A5055772907- Magnetic confinement fusion research
- Particle accelerators and beam dynamics
- Ionosphere and magnetosphere dynamics
- Gyrotron and Vacuum Electronics Research
- Superconducting Materials and Applications
- Plasma Diagnostics and Applications
- Atomic and Subatomic Physics Research
- Fusion materials and technologies
- Radiation Detection and Scintillator Technologies
- Pulsed Power Technology Applications
- X-ray Spectroscopy and Fluorescence Analysis
- Quantum, superfluid, helium dynamics
- Microwave Engineering and Waveguides
- Atomic and Molecular Physics
- Laser-Plasma Interactions and Diagnostics
- Particle Accelerators and Free-Electron Lasers
- Particle physics theoretical and experimental studies
- Crystallography and Radiation Phenomena
- Physics of Superconductivity and Magnetism
- Magnetic Field Sensors Techniques
- Advanced X-ray and CT Imaging
- Polymer Science and Applications
- Surface Treatment and Residual Stress
- Nuclear Physics and Applications
- Optical properties and cooling technologies in crystalline materials
National Institutes for Quantum Science and Technology
2021-2024
Tokyo Institute of Technology
2021-2023
The University of Tokyo
2015-2022
Plasma (Russia)
2021
University of Tsukuba
2021
Princeton Plasma Physics Laboratory
2021
Kyushu University
2021
University of Wisconsin–Madison
2021
Edgewood College
2021
Tohoku University
1995-2002
Abstract This paper reports on the evaluation of diamagnetic energy using loops in JT-60SA, largest operating tokamak world, and revisits physics behind poloidal beta (βp) internal inductance (li). During first operation phase measurements were utilized assessing parameters related to plasma equilibrium, such as stored energy, βp li. The evaluated is above 200 kJ with 1 MJ electron cyclotron heating, we observed li rise from around unity 2 during current ramp- down phase. successfully...
Views Icon Article contents Figures & tables Video Audio Supplementary Data Peer Review Share Twitter Facebook Reddit LinkedIn Tools Reprints and Permissions Cite Search Site Citation H. Yamazaki, R. J. Cvetanović; Collisional Deactivation of the Excited States Oxygen Atoms. Chem. Phys. 1 October 1963; 39 (7): 1902–1903. https://doi.org/10.1063/1.1734556 Download citation file: Ris (Zotero) Reference Manager EasyBib Bookends Mendeley Papers EndNote RefWorks BibTex toolbar search Dropdown...
Non-inductive plasma current start-up experiments were performed using the lower hybrid wave (LHW) on TST-2 spherical tokamak. The density limit, observed in previous outboard-launch antenna, disappeared after changing condition scrape-off layer, and reached about 20 kA. In order to improve LHW power deposition core through an up-shift of parallel wavenumber during first pass plasma, a new top-launch antenna was designed, fabricated installed. ramp-up 12 kA achieved alone preliminary...
The capacitively-coupled combline (CCC) antenna has been developed for current drive by the lower hybrid wave (LHW) on TST-2 spherical tokamak. was to satisfy requirements of high directionality, low reflectivity, and simple feeding. Since makes use mutual coupling between neighboring elements, only first last elements are connected external feedlines. RF powers power densities order 100 kW 1 MW m−2 can be achieved easily in small antennas 0.1 m2. two CCC installed (outboard-launch...
Non-inductive plasma start-up is a critical issue for spherical tokamaks since there not enough room to provide neutron shielding the center solenoid. Start-up using lower hybrid (LH) waves has been studied on TST-2 tokamak. Because of low magnetic field tokamak, density needs be kept at very value during current ramp-up so that core remains accessible LH waves. However, we have found higher was required sustain larger current. The achievable limited by maximum operational toroidal TST-2....
A multi-energy soft x-ray pinhole camera has been designed and built for the Madison Symmetric Torus reversed field pinch to aid study of particle thermal-transport, as well MHD stability physics. This novel imaging diagnostic technique combines best features from both pulse-height-analysis multi-foil methods employing a PILATUS3 detector in which lower energy threshold photon detection can be adjusted independently on each pixel. Further improvements implemented new cooled systems allow...
In the TST-2 spherical tokamak (ST), non-inductive start-up by lower-hybrid waves (200 MHz) has been studied and a plasma current of 27 kA was achieved. For comprehensive understanding wave sustained plasmas, fast electron transport model combined with an X-ray emission is constructed. The electrons in show velocity random walk induced collisional slowing down. Simultaneously, they diffusion real space. Electron generation loss at limiters are also considered. Using we can calculate powers,...
In the TST-2 spherical tokamak device, we carried out a fully non-inductive current startup experiment by Landau damping of Lower Hybrid Wave (LHW). Capacitively Coupled Combline Antennas (CCCAs) were used for wave injection. The antennas are located on outboard side and top vacuum vessel, reversing toroidal magnetic field, it is possible to simulate case injection from bottom side. highest plasma 26.7 kA was achieved with reversed field. According numerical calculation using ray tracing...
Thomson scattering (TS) diagnostics have been widely used in fusion studies to measure profiles of electron temperature Te and density ne. In order the low-density plasmas (ne ⩽ 1018 m−3) TST-2, which is sustained by lower hybrid wave power, signal-to-noise ratio TS measurement has improved various means. For instance, optimization detecting system, accumulation data obtained from reproducible discharges, application a coaxial multi-pass scheme were carried out. As result, measured...
In this research, the profiles of electron temperature Te and density ne for a spherical tokamak with plasma current sustained by lower hybrid waves alone have been measured first time using Thomson scattering diagnostics in TST-2 device. The profile was hollow like bell-shaped. near center were 6 eV × 1017 m−3, respectively, leading to pressure 0.6 Pa. On other hand, whole at calculated an equilibrium reconstruction code EFIT around 20 Therefore, it is suggested that fast electrons play...
