A5021330260- Magnetic confinement fusion research
- Ionosphere and magnetosphere dynamics
- Particle accelerators and beam dynamics
- Solar and Space Plasma Dynamics
- Plasma Diagnostics and Applications
- Laser-Plasma Interactions and Diagnostics
- Fusion materials and technologies
- Superconducting Materials and Applications
- User Authentication and Security Systems
- Atomic and Molecular Physics
- Ion-surface interactions and analysis
- Advanced Authentication Protocols Security
- Astronomical Observations and Instrumentation
- Physics of Superconductivity and Magnetism
- Cyclone Separators and Fluid Dynamics
- Chaos-based Image/Signal Encryption
- Flow Measurement and Analysis
- X-ray Spectroscopy and Fluorescence Analysis
- Fluid Dynamics and Turbulent Flows
- Respiratory Support and Mechanisms
- Radiation Effects in Electronics
- Astro and Planetary Science
- IPv6, Mobility, Handover, Networks, Security
- Fluid Dynamics and Mixing
- Atomic and Subatomic Physics Research
National Institute for Fusion Science
2016-2025
National Institutes of Natural Sciences
2016-2025
The Graduate University for Advanced Studies, SOKENDAI
2020-2025
Kyushu University
2023-2024
Institute of Natural Science
2024
Takasago (United States)
2023-2024
Kochi University of Technology
2000-2023
Obayashi (Japan)
2021-2023
Nagoya Institute of Technology
2022
Ushio (Germany)
2022
This Letter presents experimental confirmation of the presence zonal flows in magnetically confined toroidal plasma using an advanced diagnostic system--dual heavy ion beam probes. The simultaneous observation electric field at two distant locations (approximately 1.5 m apart) high temperature 1 keV) provides a fluctuation spectrum (or flow), spatiotemporal structure (characteristic radial length approximately cm and lifetime ms), their long-range correlation with symmetry (n=0), difference...
A thermal transport barrier resulting in a high central electron temperature of $\ensuremath{\sim}2\mathrm{keV}$ is established the core electron-cyclotron-resonance heated plasmas Compact Helical System Heliotron/Torsatron. The formation correlated with reduction density fluctuations and structural change radial electric field profile at location. results suggest that decrease fluctuation should contribute to anomalous drastic increase barrier.
The present status of experiments on zonal flows in magnetic confinement is examined. innovative use traditional and modern diagnostics has revealed unambiguously the existence flows, their spatio-temporal characteristics, relationship to turbulence effects confinement. In particular, a number observations have been accumulated oscillatory branch named geodesic acoustic modes, suggesting necessity for theories give proper description. addition these basic properties several new methods...
Extremely hollow profiles of impurities (denoted as “impurity hole”) are observed in the plasma with a steep gradient ion temperature after formation an internal transport barrier (ITB) Large Helical Device [A. Iiyoshi et al., Nucl. Fusion 39, 1245 (1999)]. The radial profile carbon becomes during ITB phase and central density keeps dropping reaches 0.1%–0.3% at end phase. diffusion coefficient convective velocity evaluated from time evolution assuming convection constant ITB. analysis gives...
We report observations of the dynamic response micro-fluctuations and turbulent flux to a low-frequency heating power modulation in Large Helical Device. The responses heat micro-fluctuation intensity differ from that change temperature gradient. This result violates local transport model, where turbulence is determined by A new relationship between flux, gradient found. In addition gradient, rate proposed as new, direct controlling parameter explain fast against periodic power.
Achievement of reactor relevant plasma condition in Helical type magnetic devices and exploration its related physics fusion engineering are the aim Large Device (LHD) project. In recent experiments on LHD, we have achieved ion-temperature 8.1 keV at 1 × 1019 m−3 by optimization wall conditioning using long pulse discharge Ion Cyclotron Heating (ICH). The electron temperature 10 1.6 was also Electron (ECH). For further improvement performance, upgrade (LHD), including deuterium experiment,...
The Chinese First Quasi-axisymmetric Stellarator (CFQS) is a joint project of international collaboration. It designed and fabricated by Southwest Jiaotong University (SWJTU) in China National Institute for Fusion Science (NIFS) Japan. In this work, plasma boundary modular-coil system the CFQS have been optimized via scan magnetic configurations with various aspect ratios. present target parameters are as follows: toroidal periodic number, ratio, field strength major radius 2, 4.0, 1.0 T, m,...
