A5073175383- Magnetic confinement fusion research
- Ionosphere and magnetosphere dynamics
- Particle accelerators and beam dynamics
- Superconducting Materials and Applications
- Plasma Diagnostics and Applications
- Laser-Plasma Interactions and Diagnostics
- Fusion materials and technologies
- Atomic and Subatomic Physics Research
- Gyrotron and Vacuum Electronics Research
- Solar and Space Plasma Dynamics
- Laser-induced spectroscopy and plasma
- Spectroscopy and Laser Applications
- Magneto-Optical Properties and Applications
- Magnetic Field Sensors Techniques
- Physics of Superconductivity and Magnetism
- Laser Design and Applications
- Dust and Plasma Wave Phenomena
- Nuclear Physics and Applications
- Advanced Frequency and Time Standards
- Microwave and Dielectric Measurement Techniques
- Atomic and Molecular Physics
- Acoustic Wave Resonator Technologies
- Meteorological Phenomena and Simulations
- Advanced Fiber Optic Sensors
- Advanced Measurement and Metrology Techniques
The University of Tokyo
2015-2024
Tokyo University of Science
1992-2016
Ube Frontier University
2005-2016
National Institute for Fusion Science
1994-2012
Fusion Academy
1995-2011
Fusion (United States)
1995-2011
General Atomics (United States)
2011
Plasma Technology (United States)
2011
Frontier Science Foundation
2004
National Institutes of Natural Sciences
1995-2002
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...
As the finalization of a hydrogen experiment towards deuterium phase, exploration best performance plasma was intensively performed in large helical device. High ion and electron temperatures, Ti Te, more than 6 keV were simultaneously achieved by superimposing high-power cyclotron resonance heating onneutral beam injection (NBI) heated plasma. Although flattening temperature profile core region observed during discharges, one could avoid degradation increasing density. Another key parameter...
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...
Two types of electrostatic modes with small-poloidal wave numbers ($\ensuremath{\sim}1$ and $10--15\text{ }\text{ }\mathrm{kHz}$) are observed in the edge region Ohmically heated plasmas JFT-2M tokamak. The envelope higher frequency coherent mode is modulated at lower mode. A bispectral analysis revealed that a significant nonlinear coupling among two fluctuations broadband background turbulent potential occurs inside last closed magnetic flux surface, suggesting process such as...
In the first four years of LHD experiment, several encouraging results have emerged, most significant which is that MHD stability and good transport are compatible in inward shifted axis configuration. The observed energy confinement at this optimal configuration consistent with ISS95 scaling an enhancement factor 1.5. over smaller heliotron devices attributed to high edge temperature. We find plasma average beta 3% stable configuration, even though theoretical conditions Mercier modes...
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...
Fully non-inductive second (2nd) harmonic electron cyclotron (EC) plasma current ramp-up was demonstrated with a newlly developed 28 GHz system in the QUEST spherical tokamak. A high of 54 kA non-inductively ramped up and sustained stably for 0.9 s 270 kW wave. higher 66 also achieved slow vertical field. We have significantly than those previously 2nd EC waves. This fully method might be useful future burning devices fusion reactors, particular operations at half magnetic field same heating...
A multichannel far-infrared laser interferometer system has been developed for the measurement of spatial and temporal behaviors electron density on Large Helical Device (LHD) at National Institute Fusion Science. Of several candidates high power sources a 119 μm CH3OH was taken as probing light. The optical configuration is Michelson type with 13 channels. mounted massive stainless frame floated three vibration isolating mounts. resolution fringe counters 1/100 fringes, it corresponds to...
A new spherical tokamak, TST-2, was constructed at the University of Tokyo and started operation in September 1999. Reliable plasma initiation is achieved with typically 1 kW ECH power 2.45 GHz. Plasma currents up to 90 kA toroidal fields 0.2 T have been during initial experimental campaign. The ion temperature 100 eV. Internal reconnection events are often observed. internal magnetic field measured r/a = 2/3 indicated growth fluctuations fourth harmonic, suggesting existence modes several...
The central electron temperature has successfully reached up to 7.5 keV in large helical device (LHD) plasmas with a high-ion of 5 and density m−3. This result was obtained by heating newly-installed 154 GHz gyrotron also the optimisation injection geometry cyclotron (ECH). carried out using ray-tracing code 'LHDGauss', which upgraded include rapid post-processing three-dimensional (3D) equilibrium mapping from experiments. For calculations, LHDGauss can automatically read relevant data...
Experiments aiming at 'day long operation high performance' have been carried out in TRIAM-1M. The record value of the discharge duration was updated to 5 h and 16 min. Steady-state tokamak is studied under localized plasma wall interaction conditions. distributions heat load, particle recycling flux impurity source are investigated understand co-deposition pumping. formation sustainment an internal transport barrier (ITB) enhanced current drive mode has by controlling lower hybrid driven...
A method for zonal flow study by using direct density fluctuation measurements is proposed. When ambient drift-wave turbulence modulated flows (i.e. in the drift-wave-zonal systems), an envelope of fluctuations has spectral peaks around frequencies. peak at geodesic acoustic mode (GAM) frequency observed measured edge plasma JFT-2M tokamak. The significant cross-bicoherence also found between and its GAM frequency. This result demonstrates that we can measure only data. provides a...
