Hideaki Nozato
A5011526779- Advanced Measurement and Metrology Techniques
- Magnetic confinement fusion research
- Scientific Measurement and Uncertainty Evaluation
- Advanced Sensor Technologies Research
- Superconducting Materials and Applications
- Particle accelerators and beam dynamics
- Fusion materials and technologies
- Structural Health Monitoring Techniques
- Plasma Diagnostics and Applications
- Ionosphere and magnetosphere dynamics
- Laser-Plasma Interactions and Diagnostics
- Optical measurement and interference techniques
- Geophysics and Sensor Technology
- Advanced Fiber Optic Sensors
- Seismic Waves and Analysis
- Flow Measurement and Analysis
- Sensor Technology and Measurement Systems
- Astronomical Observations and Instrumentation
- Advanced MEMS and NEMS Technologies
- Seismic Imaging and Inversion Techniques
- Ultrasonics and Acoustic Wave Propagation
- Advanced Thermodynamic Systems and Engines
- Laser-induced spectroscopy and plasma
- Spacecraft and Cryogenic Technologies
- Dust and Plasma Wave Phenomena
National Institute of Advanced Industrial Science and Technology
2014-2024
Osaka University
2004-2006
National Institute for Fusion Science
2004-2005
The University of Tokyo
2001-2004
Ube Frontier University
2003-2004
Tokyo University of Science
2003-2004
The Graduate University for Advanced Studies, SOKENDAI
2003
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...
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 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...
Abstract The use of high-sensitivity (∼100 V (m s −2 ) −1 piezoelectric accelerometers is becoming increasingly prevalent in microvibration (∼10 m measurement for satellite altitude stabilization and machinery health monitoring. Calibration with identical to those real scenarios needed ensure the reliability such accelerometers. We conducted primary calibration at a low vibration level (<10 from 5 Hz 6.3 kHz, resulting small half-peak-to-peak displacement amplitude 1.4 pm. uncertainties...
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...
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...
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,...
The Large Helical Device is a heliotron device with L = 2 and M 10 continuous helical coils major radius of 3.5–4.1 m, minor 0.6 m toroidal field 0.5–3 T, which candidate among magnetic confinement systems for steady state thermonuclear fusion reactor. There has been significant progress in extending the plasma operational regime various parameters by neutral beam injection power 13 MW electron cyclotron heating (ECH) MW. ion temperatures have reached up to keV collisionless regime, maximum...
The spatial structure and Z dependence of transport coefficient were studied by injecting impurity pellets (C, Al, Ti) measuring high-spatial resolution bremsstrahlung in steady-state neutral beam heated plasmas on the Large Helical Device [A. Iiyoshi et al., Fusion Techol. 17, 169 (1990)]. D V evaluated from a diffusive/convective model with minimizing residual error between experimental computational intensities taking recycling rate into account. As result, existence an inward convection...
Measuring shock acceleration with peak accelerations ranging from 200 to 5000 m s−2 is a significant concern for mechanical or electrical applications in industries. To precisely calibrate accelerometers using acceleration, we developed calibration system at the National Metrology Institute of Japan. In system, exciter generates rigid-body collisions between three metallic bars inside an air bearing. The pick-up be calibrated fixed on edge surface third bar so that moves together bar....
Abstract Recently, the demand for sensor calibration in infrasonic range has increased to obtain accurate information when monitoring infrasound generated by large-scale natural disasters. The laser pistonphone method is a primary evaluate sensors low-frequency range. In this method, sound pressure fixed sealed volume of air, change via an attached piston movement. By measuring displacement using interferometer, can be calculated multiplying velocity acoustic transfer impedance pistonphone....
Energy confinement and heat transport of net-current-free NBI heated plasmas in the large helical device (LHD) are discussed with emphasis on density power deposition profile dependences. Although apparent dependence energy time has been demonstrated a wide parameter range LHD, loss this observed high regime under specific conditions. Broad due to off-axis alignment shallow penetration neutral beams degrades global while local maintains clear temperature dependence, lying between Bohm...
An impurity pellet injector with three differential pumping systems has been developed to study the particle/impurity transport in combination bremsstrahlung profile measurement Large Helical Device (LHD) plasma. For this purpose different shaped pellets are tested; sphere, hemisphere, and cylinder. The characteristics of accelerated by pressurized helium gas were studied as a function shape mass He pressure. velocity was measured at two positions using He–Ne laser, optical fibers, lenses,...
The first successful high power heating of a dielectric constant spherical tokamak plasma by an electron Bernstein wave (EBW) is reported. An EBW was excited mode conversion (MC) $X$ cyclotron injected from the low magnetic field side TST-2 tokamak. Evidence observed as increases in stored energy and soft x-ray emission. increased emission concentrated core region. A efficiency over 50% achieved, when density gradient MC region sufficiently steep.
Precise extraction of sinusoidal vibration parameters is essential for the dynamic calibration sensors, such as accelerometers. However, several standard methods have not yet been optimized large background noise. In this work, signal processing to extract small signals from noisy data in case accelerometer discussed. The results show that spectral leakage degrades accuracy. Three based on use a filter, window function, and numerical differentiation are investigated with theoretical...
The superconducting machine LHD has conducted long pulse experiments for four years to achieve long-duration plasmas with high performance. operational regime was largely extended in discharge duration and plasma density. In this paper, the characteristics, particular, performance impurity behaviour discharges are described. Confinement studies show that global energy confinement times comparable those short discharges. Long sustainment of plasma, which is equivalent previous achievement...
We present a digital algorithm for measuring the phase of sinusoidal signal that combines modified fringe-counting method with two-sample zero crossing to enable sequential processing. This technique can be applied meter dynamic differences between two signals high resolution, particularly heterodyne interferometry. The floor noise obtained from demonstration an electrical apparatus is at frequencies above approximately 0.1 Hz 80 kHz frequency. In addition, by applying this commercial...
Impurity transport of carbon has been studied using a new method combined pellet injection with high-spatial resolution bremsstrahlung measurement on the Large Helical Device [A. Iiyoshi et al., Fusion Technol. 17, 169 (1990)]. The pellets are injected into steady phase in neutral beam heated discharges standard configuration Rax=3.6m. particle coefficients (diffusion coefficient D and convective velocity V) inferred diffusive/convective model. results compared between hydrogen helium...
This study describes the uncertainty of measurement about accelerometer sensitivity in shock calibration based on ISO 16063-13. The typical approximates to a sine-squared waveform with peak acceleration range from 200 5000 m s−2 and pulse width several milliseconds. shocks are generated by transient collision motion contact rubber surface between two rigid bodies. A laser interferometer He–Ne measures displacement change that is input be calibrated. evaluated time domain defined ratio...