A5080077705- Magnetic confinement fusion research
- Plasma Diagnostics and Applications
- Particle accelerators and beam dynamics
- Fusion materials and technologies
- Superconducting Materials and Applications
- Ionosphere and magnetosphere dynamics
- Atomic and Molecular Physics
- Laser-induced spectroscopy and plasma
- Laser-Plasma Interactions and Diagnostics
- Solar and Space Plasma Dynamics
- X-ray Spectroscopy and Fluorescence Analysis
- Nuclear Physics and Applications
- Nuclear reactor physics and engineering
- Advanced Data Storage Technologies
- Physics of Superconductivity and Magnetism
- Atomic and Subatomic Physics Research
- Laser Design and Applications
- Nuclear Materials and Properties
- Spacecraft and Cryogenic Technologies
- Dust and Plasma Wave Phenomena
- Astro and Planetary Science
- Particle Detector Development and Performance
- Electromagnetic Launch and Propulsion Technology
- Distributed and Parallel Computing Systems
- Electron and X-Ray Spectroscopy Techniques
Chubu University
2016-2019
National Institute for Fusion Science
2006-2015
The Graduate University for Advanced Studies, SOKENDAI
2002-2015
National Institutes of Natural Sciences
2000-2013
Kyoto University
1984-2005
Centre of Advanced Studies
2002
Fusion Academy
2002
Fusion (United States)
2002
Toin University of Yokohama
1999
Fukuoka Institute of Technology
1993
The Large Helical Device (LHD) has successfully started running plasma confinement experiments after a long construction period of eight years. During the and machine commissioning phases, variety milestones were attained in fusion engineering which led to first operation, was ignited on 31 March 1998. Two experimental campaigns carried out In campaign, magnetic flux mapping clearly demonstrated nested structure surfaces. conducted with second harmonic 84 82.6 GHz ECH at heating power input...
The Large Helical Device (LHD) experiments [O. Motojima, et al., Proceedings, 16th Conference on Fusion Energy, Montreal, 1996 (International Atomic Energy Agency, Vienna, 1997), Vol. 3, p. 437] have started this year after a successful eight-year construction and test period of the fully superconducting facility. LHD investigates variety physics issues large scale heliotron plasmas (R=3.9 m, a=0.6 m), which stimulates efforts to explore currentless disruption-free steady under an optimized...
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.
We have measured extreme ultraviolet (EUV) spectra from highly charged tungsten ions in low-density and high-temperature plasmas produced the Large Helical Device at National Institute for Fusion Science. The EUV emitted after injection of a pellet into hydrogen plasma were recorded temperatures 1.5 3 keV dominated by an intense transition array 4.5–6.5 nm region, profile extent which was different both spectra. Some discrete lines present identified comparison with existing spectral data...
QUEST focuses on the steady state operation of spherical tokamak by controlled PWI and electron Bernstein wave current drive. One main purposes is an achievement long duration discharge with MW-class injected power. As result, should be operated in challenging region heat particle handling. To do handling, high temperature all metal wall up to 623 K closed divertors are planned, which realize steady-state under recycling ratio, R = 1. This a dispensable check DEMO, because pumping avoided as...
This Letter presents the discovery of macroscale electron temperature fluctuations with a long radial correlation length comparable to plasma minor radius in toroidal plasma. Their spatiotemporal structure is characterized by low frequency $\ensuremath{\sim}1--3\text{ }\text{ }\mathrm{kHz}$, ballistic propagation, poloidal or mode number $m/n=1/1$ (or $2/1$), and an amplitude $\ensuremath{\sim}2%$ at maximum. Nonlinear coupling between long-range microscopic identified. A change fluctuation...
Evidence for a reduction of heat transport inside the magnetic island O point is observed from propagation cold pulse produced by tracer encapsulated solid pellet in Large Helical Device. A small peak and slow are island. significant result that electron diffusivity estimated to be 0.2 m(2)/s which smaller than outside an order magnitude.
