a well-tested way to achieve this is by using external coils to generate Resonant Magnetic Perturbations (RMPs), demonstrated on several tokamaks [1-4]. The working hypothesis for the origin of ELM suppression is that RMPs increase transport in the pedestal, thus lowering the pressure-gradient below the ideal-MHD...
Prof.
Eugenio Schuster
(Lehigh University)
19/10/2016, 08:30
EXS - Magnetic Confinement Experiments: Stability
Poster
Recent experiments on DIII-D demonstrate the potential of physics-model-based q-profile control to improve reproducibility of plasma discharges. A combined feedforward+feedback control scheme was employed to optimize the current ramp-up phase by consistently achieving target q profiles (Target 1: qmin=1.3, q95=4.4; Target 2: qmin=1.65, q95=5.0; Target 3: qmin=2.1, q95=6.2) at prescribed times...
Dr
Matthew Reinke
(ORNL)
19/10/2016, 08:30
EXS - Magnetic Confinement Experiments: Stability
Poster
Recent Alcator C-Mod research investigates mechanisms by which ion cyclotron range of frequency (ICRF) heating can effectively mitigate on-axis accumulation of high-Z impurities and explores new techniques to study their interaction with edge transport barriers (ETB). In C-Mod EDA H-modes using D(H) minority heating, modifying the minority concentration and the major radius of the minority...
Dr
Masaki Nishiura
(The University of Tokyo)
19/10/2016, 08:30
EXS - Magnetic Confinement Experiments: Stability
Poster
While the stable high-beta (~ 1) confinement by a dipole magnetic field was successfully demonstrated with high-temperature electrons (Te > 10 keV) [1, 2], the heating of ions was a challenge. We have made two major progresses in this direction. (i) We developed a system for ion cyclotron resonance of frequency (ICRF) heating, and demonstrated the active heating of ions by launching a slow...
Dr
Kenji Imadera
(Kyoto University)
19/10/2016, 08:30
THC - Magnetic Confinement Theory and Modelling: Confinement
Poster
Profile stiffness is a long standing problem, which may limit the overall performance of H-mode plasmas. In the JET experiment, while strong temperature profile stiffness is observed around the nonlinear threshold of ion temperature gradient, it can be greatly reduced by co-current toroidal rotation in weak magnetic shear plasma.
To understand such a mitigation mechanism of the stiffness, we...
Dr
Mikhail Malkov
(University of California, San Diego)
19/10/2016, 08:30
THC - Magnetic Confinement Theory and Modelling: Confinement
Poster
H-mode operation is the regime of choice for good confinement. Access to and sustainability of the H-mode requires understanding of the L $\rightarrow$ H transition power threshold and the related problem of hysteresis. To predict ITER transitions, one must also understand low collisionality, electron-heated regimes.
In this paper, we discuss a.) L $\rightarrow$ H power threshold scaling...
Diego del-Castillo-Negrete
(Fusion Energy Division. Oak Ridge National Laboratory)
19/10/2016, 08:30
THC - Magnetic Confinement Theory and Modelling: Confinement
Poster
The quantitative understanding of the role of magnetic field stochasticity on transport is critical for the confinement of fusion plasmas. Specific problems of interest include the control of ELMs by resonant magnetic perturbations and the assessment of heat fluxes at the divertor. Here we present direct numerical simulations of the time dependent parallel heat transport equation modeling heat...
Dr
K. C. Shaing
(Engineering Physics Department, University of Wisconsin)
19/10/2016, 08:30
THC - Magnetic Confinement Theory and Modelling: Confinement
Poster
Theory for neoclassical toroidal plasma viscosity is to describe the transport processes, including particle, momentum, and energy transport fluxes in real tokamaks with broken symmetry. The predictions of the theory are in agreement with the numerical results in all collisionality regimes in the large aspect ratio limit. The theory has since been extended to finite aspect ratio tokamaks. The...
Prof.
Patrick Diamond
(University of California San Diego)
19/10/2016, 08:30
THC - Magnetic Confinement Theory and Modelling: Confinement
Poster
Negative viscosity phenomena in which turbulence driven by the heat flux couples its energy to large scale structure, is a familiar and, in fact, necessary element in the success of magnetic fusion. Two prime examples of negative viscosity phenomena are zonal flow formation, where drift wave turbulence drives mesoscale shear flows which regulate large scale eddys, and intrinsic torque, where...
