A5038359442- Magnetic confinement fusion research
- Particle accelerators and beam dynamics
- Plasma Diagnostics and Applications
- Ionosphere and magnetosphere dynamics
- Particle Accelerators and Free-Electron Lasers
- Superconducting Materials and Applications
- Laser-Plasma Interactions and Diagnostics
- Atomic and Subatomic Physics Research
- Radiation Dose and Imaging
- Advanced X-ray and CT Imaging
- Fusion materials and technologies
- Medical Imaging Techniques and Applications
- Solar and Space Plasma Dynamics
- Magnetic Field Sensors Techniques
- Laser-induced spectroscopy and plasma
- Metal and Thin Film Mechanics
- Radiation Therapy and Dosimetry
- Advanced Frequency and Time Standards
- Boron Compounds in Chemistry
- Semiconductor materials and devices
- Aortic aneurysm repair treatments
- Nuclear Issues and Defense
- Radioactive Decay and Measurement Techniques
- Coronary Artery Anomalies
- Advanced Radiotherapy Techniques
Kawasaki University of Medical Welfare
2022-2024
National Institutes for Quantum Science and Technology
2016-2022
Japan Atomic Energy Agency
2015-2016
The University of Tokyo
2009-2015
Saitama University
2015
Saitama Prefecture
2015
Princeton Plasma Physics Laboratory
2015
General Atomics (United States)
2011
Fusion Academy
2011
Fusion (United States)
2011
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,...
On MAST studies of the profile evolution electron temperature (Te), density (ne), radial electric field (Er) as well novel measurements ion (Ti) and toroidal current (jϕ) in pedestal region allow further insight into processes forming defining such H-mode access conditions MHD stability. This includes fast Te, ne Er with Δt = 0.2 ms time resolution pe jϕ through an edge-localized mode (ELM) cycle. Measurements power threshold, PL−H revealed that about 40% more is required to 4He than D a...
The relative biological effectiveness (RBE) of 10B-neutron capture therapy (BNCT) on skin was analyzed using hamsters. Kyoto University Research Reactor, which has a very low contamination gamma rays and fast neutrons, used as thermal neutron source. Boron-10-para-boronophenylalanine hydrochloride ([10B]BPA.HCl) administered to the evolution time course early reactions were assessed. These compared with those produced by electron beams. maximum safe doses (no more than moist desquamation)...
Abstract In the negative-ion-based neutral beam injector (N-NBI) of JT-60SA, a hydrogen negative ion with energy 500 keV and current density 154 A m −2 for 118 s has been successfully demonstrated. This achievement exceeds requirements (500 keV, 130 , 100 s) first time. To maintain stable production long pulse, optimal temperatures chamber wall plasma grid were analytically examined experimentally It was confirmed that temperature during pulse should be <50 °C >200 grid. Damage to...
Design techniques for the vacuum insulation have been developed in order to realize a reliable voltage holding capability of multi-aperture multi-grid (MAMuG) accelerators fusion application. In this method, nested multi-stage configuration MAMuG accelerator can be uniquely designed satisfy target within given boundary conditions. The evaluation capabilities each acceleration stages was based on previous experimental results about area effect and effect. Since found extension by total facing...
Non-inductive plasma current start-up and sustainment by waves in the lower-hybrid frequency range (200 MHz) have been studied on TST-2 spherical tokamak (R0 ⩽ 0.38 m, a 0.25 Bt0 0.3 T, Ip 0.14 MA) using three types of antenna: 11-element inductively-coupled combline antenna, dielectric loaded 4-waveguide array 13-element capacitively-coupled (CCC) antenna. The maximum currents 15 kA, 10 kA 16 were achieved, respectively. highest drive figure merit was achieved CCC efficiency should improve...
In order to realize negative ion sources and accelerators be applicable International Thermonuclear Experimental Reactor JT-60 Super Advanced, a large cesium (Cs)-seeded source multi-aperture multi-stage electric acceleration have been developed at Japan Atomic Energy Agency (JAEA). Long pulse production of the beams independently carried out. The long high current has achieved 100 s beam 15 A by modifying source. duration time is increased three times longer than that before modification....
Long pulse acceleration of hydrogen negative ion beams with the power density over 70 MW/m2 and length 100 s has been demonstrated for first time by using a multi-aperture 3-stage accelerator. Such long was achieved integrating design beam optics voltage holding capability to meet requirements JT-60SA. By newly designed accelerator JT-60SA, at 500 kV stably sustained even after 5 g cesium seeded, heat load on each grid reduced below allowable level pulse, less than 5% total power. As result,...
Plasma current start-up and ramp-up using the lower hybrid wave (LHW) were investigated on TST-2 spherical tokamak. The LHW was launched by a dielectric-loaded waveguide array (grill) antenna. antenna–plasma coupling of this antenna deteriorates as input power exceeds several kW. This deterioration is believed to be caused density depletion due ponderomotive force. conjecture confirmed measurement reduction result non-linear full numerical calculation based finite element method (FEM).
A bright polychromator for compact, efficient YAG Thomson scattering measurement was designed on the basis of ray-tracing calculations. The optical input is a 2-mm-diameter fiber with numerical aperture 0.37. High refractive index glass lenses monolayer anti-reflection coatings were used to reduce aberration effects and achieve good efficiency. fast, low-noise detection system consisting an avalanche photodiode operational amplifiers tested using laser pulses; measured full width at half...