The mission of the National Spherical Torus Experiment (NSTX) is demonstration physics basis required to extrapolate next steps for spherical torus (ST), such as a plasma facing component test facility (NHTX) or an ST based (ST-CTF), and support ITER. Key issues are transport, steady state high β operation. To better understand electron new high- k scattering diagnostic was used extensively investigate gyro-scale fluctuations with varying temperature gradient scale length. Results from n = 3...
Plasma current (Ip) start-up in a spherical tokamak (ST) by waves the lower-hybrid (LH) frequency range was investigated on TST-2. A low (~1 kA) ST configuration can be formed over broad (21 MHz–8.2 GHz TST-2), but further Ip ramp-up (to ~10 is most efficient with LH range. to 15 kA achieved 60 kW of net RF power PRF fast wave (FW) polarization at 200 MHz excited inductively coupled combline antenna. X-ray measurements showed that photon flux and temperature are higher direction opposite Ip,...
A pulsating behavior of the electrostatic potential has been discovered in a low-density, high-electron-temperature plasma CHS heliotron/torsatron. The profiles were observed to swing repeatedly between two distinctive states constant external magnetic field under continuous supply particles and energy. change profile, which occurs on much faster time scale (microseconds) than diffusive (milliseconds), is accompanied by changes density temperature. This discovery clearly demonstrates that...
During the first two years of LHD experiment following results have been achieved: (i) higher Te (Te(0) = 4.4 keV at ⟨ne⟩ 5.3 × 1018 m-3 and Pabs 1.8 MW); (ii) confinement (τE 0.3 s, Te(0) 1.1 6.5 1019 2.0 (iii) stored energy, Wpdia 880 kJ B 2.75 T. High performance plasmas realized in inward shifted magnetic axis configuration (R 3.6 m) where helical symmetry is recovered particle orbit properties are improved by a trade-off MHD stability due to appearance hill. Energy was systematically...
Laser scattering signals that indicate the presence of small dust particles (diameter ⩽ 2 μm) have been occasionally observed in JIPPT-IIU tokamak chamber. This phenomenon was reproduced deliberately by spreading carbon from top vacuum No noticeable effect on plasma for falls up to at least 106 (10 μg) 20 ms during discharges. Dust falling just before startup seemed be confined but it soon ejected (in less than 30 ms)
This paper presents results of bispectral analysis applied to floating potential fluctuations in the edge region ohmically heated plasmas JAERI Fusion Torus-2 Modified (JFT-2M) tokamak. Inside outermost surface plasmas, coherent mode (CMs) were observed around frequency geodesic acoustic mode. The squared bicoherence shows significant nonlinear couplings between CMs and background fluctuations. biphase at is localized π, while that frequencies distributes a wide range. total proportional...
Non-inductive plasma current start-up by EC and RF power was carried out on the TST-2 device. Low frequency (21 MHz) sustainment demonstrated, obtained high β p spherical tokamak configuration has similar equilibrium values as (2.45 GHz) sustained plasma. Equilibrium analysis revealed detailed information three discharge phases: (i) in initial formation phase, increases with stored energy, is same order that predicted theory. (ii) In jump density profile, which peaked near outboard boundary,...
In order to measure the poloidal rotation velocity, a Doppler reflectometer has been developed in Large Helical Device (LHD). A remotely controlled antenna tilting system installed an LHD vacuum vessel. synthesizer is used as source, and operation microwave frequency ranges are ka-band V-band. last experimental campaign we obtained shifted signal, which was consistent with CXRS measurements.
The progress of physical understanding as well parameter improvement net-current-free helical plasma is reported for the Large Helical Device since last Fusion Energy Conference in Daejeon 2010. second low-energy neutral beam line was installed, and central ion temperature has exceeded 7 keV, which obtained by carbon pellet injection. Transport analysis high-Ti plasmas shows that ion-thermal conductivity viscosity decreased after injection although does not long. effort been focused on...
Abstract The driving and damping mechanism of plasma flow is an important issue because shear has a significant impact on turbulence in plasma, which determines the transport magnetized plasma. Here we report clear evidence due to stochastization magnetic field. Abrupt toroidal associated with transition from nested flux surface stochastic field observed when at rational decreases 0.5 large helical device. This resulting profile flattening are much stronger than expected Rechester–Rosenbluth...
The plasma current is ramped up primarily by a 28 GHz electron cyclotron wave (ECW) in the Q-shu University experiment Steady-State Spherical Tokamak (QUEST), with multiple harmonic resonance layers from second to fourth stay core. A steering antenna comprising two quasi-optical mirrors enhances power density of ECWs. ECW beam injected obliquely low-field side where parallel refractive index N∥ = 0.75 at second-harmonic layer. Analysis condition has found that energetic electrons moving...
Significant improvements have been achieved in the accuracy and reliability of broadband frequency-swept (FM) reflectometer measurements on DIII-D. This has through several improvements, most important which application digital complex demodulation (CDM) analysis software, can extract signal phase with subfringe accuracy. Using this new technique, results from FM system look very promising: show excellent agreement Thomson profiles Ohmic H-mode plasmas, good data L-mode. Clear resolution...