Edge cooling experiments with a tracer-encapsulated solid pellet in the large helical device (LHD) show significant rise core electron temperature (the maximum is around 1 keV) as well many tokamaks. This experimental result indicates possible presence of nonlocality heat transport plasmas where turbulence cause anomalous dominates. The nonlocal LHD takes place almost same parametric domain (e.g. low density) Meanwhile, results some new aspects rise, for example delay relative to penetration...
The Large Helical Device (LHD) and Wendelstein 7-X (W7-X, under construction) are experiments specially designed to demonstrate long-pulse (quasi steady state) operation, which is an intrinsic property of stellarators heliotrons. Significant progress has been made in establishing high performance plasmas. A crucial point the increasing impurity confinement at density observed several machines (TJ-II, W7-AS, LHD) can lead accumulation early pulse termination by radiation collapse. In...
Bright narrow band emission observed in optically thin plasmas of high-Z elements the extreme ultraviolet spectral region follows a quasi-Moseley's law. The peak wavelength can be expressed as λ=(21.86±12.09)×R∞−1×(Z−(23.23±2.87))−(1.52±0.12), where R∞ is Rydberg constant. varies from 13.5 nm to 4.0 atomic number, Z, increases Z = 50 83. range wavelengths available hot permits development bright laboratory-scale sources for applications including x-ray microscopy and absorption fine...
Transient transport experiments are performed in plasmas with and without internal barriers (ITB) on LHD JT-60U. The dependence of χe the electron temperature, Te, temperature gradient, ∇Te, is analysed an empirical non-linear heat model. In ITB, two different types non-linearity observed from cold/heat pulse propagation: depends Te ∇Te JT-60U, while weak LHD. Inside ITB region, there none or both Growth cold driven by negative inside region (LHD) near boundary (JT-60U).
Internal transport barriers with respect to electron thermal (eITB) were observed in the large helical device, when cyclotron resonance heating (ECH) power was highly localized on centre of a plasma sustained by neutral beam injection. The eITB is characterized high central temperature 6–8 keV an extremely steep gradient, as 55 m−1 and low diffusivity within normalized average radius ρ≈0.3 well existence clear thresholds for ECH collisionality.
Characteristics of MHD instabilities and their impacts on plasma confinement are studied in current free plasmas the Large Helical Device. Spontaneous L–H transition is often observed high beta close to 2% at low toroidal fields (Bt ⩽ 0.75 T). The stored energy starts rise rapidly just after accompanying clear electron density but quickly saturates due growth m = 2/n 3 mode (m n: poloidal numbers), rational surface which located edge barrier region, localized (ELM) like activities having...
Confinement of a plasma initiated and heated by electron cyclotron-resonance-frequency waves has been studied in the Heliotron-E. The observed parameters were ${T}_{e}=500\ensuremath{-}100$ eV, ${T}_{i}\ensuremath{\simeq}100$ ${\overline{n}}_{e}=4\ifmmode\times\else\texttimes\fi{}{10}^{12}$ ${\mathrm{cm}}^{\ensuremath{-}3}$ at $B=10$ kG. energy decay time was 40\ifmmode\pm\else\textpm\fi{}8 msec particle confinement estimated to be more than 70 msec. These results offer considerable...
Remarkable progress in the physical parameters of net-current free plasmas has been made Large Helical Device (LHD) since last Fusion Energy Conference Chengdu, 2006 (Motojima et al 2007 Nucl. 47 S668 ). The beta value reached 5% and a high-beta state beyond 4.5% from diamagnetic measurement maintained for longer than 100 times energy confinement time. density temperature regimes have also extended. central exceeded 1 × 10 21 m −3 due to formation an internal diffusion barrier . ion 5.2 keV...
