A5034653163- Magnetic confinement fusion research
- Particle accelerators and beam dynamics
- Fusion materials and technologies
- Superconducting Materials and Applications
- Plasma Diagnostics and Applications
- Ionosphere and magnetosphere dynamics
- Laser-Plasma Interactions and Diagnostics
- Physics of Superconductivity and Magnetism
- Atomic and Subatomic Physics Research
- Electrostatic Discharge in Electronics
- Nuclear reactor physics and engineering
- Superconductivity in MgB2 and Alloys
- Gyrotron and Vacuum Electronics Research
- Atomic and Molecular Physics
- Magnetic properties of thin films
- Magnetic Properties of Alloys
- Particle physics theoretical and experimental studies
- Dark Matter and Cosmic Phenomena
- Engineering Applied Research
- Ion-surface interactions and analysis
- Advanced Data Storage Technologies
- Electric Motor Design and Analysis
- Medical Imaging Techniques and Applications
- Mass Spectrometry Techniques and Applications
- Electrical Fault Detection and Protection
Japan Coast Guard Academy
2023-2025
Kyushu University
1995-2023
Kyoto University
1982-2016
Fully non-inductive plasma maintenance was achieved by a microwave of 8.2 GHz and 40 kW for more than 1 h 55 min with well-controlled plasma-facing wall (PFW) temperature 393 K, using hot in the middle-sized spherical tokamak QUEST, until discharge finally terminated uncontrollability density. The PFW composed atmospheric plasma-sprayed tungsten stainless steel. plays an essential role reducing amount wall-stored hydrogen facilitates recycling. behaviour fuel investigated monitoring...
Transient coaxial helicity injection (CHI) current start-up in a spherical tokamak (ST) has been demonstrated for the first time using reactor-relevant floating single biased (FSB) electrode configuration on QUEST. Unlike previous applications of CHI HIT-II and NSTX which entire ST vessel was split two toroidal ceramic rings as vacuum breaks, FSB QUEST, only lower outer divertor plate is electrically insulated from rest vessel. This injector region. A discharge generated by driving current,...
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...
Initial results from the recently implemented transient coaxial helicity injection (CHI) system on QUEST are reported. uses a new CHI electrode configuration in which insulator is not part of vacuum boundary, making this easier to implement fusion reactors. Experimental show that startup alternate indeed possible. Reliable gas breakdown was achieved, and toroidal currents up 45 kA were generated.
Coaxial Helicity Injection (CHI) has now been implemented in QUEST. The goals for the first transient CHI experiments were to establish reliable gas breakdown conditions, and measure CHI-produced toroidal current generation. Both these objectives successfully met. Toroidal currents up 29 kA measured. Interestingly, plasmas on QUEST also suggest formation of small amounts closed magnetic flux surfaces.
Abstract Electron cyclotron wall conditioning with neon gas (Ne-ECWC) has been performed on the normal conducting spherial tokamak QUEST metal walls under a trapped particle configuration O-mode EC waves including X-mode polarization frequency of 8.2 GHz and an injection power 16 kW. The Ne-ECWC removes hydrogen from small retention. decreases recycling at following discharges, contributing to improvement plasma start-up: current increases start-up timing shifts forward. However, defects...
Abstract The plasma current start-up experiment is conducted through electron cyclotron (EC) heating in the QUEST spherical tokamak. During EC heating, application of a toroidal electric field opposite direction to effectively inhibits growth energetic electrons. Observations show rapid increases and hard x-ray count immediately following cancellation retarding field. When compact tokamak configuration maintains equilibrium on high side, along with field, it leads effective bulk heating....
The controllability of particle supply during long-term discharge in a high-temperature environment was investigated at the Q-shu University Experiment with steady state spherical tokamak (QUEST). QUEST has wall capable active heating and cooling as plasma-facing wall. With this hot wall, temperature rise test conducted 673 K target temperature. It confirmed that could maintain above 600 K. Feedback control fueling to Hα emission, which is closely related influx Using setting 473 K, it...
QUEST (Q-shu university experiment with steady state spherical tokamak) is a midsize tokamak capable of steady-state operation, comprising all-metal plasma-facing walls and hot wall (HW) to address issues pertaining fuel particle balance. The HW was installed summer 2014. Quantitative analysis the at 373 K carried out, clarify quantitative impact shot history that obviously appears in stored hydrogen just before discharge temperature. model indicates plasma-induced deposition layer play an...
