Hiroshi Kasahara
A5060955225- Magnetic confinement fusion research
- Particle accelerators and beam dynamics
- Plasma Diagnostics and Applications
- Ionosphere and magnetosphere dynamics
- Fusion materials and technologies
- Superconducting Materials and Applications
- Laser-Plasma Interactions and Diagnostics
- Cryptography and Residue Arithmetic
- Advanced DC-DC Converters
- Numerical Methods and Algorithms
- Non-Invasive Vital Sign Monitoring
- VLSI and Analog Circuit Testing
- Opinion Dynamics and Social Influence
- Induction Heating and Inverter Technology
- Cardiovascular Health and Disease Prevention
- Liver Disease and Transplantation
- Organ Transplantation Techniques and Outcomes
- Vacuum and Plasma Arcs
- Multilevel Inverters and Converters
- Electrostatic Discharge in Electronics
- Electromagnetic Launch and Propulsion Technology
- Embedded Systems Design Techniques
- Atomic and Subatomic Physics Research
- Low-power high-performance VLSI design
- Metabolism and Genetic Disorders
National Institute for Fusion Science
2016-2025
National Institutes of Natural Sciences
2007-2024
UCLouvain
2019-2020
UC Irvine Health
2019-2020
The Graduate University for Advanced Studies, SOKENDAI
2016
Suwa Red Cross Hospital
2014
The University of Tokyo
2000-2011
General Atomics (United States)
2011
Kissei Pharmaceutical (Japan)
2010
Hiroshima City University
2009
As the finalization of a hydrogen experiment towards deuterium phase, exploration best performance plasma was intensively performed in large helical device. High ion and electron temperatures, Ti Te, more than 6 keV were simultaneously achieved by superimposing high-power cyclotron resonance heating onneutral beam injection (NBI) heated plasma. Although flattening temperature profile core region observed during discharges, one could avoid degradation increasing density. Another key parameter...
Extremely hollow profiles of impurities (denoted as “impurity hole”) are observed in the plasma with a steep gradient ion temperature after formation an internal transport barrier (ITB) Large Helical Device [A. Iiyoshi et al., Nucl. Fusion 39, 1245 (1999)]. The radial profile carbon becomes during ITB phase and central density keeps dropping reaches 0.1%–0.3% at end phase. diffusion coefficient convective velocity evaluated from time evolution assuming convection constant ITB. analysis gives...
Plasma production in stellarators with ion cyclotron heating is complementary to the widely used electron (ECRH). The prospective light minority scenario developed and tried on Uragan-2M Large Helical Device (LHD) had been reexamined at LHD. distinctive feature of this attempt that parameters plasma produced are better than before comparable those by ECRH. This new possibility heating, if it becomes practical, motivates rethinking role stellarator machines.
Achievement of reactor relevant plasma condition in Helical type magnetic devices and exploration its related physics fusion engineering are the aim Large Device (LHD) project. In recent experiments on LHD, we have achieved ion-temperature 8.1 keV at 1 × 1019 m−3 by optimization wall conditioning using long pulse discharge Ion Cyclotron Heating (ICH). The electron temperature 10 1.6 was also Electron (ECH). For further improvement performance, upgrade (LHD), including deuterium experiment,...
Two pairs of high-frequency magnetic probes were installed in the Large Helical Device (LHD). During injection a perpendicular neutral beam, ion cyclotron emissions (ICEs) with fundamental frequency corresponding to at plasma edge detected, which are same type ICE as measured former spare range frequencies (ICRF) heating antennas. This was further investigated regard phase and intensity signals. Another found LHD, these ICEs synchronized bursts toroidicity induced Alfvén eigenmodes (TAE)...
Background: As the global population ages, there is an increasing demand for effective strategies to maintain and improve health among older adults. Wearable technology presents a promising tool monitoring management, yet its effectiveness in comprehensive improvement adults remains uncertain. Objective: This study aimed evaluate of personalized lifestyle notifications, based on wearable device recorded data, improving outcomes, specifically cognitive physical function, adults, compared...
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...
Abstract Recently, experiments on basic plasma physics issues for solving future problems in fusion energy have been performed a Large Helical Device. There are several to be solved devices energy. Emerging burning are: alpha-channeling (ion heating by alpha particles), turbulence and transport electron dominant helium ash exhaust, reduction of the divertor heat load. To solve these problems, understanding (1) wave–particle interaction through (inverse) Landau damping, (2) characteristics...
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,...
The discharge scenario of high temperature plasma with a helical configuration has significantly progressed. increase central ion due to the reduction wall recycling was clearly observed. peaking heating profile and charge exchange loss energetic ions play an important role for further improvement heat transport in internal barrier (ITB) core. ITB electron have been successfully integrated superposition centrally focused cyclotron plasma, regime comparable (Ti ~ Te) extended. width formed is...
