Concept of Neutron Shield and Electrical Connector of Diagnostic Lower Port Integration for ITER

ITER真空容器の真空ポートの一つである下部ポート内の機器には、中性子遮蔽と搭載する計測機器に給電する役割がある。核融合反応による中性子によって下部ポート内の機器は放射化されるため、保守作業時には遠隔操作で作業（遠隔保守作業）を行い、下部ポート内から取り出す必要がある。また、ITER真空容器内の機器に要求されている清浄度、厳しい熱環境に耐えうる機器でなければならない。本件では、軽量で低放出ガス量な中性子遮蔽体及び急激な温度勾配による熱応力を緩和する構造を設けた電気コネクタについて報告する。31st Symposium on Fusion Technology (SOFT2020

Progress with Lower Port Integration

Introduction of Lower Port 02 integration and its function and requirement for tenant diagnostic, Divertor Impurity Monitor. And Guide structure and Rack locking mechanism are described to achieve the tolerances requirement from tenant diagnostic. And Mock-up and plan for the structures are introduced.41st Meeting of the ITPA Topical Group on Diagnostic

Gamma-ray irradiation effects on optical coatings and polarizers for edge Thomson scattering system in ITER

This paper reports the gamma-ray irradiation effects on optical coatings and polarizers to be used in the ITERedge Thomson scattering system (ETS). Outside a diagnostic port-plug, in the Interspace, a total dose of the orderof 1 MGy is expected through 20 years of ITER operation. In this study, gamma-ray irradiation experiments wereperformed up to 10 MGy. A high peak power laser beam, i.e. a pulse energy of 5 J and a pulse duration of∼4 ns,is needed for a Thomson scattering measurement in ITER. Laser-induced damage threshold (LIDT) of anti-re-flection (AR) and high-reflection (HR) coatings at the laser wavelengths after gamma-ray irradiation were in-vestigated. LIDT of AR coating for 0° injections was more likely higher for the irradiated samples at a wavelengthof 1064 nm. Regarding HR coatings, LIDT was not noticeably degraded by gamma-ray irradiation. Regardingpolarizers, no degradation of transmission and extinction ratio was observed at visible and near infrared wa-velength ranges when a wire-grid polarizer substrate is made of fused silica. Since a signal of ETS is almostlinearly polarized, a wire-grid polarizer enables to improve signal to noise ratio of electron temperature anddensity measurements by Thomson scattering in ITER

Note: Lossless laser beam combiner employing a high-speed rotating half-wave plate

We have developed a laser beam combiner employing a high-speed rotating half-wave plate based on the specific requirements of the Thomson scattering measurement systems in the ITER. The polarization extinction ratio of the output beam may exceed 1000 and was maintained for more than 1 h via feedback control of the half-wave plate rotation speed. The pointing fluctuations introduced by rotating the half-wave plate were in the order of microradians. The high-speed rotating half-wave plate provides a lossless means of combining laser beams together with stable beam pointing

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