A5039907331- Magnetic confinement fusion research
- Superconducting Materials and Applications
- Ionosphere and magnetosphere dynamics
- Fusion materials and technologies
- Particle accelerators and beam dynamics
- Solar and Space Plasma Dynamics
- Laser-Plasma Interactions and Diagnostics
- Plasma Diagnostics and Applications
- Atomic and Subatomic Physics Research
- Nuclear reactor physics and engineering
- Nuclear Materials and Properties
- Dust and Plasma Wave Phenomena
- Particle Accelerators and Free-Electron Lasers
- Plasma and Flow Control in Aerodynamics
- High-Velocity Impact and Material Behavior
- Spacecraft and Cryogenic Technologies
- Astro and Planetary Science
- Physics of Superconductivity and Magnetism
- Nuclear Engineering Thermal-Hydraulics
- Ammonia Synthesis and Nitrogen Reduction
- High-pressure geophysics and materials
- Non-Destructive Testing Techniques
- Theoretical and Computational Physics
- Advanced Optical Imaging Technologies
- Magnetic Bearings and Levitation Dynamics
National Institutes for Quantum Science and Technology
2016-2023
National Institute for Fusion Science
2001-2019
Fusion Academy
2019
Fusion (United States)
2019
Japan Atomic Energy Agency
2007-2016
Nagoya University
1999-2005
Forschungszentrum Jülich
2004-2005
Advanced Science Research Center
2004
The plasma rotation necessary for stabilization of resistive-wall modes (RWMs) is investigated by controlling the toroidal with external momentum input injection tangential neutral beams. observed threshold 0.3% Alfvén velocity and much smaller than previous experimental results obtained magnetic braking. This low critical has a very weak beta dependence as ideal wall limit approached. These indicate that large plasmas such in future fusion reactors rotation, requirement additional feedback...
Rseduction of heat loading appropriate for the plasma facing components such as divertor is crucial a fusion reactor. Power handling by large radiative power loss has been studied in long pulse ELMy H-mode discharges on JT-60U (τ d = 30–35 s). Case 1 argon (Ar) seeding into standard plasmas, where radiation confined region main caused change ELM characteristics from Type-I to Type-III. 2 combination Ar and nitrogen (Ne) gas plasmas with an internal transport barrier (ITB). For case 1, both...
The JT-60SA device has been designed as a highly shaped large superconducting tokamak with variety of plasma actuators (heating, current drive, momentum input, stability control coils, resonant magnetic perturbation W-shaped divertor, fuelling, pumping, etc) in order to satisfy the central research needs for ITER and DEMO. In ITER- DEMO-relevant parameter regimes DEMO-equivalent shapes, quantifies operation limits, responses operational margins terms MHD stability, transport confinement,...
The results of stabilizing neoclassical tearing modes (NTMs) with electron cyclotron current drive (ECCD) in JT-60U are described emphasis on the effectiveness stabilization. range minimum EC wave power needed for complete stabilization an m / n = 2/1 NTM was experimentally identified two regimes using unmodulated ECCD to clarify behaviours different plasma parameters: 0.2 < j BS 0.4 W sat d ∼ 3 and marg 2, 0.35 0.46 1.5 2. Here, poloidal toroidal mode numbers; EC-driven density bootstrap...
Recent high-β DIII-D (Luxon J.L. 2002 Nucl. Fusion 42 64 ) experiments with the new capability of balanced neutral beam injection show that resistive wall mode (RWM) remains stable when plasma rotation is lowered to a fraction per cent Alfvén frequency by reducing angular momentum in discharges minimized magnetic field errors. Previous yielded high threshold (of order few frequency) for RWM stabilization resonant braking was applied lower rotation. We propose previously observed can be...
Repetitive bursting instabilities with strong frequency chirping occur in highbeta, beam-heated plasmas safety factor q > 1 the DIII-D tokamak.Although mode structures differ, many ways, off-axis fishbones are similar to = first observed on Poloidal Divertor Experiment (PDX).The modes driven by energetic trapped ions at fastion precession frequency.During a burst, changes most rapidly as reaches its maximum amplitude.Larger amplitude bursts have larger growth rates and chirps.Unlike PDX...