Non-inductive plasma current start-up by EC and RF power was carried out on the TST-2 device. Low frequency (21 MHz) sustainment demonstrated, obtained high β p spherical tokamak configuration has similar equilibrium values as (2.45 GHz) sustained plasma. Equilibrium analysis revealed detailed information three discharge phases: (i) in initial formation phase, increases with stored energy, is same order that predicted theory. (ii) In jump density profile, which peaked near outboard boundary,...
Plasma heating using fast waves was successfully performed on the Experimental Advanced Superconducting Tokamak (EAST) in H minority regime deuterium plasmas at 27 MHz and B o = 2.0 T. With 1.0 MW of ion cyclotron range frequency (ICRF) power injected a line-averaged electron density 4.0 × 10 19 m −3 , temperature increased from keV to above loop voltage dropped. An increase stored energy by 30 kJ obtained. The first H-mode plasma 6.4 s achieved with combination lower hybrid wave ICRF...
The progress of physical understanding as well parameter improvement net-current-free helical plasma is reported for the Large Helical Device since last Fusion Energy Conference in Daejeon 2010. second low-energy neutral beam line was installed, and central ion temperature has exceeded 7 keV, which obtained by carbon pellet injection. Transport analysis high-Ti plasmas shows that ion-thermal conductivity viscosity decreased after injection although does not long. effort been focused on...
Abstract The driving and damping mechanism of plasma flow is an important issue because shear has a significant impact on turbulence in plasma, which determines the transport magnetized plasma. Here we report clear evidence due to stochastization magnetic field. Abrupt toroidal associated with transition from nested flux surface stochastic field observed when at rational decreases 0.5 large helical device. This resulting profile flattening are much stronger than expected Rechester–Rosenbluth...
The experiments were carried out to study the coupling characteristics of I-port antenna in ion cyclotron range frequencies (ICRF) EAST. dependencies resistance on various parameters including position, central electron density, gas injection and phasing have been studied. results obtained show that experimental data are consistent with theoretical simulations. We find loading decreases sharply at L-H transition due change plasma density profiles scrape-off layer (SOL). effect low hybrid...
Plasma start-up and sustainment without an inductive field have been studied in the TST-2@K spherical tokamak using high power RF sources (8.2?GHz/up to 170?kW). Steady state discharges with a plasma current of 4?kA were achieved. The line integrated density was about 3 ? 1017?m?2 electron temperature 160?eV. A truncated equilibrium introduced reproduce magnetic measurements. It found that positive Pfirsch?Schl?ter open region at outboard boundary makes significant contribution current....
A central ion temperature of 7 keV in a neutral beam injection (NBI)-heated plasma and central-electron 20 an electron cyclotron resonance heating were achieved the Large Helical Device (LHD) using upgraded system with newly installed perpendicular-NB injector gyrotrons. The values Ti Te significantly exceeded 5.6 15 keV, obtained previous experiments, respectively. High-Ti was carbon pellet kinetic-energy confinement improved by factor 1.5. Transport analysis high-Ti plasmas showed that...
Abstract Sawtooth oscillations in tokamaks frequently lead to the redistribution of energetic ions, mainly on passing orbits, causing their expulsion from core. This paper discusses first measurements interaction fast ions and sawteeth Large Helical Device. The crashes were caused by plasma current induced Electron Cyclotron Current Drive Neutral Beam Drive. Despite these crashes, there was no detectable effect either core or at edge plasma.
Spherical tokamaks (STs) have the advantage of high beta capability, but realization a compact reactor requires elimination central solenoid (CS). The possibility using lower hybrid wave (LHW) to ramp up plasma current ( I p ) from zero enough level required for fusion burn in ST is examined theoretically and experimentally. Excitation travelling fast (FW) by combline antenna installed on TST-2 was confirmed finite element analysis, efficient drive excitation LHW, either directly or mode...
Three-dimensional trajectories of incandescent dust particles in plasmas were observed with stereoscopic fast framing cameras a large helical device. It proved that the is located peripheral plasma and most moves along magnetic field lines acceleration direction corresponds to flow. ICRF heated long pulse discharges terminated release amounts from closed divertor region. After experimental campaign, traces exfoliation carbon rich mixed-material deposition layers found Transport investigated...
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.
The steady-state operation of high-performance plasmas in the Large Helical Device (LHD) has progressed since 2010 IAEA Conference Korea by means a newly installed ion cyclotron heating (ICH) antenna (HAS antenna) and an improved electron (ECH) system. HAS can control launched parallel wave number heat core plasma efficiently case dipole mode operation. Understanding physics technology heating, particle flow balances, plasma–wall interactions LHD also improved. power ICH ECH exceeded 1 MW...