Dr
Masatoshi Yagi
(National Institutes for Quantum and Radiological Science and Technology, Rokkasho Fusion Institute)
19/10/2016, 08:30
THC - Magnetic Confinement Theory and Modelling: Confinement
Poster
The transient transport events are observed in toroidally magnetic confinement devices. For example, the cold pulse experiment shows a rapid transient increase of electron temperature in the plasma core in response to an abrupt cooling at the edge. Understanding the nonlocal transport is important to control plasma core and/or fuel supply in ITER and DEMO. The nonlocal particle transport has...
Dr
Naohiro Kasuya
(Kyushu University)
19/10/2016, 08:30
THC - Magnetic Confinement Theory and Modelling: Confinement
Poster
Recent simulations in three-dimensional (3-D) magnetically confined plasmas show various aspects of plasma turbulence, and numerical diagnostics using 3-D simulation data of helical plasmas have been carried out. Here we present results of turbulence analyses (i) in simplified geometry for detailed nonlinear mechanism of heat transport, and (ii) in real 3-D geometry for comprehensive...
Richard Majeski
(Princeton Plasma Physics Lab)
19/10/2016, 08:30
EXS - Magnetic Confinement Experiments: Stability
Poster
Discharges with high edge electron temperatures and flat radial electron temperature profiles, extending to the last closed flux surface, and into the low field side scrape-off layer, have now been achieved in the Lithium Tokamak eXperiment (LTX), with lithium-coated walls. Flat temperature profiles are a long-predicted consequence of low recycling boundary conditions [S. Krasheninnikov, L....
Dr
Michio Okabayashi
(Princeton Plasma Physics Laboratory)
19/10/2016, 08:30
EXS - Magnetic Confinement Experiments: Stability
Poster
Resistive and quasilinear 3D modeling is improving the understanding of recent experiments [1] carried out in DIII-D and RFX-Mod, in which disruptions were prevented by means of electromagnetic torque applied by non-axisymmetric (3D) coils. We will report the 3D aspects of experimental observations in comparison with finite resistivity (tearing) response by MARS-F and a time dependent torque...
Dr
Brian LaBombard
(MIT Plasma Science and Fusion Center)
19/10/2016, 08:30
EXS - Magnetic Confinement Experiments: Stability
Poster
The improved impurity screening characteristics of the high-field side scrape-off layer to local impurity sources, previously reported for single null geometries, is found to be retained in double null configurations - strengthening the argument for locating current drive and heating actuators on the high-field side.
The high-field-side (HFS) scrape-off layer (SOL) is known to exhibit...
Dr
Aaron Hossack
(University of Washington)
19/10/2016, 08:30
EXS - Magnetic Confinement Experiments: Stability
Poster
The Helicity Injected Torus - Steady Inductive (HIT-SI) program studies efficient, steady-state current drive for magnetic confinement plasmas using a novel experimental method. Stable, high-beta spheromaks have been sustained using steady, inductive current drive which is significantly more efficient than RF or neutral beams when scaled to a reactor. Externally induced loop voltage and...
Dr
Milan Rajkovic
(University of Belgrade, Institute of Nuclear Sciences Vinca)
19/10/2016, 08:30
THC - Magnetic Confinement Theory and Modelling: Confinement
Poster
Recently, we have developed a comprehensive mathematical and computational framework for the analysis and quantification of self-organization [1]. Application of this method may resolve some of the important issues of fusion plasmas such as prediction of changes in the pattern formation and transport properties, to name a few. We assume that the system self-organizes if its complexity...
Dr
Mitsuru Honda
(Japan Atomic Energy Agency)
19/10/2016, 08:30
THC - Magnetic Confinement Theory and Modelling: Confinement
Poster
Capabilities of the integrated framework consisting of TOPICS, OFMC, VMEC and FORTEC-3D, have been extended to calculate toroidal rotation in fully non-axisymmetric perturbed magnetic fields, for demonstrating operation scenarios in actual tokamak geometry and conditions. It was found for the first time that the toroidally localized perturbed fields due to the test blanket modules (TBMs) and...
Dr
Daniele Bonfiglio
(Consorzio RFX, Padova, Italy)
19/10/2016, 08:30
THC - Magnetic Confinement Theory and Modelling: Confinement
Poster
Recent theoretical studies of the reversed-field pinch (RFP) have demonstrated the possibility of stimulating new quasi-single helicity (QSH) regimes by allowing a small helical deformation of the magnetic boundary. In particular, 3D nonlinear MHD modeling predicted QSH states based on non-resonant helicities are predicted to be more resilient to magnetic stochasticity induced by secondary...