The characteristics of momentum transport and plasma rotation in the toroidal direction are studied, using near-perpendicular neutral beam injection (PERP-NBI), co tangential counter (CTR) NBI JT-60U. Diffusive non-diffusive terms evaluated from transient analysis by source modulation. Fast ion losses due to field ripple, which locally induces edge CTR rotation, used as a novel source. Parameter dependence these coefficients i.e. diffusivity (χϕ) convection velocity (Vconv), relation between...
The first results of the Dynamic Ergodic Divertor in TEXTOR, when operating m/n=3/1 mode configuration, are presented. deeply penetrating external magnetic field perturbation this configuration increases toroidal plasma rotation. Staying below excitation threshold for m/n=2/1 tearing mode, rotation is always direction current, even if projection rotating opposite direction. observed consistent with a radial electric field, generated by an enhanced electron transport ergodic layers near...
The toroidal plasma rotation generated by the external momentum input and itself (intrinsic rotation) has been separated through a novel transport analysis in JT-60U tokamak device. rotation, which is not determined coefficients input, observed. It found that this intrinsic locally local pressure gradient increases with increasing gradient. This trend almost same for various plasmas: low high confinement mode, co counterrotating plasmas.
Abstract In the late 1990s, fusion scientists at Japanese tokamak JT-60U discovered abrupt large-amplitude events during beam-driven deuterium plasma experiments. A large spike in magnetic fluctuation signal followed by a drop neutron emission rate indicates that energetic ions abruptly migrate out of core an intense burst Alfvén waves lasts only 0.3 ms. With continued beam injection, ion population recovers until next event occurs 40–60 ms later. Here we present results from simulations...
Recent results of energetic ion driven MHD instabilities observed in the heliotron/torsatron devices Compact Helical System (CHS) and Large Device (LHD) are presented. Alfvén eigenmodes (AEs) fishbone-like burst modes (FBs) destabilized by ions were NBI heated plasmas CHS. The AEs toroidicity induced (TAEs) global (GAEs), where identified toroidal mode numbers n = 1 2 for TAEs 0 GAEs. frequencies FBs less than, at most, half minimum TAE gap frequency do not exhibit obvious density dependence...
We have observed a bursting mode in the high-$\ensuremath{\beta}$ plasmas above ideal $\ensuremath{\beta}$ limit without conducting wall. The frequency is chirping down as amplitude increases, and its initial value close to precession of trapped energetic particle from perpendicular neutral beams. structure radially extended with peak around $q=2$ surface. This can finally trigger resistive wall (RWM) despite enough plasma rotation for RWM stabilization. It concluded that driven by...
Aiming at optimization of current profile in high-β plasmas for higher confinement and stability, a real-time control system the minimum safety factor ( q min ) using off-axis drive has been developed. The can raise centre help to avoid instability that limits performance plasma. controls injection power lower-hybrid waves, hence its driven order . is demonstrated plasma, where follows temporally changing reference min,ref from 1.3 1.7. Applying another discharge (β N = 1.7, β p 1.5) with m...
The performance and sustained duration of long-pulse discharges for the ‘ITER hybrid scenario’ have been improved in JT-60U. modification power supply systems three perpendicular neutral beam (NB) injections provides a long period central NB heating up to 30 s, which is important keeping internal transport barrier (ITB). peaked density profile core plasma can be maintained even when at pedestal increased latter phase discharge due increase divertor recycling. Then, pressure attributed ITB...
This paper reports the recent development of reversed shear plasmas with a high bootstrap current fraction (fBS) towards reactor relevant regime. The previous operation regime fBS is limited at q95 > 8 because low beta limit, whereas = 5–6 envisaged in DEMO reactor. In 2008 JT-60U experimental campaign, plasma was emphasized lower by developing large volume configuration close to conducting wall for stabilization. Thanks stabilization, exceeding no-wall limit are obtained ∼ 5.3. Though...
