球状トカマク合体立ち上げにおける電子エネルギー付与過程の検証と応用

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 高瀬 雄一, 東京大学教授 小野 靖, 東京大学准教授 江尻 晶, 京都工芸繊維大学教授 政宗 貞男University of Tokyo(東京大学

Reconstruction of plasma shape and eddy current profile based on modified cauchy condition surface method in merging spherical tokamak

The spherical tokamak merging start-up is one of the central solenoid-free start-up method. For controlling the merging actively, it is essential to identify the plasma shapes during the merging process. In the present work, the modified Cauchy condition surface method is applied to demonstrate the reconstruction of the plasma boundary shapes as well as the eddy current profiles at three different representative phases in the merging start-up process (a. initial phase, b. merging phase, c. after merging). Profiles of magnetic flux and plasma boundary have been reconstructed accurately using noiseless magnetic sensor signals and reconstructed with a fairly good accuracy using sensor signals with 3% noise. The eddy current profile have been also reconstructed with a fairly accuracy

Error estimations of the heat flux reconstruction for ITER divertor infrared thermography

This study developed a new heat flux reconstruction code based on the dual reciprocity boundary element method for the International Thermonuclear Experimental Reactor (ITER) divertor infrared (IR) thermography system. To use divertor heat flux reconstruction in ITER, we modeled the boundary condition between the coolant pipe inner wall and the coolant based on the temperature-dependent heat transfer coefficient and also considered the temperature dependence of tungsten thermal properties. Using this reconstruction code, we evaluated the sensitivity of the input data errors, divertor coolant temperature, and surface temperature errors on the accuracy of heat flux reconstruction by using simplified heat flux profiles, which are spatially uniform on the top surface of the monoblocks. This heat flux reconstruction method demonstrated that highly accurate heat flux reconstruction can be achieved for high heat flux cases in ITER; however, further studies are needed for low heat flux reconstruction

Expanded two-color thermography considering temperature-dependent emissivity of tungsten for ITER divertor infrared thermography

This study developed a new correction method to reduce errors in temperature measurement caused by temperature-dependent emissivity for ITER divertor infrared (IR) thermography. In order to develop the method, we measured the spectral emissivity of tungsten from 200 °C to 1900 °C in the wavelength range of 1.5 μm to 4.5 μm and evaluated temperature measurement error of the two-color method. The results indicate that temperature-dependent emissivity is a major factor in temperature measurement errors, which suggests that accurately measuring temperature by using the conventional two-color method would prove difficult. The new correction method uses two emissivity inputs at different temperature points, in contrast to the conventional method, which uses emissivity measured at a single temperature point. Using this new correction method with a suitable wavelength combination for the two-color method, temperature measurement error was reduced to less than 5% at 1900 °C

Gamma ray Irradiation Experiment for ITER Diagnostic Systems in JADA

JADA (ITER Japan Domestic Agency) are developing to procure five diagnostic systems, microfission chamber (MFC), poloidal polarimeter (PoPola), Edge Thomson Scattering (ETS), divertor impurity monitor (DIM) and divertor infrared thermography (IRTh). The reliability in the ITER radiation conditions of relevant equipment to be installed in the vacuum vessel, in the interspaces (IS) between the vacuum boundary and the biological shield and in the port cells (PC) outside the biological shields should be evaluated. In this study, we have launched gamma-ray irradiation experiments in QST Takasaki Advanced Radiation Research Institute from 2018