Dr
David Gates
(PPPL)
19/10/2016, 08:30
EXS - Magnetic Confinement Experiments: Stability
Poster
Computational optimization has revolutionized the field of stellarator design. To date, optimizations have focused primarily on optimization of neoclassical confinement and ideal MHD stability, although limited optimization of other parameters has also been performed. One of the criticisms that has been levelled at this method of design is the complexity of the resultant field coils. Recently,...
Prof.
Yasushi Ono
(University of Tokyo)
19/10/2016, 08:30
EXS - Magnetic Confinement Experiments: Stability
Poster
A series of merging experiments: TS-3, TS-4 and MAST made clear the promising characteristics of reconnection heating for merging formation of high-beta spherical tokamak (ST) and field-reversed configuration (FRC). We found the reconnection outflow produces MW-class (<30MW in TS-3) ion heating power based on the findings:
(i) its ion heating energy that scales with square of the reconnecting...
Prof.
Luis Garcia
(Universidad Carlos III de Madrid)
19/10/2016, 08:30
THC - Magnetic Confinement Theory and Modelling: Confinement
Poster
Turbulence induced transport is one of the outstanding physics problems in plasma physics. In the turbulence induced transport issue, we began with the identification of turbulent flow structures using topological and geometric techniques on the framework of resistive MHD. The structure of the flow is filamentary. The filaments are vortices that are linked to the rational surfaces. At a given...
Dr
Helen Kaang
(National Fusion Research Institute)
19/10/2016, 08:30
THC - Magnetic Confinement Theory and Modelling: Confinement
Poster
We study how electromagnetic (EM) fluctuations impact on residual Reynolds stress in the context of the quasi-linear theory. Two-fluid model is employed to describe EM ion temperature gradient turbulence. Analyses show that not only the conventional parallel residual stress but also additional stress due to EM fluctuations strongly increase with plasma beta (=plasma thermal energy/magnetic...
Prof.
Uri Shumlak
(UsUWash)
19/10/2016, 08:30
EXS - Magnetic Confinement Experiments: Stability
Poster
The sheared-flow stabilized Z-pinch has been experimentally demonstrated to produce long-lived plasmas that satisfy radial force balance and are stable for thousands of exponential growth times. The sheared-flow stabilized Z-pinch has the potential to lead to a compact plasma confinement device that scales to fusion conditions. The stabilizing effect of a sheared axial flow on the m=1 kink...
Prof.
Geert Verdoolaege
(Ghent University)
19/10/2016, 08:30
EXS - Magnetic Confinement Experiments: Stability
Poster
The standard scaling law for the global energy confinement in H-mode tokamak plasmas provides a guideline for machine design and planning of operational scenarios. In addition, it is used as a benchmark to assess the quality of confinement in present experiments. However, owing to the complexity of the multi-machine data sets from which the scaling is derived, the coefficient estimates may...
Dr
Anthony W. Leonard
(USA)
19/10/2016, 08:30
EXS - Magnetic Confinement Experiments: Stability
Poster
Experiments on DIII-D have advanced the physics basis for simultaneously achieving a high pressure H-mode pedestal for high core plasma confinement with a highly dissipative divertor for protection of plasma facing components in future reactor tokamaks. These studies show achievement of this goal is governed by the coupling of several pedestal and divertor processes including: 1) the pedestal...
Dr
Sergey Medvedev
(Keldysh Institute of Applied Mathematics)
19/10/2016, 08:30
ICC - Innovative Confinement Concepts
Poster
Fusion research has to solve the power handling problem toward fusion demonstration reactor (DEMO). Tokamak plasma with negative triangularity and an outboard divertor X-point may offer such an opportunity as an innovative concept. The present paper extends this concept investigating single null negative triangularity tokamak (SN-NTT). Double null negative triangularity tokamak (DN-NTT)...
Dr
Vsevolod Soukhanovskii
(Lawrence Livermore National Laboratory)
19/10/2016, 08:30
EXS - Magnetic Confinement Experiments: Stability
Poster
Analyses of snowflake (SF) divertor experiments in NSTX and DIII-D show that the SF divertor can increase edge magnetic shear and modify pressure profiles of the H-mode pedestal enabling pedestal stability control while maintaining good H-mode confinement (H_98y2~1). The scrape-off layer (SOL) geometry modifications lead to reduced peak temperature of plasma-facing components (PFC) via...
Dr
Aaron Sontag
(Oak Ridge National Laboratory)
19/10/2016, 08:30
EXS - Magnetic Confinement Experiments: Stability
Poster
Core transport models predict that fusion power scales roughly as the square of the pressure at the top of the pedestal, so understanding the effects that determine pedestal structure in steady-state operational scenarios is important to project steady-state tokamak operational scenarios developed in DIII-D to ITER and other devices. Both experiments and modeling indicate that SOL conditions...