An energetic-particle (EP)-driven “off-axis-fishbone-like mode (OFM)” often triggers a resistive wall (RWM) in JT-60U and DIII-D devices, preventing long-duration high-βN discharges. In these experiments, the EPs are energetic ions (70–85 keV) injected by neutral beams to produce high-pressure plasmas. EP-driven bursting events reduce EP density plasma rotation simultaneously. These changes significant low-rotation plasmas, where RWM stability is predicted be strongly influenced precession...
Recurring bursts of chirping Alfvén modes that were observed in JT-60U tokamak plasmas driven by negative-ion-based neutral beams (N-NB) are reproduced first-principle simulations performed with an extended version the hybrid code MEGA. This simulates interactions between gyrokinetic fast ions and magnetohydrodynamic (MHD) presence a realistic ion source collisions, so it self-consistently captures dynamics across wide range time scales (0.01–100 ms). The simulation confirms experimentally...
To investigate energetic ion transport induced by bursting modes in the frequency range of Alfvén eigenmodes, which is called abrupt large-amplitude events (ALEs) driven negative-ion-based neutral beam (N-NB) injection, neutron emission profile measurement and charge exchange (CX) particle (flux) using a natural diamond detector have been performed simultaneously JT-60U. It found from CX that particles limited energy (100–370 keV) are enhanced due to ALEs, radial flattened. The change...
The magnetic field penetration process into a magnetized plasma is of basic interest both for physics and astrophysics. In this context special measurements on the amplification are performed by Hall probe dynamic ergodic divertor (DED) TEXTOR tokamak data interpreted two-fluid model. It observed that growth forced reconnection rotating DED accompanied change fluid rotation. differential rotation frequency between plays an important role in excitation tearing modes. momentum input from to...
A spontaneous transition phenomena between two states of a plasma with an internal transport barrier (ITB) is observed in the steady-state phase magnetic shear negative JT-60U tokamak. These ITB are characterized by different profiles second radial derivative ion temperature inside region (one has weak concave shape and other strong convex shape) degrees sharpness interfaces L mode region, which determined turbulence penetration into region.
A complex multistage transition of the edge radial electric field is observed in JT-60U H-mode phase without localized mode. An interesting feature that poloidal rotation velocity carbon impurity ions changes later H-phase a comparable change main ion pressure gradient, indicating parallel momentum (and particle) balance channel.
This paper summarizes the main achievements of RFX fusion science program in period between 2008 and 2010 IAEA Fusion Energy Conferences. RFX-mod is largest reversed field pinch world, equipped with a system 192 coils for active control MHD stability. The discovery understanding helical states electron internal transport barriers core temperature >1.5 keV significantly advances perspectives configuration. Optimized experiments plasma current up to 1.8 MA have been realized, confirming...
We have observed a fishbone-like mode in high-β plasmas above the ideal β limit without conducting wall. The frequency chirps down, and its initial value is close to precession of trapped fast ions produced by perpendicularly injected neutral beams. This can often induce resistive wall (RWM). mainly N plasma where an kink-ballooning (IKBM) RWM are marginally stable. Since this were simultaneously observed, attributed interaction between stable IKBM stabilized Actually, MARG2D analysis shows...
Variation of the plasma position relative to centre helical coil winding is a very effective means controlling MHD stability and trapped particle confinement in heliotron/torsatron systems, but improving one these two characteristics with this parameter simultaneously has detrimental effect on other. The inward shifted configuration favourable for drift orbit optimization predicted be unstable according Mercier criterion. Various physics problems, such as electric field structure, rotation...
Dynamics of ion internal transport barrier (ITB) formation and impurity both in the Large Helical Device (LHD) heliotron JT-60U tokamak are described. Significant differences between plasmas observed. The location ITB moves outwards during regardless sign magnetic shear JT-60U, becomes more localized with negative shear. In LHD, a low T e / i ratio (<1) target plasma high power heating is found to be necessary achieve tends expand or inwards depending on condition plasmas. Associated ITB,...