In tokamak operations, breakdown of plasma is the first step build-up. this paper, we present a combinative investigation radio frequency (RF)-induced experiments in QUEST (Q-shu University Experiment with Steady-State Spherical Tokamak) and one-point model hydrogen ionization. Experimental results two different frequencies 2.45 GHz 8.2 showed that clear threshold on connection length, L, existed for negative n-index configuration n=−(R/Bv)·(∂Bv/∂R), where R major radius Bv vertical magnetic...
In toroidal electron cyclotron resonance (ECR) plasmas under a weak external vertical field part of the pressure driven charge separation current returns along helical lines, generating current. The rest circulates via conducting vacuum vessel. Only contributes to production closed flux surface. Both and currents are an equilibrium that provides radial force by interaction with field, respectively, counter-balance outward ballooning force.
Nonlinear current-voltage I-V characteristics in Y/sub 1/Ba/sub 2/Cu/sub 3/O/sub 7-/spl delta// thin films have been studied for flux creep taking into account the inhomogeneous pinning strength. By measuring frequency dependence of characteristics, we separated and flow properties. curves split low electric-field region depending on measurement frequency. From dependant curves, obtained maximum field, at which crossed over to flow. use Weibull function, describes depinning probability lines...
A spectroscopic system with multiple viewing chords was developed for QUEST (Q-shu University Experiment Steady-State Spherical Tokamak) to measure the spatial distribution of ion toroidal velocities in discharges sustained by electron cyclotron resonance heating (ECH). Twenty-four were aligned midplane and C III emission line spectra measured three types ECH discharge under different magnetic field configurations. By applying an inversion method spectra, we evaluated radial distributions...
Abstract Spatially resolved rotational temperature of ground state hydrogen molecules desorbed from plasma-facing surface was measured in QUEST, LTX-β, and DIII-D tokamaks, the increases with due to collisional-radiative processes plasmas were evaluated. The increase calculated by solving rate equations considering electron proton collisional excitation deexcitation spontaneous emission. calculation results suggest a high sensitivity for densities, but negligible electron, proton,...
Abstract Results from the successful solenoid-free plasma startup using method of transient coaxial helicity injection (transient CHI) in QUEST spherical tokamak (ST) are reported. Unlike previous applications CHI on HIT-II and NSTX which required two toroidal insulating breaks to vacuum vessel, uses a first its kind, floating single biased electrode configuration, does not use such break. Instead, is simply insulated outer lower divertor plate support structure. This configuration much more...
This research investigated fuel particle balance during long duration discharge in an all-metal plasma facing wall (PFW) through intensive QUEST execution. A simple model including the plasma-induced deposition layer that creates hydrogen (H) barriers, called H barrier model, was established. calculation, based on a combination of state rate equations and applied to real early phase its longest discharge. The accurately reconstructed evolutions electron density wall-stored over time, proper...
We have investigated the electron and ion flows in toroidal cyclotron resonance (ECR) plasmas maintained by a 2.45 GHz microwave power around 1 kW under simple field low aspect ratio torus experiment (LATE) device. found that vertically uniform ridge of pressure also constitutes source belt impact ionization is formed along just lower side ECR layer cross-field potential hill (30 V while 10 eV), eccentrically shifted toward corner top panel layer, arises. Combination hill-driven drift...
High field side (HFS) injection of eXtra-ordinary X-mode for electron Bernstein wave (EBW) conversion was conducted in the QUEST tokamak. Radio frequency (RF; 8.2 GHz) power delivered from low (LFS) to high HFS through waveguides, and placed 20 cm above mid-plane vacuum vessel. The aim compare RF launches LFS HFS. plasma brightness, measured by a fast camera, as well Hα signal captured along mid-plane, noticeably higher launch than launch. achieved current approximately 130 A, versus 35 A...
Interstrand eddy current induced in the samples of flat two-layer superconducting cables finite length by ramping up uniform magnetic field are found to be periodic. Corresponding energy losses compared with those calculated for currents being along sample length. Dependence amplitude oscillations on geometry is considered.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">></ETX>