Alfvén eigenmode (AE) activity driven by NBI-produced fast ions is observed in TJ-II plasmas. A two-step response of the measured AEs to electron cyclotron heating (ECH) power seen. In a first step, continuous character unstable changes chirping marginally when moderate values ECH are applied NBI-only-heated plasma. second significant reduction AE amplitude doubled. This stabilizing effect has been experimentally confirmed both on shot-by-shot basis and along single discharge means...
A new bursting m=1/n=1 instability (m,n: poloidal and toroidal mode numbers) with rapid frequency chirping down has been observed for the first time in a helical plasma intense perpendicular neutral beam injection. This is destabilized peripheral region by resonant interaction between helically trapped energetic ions resistive interchange mode. large radial electric field induced near edge due to enhanced transport of mode, leads clear change flow, suppression microturbulence, triggering an...
The Chinese First Quasi-axisymmetric Stellarator (CFQS) is a new quasi-axisymmetric experimental device planned for construction at South West Jiaotong University (SWJTU), China. This joint project of the National Institute Fusion Science (NIFS) and SWJTU. present paper discusses equilibrium configuration CFQS with major radius 1.0 m, toroidal magnetic field strength T, an aspect ratio 4.0. As stellarator, tokamak-like bootstrap current expected. magnitude was estimated by BOOTSJ code. Next,...
Abrupt and strong excitation of a mode has been observed when the frequency chirping energetic-particle driven geodesic acoustic (EGAM) reaches twice (GAM) frequency. The secondary is GAM frequency, which half-frequency primary EGAM. Based on analysis spatial structures, identified as GAM. phase relation between EGAM locked, evolution growth rate indicates nonlinear excitation. results suggest that contributes to destabilization subcritical mode.
The deuterium (D) operation was initiated in the LHD 2017. In first campaign of D experiments, we successfully extended high temperature regime LHD. new record ion (Ti) 10 keV associated with internal transport barrier (ITB) achieved due to several operational optimization. thermal confinement characteristics ITB plasmas were compared between hydrogen and discharges. effective diffusivity ion-ITB found be smaller discharges than that H profiles Ti, electron density, impurity Ti strongly...
In accelerators, ion beams are often accelerated using electrostatic accelerating tubes. This paper reports on a method to improve the beam transport efficiency without adding new components system. High currents suffer from loss in line. When Au negative injected into tandem accelerator, numerical simulations of low-energy have found that increases significantly when or Cu current exceeds 100 ${\mu}$A due space-charge effects. We is improved by remaining constant energy at multi-stage...
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...
The bifurcation nature of the electrostatic structure is studied in toroidal helical plasma Compact Helical System (CHS) [K. Matsuoka et al., Proceedings 12th International Conference on Plasma Physics and Controlled Nuclear Fusion Research, Nice, 1988 (International Atomic Energy Agency, Vienna, 1989), Vol. 2, p. 411]. Observation bifurcation-related phenomena introduced, such as characteristic patterns discrete potential profiles, various self-sustained oscillations termed electric...
Energetic-ion losses induced by toroidicity-induced Alfvén eigenmodes (TAEs) and resistive interchange modes (RICs) were observed in neutral-beam heated plasmas of the Large Helical Device (LHD) at a relatively low toroidal magnetic field level (⩽0.75 T). The energy pitch angle lost ions are detected using scintillator-based lost-fast ion probe. Each instability increases having certain energy/pitch angle. TAE bursts preferentially induce energetic beam co-passing orbits from injection E =...
Reversed-shear Alfvén eigenmodes were observed for the first time in a helical plasma having negative q₀'' (the curvature of safety factor q at zero shear layer). The frequency is swept downward and upward sequentially via variation maximum q. calculated by ideal MHD theory are consistent with experimental data. sweeping mainly determined effects energetic ions bulk pressure gradient. Coupling reversed-shear ion driven geodesic acoustic modes generates multitude frequency-sweeping modes.
The peaked ion-temperature profile with steep gradient, the so-called ion internal transport barrier (ion ITB), was formed in neutral beam heated plasmas on Large Helical Device and high-ion-temperature regime of helical has been significantly extended. thermal diffusivity ITB plasma decreases down to neoclassical level. heavy probe observed smooth potential negative radial electric field root) core region where significantly. large toroidal rotation also momentum analysed qualitatively....
The discharge scenario of high temperature plasma with a helical configuration has significantly progressed. increase central ion due to the reduction wall recycling was clearly observed. peaking heating profile and charge exchange loss energetic ions play an important role for further improvement heat transport in internal barrier (ITB) core. ITB electron have been successfully integrated superposition centrally focused cyclotron plasma, regime comparable (Ti ~ Te) extended. width formed is...