Ms
Linda Sugiyama
(Laboratory for Nuclear Science, UsMIT)
19/10/2016, 08:30
THC - Magnetic Confinement Theory and Modelling: Confinement
Poster
A large amount of evidence suggests that the bright loops that are
regularly observed in the sun's corona are magnetic flux ropes that confine plasma,
tied at both ends to structures in the photosphere.
Due to the difficulties of observation,
their steady states have never been explained.
Coronal loops resemble partial magnetic tori and
ideas from the equilibrium and stability of...
Dr
Jeremy Hanson
(Columbia University)
19/10/2016, 08:30
EXS - Magnetic Confinement Experiments: Stability
Poster
DIII-D experiments demonstrate high-performance, negative central shear (NCS) equilibria with enhanced stability when the minimum safety factor qmin exceeds 2, qualitatively confirming theoretical predictions of favorable stability in the NCS regime. The discharges exhibit good confinement and performance (H89 = 2.5, H98,Y2 = 1.5, βN = 4), and are ultimately limited by the ideal-wall...
Dr
Wendell Horton
(Institute of Fusion Studies, The University of Texas at Austin)
19/10/2016, 08:30
THC - Magnetic Confinement Theory and Modelling: Confinement
Poster
First stability and transport in RF driven plasmas in ITER-like geometries are investigated using new kinetically modified MHD stability equations analyzed with theory and advanced simulations. Extended MHD stability analysis describes in detail the outer most closed flux surfaces inside the magnetic separatrix where ions and electrons dynamics differ. The new physics includes the effect of...
Dr
Julio Martinell
(Nuclear Sciences Institute, National Autonomous University of Mexico)
19/10/2016, 08:30
THC - Magnetic Confinement Theory and Modelling: Confinement
Poster
In the first part we study the magnetic equilibrium of TJ-II using the VMEC code together SIESTA MHD code. The pressure profiles determine island geometry. For each island width we obtain the associated MHD energy in order to find a correlation between them and identify an island width that has better stability properties.
A dynamical analysis of magnetic islands is aimed at explaining the...
Prof.
Miklos Porkolab
(MIT)
19/10/2016, 08:30
EXS - Magnetic Confinement Experiments: Stability
Poster
Experimental results are presented where the macroscopic plasma conditions were manipulated by external actuators, such as injection of medium to low Zi impurity gases with ohmic heating (Alcator C-Mod) to dilute the main deuterium ion species, or deploy a different mix of NBI and ECH heating methods (DIII-D), thus enabling us to study the resulting changes in transport and turbulence....
Dr
Dmitri Orlov
(University of California San Diego)
19/10/2016, 08:30
EXS - Magnetic Confinement Experiments: Stability
Poster
In this work we show that the application of a “square wave” n=1 toroidal perturbation on DIII-D and KSTAR leads to significant n=3 toroidal sidebands. In the vacuum model, these n=3 sidebands assist in creation of wide stochastic field in the edge of the plasma. In KSTAR, the n=3 sideband fields create vacuum islands in the right places to extend the vacuum island overlap width to more than...
Mr
Robert Chahine
(LMFA, FrECL)
19/10/2016, 08:30
THC - Magnetic Confinement Theory and Modelling: Confinement
Poster
A notable influence of the shape of the plasma on the dynamics of RFPs is clearly illustrated by simulations of fully nonlinear visco-resistive magnetohydrodynamics. The axial mode-spectrum is qualitatively changed in cylinders with elliptic cross-section. The results suggest that shaping will change, and possibly improve the confinement of RFPs.
Dr
Sung Sik Kim
(National Fusion Research Institute)
19/10/2016, 08:30
THC - Magnetic Confinement Theory and Modelling: Confinement
Poster
Development of a self-consistent, core-edge integrated simulation capability is a long standing problem in fusion simulation program. Such capability would yield insight into questions related to global profile dynamics originating from L to H transition and internal transport barrier formation. Starting from a tokamak edge plasma simulation code, BOUT++ has evolved into a versatile framework...
Dr
Robert S. Wilcox
(Oak Ridge National Laboratory)
19/10/2016, 08:30
EXS - Magnetic Confinement Experiments: Stability
Poster
When resonant magnetic perturbations are applied to suppress edge localized modes using the internal coil set in the DIII-D tokamak with toroidal mode number n=3, measurements of density fluctuations at toroidally separate locations using beam emission spectroscopy (BES) and Doppler back-scattering show larger fluctuation amplitudes in one toroidal phasing than the other. This relationship is...