The method of tracer-encapsulated solid pellet (TESPEL) is now flourishing in various fields. original purpose to study impurity transport without giving substantial perturbation on the plasma implemented successfully for years. In addition this, TESPEL being intensively applied thermal (especially non-local) transport, high energy particles with use ablation cloud, and spectroscopy from viewpoint atomic data. It further growing up utilization multiple tracer methods which was not planned at...
Pellet injection has been used as a primary fuelling scheme in the Large Helical Device. With pellet injection, operational region of NBI plasmas extended to higher densities while maintaining favourable dependence energy confinement on density, and several important values, such plasma stored 0.88 MJ, time 0.3 s, β 2.4% at 1.3 T density 1.1 × 1020 m -3, have achieved. These parameters cannot be attained by gas puffing. Ablation subsequent behaviour investigated. The measured penetration...
In LHD discharges a significant enhancement of the global energy confinement has been achieved for first time in helical device with an edge thermal barrier, which exhibits sharp gradient at temperature profile. Key features associated barrier are quite different from those seen tokamaks: (i) almost no change particle (including impurity) transport, (ii) gradual formation (iii) very high ratio to average temperature, and (iv) relaxation phenomenon. These attractive applying future reactor...
Recent large helical device experiments revealed that the transition from ion root to electron occurred for first time in neutral-beam-heated discharges, where no nonthermal electrons exist. The measured values of radial electric field were found be qualitative agreement with those estimated by neoclassical theory. A clear reduction thermal diffusivity was observed after mode as predicted theory when loss is more dominant than anomalous loss.
An internal transport barrier (ITB) was observed in the electron temperature profile Large Helical Device [O. Motojima et al., Phys. Plasmas 6, 1843 (1999)] with a centrally focused intense cyclotron resonance microwave heating. Inside ITB core improved, and high temperature, exceeding 10 keV low density, achieved collisionless regime. The formation of electron-ITB is correlated neoclassical root strong radial electric field determined by ambipolar flux. direction tangentially injected...
Bolometer diagnostics are installed on the Large Helical Device (LHD) to provide measurements of total (broad spectrum) electromagnetic radiation emitted by plasma. Three types detectors used: resistive metal film bolometers, absolute extreme ultraviolet photodiodes and infrared imaging video bolometers. Details installation in LHD given for each type detector. The detector calibration, data analysis tomography techniques described compared sample results shown.
The structure of the radial electric field and heat transport at magnetic island in large helical device (LHD) are investigated by measuring profile poloidal flow with charge exchange spectroscopy time evolution electron temperature ECE. A vortex-like plasma along flux surface inside is observed when n/m = 1/1 external perturbation becomes enough to increase width above a critical range (15–20% minor radius) LHD. This convective results non-flat space potential island. sign curvature...
Quantitative tungsten study with reliable atomic modeling is important for successful achievement of ITER and fusion reactors.We have developed understanding the behavior in plasmas.The applied to analysis spectra observed from plasmas Large Helical Device (LHD) pellet injection.We found that extreme ultraviolet (EUV) emission W 24+ 33+ ions at 1.5-3.5nmare sensitive electron temperature useful examine edge plasmas.We can reproduce measured EUV 1.5-3.5nmby calculated model obtain charge...
In the Large Helical Device plasma discharges, size of an externally imposed island with mode number ( n/m = 1/1) decreases substantially when is collisionless nu(*)< approximately 1) and beta finite > 0.1%) at location. For collisional plasmas beta, on other hand, increases. However, there a threshold in terms vacuum below which enlargement not seen.
Characteristics of transport in electron internal barriers (ITB) and the vicinity a rational surface with magnetic island are studied transient analysis as well steady state analysis. Associated transition radial electric field from small negative value (ion-root) to large positive (electron-root), an ITB appears Large Helical Device [M. Fujiwara et al., Nucl. Fusion 41, 1355 (2001)], when heating power cyclotron exceeds threshold. Transport shows that both standard thermal diffusivity, χe,...