Collective Thomson scattering diagnostic with in situ calibration system for velocity space analysis in large helical device

A collective Thomson scattering (CTS) diagnostic with a ±3 GHz band around a 77 GHz gyrotron probe beam was developed to measure the velocity distribution of bulk and fast ions in high-temperature plasmas. We propose a new in situ calibration method for a CTS diagnostic system combined with a raytracing code. The method is applied in two situations for electron cyclotron emission in plasmas and in a CTS diagnostic with a modulated probe beam. Experimental results highlight the importance of refraction correction in probe and receive beams. The CTS spectrum is measured with the in situ calibrated CTS receiver and responds to fast ions originating from a tangential neutral beam with an energy of 170 keV and from a perpendicular beam with an energy of 60 keV, both in the large helical device. From a velocity space analysis model, the results elucidate the measured anisotropic CTS spectrum caused by fast ions. The calibration methods and analyses demonstrated here are essential for CTS, millimeter-wave diagnostics, and electron cyclotron heating required under fusion reactor conditions

Impact of Magnetic Field Configuration on Heat Transport in Stellarators and Heliotrons

We assess the magnetic field configuration in modern fusion devices by comparing experiments with the same heating power, between a stellarator and a heliotron. The key role of turbulence is evident in the optimized stellarator, while neoclassical processes largely determine the transport in the heliotron device. Gyrokinetic simulations elucidate the underlying mechanisms promoting stronger ion scale turbulence in the stellarator. Similar plasma performances in these experiments suggests that neoclassical and turbulent transport should both be optimized in next step reactor designs

回転磁場法を用いた弱電離プラズマ中の長パルス磁気リコネクション実験の実現

学位の種別: 課程博士審査委員会委員 : （主査）東京大学准教授 井 通暁, 東京大学教授 大崎 博之, 東京大学教授 小野 靖, 東京大学准教授 小野 亮, 宇宙航空研究開発機構准教授 清水 敏文University of Tokyo(東京大学

Transient Electron Thermal Transport Analysis Accounting Oblique Electron Cyclotron Resonance Heating Injection to Magnetic Field Line

In response to recent upgrade of the raytracing code for the electron cyclotron resonance heating (ECH) in LHD, transient electron thermal transport is reanalyzed. The upgraded code LHDGauss-U takes into account the oblique injection of the ECH ray to magnetic field line. The obtained results show reduced transport hysteresis widths by up to ∼ 20% where the heating absorption is less significant, but qualitative features of the transport hysteresis reported in previous studies are found to be preserved

Protective Effects of Fucoidan Against Interleukin-1β-induced Inflammation in SW982 Human Synovial Cells

Fucoidan, a natural sulfated polysaccharide found in the extracellular matrix of brown algae, is rich in L-fucose and sulfate. Fucoidan has a variety of biological actions, including anti-oxidative, anti-coagulative, anti-cancer, and anti-inflammatory activity. However, the cellular molecular mechanism underlying the anti-inflammatory effects of fucoidan remains poorly understood. Rheumatoid arthritis (RA) is a chronic inflammatory disease that causes synovitis and progressive joint destruction. Interleukin (IL) -1β, one of the important mediators involved in the pathogenesis of RA, is known to activate various intracellular signaling pathways. Therefore, in the present study we investigated the inhibitory effects of fucoidan on IL-1β-induced inflammation in human synovial (SW982) cells. SW982 cells were pretreated with fucoidan (100µg/mL) for 1h before cotreatment with 5ng/mL IL-1β plus fucoidan for periods ranging from 20min to 24h. Levels of the proinflammatory mediators IL-6, tumor necrosis factor-α, and cyclooxygenase-2 were then determined. We also assayed translocation of nuclear factor (NF) -κB into the nucleus and activation of mitogen-activated protein kinase (MAPK). Significant increases in the production of proinflammatory mediators were observed from 6 to 24h of IL-1β treatment. The translocation of NF-κB into the nucleus peaked after approximately 6h incubation. After 20min incubation, IL-1β activated c-jun N-terminal kinase and p38 MAPK in SW982 cells. This effect was ameliorated by the coincubation of cells with fucoidan. These results suggest that fucoidan exerts its anti-inflammatory effect by regulating the gene expression of proinflammatory mediators by suppressing the activity of transcription factors and MAPK. Thus, fucoidan may have therapeutic potential for the treatment of RA

Magnetic properties of Fe-Ni-system films prepared by electroless deposition

We prepared Fe-Ni thick-films (> 1 μm) using an electroless deposition method and evaluated the magnetic properties and the crystal structures. The deposition rate depended on the concentration of dimethylamine-borane (DMAB), which is a reducing agent used in the present study, and we obtained a high deposition rate (> 10 μm/h) for Fe30Ni70 films when the DMAB concentration is higher than 3 g/L. From structural analyses of the films, we found that the films have very fine fcc Fe-Ni crystals in the amorphous magnetic phase. From the investigation of Co additives for the improvement in the surface conditions, we confirmed that a small amount of Co effectively works to obtain the smooth surfaces. As a result, we could obtain the Fe-Ni-system thick-films with low coercivity (50 A/m) and smooth surfaces

Upgrading LHDGauss Code by Including Obliquely Propagating Wave Absorption Effect for ECH

LHDGauss is a multi-ray tracing code to calculate microwave beam propagation and power deposition of electron cyclotron heating (ECH) using the electron density and electron temperature profiles in the Large Helical Device (LHD) plasma. LHDGauss also takes into account the injected wave polarization purity. LHDGauss uses the cold plasma dispersion to calculate ray propagation and derives the power absorption profile of ECH by using the absorption coefficient based on weakly relativistic plasmas and the wave propagating perpendicularly to the magnetic field. However, the ECH beam propagation is mainly oblique to the magnetic field in the LHD and it is necessary to take into account the angular dependence of the absorption coefficient in order to derive more accurate ECH power deposition profiles. We upgraded LHDGauss and were able to calculate the absorption coefficient using the weakly relativistic dielectric tensor which considers the influence of the angle between the magnetic field and the wave vector. We compared the power deposition profiles calculated by previous and upgraded LHDGauss with the changes of the electron temperature profile of the LHD plasma in the oblique and the perpendicular O1-mode ECH injection cases. We have obtained more reasonable power deposition profiles by using the upgraded LHDGauss in both the perpendicular and the oblique injection cases