Dr
Yusuke Kosuga
(Institute for Advanced Study, Kyushu University)
19/10/2016, 08:30
THC - Magnetic Confinement Theory and Modelling: Confinement
Poster
Recent progress on the modeling of turbulent transport of parallel flow momentum is reported. Compared to the Reynolds stress or the convective term, the role of the triplet (nonlinear) flux is emphasized. The triplet term is calculated in the wave turbulence limit. The result indicates that the nonlinear flux becomes important compared to the stress term in the region with the steep intensity...
Dr
George McKee
(University of Wisconsin-Madison)
19/10/2016, 08:30
EXS - Magnetic Confinement Experiments: Stability
Poster
Low-wavenumber density fluctuations exhibit rapidly changing characteristics during the current ramp-up phase of ITER-like discharges that reflect a complex interaction between evolving electron transport, safety factor (q) and kinetic profiles and low-order rational surfaces. These measurements and analysis can explain discrepancies between various transport models and measurements during the...
Mr
L. Schmitz
(University of California-Los Angeles)
19/10/2016, 08:30
EXS - Magnetic Confinement Experiments: Stability
Poster
Understanding flow drive and damping across the relevant ion collisionality range is crucial for connecting the L-H transition trigger physics to the macroscopic L-H power threshold scaling. This is of utmost importance for minimizing the auxiliary heating power required for H-mode access in burning plasmas. It is shown here for the first time that the main-ion poloidal flow acceleration is...
Dr
Chris McDevitt
(Los Alamos National Laboratory)
19/10/2016, 08:30
THC - Magnetic Confinement Theory and Modelling: Confinement
Poster
In this work we discuss the efficiency of various turbulent mechanisms for modifying the plasma current. The first mechanism results from the establishment of an equilibrium between trapped and passing electrons due to resonant scattering by microturbulence. This mechanism is closely analogous to the familiar neoclassical bootstrap current except that it relies on wave-particle interactions to...
Dr
Weixing Wang Wang
(Princeton University Plasma Physics Laboratory)
19/10/2016, 08:30
THC - Magnetic Confinement Theory and Modelling: Confinement
Poster
The main focus of this paper is on developing physical understanding and a first-principles-based model for predicting intrinsic rotation profiles in magnetic fusion experiments, including ITER. It is shown for the first time that turbulent fluctuation-driven residual stress can account for both the shape and magnitude of the observed intrinsic toroidal rotation profile. Specifically, nonlinear,...
Morgan Shafer
(Oak Ridge National Laboratory)
19/10/2016, 08:30
EXS - Magnetic Confinement Experiments: Stability
Poster
Measurements of islands induced by resonant magnetic perturbations (RMP) in the core of a L-mode DIII-D plasma are used to challenge predicted screening trends from linearized extended MHD and to examine modeling of the nonlinearly saturated island state. In these plasmas, fine torque scans reveal that large n=1 RMP-induced islands are present at multiple mode-rational surfaces at low...
Dr
Guilhem Dif-Pradalier
(CEA, IRFM, F-13108 Saint-Paul-lez-Durance cedex, France)
19/10/2016, 08:30
THC - Magnetic Confinement Theory and Modelling: Confinement
Poster
Large-scale global organisation of turbulence has attracted persistent interest in fusion plasmas as a means to control transport and access improved confinement. It has practical consequences on zonal flow formation and sustainment, on front propagation—a natural tendency in heat flux-driven turbulence—or on the spreading of turbulence in regions of quasi-linear stability.
In this paper we...
Dr
Brent Covele
(General Atomics)
19/10/2016, 08:30
EXS - Magnetic Confinement Experiments: Stability
Poster
Highly flared, highly flux-expanded X-Divertors (XDs) on DIII-D detached at a lower Greenwald fraction and higher pedestal pressure than standard divertors (SDs), strongly reducing problematic plasma exhaust at the target, allowing for improved control of the detachment front, and maintaining a higher-confinement H-mode necessary for a future fusion reactor. XDs exhibit lower parallel ion...
Dr
Klaus Hallatschek
(Max-Planck-Institute for Plasma Physics)
19/10/2016, 08:30
THC - Magnetic Confinement Theory and Modelling: Confinement
Poster
Fluid turbulence simulations cannot describe the kinetic effects due to the scarcity of collisions in tokamak plasmas but allow for much higher spatial resolution than kinetic simulations and become more reliable at large collision frequencies. Conversely, gyrokinetic simulations, the standard in current tokamak turbulence modeling, cannot be performed with the full set of nonlinearities that...