Abstract A gyrotron and a matching optics unit (MOU) for the multi-frequency electron cyclotron heating current drive (ECH/CD) system in JT-60SA have been developed successfully. The demonstrated stable operation at high powers of 1.5 MW 5 s 1.9 1 110 GHz. To obtain HE 11 mode purity (>90%) outlet waveguide ECH/CD launcher, MOU operating three frequencies 82 GHz, 138 GHz that includes pairs water-cooled phase correcting mirrors has developed, which allows to be changed without opening...
Abstract Emissions of ion-cyclotron-range-of-frequency (ICRF) waves have been observed in a solely electron-cyclotron-resonance-heated plasma, namely no fast-ion on the JT-60U tokamak for first time. The mode frequencies are around ion cyclotron frequency at low-field-side plasma edge. considered to be electromagnetic and standing from poloidal toroidal phase differences measured with ICRF antennas. Wave characteristics emissions such as frequency, polarization propagation similar those...
Measurements of edge plasma parameters such as current density, electron and temperature were performed during internal reconnection events in TST-2 Ohmic plasmas. The measured density consists two components: a slowly varying component spiky bipolar component. magnitude the is comparable to mean averaged over poloidal cross section, it seems represent global transport from core edge. about an order larger than component, but spatial structure be localized its effect on confinement not catastrophic.
We investigated electron cyclotron (EC) wave assisted low voltage Ohmic start-up in the conventional field null configuration (FNC) and trapped-particle (TPC) TST-2 spherical tokamak device. The upper pressure limit for successful burn-through increased when EC power was applied both FNC TPC. On other hand, at prefill pressure, breakdown delayed start-up. achievable plasma current also decreased especially high power. By applying TPC, fast recovered even ramp-up rate greater with TPC...
A multi-energy soft x-ray pinhole camera has been designed, built, and deployed at the Madison Symmetric Torus to aid study of particle thermal transport, as well MHD stability physics. This novel imaging diagnostic technique employs a pixelated detector in which lower energy threshold for photon detection can be adjusted independently on each pixel. The choice is PILATUS3 100 K with 450 μm thick silicon sensor nearly 000 pixels sensitive energies between 1.6 30 keV. An ensemble cubic spline...
Abstract High-power (1 MW), long-pulse operations up to 300 s were demonstrated by multi-frequency oscillations at 170 GHz, 137 and 104 GHz. A gyrotron based on the design of ITER has been developed studied. By redesigning built-in mode convertor internal mirrors gyrotron, scattered power was reduced while maintaining same output beam size direction for three frequencies. In addition, a matching optics unit designed efficiently couple RF GHz waveguide 50 mm in diameter, that will be used...
The RF central solenoid operation is a method for generating an inductive electric field in device by which plasma can be produced and ohmically heated. Furthermore, it may drive the DC current via heating. Experiments were carried out TST-2 to clarify this potential under limited amount of flux swing (±0.5 mVs) solenoid. It was found that produce up approximately 0.6 kA on average when external equilibrium applied. In addition, ramped applied ECW power-sustained plasmas.
A new Langmuir probe has been designed and installed in TST-2 for measurements of Scrape-Off Layer plasmas (SOL). Non-inductive current drive is considered essential spherical tokamak reactors. It previously shown that a large amount injected Lower Hybrid Wave (LHW) power lost the SOL [1]. full density profile conditions necessary to accurately simulate propagation LHW TST-2. was durability, larger signal Mach measurements. The results have obtained. Temperature show Te = 30 - 50 eV during...
AC Ohmic coil operation experiments with frequencies up to 10 kHz were performed on the TST-2 spherical tokamak device, and pre-ionization process was studied in detail. The minimum loop voltage for 0.4 V, which corresponds 0.5 V at inboard limiter. Dependences of growth rate saturation level various parameters obtained, they are compared a time-dependent 0-dimensional model based Townsend avalanche loss along field lines. Most dependences reproduced qualitatively by model, quantitative...
Removal of the central solenoid is considered essential to realize a spherical tokamak fusion reactor, but non-inductive plasma start-up challenge. Start-up using lower-hybrid (LH) waves has been studied on TST-2 at University Tokyo. The equilibrium poloidal field believed be generated mostly by wave driven fast electrons, which are highly non-thermal and have large orbit excursions from flux surfaces due low current. Such an can qualitatively different Grad-Shafranov routinely used for...
A compact hard X-ray measurement system was developed to measure bremsstrahlung of fast electrons generated by lower hybrid wave (LHW) in the TST-2 spherical tokamak. The system, which consists an NaI scintillator, a photomultiplier tube, curved acrylic lightguide, lead collimator, and linear rotational stages,enables us energy flux profile on midplane with resolution 10 - 15 eV at 122 keV range from few tens several hundreds keV. Preliminary measurements were performed for LHW-driven...
Plasma merging is a unique method of plasma start-up, and magnetic reconnection key process for heating in this method.On the University Tokyo Spherical Tokamak (UTST), we use pickup coil array to obtain macroscopic behavior reconnection, but direct measurement localized current still necessary study details process.A small Rogowski useful tool measuring scale currents, used five such coils measure radial structure near X-points plasmas on UTST.As result, have found densities up 1.5 MA/m 2 ,...
A new tool has been developed to calculate the spectral, spatial, and temporal responses of multi-energy soft x-ray (ME-SXR) pinhole cameras for arbitrary plasma densities (ne,D), temperature (Te), impurity (nZ). ME-SXR imaging provides a unique opportunity obtaining important properties (e.g., Te, nZ, Zeff) by measuring both continuum line emission in multiple energy ranges. This technique employs pixelated detector which lower threshold photon detection can be adjusted independently....