An innovative magnetic configuration called ADCM (Asymmetric Deflection Compensation Magnets) has been recently proposed for the cancellation of "criss-cross" deflection ion trajectories in multi-beamlet negative accelerators. Such undesired occurs due to transverse field, which is necessary suppression co-extracted electrons. In view application this concept ITER Heating Neutral Beam Injector, new experimentally tested first time 2016, framework a research collaboration between Consorzio...
For the realization of ITER neutral beam (NB) system, a method for achieving acceleration voltage 1 MV vacuum insulated source (VIBS) has been developed. Additionally, design basis insulation also developed by integrating previous empirical scaling holding capability plane and coaxial electrodes with new corner region where locally-concentrated electric field is generated. The clarified that product obtained analysis in vessel was much higher than allowable level. Therefore, order to improve...
The Thomson scattering system in the TST-2 has been upgraded to improve reliability and accuracy of measurements. signal intensity increased because a new high-energy (1.6 J) laser. A large-numerical-aperture (N.A.) fiber was tested, it found that 6-m-long can be used without significant transmission loss. With system, typical central electron temperature density for ohmic discharges (with plasma current 60 kA) are 150 eV 1.5 × 1019 m−3, respectively. profile maximum near center plasma.
In the framework of program for construction 1 MeV-16 MW negative neutral beam injector (NNBI) ITER, a research and development activity on voltage holding in vacuum has been initiated since 2009, aimed at supporting design, construction, NNBI accelerator. For this purpose, prediction model (VHPM) previously developed updated. VHPM, effect anodic electric field cathodic probability breakdown is evaluated by means two exponents: α y. On basis experimental results from different test stands...
This paper presents an experimental demonstration to determine electron temperature (Te) with unknown spectral sensitivity (transmissivity) in a Thomson scattering system. In this method, double-pass configuration is used and the scattered lights from each pass (with different angles) are measured separately. Te can be determined ratio of signal intensities without knowing real chromatic dependence sensitivity. Note that wavelength range for channel must known. method was applied TST-2 As...
To understand the physics of cesium (Cs) recycling in large Cs-seeded negative ion sources relevant to ITER and JT-60SA with extraction area 45-60 cm × 110-120 cm, time evolution profile was precisely measured where is longitudinally segmented into 5. The Cs seeded from oven at 180 °C source. After 1 g input, surface production ions appeared only central segment a nozzle located. Up 2 Cs, expanded over full area. has similar tendency distribution atoms that calculated. From results, it...
A multi-pass Thomson scattering (TS) system based on confining laser pulses in an optical cavity was constructed for measuring very low-density plasma the TST-2 spherical tokamak device. This paper describes setup of system, injection pulse into cavity, and properties confined pulse. combination Pockels cell plus polarizer, which serves as shutter, allows us to inject then confine intense cavity. photodiode signal monitoring weak light leaking from mirrors demonstrated that makes many round...
A double-pass Thomson scattering system, in which a laser pulse makes round trip through the plasma, was constructed. Using same optics and fast detection unit, we can resolve backward forward pulses signal. Because these scatterings reflect velocity distribution along different directions, electron temperature anisotropy be estimated from system.
The physical mechanism of the formation negative ion beam halo and heat loads multi-stage acceleration grids are investigated with 3D PIC (particle in cell) simulation. following is verified: core consist ions extracted from center periphery meniscus, respectively. This difference extraction location results a geometrical aberration. Furthermore, it shown that on first grid second quantitatively improved compared those for 2D simulation result.
The electrical insulation of the Megavolt ITER Injector and Concept Advancement (MITICA) beam source (BS) at 1 MV in vacuum is a challenging issue, which could not be fully addressed so far on basis experimental results theoretical models available literature. A specific high-voltage (HV) test campaign being prepared to validate optimize voltage holding capability BS under realistic conditions, using full-size mockup electrodes reproducing detail geometry accelerator. proposed strategy will...
The purpose of this study was to develop a novel scintillation dosimeter for in vivo dosimetry Ir-192 brachytherapy via the pulse-counting mode. new made from plastic scintillator shaped into hemisphere diameter 1 mm and connected tip optical fiber. relationship between pulse counts absorbed dose derived based on assumption that photons incident gamma ray are proportional dose. An equation conversion water-equivalent deduced wherein height spectrum assumed be exponential. To confirm its...
Multi-pass Thomson scattering is an attractive method for measuring electron temperature and density in low plasmas. The feasibility of multi-pass laser optics consisting two confocal spherical mirrors has been studied, analytic expressions the path have obtained. These can be used to optimize design under given conditions. effects aberration, as well positioning alignment errors, were found critical obtaining large transit numbers. Beam expansion resulting from surface roughness diffraction...
We have developed a multi-point Thomson scattering system with double-pass configuration for the TST-2 device and installed new collection optics same. Temperature density can now be measured simultaneously at four points by using fibers polychromators. Herein, we present results of off-axis temperature anisotropy measurements performed this system, in which no beyond error bar was observed ohmic plasmas.