A5111540827- Magnetic confinement fusion research
- Fusion materials and technologies
- Particle accelerators and beam dynamics
- Ionosphere and magnetosphere dynamics
- Superconducting Materials and Applications
- Plasma Diagnostics and Applications
- Laser-Plasma Interactions and Diagnostics
- Atomic and Subatomic Physics Research
- Nuclear Materials and Properties
- Laser-induced spectroscopy and plasma
- Induction Heating and Inverter Technology
- Solar and Space Plasma Dynamics
- Engineering Applied Research
- Fluid Dynamics and Heat Transfer
- Non-Destructive Testing Techniques
- Gyrotron and Vacuum Electronics Research
- Advanced Data Storage Technologies
- Electrostatic Discharge in Electronics
- Multilevel Inverters and Converters
- Laser Design and Applications
- Algebraic and Geometric Analysis
- Fluid Dynamics Simulations and Interactions
- Advanced DC-DC Converters
- Nuclear Physics and Applications
- Nuclear reactor physics and engineering
Kyushu University
2016-2025
National Institute for Fusion Science
2012
Fusion (United States)
2002-2012
Kyushu Okinawa Agricultural Research Center
2012
Tokyo University of Science
1997
The University of Tokyo
1995-1997
Institute of Science Tokyo
1995
Kyoto University
1988-1994
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...
The extreme heat fluxes in the divertor region of tokamaks may require an alternative to solid plasma-facing components, for extraction and protection surrounding walls. Flowing liquid metals are proposed as alternative, but raise additional challenges that investigation numerical simulations. Free surface designs desirable steady flow profiles stability must be ensured limit undesirable interactions with plasma. Previous studies have mainly used steady-state, 2D, or simplified models...
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,...
After intensive discharge cleaning of the chamber wall, non-inductive current start-up experiments have been successfully performed in QUEST moderate vertical fields about 1.0–1.5 mT with positive n-index. Simultaneously, increasing plasma current, an asymmetric toroidal flow energetic electrons was observed and direct measurements driven by this were taken a newly developed Langmuir probe technique. A numerical study electron orbits indicates that total is enough to play dominant role...
divertors due to concerns regarding their structural integrity at high energy fluxes. The operation of such a device gives rise phenomena spanning multiple disciplines physics as fluid dynamics, electromagnetics, thermodynamics and plasma physics. Smoothed Particle Hydrodynamics (SPH) is Lagrangian, mesh-free numerical method that has been proven effective in variety disciplines. In this work, the hydrodynamic aspect liquid metal divertor simulated using SPH, paving way implement additional...
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...
Plasma current start-up and ramp-up to 10 kA have been demonstrated in the TST-2 spherical tokamak without use of central solenoid. Only electron cyclotron wave (ECW) outer equilibrium field coils are used. The plasma evolution depends on poloidal coil arrangement. It is also that can take place null.
A CW phased-array antenna system for electron cyclotron/Bernstein wave heating and current drive (ECWH/CD, EBWH/CD) experiments was developed in the QUEST. The designed to excite an elliptically polarized pure O-mode oblique injection O-X-B mode conversion scenario, its good performance confirmed at a high power level. Long pulse discharges with plasma of 10 kA 15 were non-inductively attained 37 s 20 s, respectively, only radio frequency (RF) power. Divertor configurations also obtained...
In order to identify plasma shape, there is a way represent the current profile with several parameters, and adjust these parameters least-square technique in for calculated magnetic values accord measured ones. Here, shape such as minor radius, elongation, triangularity are chosen fitting more directly, applicability control of described by evaluating its calculation time. find minimum an objective function technique, two methods compared, namely linear approximation method downhill simplex...
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...
Research activities of the Japanese tokamaks JT-60U, JFT-2M, and TRIAM-1M are described. The recent JT-60 program is focused on establishment a scientific basis advanced steady-state operation. Plasma performance in transient quasi steady states has been significantly improved, utilizing reversed shear weak (high-βp) ELMy H-modes characterized by both internal edge transport barriers high bootstrap current fractions. Development each key issue for operation also advanced. Advanced basic...
High βp (εβp ∼ 1) equilibria obtained in a ECW heated Ohmic plasma is investigated using simple analytic solution of Grad-Shafranov equation. The formation natural inboard poloidal null associated with high explained consistently by diamagnetism and negative triangularity. As increased, the point penetrates further into vacuum vessel, which qualitatively model. Transition from (high field side) limiter bound to divertor configuration reduction edge safety factor without appreciable...
Comparison between non-inductive plasma current start-up using electron cyclotron resonance heating (ECRH) with and without fundamental (1st) 8.2-GHz microwave is experimentally performed on QUEST. Results of soft X-ray measurements in different energy ranges indicate significant difference the number current-carrying electrons resonance. Numerical calculations show effective extendibility ECRH
Two dimensional electron density profile measurement has been performed in the spherical tokamak CPD (Compact PWI experimental Device) using Li sheet beam imaging technique. The topological change from open magnetic field line configuration to closed one is visualized by this plasma current can be driven RF waves itself a weak mirror and clear observed boundary as well topology associated with transition of low (∼1 kA) high (∼3 value.
Electron Bernstein Wave Heating and Current Drive (EBWH/CD) experiments have been conducted to sustain a spherical tokamak configuration in steady state QUEST. In the EBWH/CD on QUEST, O-X-B mode conversion scenario was selected for plasma current sustainment rather low-density plasmas. A new phased-array antenna system proposed launch pure elliptically-polarized O-mode oblique injection. The prototype designed its performance checked at low power test facilities. Good focusing steering...
In magnetized plasmas, the presence of a significant number energetic electrons has been observed but quantitative characteristics these are proving difficult to investigate. A Langmuir probe offers means provide measurement that takes into account electron emissions (secondary emission and reflection) from tips sheath expansion around caused by considerable negative potential. this paper, effects experimentally confirmed an analytical measure proposed. An analysis plasmas produced high...
The runaway phase phenomenon is a problem in reflectometry measurements. change the difference between reflected wave and reference one cannot be explained by movement of cut-off layer when occurs. It difficult to extract information density fluctuation from data with phase. We show model which comes scattered fluctuations, describe new analysis method based on this model. obtained results plasma displacement spectrum are presented.